This report contains the collective views of an international group of experts and does not necessarily represent the decisions or the stated policy of the United Nations Environment Programme, the International Labour Organisation, or the World Health Organization.

Concise International Chemical Assessment Document 20

MONONITROPHENOLS

First draft prepared by Dr A. Boehncke, Dr G. Koennecker, Dr I. Mangelsdorf, and Dr A. Wibbertmann, Fraunhofer Institute for Toxicology and Aerosol Research, Hanover, Germany

Please note that the layout andpagination of this pdf file are not identicalto those of theprinted CICAD

Published under the joint sponsorship of the United Nations Environment Programme, the International Labour Organisation, and the World Health Organization, and produced within the framework of the Inter-Organization Programme for the Sound Management of Chemicals.

World Health Organization Geneva, 2000 The International Programme on Chemical Safety (IPCS), established in 1980, is a joint venture of the United Nations Environment Programme (UNEP), the International Labour Organisation (ILO), and the World Health Organization (WHO). The overall objectives of the IPCS are to establish the scientific basis for assessment of the risk to human health and the environment from exposure to chemicals, through international peer review processes, as a prerequisite for the promotion of chemical safety, and to provide technical assistance in strengthening national capacities for the sound management of chemicals. The Inter-Organization Programme for the Sound Management of Chemicals (IOMC) was established in 1995 by UNEP, ILO, the Food and Agriculture Organization of the United Nations, WHO, the United Nations Industrial Development Organization, the United Nations Institute for Training and Research, and the Organisation for Economic Co-operation and Development (Participating Organizations), following recommendations made by the 1992 UN Conference on Environment and Development to strengthen cooperation and increase coordination in the field of chemical safety. The purpose of the IOMC is to promote coordination of the policies and activities pursued by the Participating Organizations, jointly or separately, to achieve the sound management of chemicals in relation to human health and the environment.

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Mononitrophenols.

(Concise international chemical assessment document ; 20)

1.Nitrophenols - toxicity 2.Risk assessment 3.Environmental exposure I.International Programme on Chemical Safety II.Series

ISBN 92 4 153020 0 (NLM classification: QD 341.P5) ISSN 1020-6167

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Printed by Wissenschaftliche Verlagsgesellschaft mbH, D-70009 Stuttgart 10 TABLE OF CONTENTS

FOREWORD ...... 1

1. EXECUTIVE SUMMARY ...... 4

2. IDENTITY AND PHYSICAL/CHEMICAL PROPERTIES ...... 5

3. ANALYTICAL METHODS ...... 6

4. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE ...... 6

5. ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION ...... 8

6. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE ...... 10

6.1 Environmental levels ...... 10 6.2 Human exposure ...... 10

7. COMPARATIVE KINETICS AND METABOLISM IN LABORATORY ANIMALS AND HUMANS ...... 11

7.1 2-Nitrophenol ...... 11 7.2 4-Nitrophenol ...... 11

8. EFFECTS ON LABORATORY MAMMALS AND IN VITRO TEST SYSTEMS ...... 11

8.1 Single exposure ...... 11 8.2 Irritation and sensitization ...... 12 8.3 Short-term exposure ...... 12 8.3.1 Oral exposure ...... 12 8.3.2 Inhalation exposure ...... 13 8.3.2.1 2-Nitrophenol ...... 13 8.3.2.2 4-Nitrophenol ...... 13 8.3.3 Dermal exposure ...... 13 8.4 Long-term exposure ...... 13 8.4.1 Subchronic exposure ...... 13 8.4.2 Chronic exposure and carcinogenicity ...... 14 8.5 Genotoxicity and related end-points ...... 14 8.6 Reproductive and developmental toxicity ...... 14 8.6.1 Reproductive toxicity ...... 14 8.6.2 Developmental toxicity ...... 18 8.6.2.1 2-Nitrophenol ...... 18 8.6.2.2 4-Nitrophenol ...... 18 8.7 Immunological and neurological effects ...... 18 8.8 Methaemoglobin formation ...... 18

9. EFFECTS ON HUMANS ...... 18

10. EFFECTS ON OTHER ORGANISMS IN THE LABORATORY AND FIELD ...... 19

10.1 Aquatic environment ...... 19 10.2 Terrestrial environment ...... 20

iii Concise International Chemical Assessment Document 20

11. EFFECTS EVALUATION ...... 21

11.1 Evaluation of health effects ...... 21 11.1.1 Hazard identification and dose–response assessment ...... 21 11.1.2 Criteria for setting guidance values for 2- and 4-nitrophenol ...... 22 11.1.3 Sample risk characterization ...... 22 11.2 Evaluation of environmental effects ...... 22

12. PREVIOUS EVALUATIONS BY INTERNATIONAL BODIES ...... 23

13. HUMAN HEALTH PROTECTION AND EMERGENCY ACTION ...... 23

14. CURRENT REGULATIONS, GUIDELINES, AND STANDARDS ...... 23

INTERNATIONAL CHEMICAL SAFETY CARD ...... 24

REFERENCES ...... 26

APPENDIX 1 — 3-NITROPHENOL ...... 31

APPENDIX 2 — SOURCE DOCUMENTS ...... 33

APPENDIX 3 — CICAD PEER REVIEW ...... 33

APPENDIX 4 — CICAD FINAL REVIEW BOARD ...... 34

RÉSUMÉ D’ORIENTATION ...... 35

RESUMEN DE ORIENTACIÓN ...... 38

iv Mononitrophenols

FOREWORD While every effort is made to ensure that CICADs represent the current status of knowledge, new Concise International Chemical Assessment information is being developed constantly. Unless Documents (CICADs) are the latest in a family of otherwise stated, CICADs are based on a search of the publications from the International Programme on scientific literature to the date shown in the executive Chemical Safety (IPCS) — a cooperative programme of summary. In the event that a reader becomes aware of the World Health Organization (WHO), the International new information that would change the conclusions Labour Organisation (ILO), and the United Nations drawn in a CICAD, the reader is requested to contact Environment Programme (UNEP). CICADs join the IPCS to inform it of the new information. Environmental Health Criteria documents (EHCs) as authoritative documents on the risk assessment of Procedures chemicals. The flow chart shows the procedures followed to CICADs are concise documents that provide produce a CICAD. These procedures are designed to summaries of the relevant scientific information take advantage of the expertise that exists around the concerning the potential effects of chemicals upon world — expertise that is required to produce the high- human health and/or the environment. They are based quality evaluations of toxicological, exposure, and other on selected national or regional evaluation documents or data that are necessary for assessing risks to human on existing EHCs. Before acceptance for publication as health and/or the environment. CICADs by IPCS, these documents undergo extensive peer review by internationally selected experts to ensure The first draft is based on an existing national, their completeness, accuracy in the way in which the regional, or international review. Authors of the first original data are represented, and the validity of the draft are usually, but not necessarily, from the institution conclusions drawn. that developed the original review. A standard outline has been developed to encourage consistency in form. The primary objective of CICADs is The first draft undergoes primary review by IPCS to characterization of hazard and dose–response from ensure that it meets the specified criteria for CICADs. exposure to a chemical. CICADs are not a summary of all available data on a particular chemical; rather, they The second stage involves international peer include only that information considered critical for review by scientists known for their particular expertise characterization of the risk posed by the chemical. The and by scientists selected from an international roster critical studies are, however, presented in sufficient compiled by IPCS through recommendations from IPCS detail to support the conclusions drawn. For additional national Contact Points and from IPCS Participating information, the reader should consult the identified Institutions. Adequate time is allowed for the selected source documents upon which the CICAD has been experts to undertake a thorough review. Authors are based. required to take reviewers’ comments into account and revise their draft, if necessary. The resulting second draft Risks to human health and the environment will is submitted to a Final Review Board together with the vary considerably depending upon the type and extent reviewers’ comments. of exposure. Responsible authorities are strongly encouraged to characterize risk on the basis of locally The CICAD Final Review Board has several measured or predicted exposure scenarios. To assist the important functions: reader, examples of exposure estimation and risk characterization are provided in CICADs, whenever – to ensure that each CICAD has been subjected to possible. These examples cannot be considered as an appropriate and thorough peer review; representing all possible exposure situations, but are – to verify that the peer reviewers’ comments have provided as guidance only. The reader is referred to EHC been addressed appropriately; 1701 for advice on the derivation of health-based – to provide guidance to those responsible for the guidance values. preparation of CICADs on how to resolve any remaining issues if, in the opinion of the Board, the author has not adequately addressed all comments of the reviewers; and 1 International Programme on Chemical Safety (1994) to approve CICADs as international assessments. Assessing human health risks of chemicals: derivation – of guidance values for health-based exposure limits. Geneva, World Health Organization (Environmental Board members serve in their personal capacity, not as Health Criteria 170). representatives of any organization, government, or

1 Concise International Chemical Assessment Document 20

CICAD PREPARATION FLOW CHART

SELECTION OF PRIORITY CHEMICAL

SELECTION OF HIGH QUALITY NATIONAL/REGIONAL ASSESSMENT DOCUMENT(S)

FIRST DRAFT PREPARED

PRIMARY REVIEW BY IPCS ( REVISIONS AS NECESSARY)

REVIEW BY IPCS CONTACT POINTS/ SPECIALIZED EXPERTS

REVIEW OF COMMENTS (PRODUCER/RESPONSIBLE OFFICER), PREPARATION OF SECOND DRAFT 1

FINAL REVIEW BOARD 2

FINAL DRAFT 3

EDITING

APPROVAL BY DIRECTOR, IPCS

PUBLICATION

1 Taking into account the comments from reviewers. 2 The second draft of documents is submitted to the Final Review Board together with the reviewers’ comments. 3 Includes any revisions requested by the Final Review Board.

2 Mononitrophenols

industry. They are selected because of their expertise in human and environmental toxicology or because of their experience in the regulation of chemicals. Boards are chosen according to the range of expertise required for a meeting and the need for balanced geographic representation.

Board members, authors, reviewers, consultants, and advisers who participate in the preparation of a CICAD are required to declare any real or potential conflict of interest in relation to the subjects under discussion at any stage of the process. Representatives of nongovernmental organizations may be invited to observe the proceedings of the Final Review Board. Observers may participate in Board discussions only at the invitation of the Chairperson, and they may not participate in the final decision-making process.

3 Concise International Chemical Assessment Document 20

1. EXECUTIVE SUMMARY phase, wet deposition of nitrophenols from air to surface waters and soil is to be expected. The major transformation pathway for 2-nitrophenol emitted to the This CICAD on the isomers 2-, 3-, and 4-nitro- troposphere should be rapid nitration to 2,4-dinitro- phenol was prepared by the Fraunhofer Institute for phenol, whereas the major portion of airborne 4-nitro- Toxicology and Aerosol Research, Hanover, Germany. It phenol is expected to be particle bound and therefore was based on reviews compiled by the German Advisory only to a minor extent available for photochemical Committee on Existing Chemicals of Environmental reactions. Most of the 4-nitrophenol should be washed Relevance (BUA, 1992) and the US Agency for Toxic out from air by wet and dry deposition. Nitrophenols are Substances and Disease Registry (ATSDR, 1992) to not considered to contribute directly to the depletion of assess the potential effects of 2- and 4-nitrophenol on the stratospheric ozone layer or to global warming. the environment and on human health. Data identified up Measured half-lives for the photochemical decomposi- to 1992 were considered in these reviews. A compre- tion of 4-nitrophenol in water ranged from 2.8 to hensive literature search of several databases was con- 13.7 days. Numerous studies on the biodegradation of ducted in 1998 to identify any relevant references on 2- 2- and 4-nitrophenol indicate the isomers to be inher- and 4-nitrophenol published subsequent to those in the ently biodegradable in water under aerobic conditions. source documents and to identify all references contain- Mineralization of nitrophenols under anaerobic condi- ing relevant data on the isomer 3-nitrophenol. Informa- tions requires extended adaptation of microbial commu- tion found on 3-nitrophenol was very scarce, precluding nities. a meaningful assessment. As a result, data on this isomer are summarized in Appendix 1. Information on the Measured coefficients of soil sorption (Koc) in the nature of the peer review and the availability of the range of 44–530 indicate a low to moderate potential for source documents is presented in Appendix 2. Informa- soil sorption. Nitrophenols released to soil should be tion on the peer review of this CICAD is presented in biodecomposed under aerobic conditions. Infiltration Appendix 3. This CICAD was approved as an interna- into groundwater is expected only under conditions tional assessment at a meeting of the Final Review unfavourable to biodegradation. For 2- and 4-nitrophe- Board, held in Washington, DC, USA, on 8–11 December nol, measured bioconcentration factors ranging from 11 1998. Participants at the Final Review Board meeting are to 76 indicate a low potential for bioaccumulation. listed in Appendix 4. The International Chemical Safety Card (ICSC 1342) for mononitrophenols, produced by the There is only limited information concerning the International Programme on Chemical Safety (IPCS, toxicological profiles of 2- and 4-nitrophenol. In experi- 1998), has also been reproduced in this document. mental animals given 4-nitrophenol orally, intravenously, or intraperitoneally, most of the applied dose was The nitrophenol isomers are water-soluble solids excreted via the urine within 24–48 h as glucuronide and that are moderately acidic in water as a result of dissoci- sulfate conjugates, while only very small amounts were ation. 2-Nitrophenol and 4-nitrophenol are used as inter- excreted via faeces or as unchanged 4-nitrophenol. The mediates in the synthesis of a number of organophos- percentages of glucuronide and sulfate conjugates were phorus pesticides and some medical products. Releases shown to be species and dose dependent. After oral into the environment are primarily emissions into air, dosing in rabbits, 4-nitrophenol undergoes reduction to water, and soil from diffuse sources, such as vehicle p-aminophenol as well as glucuronidation and sulfation. traffic and hydrolytic and photolytic degradation of the The available data from in vivo and in vitro studies give respective pesticides. Further releases into the hydro- an indication for dermal uptake of 4-nitrophenol. The sphere and the geosphere are caused by the dry and wet data for 2-nitrophenol are very limited. However, based deposition of airborne nitrophenols from the atmos- on the available data, a comparable metabolic transfor- phere. The photo-oxidative formation of 2- and 4-nitro- mation is assumed. Bioaccumulation of 2- and 4-nitro- phenol in the atmosphere is still under discussion. phenol in organisms is not to be expected owing to their rapid metabolism and excretion. From the available data, only a slow rate of volati- lization of 2-nitrophenol and no significant volatilization In acute studies, 4-nitrophenol is harmful after oral of 4-nitrophenol from water to air are to be expected. uptake and was found to be more toxic than 2-nitrophe- 2-Nitrophenol is enriched in the liquid phase of clouds, nol. A dose-dependent increase in the formation of whereas more 4-nitrophenol than expected from physico- methaemoglobin was seen in cats after oral exposure to chemical data can be found in the gas phase owing to 2-nitrophenol and in rats after exposure by inhalation to extensive binding to particles. In view of the water 4-nitrophenol. After repeated exposure to 4-nitrophenol, solubilities and the expected occurrence in the vapour the formation of methaemoglobin was shown to be the

4 Mononitrophenols

most critical end-point for exposure by inhalation and is From valid test results available on the toxicity of assumed to be relevant for oral exposure too. Other 2- and 4-nitrophenol to various aquatic organisms, noted effects included decreases in body weight gain, nitrophenols can be classified as substances exhibiting differences in organ weights, focal fatty degeneration of moderate to high toxicity in the aquatic compartment. the liver, and haematological changes. For these effects, The lowest effect concentrations found in chronic it was not possible to identify a clear dose–response or studies with freshwater organisms (Scenedesmus reliable no-observed-(adverse-)effect levels (NO(A)ELs). subspicatus, 96-h EC50: 0.39 mg 2-nitrophenol/litre; Entosiphon sulcatum, 72-h minimum inhibitory concen- 2-Nitrophenol is slightly irritating to the skin but tration, or MIC: 0.83 mg 4-nitrophenol/litre) were 40– non-irritating to the eye. The substance proved to have 50 times higher than maximum levels determined in a no sensitizing effects in a Buehler test. Based on valid densely populated and highly industrialized Asian river studies with experimental animals, irritating effects on basin (0.0072 mg 2-nitrophenol/litre and 0.019 mg 4- skin and eye are assumed for 4-nitrophenol. In a guinea- nitrophenol/litre). Therefore, despite biotic and photo- pig maximization test, 4-nitrophenol was considered as chemical decomposition, nitrophenols emitted to water slightly sensitizing. In humans, a possible sensitization could pose some risk to sensitive aquatic organisms, after contact with 4-nitrophenol cannot be excluded, particularly under surface water conditions not favour- especially as skin sensitization has been found in patch ing both elimination pathways. Because of their use tests on factory workers who may have been exposed to patterns and release scenarios, it is likely that nitrophe- 4-nitrophenol. nols pose only a minor risk to aquatic organisms.

Neither of the two isomers of nitrophenol has been The available data indicate only a moderate toxicity fully tested for genotoxicity. Insufficient data are avail- potential of nitrophenols in the terrestrial environment. able on 2-nitrophenol to allow any conclusions to be From calculations of the toxicity exposure ratio (TER) of made about its possible mutagenicity. More mutageni- nitrophenols from the degradation of pesticides, only a city studies are available for 4-nitrophenol, although minor risk for organisms in this compartment is to be some were inadequately reported. There is evidence to expected, even under a worst-case scenario. suggest that 4-nitrophenol can cause chromosomal aberrations in vitro. In the absence of any in vivo mutagenicity studies in mammals, it is not possible to conclude whether or not the mutagenic potential of 4- 2. IDENTITY AND PHYSICAL/CHEMICAL nitrophenol is expressed in vivo. PROPERTIES

In mice, the dermal application of 4-nitrophenol for 78 weeks gave no indication of carcinogenic effects. In 2-Nitrophenol (CAS No. 88-75-5; 2-hydroxy-1- another study with mice, which has several limitations, nitrobenzene, o-nitrophenol) and 4-nitrophenol (CAS no skin tumours were noted after dermal application of 2- No. 100-02-7; 4-hydroxy-1-nitrobenzene, p-nitrophenol) or 4-nitrophenol over 12 weeks. Carcinogenicity studies share the empirical formula C6H5NO3. Their structural using the oral or inhalation routes were not available for formulas are shown below. either of the isomers. OH OH For 4-nitrophenol, the available data gave no evidence of specific or statistically significant reproduc- NO2 tive or developmental toxicity effects after dermal or oral application to rats and mice. In an oral study with rats, 2- nitrophenol induced developmental effects in the offspring only at doses that also produced maternal toxicity. However, in these studies, the fetuses were not NO2 examined for internal malformations. 2-nitrophenol 4-nitrophenol The database for 2-nitrophenol is extremely limited, and the database for 4-nitrophenol is insufficient for Technical-grade 2- and 4-nitrophenol from the deriving reliable NO(A)EL values. Therefore, at present, German producer have a typical purity of >99%. Named no tolerable daily intakes (TDIs) or tolerable con- impurities are the corresponding isomer for each product centrations (TCs) can be derived for either 2- or 4-nitro- (0.3%) and traces of 3-nitrochlorobenzene (<0.05%). phenol. Polychlorinated dibenzo-p-dioxin/dibenzofuran (PCDD/

5 Concise International Chemical Assessment Document 20

PCDF) and tetrachlorodibenzo-p-dioxin/dibenzofuran 1994; Luettke & Levsen, 1994; Mussmann et al., 1994). (TCDD/TCDF) isomers were not detected at detection For liquid samples (water, urine, blood), high- limits between 0.1 and 0.4 :g/kg product (BUA, 1992). performance liquid chromatography in combination with concentration-gradient elution (acetonitrile/methanol or The pure nitrophenol isomers form pale yellow to ammonium acetate, acetic acid with potassium chloride/ yellow crystals at room temperature. The substances are methanol) and ultraviolet or electrochemical detection, characterized by the physicochemical properties given in which can be carried out without derivatization, is also Table 1 (Sax & Lewis, 1987). used (BUA, 1992; Nasseredine-Sebaei et al., 1993; Ruana et al., 1993; Paterson et al., 1996; Pocurull et al., 1996; Thompson et al., 1996). The separation of the different Table 1: Physicochemical properties of 2- and 4-nitrophenol. isomers is carried out either by steam distillation (BUA, 1992) or by the formation and subsequent extraction of Parameter 2-Nitrophenol 4-Nitrophenol different ion pairs (León-González et al., 1992). Molecular mass 139.11 139.11 (g/mol) The following enrichment techniques are used Melting point (°C) 44–45 (1)(2)(3) 113–114 (1)(2)(3) (BUA, 1992; see also review by Puig & Barcelo, 1996): Boiling point (°C) 214–217 (1) 279 (decomposition)(3) # solid-phase adsorption with thermal or liquid extraction for air and water samples (Luettke & Vapour pressure 6.8 × 10–3 3.2 × 10–6 (kPa) (19.8 °C) (4) (20 °C) (5) Levsen, 1994; Mussmann et al., 1994)

Water solubility 1.26 12.4 # liquid/liquid extraction after derivatization for water (g/litre) (20 °C) (4) (20 °C) (6) samples (initial purification by acid/base n-Octanol/water 1.77–1.89 (7) 1.85–2.04 (7) fractionation of highly polluted samples, increased partition coefficient recovery rates with continuous extraction (log Kow) methods) (León-González et al., 1992; Nick & Dissociation constant 7.23 7.08 Schoeler, 1992; Geissler & Schoeler, 1994; Harrison (pKa) (21.5 °C) (8) (21.5 °C) (8) et al., 1994) Ultraviolet spectrum 8max (water): 8max (methanol): 230; 276 nm; no absorption # liquid extraction with acid/base fractionation or log ,max: 3.57; maxima #290 nm(9) 3.80 (9) solid-phase enrichment and subsequent desorption following aqueous extraction for soil Conversion factors 1 mg/m3 = 0.173 ppmv 1 ppmv = 5.78 mg/m3 samples (Vozñáková et al., 1996)

References: (1) Budavari et al. (1996); (2) Booth (1991); # acid hydrolysis of the glucuronide with (3) Verschueren (1983); (4) Koerdel et al. (1981); subsequent derivatization for blood and urine (5) Sewekow (1983); (6) Andrae et al. (1981); (7) BUA (1992); samples or denaturation (Nasseredine-Sebaei et al., (8) Schwarzenbach et al. (1988); (9) Weast (1979) 1993; Thompson et al., 1996).

Additional physicochemical properties for The detection limits are <10 ng/m3 for air, 0.03– mononitrophenols are presented in the International 10 :g/litre for water, and 200–1600 :g/kg for soil. A Chemical Safety Card (ICSC 1342) reproduced in this detection limit for the determination of the nitrophenol document. isomers in biological materials was given only for rat liver perfusate (0.5–1 mg/litre; Thompson et al., 1996).

3. ANALYTICAL METHODS 4. SOURCES OF HUMAN AND

The nitrophenol isomers are usually determined by gas chromatography combined with mass spectrometric detection, flame ionization detection, electron capture There are no known natural sources of the nitro- detection, or nitrogen-sensitive detection, which are phenol isomers. generally applied after derivatization (BUA, 1992; Nick & Schoeler, 1992; Geissler & Schoeler, 1994; Harrison et al.,

6 Mononitrophenols

Within the European Union, 2- and 4-nitrophenol and to about 2% at normal motor load (Tremp et al., are produced mainly by three companies. Six other large 1993). A rough estimation combining the above- manufacturers are known in the USA and Japan (as of mentioned exhaust gas concentrations with estimations 1989). In 1983, the production volume for Western of the total exhaust gas volumes from vehicle traffic for Europe was estimated at about 6400 t 2-nitrophenol and Germany resulted in an airborne nitrophenol load of at about 20 500 t 4-nitrophenol. In 1988–89, the German least several tonnes per year from this source (BUA, production volumes originating from one manufacturer 1992). Data concerning nitrophenol releases from other were approximately 500 t 2-nitrophenol and about 2000 t combustion processes (heating, burning of refuse) were 4-nitrophenol, with about 20 t of each being exported. not identified. Both 2- and 4-nitrophenol are intermediates in the synthesis of azo dyes and a number of pesticides, mainly From laboratory experiments, there is some insecticides (2-nitrophenol: carbofuran, phosalon; 4- evidence that 2- and 4-nitrophenol are generated in the nitrophenol: parathion, parathion-methyl, fluorodifen) atmosphere during the photochemical degradation of and, to a lesser extent, herbicides (4-nitrophenol: aromatic compounds such as benzene and toluene in the nitrofen, bifenox). The corresponding aminophenols that presence of nitric oxide or hydroxyl radicals and nitrous are gained by reduction are used as a photographic dioxide. These results were at least partly obtained in developer (2-aminophenol) and as an intermediate in the model experiments with unrealistically high nitric oxide synthesis of the tuberculostatic 4-aminosalicylic acid concentrations, and there are competing reactions with- and the analgesic 4-acetaminophenol (paracetamol) (4- out nitrophenol formation for which the rate constant is aminophenol) (see also Booth, 1991). In the 1980s, the not known (BUA, 1992). However, smog chamber production volumes for 2- and 4-nitrophenol showed a experiments confirmed the formation of nitrophenol decreasing tendency in Germany as a result of changes isomers during irradiation (Leone & Seinfeld, 1985; in and termination of the production of some organo- Leone et al., 1985). Recent cloud water model experi- phosphorus pesticides. ments showed that 2- and 4-nitrophenol are also formed from the reaction of phenol with nitrogen pentoxide or The releases of 2- and 4-nitrophenol during pro- monochloronitrogen dioxide, especially under alkaline duction and processing at the only German manufacturer conditions (Scheer et al., 1996). Estimations of the appear to be of minor importance. In 1988–89, about contribution of photochemically formed nitrophenols to 2.5 kg 2-nitrophenol and 10 kg 4-nitrophenol were total emissions into the atmosphere are not possible with emitted to air, and #93 kg 2-nitrophenol and <64 kg 4- the available data. nitrophenol were emitted to surface water. Significant releases of 4-nitrophenol into the For 1996, the following releases of 2- and 4-nitro- hydrosphere may occur from the hydrolytic degradation phenol to the environment were reported by manufac- of the insecticides parathion and parathion-methyl and turers in the USA (TRI, 1998): — although to a lesser extent — from the photolytic degradation of the herbicides nitrofen and bifenox. # 2-nitrophenol: from three manufacturers (one Quantification of releases is not possible with the avail- production site each) with production volumes able data. Furthermore, a considerable portion of air- between 450 and 45 000 kg/year, total releases of 15 borne nitrophenols, especially 4-nitrophenol, can be kg to air and 23 kg into water were reported. released to the hydrosphere and the geosphere by wet and dry deposition (see section 5) (Herterich & Herr- # 4-nitrophenol: from three manufacturers (six mann, 1990; Luettke et al., 1997). Numerous studies production sites) with production volumes of concerning the concentrations of 2- and 4-nitrophenol in 45–450 kg/year up to 45 000–450 000 kg/year, a wet deposition samples are available (see section 6.1). total release of 420 kg to air was reported. Data on From precipitation data (average 746 mm rain per year for releases into water were not given. land masses, according to Baumgartner & Liebscher, 1990) and the measured concentrations of 2- and 4- 2-Nitrophenol and 4-nitrophenol have been nitrophenol in rainwater, the release of nitrophenols via detected in the exhaust gases of light-duty gasoline and rain can be estimated to be at least in the order of several diesel vehicles. Depending on the motor load, the thousand tonnes per year on a global basis. exhaust concentrations of the isomers were <50 :g/m3 exhaust gas (idle) and about 1000 :g 4-nitrophenol/m3 The application of the herbicides nitrofen and and 2000 :g 2-nitrophenol/m3 (driving at constant bifenox, which are photolytically degraded to 4-nitro- velocity) (Nojima et al., 1983; Tremp et al., 1993). A phenol in aqueous solutions, may especially lead to regulated three-way catalytic converter reduced the emissions into the geosphere and the biosphere. Further, nitrophenol emissions to about 8% at high motor load nitrophenol-contaminated rain, snow, and other wet and

7 Concise International Chemical Assessment Document 20

dry deposition may contribute to nitrophenol levels in From experimental results on direct photodegrada- soils. Data concerning the release of nitrophenols into tion (Koerdel et al., 1981) and the atmospheric photo- the biosphere are not available. oxidation by hydroxyl radicals (Zetzsch et al., 1984), both pathways were found to be of minor importance for the removal of 2-nitrophenol emitted to the troposphere. Thus, the major degradation pathway for airborne 2- 5. ENVIRONMENTAL TRANSPORT, nitrophenol should be rapid nitration to 2,4-dinitrophe- DISTRIBUTION, AND TRANSFORMATION nol (Herterich & Herrmann, 1990; Luettke et al., 1997). The major portion of airborne 4-nitrophenol is expected to be particle bound and therefore only to a minor extent Environmental releases of nitrophenols are mostly available for photochemical reactions. Thus, most of the to ambient air, surface waters, and — to a smaller extent 4-nitrophenol can be washed out from air by wet and dry — soil. Using a non-steady-state equilibrium model, the deposition. Measured half-lives for the photochemical following distribution of 4-nitrophenol in different envi- decomposition of 4-nitrophenol in water exposed to ronmental compartments was predicted: air, 0.0006%; sunlight ranged from 2.8 to 13.7 days (Hustert et al., water, 94.6%; sediment, 4.44%; soil, 0.95%; biota, 1981; Mansour, 1996), being longer with increasing pH 0.000 09% (Yoshida et al., 1983). The distribution pat- (Hustert et al., 1981). Traces of 4-aminophenol were terns of 2- and 4-nitrophenol sprayed on a natural soil in found as a photoproduct in river water (Mansour, 1996). a standardized terrestrial ecosystem were determined via In experiments conducted according to OECD guide- radiotracer technique (14C). Of the applied radioactivity lines, Andrae et al. (1981) and Koerdel et al. (1981) found (2-nitrophenol/4-nitrophenol), 49.45%/20.01% was no hydrolysis of 2- or 4-nitrophenol under environmental recovered in air, 27.38%/40.21% in soil (including conditions. animals), 12.73%/7.57% in plants, and 0.05%/0.02% in leachate (Figge et al., 1985). Distribution of 4-nitrophenol Numerous studies on the biodegradation of 2- and in a terrestrial microcosm chamber with artificial soil 4-nitrophenol have been conducted. Standardized tests largely corresponded to this result (Gile & Gillett, 1981). on ready or inherent biodegradability provide data of Owing to the expected decomposition within the incuba- large variability, indicating 2- and 4-nitrophenol to be tion periods of 30 and 28 days, respectively, it can be inherently biodegradable under aerobic conditions assumed that most of the recovered radioactivity referred (depending on origin and density of inoculum and the to breakdown products of the applied nitrophenols. applied test method) (see Table 2). Results from different tests point to a possible bacteriotoxic effect of 4- In volatility experiments conducted according to nitrophenol at concentrations above 300 mg/litre (Gerike Organisation for Economic Co-operation and Develop- & Fischer, 1979; Nyholm et al., 1984; Kayser et al., 1994). ment (OECD) guidelines, half-lives of 2-nitrophenol in water ranged from 14.5 to 27.3 days, indicating a slow Non-standardized experiments with different rate of volatilization (Koerdel et al., 1981; Rippen et al., inocula (e.g., natural water, soil, sediment) showed that 1984; Scheunert, 1984; Schoene & Steinhanses, 1984). microbial decomposition of nitrophenols can occur in Measurements concerning the partitioning between the different environmental compartments after adaptation of gas and liquid phases of clouds during different rain the microflora (Rubin et al., 1982; Subba-Rao et al., 1982; events showed that 2-nitrophenol is enriched in the Van Veld & Spain, 1983; Spain et al., 1984; Ou, 1985; liquid phase to a larger extent than would be predicted Hoover et al., 1986; Aelion et al., 1987; Wiggins et al., from its water solubility and vapour pressure. On the 1987). Time for acclimation and degree of removal other hand, 4-nitrophenol is extensively adsorbed to depended mostly on substance concentration, microbial particles. Therefore, elevated levels of this isomer are population, climate, and additional substrates. detected in the gaseous phase of clouds (Luettke et al., 1997). From the available data, a significant volatilization Biotic degradation of nitrophenols under anaerobic of 4-nitrophenol from water to air is not expected. Since conditions requires extended acclimatization of microbial nitrophenols dissociate in aqueous solution, volatiliza- communities. In tests with sewage sludge and sludge tion may further decrease with increasing pH in surface from the primary anaerobic stage of a municipal sewage waters. This leads to the conclusion that dry and wet treatment plant, respectively, initial 2- and 4-nitrophenol deposition of nitrophenols from air to surface waters and concentrations in the range of 96.5–579 mg/litre were not soil are to be expected. The occurrence of this partition degraded at all within 7–60 days (Wagner & Braeutigam, mechanism is supported by the detection of 2- and 4- 1981; Battersby & Wilson, 1989). Boyd et al. (1983) nitrophenol in rainwater and wet deposition samples (see found complete anaerobic removal of 50 mg/litre for all section 6.1). nitrophenol isomers within 1 week, but complete

8 Mononitrophenols

Table 2: Biotic degradation of nitrophenols under aerobic conditions.

Concentration Additional Test duration Removal Test Substance (mg/litre) carbon source (days) (%) Reference Tests on ready biodegradability AFNOR test 2-NP 40 OC no 14 16 Gerike & Fischer (1979)

Sturm test 2-NP 10 no 28 32 Gerike & Fischer (1979) MITI I 2-NP 100 no 14 0 Urano & Kato (1986) 50 no 14 7 Gerike & Fischer (1979)

Closed bottle test 4-NP 2 no 28 55 Rott et al. (1982)

Modified OECD 4-NP 20 DOC no 28 1 Rott et al. (1982) screening test

Shake flask test 4-NP 20 OC no 21 50 Means & Anderson (1981) AFNOR test 4-NP 40 OC no 14 97 Gerike & Fischer (1979)

Sturm test 4-NP 10 no 28 90 Gerike & Fischer (1979)

MITI I 4-NP 50 no 14 1 Gerike & Fischer (1979) 100 no 14 0 Urano & Kato (1986) 100 no 14 4.3 CITI (1992)

Tests on inherent biodegradability Zahn-Wellens test 2-NP 400 no 14 80 Gerike & Fischer (1979)

SCAS test 2-NP 20 TOC yes 24 107 Broecker et al. (1984) 13.3 TOC yes 24 110

Bunch & Chambers 2-NP 5–10 yes 28 100 Tabak et al. (1981) Coupled units test 2-NP 12 OC yes 7 61 Gerike & Fischer (1979)

Batch test, aerated 2-NP 200 COD no 5 97 Pitter (1976)

Zahn-Wellens test 4-NP 300 no 14 8 Andrae et al. (1981) 100 DOC no 28 100 Pagga et al. (1982)

Activated sludge test 4-NP 50 no 19 100 Means & Anderson 100 no 19 90 (1981) SCAS test 4-NP 20 TOC yes 33 >90 Marquart et al. (1984) 27 >97 Scheubel (1984) 25/39 100 Ballhorn et al. (1984) 12–15 100 Koerdel et al. (1984)

Coupled units test 4-NP 12 OC yes 7 100 Gerike & Fischer (1979)

Batch test, aerated 4-NP 200 COD no 5 95 Pitter (1976)

Abbreviations used: 2-NP = 2-nitrophenol; 4-NP = 4-nitrophenol; OC = organic carbon; DOC = dissolved organic carbon; TOC = total organic carbon; COD = chemical oxygen demand.

mineralization was demonstrated only if the incubation and from 56 to 530 (4-nitrophenol) (Boyd, 1982; Broecker period was extended to 10 weeks. Anaerobic degradation et al., 1984; Koerdel et al., 1984; Løkke, 1984; Marquart et even of high initial nitrophenol concentrations was al., 1984). Nitrophenols emitted to soil are expected to be found by Tseng & Lin (1994), who observed >90% biodecomposed under aerobic conditions. Infiltration removal of 2- and 4-nitrophenol (350–650 mg/litre) in a into groundwater is expected only under conditions biological fluidized bed reactor with three different kinds unfavourable for biodegradation (e.g., anaerobic of wastewater. From the available results, a slow conditions). From the available experimental results, degradation of nitrophenols under anaerobic conditions nitrophenols have to be classified as substances with a by adapted microorganisms can be expected. low to moderate potential for soil sorption.

Soil sorption coefficients (Koc) were found to A low potential for bioaccumulation is to be increase with increasing organic carbon content. Mea- expected from the available valid test results for 2- and 4- sured Koc values ranged from 44 to 230 (2-nitrophenol) nitrophenol. Bioconcentration factors ranging from 14.6

9 Concise International Chemical Assessment Document 20 to 24.4 were determined for 2-nitrophenol in a semistatic these concentration ranges (Herterich & Herrmann, 1990; test system with zebra fish (Brachydanio rerio) (Koerdel Levsen et al., 1990; Richartz et al., 1990; Capel et al., 1991; et al., 1984); in a flow-through experiment, Geissler & Schoeler, 1993; Levsen et al., 1993; Luettke et bioconcentration factors ranged from 30 to 76 for al., 1997). The 2-nitrophenol levels are mostly below or common carp (Cyprinus carpio), including possible slightly above the detection limit (i.e., <0.1 :g/litre), conjugates (Broecker et al., 1984). In static tests, whereas mean 4-nitrophenol concentrations of about 5 accumulation factors for 4-nitrophenol of 11 for the :g/litre rainwater and cloud water and 20 :g/litre fog green alga Chlorella fusca after 1 day (Geyer et al., 1981) water were detected. The nitrophenol concentrations in and 57 for the freshwater golden orfe (Leuciscus idus fog are significantly higher than those in rainwater or melanotus) after 3 days of exposure were determined cloud water owing to the higher droplet surface and (Freitag et al., 1982). Zebra fish exposed in tap and river longer residence times of the droplets in air compared water nearly completely eliminated the accumulated 14C- with rain. The lower concentrations of 2-nitrophenol in 4-nitrophenol within 48 h (Ensenbach & Nagel, 1991). the deposition samples compared with 4-nitrophenol are Star fish (Pisaster ochraceus) and sea urchin presumably due to the lower photochemical stability of (Strongylocentrotus purpuratus) eliminated 89% and this compound (see section 5). 36%, respectively, of injected 14C-4-nitrophenol (3.48 and 3.70 mg/kg body weight, respectively) within 8 h In the 1970s and early 1980s, the 2- and 4-nitro- (Landrum & Crosby, 1981). phenol concentrations in the German and Dutch parts of the river Rhine and some of its tributaries were between 0.1 and 1 :g/litre (BUA, 1992). 2-Nitrophenol and 4- nitrophenol were not detected in 177 samples of Japa- 6. ENVIRONMENTAL LEVELS AND nese surface waters (detection limits 0.04–10 :g/litre) or HUMAN EXPOSURE in 177 sediment samples (detection limits between 0.002 and 0.8 :g/kg) in 1978, 1979, and 1994 (Japan Environ- ment Agency, 1979, 1980, 1995). Whereas 4-nitrophenol 6.1 Environmental levels was not detected in 129 fish samples (detection limits 0.005–0.2 :g/kg) in Japan in 1979 and 1994, 2-nitro- From the concentrations in rainwater, the total phenol was detected in 1 out of 129 saltwater fish atmospheric nitrophenol pollution in Switzerland is samples (detection limits 0.005–0.3 :g/kg) in 1994 (Japan estimated at about 1 :g/m3 (Leuenberger et al., 1988). Environment Agency, 1980, 1995). 2-Nitrophenol Recent measurements in the air of remote areas in Europe concentrations between <0.15 :g/litre (detection limit) (German Alps, Fichtelgebirge, Germany; Mount Brocken, and 7.2 :g/litre and 4-nitrophenol levels between <0.1 Germany; Great Dun Fell summit, United Kingdom) gave and 18.8 :g/litre were reported for the densely populated 2-nitrophenol concentrations between 0.8 and 25 ng/m3 and highly industrialized Malaysian Klang river basin in and 4-nitrophenol levels between 1.2 and 360 ng/m3 1990 and 1991 (Tan & Chong, 1993). (Herterich & Herrmann, 1990; Luettke et al., 1997). The higher atmospheric 4-nitrophenol levels are apparently 6.2 Human exposure due to the higher photochemical stability of this isomer (see section 5). 2-Nitrophenol was found in 22 out of 27 Workers may be exposed to 2- and 4-nitrophenol samples of air (range 1–140 ng/m3; detection limit 1 via inhalation and skin contact during production and ng/m3) in Japan in 1994, and 4-nitrophenol was detected processing (mainly in the manufacturing of pesticides). in 27 out of 27 air samples (range 1–71 ng/m3; detection However, data on nitrophenol concentrations at the limit 1 ng/m3) (Japan Environment Agency, 1995). In workplace were not identified. street dust samples from a Japanese city, up to 3.9 mg 2- nitrophenol/kg and up to 42 mg 4-nitrophenol/kg were Based on the measured concentrations given in detected (Nojima et al., 1983). section 6.1, an exposure of the general population to nitrophenols via the environment — predominantly Numerous studies deal with the distribution, depo- through ambient air and drinking-water — cannot be sition, and degradation behaviour of airborne 2- and 4- excluded. nitrophenol in clouds and rainwater. 2-Nitrophenol levels in rainwater and snow between 0.03 and 5.7 :g/litre and 4-Nitrophenol accumulates in fog, whereas 2- 4-nitrophenol concentrations from <0.5 to 19 :g/litre are nitrophenol is rapidly photochemically transformed (see given in reports mainly from Germany and the USA sections 5 and 6.1). The mean measured level of 4- (BUA, 1992). The recent measurements in rainwater, nitrophenol in fog water is about 20 :g/litre. cloud water, and “fog” (water vapour; not further char- acterized) from rural and urban areas in Europe confirm

10 Mononitrophenols

In Dutch drinking-water samples, maximum con- nitrophenyl glucoside was identified as a minor centrations of 1 :g 2-nitrophenol/litre and <0.1 :g metabolite of 4-nitrophenol (about 1–2% of the 4-nitrophenol/litre were reported in 1988 (BUA, 1992). administered dose) (Gessner & Hamada, 1970). Further data are not available. For 4-nitrophenol, the pretreatment of laboratory animals with ethanol (induction of cytochrome P-450) resulted in a marked increase in hepatic microsomal 7. COMPARATIVE KINETICS AND hydroxylation. The 4-nitrocatechol then formed com- METABOLISM IN LABORATORY ANIMALS peted with 4-nitrophenol for the glucuronidation and AND HUMANS sulfation pathways (Reinke & Moyer, 1985; Koop, 1986; McCoy & Koop, 1988; Koop & Laethem, 1992).

Studies providing quantitative information on the Specific investigations on dermal resorption under absorption, metabolism, or elimination of 2- or 4-nitro- non-occlusive conditions showed dermal uptake of 14 phenol in humans were not identified. about 35% and 11% of the applied dose of C-4-nitro- phenol within 7 days in rabbits and dogs, respectively. 7.1 2-Nitrophenol Skin permeation for 4-nitrophenol was also shown in several in vitro experiments (Huq et al., 1986; Jetzer et al., There is only very limited information available for 1986; Ohkura et al., 1990). 2-nitrophenol. In rabbits given a single dose of 200–330 mg/kg body weight via gavage, most of the Owing to its rapid metabolism and excretion, applied dose (o80%) was excreted via the urine within 24 bioaccumulation of 4-nitrophenol in organisms is not to h. About 71% was conjugated with glucuronic acid and be expected. about 11% with sulfate, whereas about 3% was reduced to aminophenols (Robinson et al., 1951).

Skin permeation for 2-nitrophenol was shown in 8. EFFECTS ON LABORATORY several in vitro experiments (Huq et al., 1986; Jetzer et al., MAMMALS AND IN VITRO TEST SYSTEMS 1986; Ohkura et al., 1990).

Although the information is limited, bioaccumula- 8.1 Single exposure tion of 2-nitrophenol in organisms is not to be expected owing to its rapid metabolism and excretion. For 2-nitrophenol, the oral LD50 is in the range of 2830–5376 mg/kg body weight in rats (BASF AG, 1970; 7.2 4-Nitrophenol Vasilenko et al., 1976; Vernot et al., 1977; Koerdel et al., 1981) and 1300–2080 mg/kg body weight in mice After oral, dermal, intravenous, or intraperitoneal (Vasilenko et al., 1976; Vernot et al., 1977). Clinical signs application of 4-nitrophenol to several test species (rats, following oral exposure were unspecific and included mice, dogs, or rabbits), most of the applied dose (up to dyspnoea, staggering, trembling, somnolence, apathy, 95%) was excreted as glucuronide and sulfate conjugates and cramps. The macroscopic examination performed in of 4-nitrophenol via the urine within 24–48 h. Only small some studies revealed congestion in liver and kidneys amounts were excreted via faeces (about 1%) or as and ulcers of the stomach in high-dose rats. The unchanged 4-nitrophenol (about 2–7%). The inhalation exposure of rats to an atmosphere saturated percentages of glucuronide and sulfate conjugates were with the test substance at 20 °C for 8 h (no further shown to be species, sex, and dose dependent. information available) resulted in no mortality and no Although sulfate conjugation dominates at lower 4- signs of toxicity (BASF AG, 1970). In a limit test, the nitrophenol concentrations, the percentage of dermal LD50 for the rat was >5000 mg/kg body weight glucuronide conjugates increases at higher dosages (Koerdel et al., 1981). In cats (two animals per dose (Robinson et al., 1951; Gessner & Hamada, 1970; group), the oral application of 2-nitrophenol (50, 100, or Machida et al., 1982; Rush et al., 1983; Snodgrass, 1983; 250 mg/kg body weight; no controls) resulted in a dose- Tremaine et al., 1984; Meerman et al., 1987). As shown in dependent increase in methaemoglobin (6, 44, and 57%, rabbits after oral dosing, 4-nitrophenol undergoes respectively).1 One animal dosed with 250 mg/kg body reduction to 4-aminophenol as well as glucuronidation and sulfation. Up to 14% of the administered dose was detected as amino compounds in the urine (Robinson et 1 Methaemoglobin formation is discussed in greater al., 1951). After intraperitoneal administration in mice, 4- detail in section 8.8.

11 Concise International Chemical Assessment Document 20 weight died. No formation of methaemoglobin was given; Hoechst AG, 1977c). Results with the non- detected after dermal application of a 50% solution of 2- dissolved substance were either strongly irritating in a nitrophenol in water to rabbits (dose not specified, test conducted according to FDA guidelines (scores not exposure time 1 min to 20 h on the back or 20 h on the given; Hoechst AG, 1977c) or slightly irritating in a test ear) (BASF AG, 1970). comparable to OECD Guideline 405 (score 1–2 of 4; Andrae et al., 1981).

The oral LD50 of 4-nitrophenol is in the range of 220–620 mg/kg body weight in rats (BASF AG, 1969; In a guinea-pig maximization test comparable to Vasilenko et al., 1976; Hoechst AG, 1977a; Vernot et al., OECD Guideline 406, skin sensitization was shown in 5 1977; Andrae et al., 1981) and 380–470 mg/kg body of 20 animals (Andrae et al., 1981). weight in mice (Vasilenko et al., 1976; Vernot et al., 1977). Clinical signs following oral exposure of rats were Data on respiratory tract sensitization for 2- and 4- unspecific and included tachypnoea and cramps, and the nitrophenol were not identified in the literature. macroscopic examination performed in some studies revealed a greyish discoloration with dark red patches of 8.3 Short-term exposure the lungs. No mortality was observed in rats after single exposure (head only) to 4700 mg/m3 (application as dust 8.3.1 Oral exposure [sodium salt]; particle size not given) for 4 h. In four of six rats, a corneal opacity was observed at the end of The effect of 2-nitrophenol in rats was studied in a exposure, which persisted through the 14-day 28-day study to evaluate OECD Guideline 407 (five observation period. In two extra rats exposed to animals per sex per dose group; daily oral doses of 0, 22, 1510 mg/m3, the methaemoglobin concentrations were 67, or 200 mg/kg body weight via gavage). Food intake not altered compared with controls. A determination of decreased in high-dose males and in mid- and high-dose methaemoglobin concentrations after exposure to females, and final body weight decreased non-signifi- 4700 mg/m3 was not performed (Smith et al., 1988). In cantly in all dosed animals. The absolute liver and kid- another inhalation study with rats (exposure to an ney weights were decreased in mid-dose animals, and atmosphere saturated with the test substance at 20 °C for the relative testes weight increased in low- and mid-dose 8 h; no further information available), no mortality and males and decreased in high-dose males. In all dosed no signs of toxicity were seen (BASF AG, 1969). The animals, the relative and absolute weights of the adrenal dermal LD50 for rats and guinea-pigs is $1000 mg/kg glands increased. The haematological examination, body weight (Hoechst AG, 1977b; Eastman Kodak Co., clinical chemistry, and histopathological examination of 1980; Andrae et al., 1981). In contrast to 2-nitrophenol, the major organs and tissues did not give any indication no formation of methaemoglobin was noted in cats (two of a substance-related toxic effect in comparison with animals per dose group) after oral dosing with 100, 200, controls (Koerdel et al., 1981). Owing to insufficient or 500 mg 4-nitrophenol/kg body weight. The mortality documentation and the fact that there were minor effects rate was 0/2, 1/2, and 2/2, respectively (BASF AG, 1969). (weight of adrenal glands) shown by all exposed animals, a reliable NO(A)EL cannot be deduced. 8.2 Irritation and sensitization In a 28-day study that was also conducted to eval- From studies comparable to OECD Guidelines 404 uate OECD Guideline 407, Sprague-Dawley rats (10 per and 405, it can be concluded that 2-nitrophenol is sex per dose group) received daily oral doses of 0, 70, slightly irritating to the skin but not to the eye (scores 210, or 630 mg 4-nitrophenol/kg body weight via gavage. not given). In a Buehler test with guinea-pigs compa- After dosing, locomotor inhibition, which lasted for rable to OECD Guideline 406, the substance showed no about 2 h, was seen in mid- and high-dose animals. In skin-sensitizing effects (Koerdel et al., 1981). mid-dose animals, 1/10 males died; in high-dose males and females, the mortality rate was 4/10 and 6/10, respec- In a study performed according to US Food and tively (specific signs of intoxication were not given). In Drug Administration (FDA) guidelines, non-dissolved 4- the lowest dose group, the macroscopic examination nitrophenol was slightly irritating to the skin (score 2 of revealed seven cases of pale liver, and the histo- 8) (Hoechst AG, 1977c); in another study comparable to pathological examination showed 14 cases of finely OECD Guideline 404, however, the non-dissolved dispersed fatty degeneration. A focal fatty degeneration substance showed no skin-irritating effects (score 0 of 4) of the liver was also observed in 13/20 rats of the mid- (Andrae et al., 1981). 4-Nitrophenol applied as a 10% dose group, but not in high-dose animals. However, it solution to the eyes was slightly irritating in a test must be noted that finely dispersed fatty degeneration conducted according to FDA guidelines (scores not was also seen in 6/20 control animals. In 4/10 high-dose

12 Mononitrophenols males but not females, a hydropic liver cell swelling was absolute spleen weight was significantly lower than that noted, and all high-dose rats that died before the end of of controls after 10 exposures, and the absolute/relative the study showed vascular congestion of the liver. A spleen and lung weights were significantly lower in slight increase in the leukocyte count was seen at 210 comparison with controls at the end of the recovery and 630 mg/kg body weight in males and females; the period. According to the authors, the biological signifi- increase was significant in high-dose females. In high- cance of the changes in organ weights is unknown dose males, the alanine aminotransferase (ALAT) owing to the absence of corroborating pathological activity was significantly increased. Other substance- effects (Smith et al., 1988). related effects in high-dose animals included increased nephrosis (two males and five females), testicular In a second trial (exposure to 0, 30, or 130 mg/m3; atrophy and inhibition of spermatogenesis (one and two MMAD 4.0–4.8 :m), both exposure concentrations males, respectively), and follicular atresia in the ovaries again resulted in signs of irritation (not further speci- (four females) (Andrae et al., 1981). Because of unclear fied). Methaemoglobinaemia, an effect that was rever- effects in the liver, a NO(A)EL cannot be deduced. sible within a 14-day recovery period, was seen only at 130 mg/m3. The methaemoglobin values were 0.5, 0.3, and 8.3.2 Inhalation exposure 1.5% after 10 exposures and 0.4, 0.5, and 0.2% after 14 days’ recovery. The gross and histopathological 8.3.2.1 2-Nitrophenol examination revealed no adverse effects in any dose group. From these results, the authors of the study In Sprague-Dawley rats (15 per sex per group), no decided upon a NO(A)EL of 30 mg/m3 (Smith et al., 1988). mortality was observed after exposure to 0, 5, 30, or 60 mg 2-nitrophenol vapour/m3 (“whole body” exposure; Groups of Sprague-Dawley rats (15 per sex) were to generate the vapour, melted 2-nitrophenol was used) exposed to 0, 1, 5, or 30 mg 4-nitrophenol dust/m3 for 6 h/day, 5 days/week, over a period of 4 weeks. (“whole body” exposure; MMAD 5.2–6.7 :m) for Except for squamous metaplasia of the epithelium lining 6 h/day, 5 days/week, over a period of 4 weeks. The the maxilloturbinates and nasoturbinates in all high-dose exposure resulted in no deaths, and no exposure-related animals, the clinical and histopathological examinations effects were noted in terms of haematology or clinical gave no consistent exposure-related effects. The met- chemistry values, gross examination, histopathology, haemoglobin values determined after the 11th exposure and body or organ weights. In high-dose animals, were significantly increased only in low-dose animals unilateral and bilateral diffuse anterior capsular cataracts (males: 1.0, 2.3, 1.8, and 1.6%; females: 2.0, 4.1, 2.1, and were observed. The methaemoglobin values determined 1.1%), but were within control values at the end of the after 2 weeks of exposure showed great variability and study (Hazleton Lab., 1984). appeared to be unusually high (>3 %) in some unex- posed controls. However, the group total methaemo- 8.3.2.2 4-Nitrophenol globin value was increased at a concentration of 5 mg/m3, which was significant in males and not R No mortality was observed in male albino Crl:CD significant in females (males: 0.8, 0.5, 2.2, and 1.1%; rats (10 per group) after exposure to 0, 340, or 2470 mg 4- females: 1.3, 1.1, 2.0, and 1.0%) (Hazleton Lab., 1983). 3 nitrophenol dust/m (application as sodium salt; “head Therefore, a NO(A)EL of 5 mg/m3 can be derived for local only” exposure; mass median aerodynamic diameter effects (cataracts), whereas the NO(A)EL for systemic [MMAD] 4.6–7.5 :m) for 6 h/day, 5 days/week, over a effects (formation of methaemoglobin) may be lower. period of 2 weeks. Both exposure concentrations resulted in signs of irritation (not further specified). After 8.3.3 Dermal exposure exposure to 340 and 2470 mg/m3, darker urine, proteinuria, elevated aspartate aminotransferase (ASAT) Data concerning short-term dermal exposure were values, and a dose-dependent increase in methaemo- not identified in the literature. globin values were observed. These effects were still evident after a 14-day recovery period; however, the 8.4 Long-term exposure methaemoglobin value was then still elevated in only 2/5 high-dose animals. The methaemoglobin values were 0.2, In the literature, subchronic and chronic studies 0.87, and 1.53% after 10 exposures and 0.2, 0.13, and are available only for 4-nitrophenol. 0.7% after 14 days’ recovery. The erythrocyte, haemoglobin, and haematocrit values decreased during 8.4.1 Subchronic exposure exposure but were elevated after the 14-day recovery period. In treated rats, the urine volume decreased in a In a 13-week gavage study with Sprague-Dawley dose-dependent manner during exposure and during the rats (20 per sex per dose group) given 0, 25, 70, or 140 mg 14-day recovery period. In high-dose animals, the 4-nitrophenol/kg body weight in water 5 days/week,

13 Concise International Chemical Assessment Document 20 premature deaths were seen in animals dosed with 8.5 Genotoxicity and related end-points 70 and 140 mg/kg body weight (1 male/1 female at 70 mg/kg body weight and 15 males/6 females at The available in vitro and in vivo genotoxicity 140 mg/kg body weight); these were usually preceded by studies on 2- and 4-nitrophenol are summarized in clinical signs, including pale appearance, languid behav- Table 3. iour, prostration, wheezing, and dyspnoea, shortly after dosing. The histopathological examination of these 2-Nitrophenol showed no mutagenicity in several animals revealed minimal to moderately severe conges- limited bacterial assays. From the available data, it is not tion in the lung, liver, kidney, adrenal cortex, and pitui- possible to draw any conclusions regarding its mutagen- tary; in surviving animals, no treatment-related changes icity. compared with controls were reported. A statement concerning altered methaemoglobin values cannot be For 4-nitrophenol, positive results were obtained in given owing to a non-reliable analytical method (about in vitro tests for chromosomal aberrations in mammalian 13% in controls at week 7) (Hazleton Lab., 1989). cells. However, apart from one well-documented study Therefore, only a provisional NO(A)EL (changes in liver, published by NTP (1993), the other available assays kidneys, and lungs) of 25 mg/kg body weight can be were inadequately reported. 4-Nitrophenol was shown to derived from this study. The NO(A)EL based on the be mutagenic in some but not all of the bacterial assays, formation of methaemoglobin may be lower. whereas other studies (i.e., host-mediated bacterial assay, mouse lymphoma assay, unscheduled DNA The dermal application of 4-nitrophenol to Swiss- synthesis assay [apparently in vitro], sister chromatid Webster mice (10 per sex and dose group; given 0, 22, exchange assay, sex-linked recessive lethal [SLRL] assay 44, 88, 175, or 350 mg/kg body weight in acetone, 3 times in Drosophila) gave negative results. In the absence of per week over 13 weeks) resulted in dose-dependent any in vivo mutagenicity studies in mammals, it is not mortality as well as skin irritation/inflammation and possible to conclude whether or not the mutagenic necrosis at $175 mg/kg body weight.1 potential of 4-nitrophenol is expressed in vivo.

8.4.2 Chronic exposure and carcinogenicity 8.6 Reproductive and developmental toxicity In a long-term study with Swiss-Webster mice (50 per sex per dose group), 4-nitrophenol in acetone was 8.6.1 Reproductive toxicity applied to the interscapular skin at doses of 0, 40, 80, or 160 mg/kg body weight, 3 days/week for 78 weeks. At In a valid two-generation study with groups of termination of the study, the survival rates were 29/60, 24 female and 12 male Sprague-Dawley rats carried out 17/60, 26/60, and 24/60 for males and 35/60, 26/60, 33/60, by Angerhofer (1985), 4-nitrophenol dissolved in ethanol and 27/60 for females. The increased mortality after 60 was applied dermally at doses of 0, 50, 100, or 250 mg/kg weeks was due to a generalized amyloidosis (the severity body weight per day, 5 days/week. The F0 generation of the amyloidosis was similar among dosed and control was exposed over a period of 140 days before mating. animals) and secondary kidney failure. The final mean Dosing of the F0 females continued throughout body weights of the dosed animals were similar to those breeding, gestation, and lactation. Groups of 26 females of the controls. NTP (1993) stated that there were no and 13 males of the F1 generation were then exposed for substance-related neoplastic or non-neoplastic effects 168 days in the same manner as had been the F0 rats; the associated with the dermal administration of 4-nitro- females were again exposed throughout breeding, gesta- phenol and that there was no evidence of a carcinogenic tion, and lactation. Apart from dose-related signs of skin activity of the substance in male or female mice. irritation (erythema, scaling, scabbing, and cracking) in dosed animals, the gross and histopathological examina- In another study, which had several procedural tions provided no indication of significant adverse deficiencies (only the skin was examined; only 12 weeks effects. The calculated indices concerning fertility, gesta- of exposure), no skin tumours were observed in tion, viability, and lactation were not different from those

31 female Sutter mice after dermal application of a 20% of controls. The testis to body weight ratios in the F0 solution (25 :l of solution applied twice weekly) of 2- or generation were not affected, and histological lesions 4-nitrophenol in dioxane (Boutwell & Bosch, 1959). were not observed in the testes. In a 28-day study in rats (see section 8.3.1), testicular atrophy and inhibition of spermatogenesis were observed in some animals after oral dosing at a level of 630 mg/kg body weight, but not at 210 mg/kg body weight. 1 Gulf South Research Institute, not dated; no further information available; results cited from NTP (1993).

14 Table 3: Genotoxicity of 2- and 4-nitrophenol in vitro and in vivo.

Results a Without With metabolic metabolic Species (test system) End-point Concentration range activation activation Remarks Reference 2-Nitrophenol (in vitro studies) 8 phage DNA Induction of DNA breakage 35 mg ! 0 Yamada et al. (1987) Bacillus subtilis H17, Recombination assay 0.01–0.5 mg/plate ! 0 Shimizu & Yano (1986) M45 Salmonella Reverse mutations 0.003–2.5 mg/plate ! ! Koerdel et al. (1981); Haworth et al. typhimurium (1983); Shimizu & Yano (1986) TA1535, TA1537 Salmonella Reverse mutations 0.01–2.5 mg/plate ! ! Koerdel et al. (1981); Shimizu & typhimurium Yano (1986) TA1538 Salmonella Reverse mutations 0.0007–5 mg/plate ! ! Suzuki et al. (1983) also tested both Chiu et al. (1978); Koerdel et al. typhimurium strains in the presence of norharman, (1981); Haworth et al. (1983); Suzuki TA98, TA100 which also gave negative results et al. (1983); Shimizu & Yano (1986); Kawai et al. (1987); Dellarco & Prival (1989); Massey et al. (1994) 2-Nitrophenol (in vivo studies) Drosophila SLRL assay via feed (400 and 500 ! Foureman et al. (1994) melanogaster ppm) or injection (2500 and 5000 ppm) 4-Nitrophenol (in vitro studies) 8 phage DNA Induction of DNA breakage 35 mg ! 0 Yamada et al. (1987) Bacillus subtilis H17, Recombination assay 0.01–5 mg/plate + 0 positive at 0.5 mg/plate Shimizu & Yano (1986) M45 Escherichia coli Gene mutation 0.001–2.5 mg/plate ! ! Hoechst AG (1980) WP2uvrA Escherichia coli K-12 Gene mutation 0.125–2 mg/plate ! 0 Rashid & Mumma (1986) (Pol A1+/Pol1!), WP2 (WP2, WP2uvrA, WP67, CM611, CM571) Escherichia coli Q13 DNA cell binding assay 7 or 70 mg + + positive at 70 mg Kubinski et al. (1981) Saccharomyces Mitotic gene conversion 2.9 mg/ml (+) 0 Fahrig (1974) cerevisiae ade 2, trp 5 Salmonella DNA damage (umu test) up to 0.75 mg/ml ! ! Nakamura et al. (1987) typhimurium TA1535/pSK 1002 Table 3 (Contd). Results a Without With metabolic metabolic Species (test system) End-point Concentration range activation activation Remarks Reference Salmonella Reverse mutation 0.001–2.5 mg/plate + ! positive at $0.1 mg/plate Hoechst AG (1980) typhimurium TA1538 Salmonella Reverse mutation 0.01–5 mg/plate ! ! Andrae et al. (1981); Shimizu & typhimurium Yano (1986) TA1538 Salmonella Reverse mutation 0.125–2 mg/plate ! 0 Rashid & Mumma (1986) typhimurium TA1538, TA1978 Salmonella Reverse mutation 0.0007– 5 mg/plate ! ! Suzuki et al. (1983) also tested both McCann et al. (1975); Hoechst AG typhimurium strains in the presence of norharman, (1980); Andrae et al. (1981); Haworth TA98, TA100 which also gave negative results et al. (1983); Suzuki et al. (1983); Shimizu & Yano (1986); Kawai et al. (1987); Dellarco & Prival (1989); Massey et al. (1994) Salmonella Reverse mutation 0.001–5 mg/plate ! ! McCann et al. (1975); Hoechst AG typhimurium (1980); Andrae et al. (1981); Haworth TA1535, TA1537 et al. (1983); Shimizu & Yano (1986) Rat hepatocytes DNA damage (alkaline 42–417 mg (+) 0 Weakly positive at $97 mg Storer et al. (1996) elution) Rat hepatocytes DNA repair 4.2–417 mg ! 0 Andrae et al. (1981) Chinese hamster ovary Chromosomal aberration without S9 mix: ! + NTP (1993) (CHO) cells 0.1–0.5 mg/ml with S9 mix: 1.25–2 mg/ml Chinese hamster ovary Sister chromatid exchange without S9 mix: ! ! NTP (1993) (CHO) cells 0.00017–0.025 mg/ml with S9 mix: 0.05–1.5 mg/ml Mouse lymphoma Forward mutation without S9 mix: ! ! Oberly et al. (1984) assay L5178Y TK+/– 0.7–1.5 mg/ml cells with S9 mix: 0.0001–0.03 mg/ml Mouse lymphoma Forward mutation 0.06–0.78 mg/ml 0 ! Amacher & Turner (1982) assay L5178Y TK+/– cells Rat hepatocytes Unscheduled DNA 0.00007–0.14 mg/ml ! 0 Probst et al. (1981) synthesis Human lymphocytes Chromosomal aberration not given + No data about metabolic activation; Huang et al. (1996) validity cannot be judged (documentation and study design insufficient for assessment) lowest positive concentration: 1.4 mg/ml Table 3 (Contd). Results a Without With metabolic metabolic Species (test system) End-point Concentration range activation activation Remarks Reference Human lymphocytes Chromosomal aberration 0.001–0.3 mg/ml + No data about metabolic activation; Huang et al. (1995) validity cannot be judged (documentation and study design insufficient for assessment) Human fibroblasts (WI- DNA repair 0.14–139 mg + No data about metabolic activation; Poirier et al. (1975) 38) validity cannot be judged (documentation insufficient for assessment) positive at $13.9 mg 4-Nitrophenol (in vivo studies) NMRI mice Host-mediated assay (tester single subcutaneous ! application of test substance Buselmaier et al. (1972) strains Salmonella injection of 75 mg/kg immediately after the bacteria had been typhimurium G 46 and body weight injected into the abdominal cavities; test Serratia marcescens a 21 duration 3 h Leu–) Drosophila SLRL assay via feed (1000, 2500, ! Zimmering et al. (1985); Foureman melanogaster 6000, or 7500 ppm) et al. (1994) or injection (1000 or 1500 ppm)

a !, negative; +, positive; (+), weakly positive; 0, not tested. Concise International Chemical Assessment Document 20

8.6.2 Developmental toxicity overt malformations, and perinatal loss were recorded. In dams, the mortality was increased at a dose level of 8.6.2.1 2-Nitrophenol $667 mg/kg body weight; at a dose level of $333 mg/kg body weight, the litter size on postnatal days 1 and 6 © In a range-finding study with Charles River COBS was non-significantly decreased. CD© rats (five dams per group; application of 0, 50, 125, 250, 500, or 1000 mg/kg body weight via gavage from day 8.7 Immunological and neurological 6 to day 15 of gestation; uterine examination on day 20), effects dose levels of 500 and 1000 mg/kg body weight caused signs of maternal toxicity (transient but dose-related There are no studies available dealing specifically decrease in weight gain early during treatment). One with immunological or neurological effects. There is an high-dose animal died, but no cause of death could be indication from an in vitro study that 4-nitrophenol may determined. Other clinical findings included darkly act as a suppressor of cell-mediated immune response coloured urine at $250 mg/kg body weight and yellow (Pruett & Chambers, 1988). However, the biological staining of haircoat (at the nose, mouth, anogenital area) significance is uncertain. at $125 mg/kg body weight; the necropsy findings gave no biologically meaningful differences in surviving 8.8 Methaemoglobin formation dams. At the highest dose level of 1000 mg/kg body weight, a slight but statistically significant (also com- Methaemoglobin formation by 2-nitrophenol and pared with historical controls) increase in group mean 4-nitrophenol has been tested in several studies using post-implantation losses (13.8% versus 8.2% in controls) different species, routes, and durations of applications. and mean early resorptions (2.3 versus 1.2 in controls) An overview is given in Table 4. was seen. No effects were observed on the number of viable fetuses, implantations, or corpora lutea 2-Nitrophenol clearly leads to the formation of (International Research and Developmental Corporation, methaemoglobin in a dose-dependent manner in cats 1983). (BASF AG, 1970), the most sensitive species. The lowest dose tested, 50 mg/kg body weight, produced increased 8.6.2.2 4-Nitrophenol methaemoglobin levels. In inhalation experiments in rats, elevated methaemoglobin levels were observed at an In both studies cited below, a complete examina- exposure level of 5 mg/m3; methaemoglobin levels were tion of the pups for possible teratogenic effects was not less elevated at exposure levels of 30 and 60 mg/m3 performed. In addition, owing to limitations of these (Hazelton Lab., 1984). studies (i.e., use of only one dose group or exposure to a mixture), reliable NO(A)EL values cannot be derived. 4-Nitrophenol, in contrast, did not lead to methae- moglobin formation in cats at concentrations up to In a study performed by Booth et al. (1983), groups 500 mg/kg body weight (BASF AG, 1969). In rats, at high of 50 female CD-1 mice received daily oral doses of concentrations in inhalation experiments, the met- 400 mg 4-nitrophenol/kg body weight via gavage from haemoglobin-forming capacity seemed to be very low day 7 to day 14 of gestation. The survival rate in (1.5% at 2470 mg/m3). In conclusion, 4-nitrophenol may pregnant mice (n = 36) was 81% versus 100% in controls, induce methaemoglobin formation, but the effect seems and dosed animals showed less maternal weight gain. No to be rather weak, without clear dose–response. changes were observed in the reproductive index (ratio between survivors delivered and pregnant survivors). The average number of live pups per litter was slightly decreased, but 4-nitrophenol produced no gross 9. EFFECTS ON HUMANS abnormalities.

Kavlock (1990) studied the developmental toxicity Naniwa (1979) performed patch tests with 4- of 4-nitrophenol in Sprague-Dawley rats. The substance nitrophenol, 4-aminophenol, 2-amino-4-chlorophenol, 3'- (dissolved in a mixture of water, Tween 20, propylene chlorodiphenylamine-2-carboxylic acid, and 4-dichloro- glycol, and ethanol [4:4:1:1]) was applied via gavage to nitrobenzene (0.1, 0.5, or 1% in petrolatum) on groups of 12–13 animals at doses of 0, 100, 333, 667, or 31 employees probably exposed to these chemicals in a 1000 mg/kg body weight on day 11 of gestation. End- chemical factory and on 5 control persons. In four points concerning maternal toxicity included signs of employees, a positive reaction to 4-nitrophenol was toxicity, mortality, body weight gain, and the number of observed, although none of these persons reacted implantation scars in the uteri at weaning. In the off- positively to all three tested concentrations. All four spring, viability, body weight on postnatal days 1–6,

18 Mononitrophenols

Table 4: Methaemoglobin formation by 2-nitrophenol and 4-nitrophenol.

Species (strain/number/ Frequency/ Results dose/sex) Route duration Dose (% metHb) Reference 2-Nitrophenol cat oral 1 x 50 mg/kg body weight 6 BASF AG (1970) 2 100 44 sex not given 250 57

rabbit dermal 1 x 50% solution no increase BASF AG (1970) number and sex in water not given

rat inhalation 6 h/day m f Hazleton Lab. Sprague-Dawley 5 days/week 0 mg/m3 1.0 2.0 (1984) 15 m/15 f 4 weeks 5 2.3 4.1 30 1.8 2.1 60 1.6 1.1 11th day of treatment

4-Nitrophenol cat oral 1 x 100 mg/kg body weight no increase BASF AG (1969) 2 200 sex not given 500

rat oral 5 days/week 0 mg/kg body weight analytical method not Hazleton Lab. Sprague-Dawley 13 weeks 25 reliable (13% in controls) (1989) 20 m/20 f 70 140

rat inhalation 6 h/day 0 mg/m3 0.2 0.2 Smith et al. (1988) Crl:CDR 5 days/week 340 0.87 0.13 10 m 2 weeks 2470 1.53 0.7 end of treatment and after 14 days of recovery

rat inhalation 6 h/day 0 mg/m3 0.5 0.4 Smith et al. (1988) Crl:CDR 5 days/week 30 0.3 0.5 10 m 2 weeks 130 1.5 0.2 end of treatment and after 14 days of recovery

rat inhalation 6 h/day m f Hazleton Lab. Sprague-Dawley 5 days/week 0 mg/m3 0.8 1.3 (1983) 15 m/15 f 4 weeks 1 0.5 1.1 5 2.2 2.0 30 1.1 1.0 after 2 weeks of exposure, values unusually high in some control animals

Abbreviations used: m = male; f = female; metHb = methaemoglobin. employees also reacted positively to 2-amino-4-chloro- 10. EFFECTS ON OTHER ORGANISMS IN phenol, which was shown to be a strong sensitizer. THE LABORATORY AND FIELD Therefore, 2-amino-4-chlorophenol may act as the primary allergen, and the effects observed with 4-nitro- phenol may be due to cross-sensitization. 10.1 Aquatic environment

In 27 patients primarily sensitized to 1-chloro-2,4- Experimental test results for the most sensitive dinitrobenzene, no cross-sensitization due to 4-nitro- species are summarized in Table 5. Additional data on phenol (1–2% in petrolatum) was observed. In addition, the toxicity of 2- and 4-nitrophenol to aquatic organisms 15 patients with a chloramphenicol allergy failed to react to 4-nitrophenol (Eriksen, 1978).

19 Concise International Chemical Assessment Document 20

Table 5: Aquatic toxicity of nitrophenols.

Most sensitive species Effective concentration (test method/end-point) Substance (mg/litre) Reference Bacteria

Pseudomonas putida 2-NP 16-h MICa: 0.9 Bringmann & Kuehn (1977) (cell multiplication inhibition test) 4-NP 16-h MIC: 4.0

Protozoa Entosiphon sulcatum 2-NP 72-h MIC: 0.40 Bringmann (1978); Bringmann et (cell multiplication inhibition test) 4-NP 72-h MIC: 0.83 al. (1980)

Algae

Scenedesmus subspicatus 2-NP 96-h EC50: 0.39 Broecker et al. (1984); Kramer et

Chlorella vulgaris 2-NP 6-h EC50: 1.53 al. (1986)

(cell multiplication inhibition test) 4-NP 6-h EC50: 6.97

Invertebrates

Moina macrocopa (acute) 2-NP 3-h LC50: 1.9 Yoshioka et al. (1985)

(immobilization) 4-NP 3-h LC50: 1.3 Daphnia magna (long-term) 2-NP 21-day LOEC: 1.0 Koerdel et al. (1984) (immobilization/reproduction) 4-NP 21-day NOEC: 1.3

Barentsia matsushimana (marine) 4-NP 49-day EC50: 0.21 Kuehn et al. (1988) b (growth of germinated spores) 4-NP 49-day ECm : 0.03 Scholz (1986)

Fish

Cyprinus carpio (static) 2-NP 96-h LC50: 36.6 Lang et al. (1996)

Oncorhynchus mykiss (static) 4-NP 96-h LC50: 3.8 Howe et al. (1994)

Oncorhynchus mykiss (flow-through) 4-NP 96-h LC50: 7.93

Abbreviations used: 2-NP = 2-nitrophenol; 4-NP = 4-nitrophenol. a MIC = minimum inhibitory concentration. b ECm = minimal effective concentration. are cited in BUA (1992). Among all tested organisms, the 10.2 Terrestrial environment protozoan Entosiphon sulcatum and the green alga Scenedesmus subspicatus proved to be most sensitive in The toxicity of 2- and 4-nitrophenol on higher chronic cell multiplication inhibition tests with fresh- plants according to OECD Guideline 208 was tested in water species. Daphnia magna exhibited a 21-day independent studies. After incubation of seeds with lowest-observed-effect concentration (LOEC) of 1.0 mg different test substance concentrations, 14-day EC50 2-nitrophenol/litre in the Daphnia reproduction test values for reduced fresh weight of grown shoots were in (Koerdel et al., 1984). The entoproct Barentsia the range of 52–420 mg 2-nitrophenol/kg soil (Broecker et matsushimana was the most sensitive marine inverte- al., 1984; Koerdel et al., 1984) and 35–260 mg 4- brate species tested, exhibiting a 49-day EC50 value of nitrophenol/kg soil (Ballhorn et al., 1984; Marquart et al., 0.21 mg 4-nitrophenol/litre and a minimal effective 1984). The 14-day EC10 value for 2-nitrophenol was 10 concentration (ECm) of 0.03 mg/litre (end-point: growth mg/kg soil for both species. Overall, turnip (Brassica of germinated spores) (Scholz, 1986). Freshwater fish rapa) proved to be more sensitive than oat (Avena showed less sensitivity. The lowest 96-h LC50 value of sativa). 3.8 mg 4-nitrophenol/litre was determined for rainbow trout (Oncorhynchus mykiss) (Howe et al., 1994). The In tests conducted according to OECD Guideline measured no-observed-effect concentration (NOEC) for 207, the adverse effects of 2- and 4-nitrophenol on behavioural changes in a 28-day flow-through test with earthworms were examined in several independent zebra fish was 2 mg 2-nitrophenol/litre (Broecker et al., studies. In the contact test, in which the animals are 1984). After prolonged exposure of zebra fish to 4- exposed on filter paper soaked with the test substance, nitrophenol, minor morphological alterations of the liver, Neuhauser et al. (1985) established a 48-h LC50 value of even at a concentration of 0.1 mg/litre, were observed. 5.9 :g/cm² for the toxicity of 2-nitrophenol on Eisenia

At 1 and 5 mg/litre, about 25% of the animals showed fetida. For 4-nitrophenol, the 48-h LC50 values were in symptoms of degenerative transformation of the liver the range of 0.7–2.7 :g/cm², with Eisenia fetida and tissue (Braunbeck et al., 1989). Eudrilus eugeniae being the most sensitive species tested (Roberts & Dorough, 1984; Neuhauser et al., 1985, 1986). When exposed in an artificial soil mixture, 28-day

LC50 values for 2-nitrophenol were in the range of 250–500 mg/kg soil (Eisenia fetida) (Broecker et al., 1984;

20 Mononitrophenols

Koerdel et al., 1984), and 14-day LC50 values for 4- For 4-nitrophenol, irritating effects on skin and eye are nitrophenol were in the range of 38–67 mg/kg soil, again assumed based on the studies performed according to with Eisenia fetida and Eudrilus eugeniae as the most OECD/FDA guidelines; in addition, signs of irritation sensitive species tested (Ballhorn et al., 1984; Marquart were reported after exposure by inhalation as well as et al., 1984; Neuhauser et al., 1985, 1986). subchronic dermal exposure. In a guinea-pig maximiza- tion test, 4-nitrophenol was considered to be sensitizing. The environmental relevance, particularly of the Positive patch tests were recorded in humans exposed to earthworm contact test, seems questionable. Critical 4-nitrophenol. Although this may have been due to results from this test, as sole effect data on terrestrial cross-sensitization, sensitization to 4-nitrophenol in organisms, should not justify a classification of tested humans cannot be excluded. substances as highly toxic to earthworms or other soil organisms. The available data on microorganisms and Only a few limited studies concerning repeated oral plants indicate only a moderate toxicity potential in the exposure to 2- and 4-nitrophenol in experimental animals terrestrial environment. were identified. With 2-nitrophenol, decreases in body weight gain accompanied by decreased food con- sumption and differences in organ weights without clear dose dependency were found. However, the haema- 11. EFFECTS EVALUATION tological examination, clinical chemistry, and histopathological examination of the major organs and tissues gave no indication for a substance-related toxic 11.1 Evaluation of health effects effect compared with controls. In rats dosed with 4- nitrophenol, a focal fatty degeneration of the liver as well 11.1.1 Hazard identification and dose–response as congestion in several organs were the major assessment histopathological findings. Other reported effects included haematological changes, nephrosis, testicular In general, there is only limited information con- atrophy, and follicular atresia in the ovaries. The cerning the toxicological profiles of 2- and 4-nitrophenol. exposure by inhalation to 2-nitrophenol vapour caused squamous metaplasia of the epithelium of the upper In experimental animals given 4-nitrophenol orally, respiratory tract; with 4-nitrophenol dust (applied as intravenously, or intraperitoneally, most of the applied sodium salt), haematological changes, increased met- dose was excreted via the urine within 24–48 h as glucur- haemoglobin values, and differences in organ weights onide and sulfate conjugates, while only very small were noted. For the effects given in these studies, it was amounts were excreted via faeces or as unchanged 4- not possible to identify a clear dose–response or reliable nitrophenol. In rabbits, after oral dosing, 4-nitrophenol NO(A)EL values. undergoes reduction to 4-aminophenol as well as glucuronidation and sulfation. In vivo and in vitro Insufficient data are available on 2-nitrophenol to studies gave an indication for dermal uptake. For 2- allow any conclusions to be made about its possible nitrophenol, the information is very limited. However, a mutagenicity. For 4-nitrophenol, more mutagenicity comparable metabolic transformation is assumed based studies are available, and the substance was shown to on the available data. Owing to their rapid metabolism be mutagenic in some but not all of the bacterial assays. and excretion, bioaccumulation of 2- and 4-nitrophenol in In addition, positive results were obtained in in vitro organisms is not to be expected. tests for chromosomal aberrations in mammalian cells; however, apart from one well-documented study, the

With oral LD50 values of 220–620 mg/kg body available assays were inadequately reported. In the weight in rats and 380–470 mg/kg body weight in mice, 4- absence of any in vivo mutagenicity studies in mammals, nitrophenol is harmful after oral uptake and was found to it is not possible to conclude whether or not the muta- be more toxic than 2-nitrophenol. A dose-dependent genic potential of 4-nitrophenol is expressed in vivo. increase in the formation of methaemoglobin was seen in cats after oral exposure to 2-nitrophenol — but not after 4-Nitrophenol was not carcinogenic in male or exposure to 4-nitrophenol — and in rats after exposure female mice after dermal application over 78 weeks. In a by inhalation to 4-nitrophenol. limited study with female mice, no skin tumours were seen after dermal application of 2- or 4-nitrophenol over Most of the studies concerning skin- or eye- 12 weeks. No carcinogenicity studies using the oral or irritating effects in experimental animals are limited as a inhalation routes were available for either of the isomers. result of insufficient documentation. However, from the available data, it can be concluded that 2-nitrophenol is No reproductive effects were observed in rats slightly irritating to the skin but non-irritating to the eye, exposed to 4-nitrophenol in a two-generation study. For and the substance proved to have no sensitizing effects. developmental toxicity, the available studies were inade-

21 Concise International Chemical Assessment Document 20 quately performed (i.e., only one dose was applied, or accumulates in fog. From the mean measured level of 20 animals were dosed only on one day with a mixture). In :g/litre, the uptake of the substance by inhalation an oral study with rats, 2-nitrophenol induced develop- (using the same assumptions as above) can be mental effects in the offspring only at doses that also calculated to be about 8 ng during a 1-h exposure period produced maternal toxicity. However, the fetuses were (i.e., 0.12 ng/kg body weight), assuming a maximum water not examined for internal malformations. content of fog of 0.1 g/m3 (Pruppacher & Klett, 1978). The uptake via drinking-water for 2- and 4-nitrophenol Data on humans relevant for the assessment of can be calculated to be about 0.02 :g/kg body weight potential adverse effects are limited to some patch tests per day, assuming a maximum concentration of 1 :g/litre performed with 4-nitrophenol. drinking-water, a daily drinking-water consumption of 1.4 litres, and a mean body weight of 64 kg for males and 11.1.2 Criteria for setting guidance values for females. 2- and 4-nitrophenol From these data, it can be concluded that exposure As given in section 8, the database for 2-nitrophe- of the general population to the nitrophenol isomers is nol is inadequate for calculating a tolerable daily intake mainly through ambient air and drinking-water. (TDI) or a tolerable concentration (TC). 11.2 Evaluation of environmental effects For 4-nitrophenol, the formation of methaemo- globin was shown to be the most critical end-point after Releases of 2- and 4-nitrophenol into the environ- exposure by inhalation and is assumed to be relevant for ment are primarily emissions into air, water, and soil from oral exposure too. However, owing to the inaccuracy of diffuse sources, such as vehicle traffic and hydrolytic the analytical method used in the 13-week study with and photolytic degradation of the respective pesticides. oral application, a reliable NO(A)EL cannot be derived. Therefore, at present, no TDI for 4-nitrophenol can be 2-Nitrophenol emitted to the troposphere will stay developed owing to inadequacy of the database. predominantly in the gaseous phase and should be rapidly removed by nitration. The major portion of Longer-term toxicity studies concerning inhalation airborne 4-nitrophenol is expected to be particle bound exposure were not identified in the literature, and the and can be washed out to surface waters and soil by wet NO(A)EL values derived for 4-nitrophenol from short- and dry deposition. Because of their removal from air term studies gave considerable differences (2-week and their insignificant volatility, nitrophenols are not exposure: NO(A)EL of about 30 mg/m3; 4-week exposure: considered to contribute directly to the depletion of the NO(A)EL of about 5 mg/m3). The NO(A)EL of 5 mg/m3 stratospheric ozone layer or to global warming. Mea- was derived for local effects (cataracts), whereas the sured bioconcentration factors indicate a low potential NO(A)EL for systemic effects (formation of for bioaccumulation. methaemoglobin) may be lower. Therefore, a reliable TC for exposure by inhalation cannot be calculated, as the Nitrophenols exhibit moderate to high toxicity to formation of methaemoglobin is the critical end-point. aquatic organisms, with lowest effect concentrations reported from chronic studies on algae, Daphnia, and 11.1.3 Sample risk characterization aquatic invertebrates. The lowest effect concentrations found in chronic studies with freshwater organisms As given in section 6.2, workers may be exposed to (Scenedesmus subspicatus, 96-h EC50: 0.39 mg 2-nitro- 2- and 4-nitrophenol via inhalation and skin contact phenol/litre; Entosiphon sulcatum, 72-h MIC: 0.83 mg 4- during production and processing (mainly in the manu- nitrophenol/litre) were 40–50 times higher than maximum facturing of pesticides). However, data on nitrophenol levels determined in a densely populated and highly concentrations at the workplace were not identified. industrialized Asian river basin (0.0072 mg 2-nitrophenol/litre and 0.019 mg 4-nitrophenol/litre). For the general population, an exposure to nitro- From these data, the safety margin between the LOEC phenols via the environment cannot be excluded (see and maximum surface water concentrations is insufficient also section 6.2). Assuming an ambient atmospheric to exclude any risk for sensitive aquatic organisms, 3 concentration of about 1 :g/m , an inhalation uptake of particularly under surface water conditions not favour- 3 100%, a daily respiratory volume of 22 m for adults, a ing both elimination pathways. Taking into account the mean body weight of 64 kg for males and females, and missing chronic effect data for fish, an uncertainty/ that 4 of 24 h are spent outdoors (IPCS, 1994), the uptake assessment factor of 100 has to be applied to derive a by inhalation of nitrophenols is calculated to be 0.06 predicted no-effect concentration (PNEC) according to :g/kg body weight per day. In addition, 4-nitrophenol standard procedures for environmental risk assessment.

22 Mononitrophenols

From acute tests (see section 10.1), however, fish 12. PREVIOUS EVALUATIONS BY obviously seem to be the least sensitive aquatic species INTERNATIONAL BODIES tested. Thus, an assessment factor of 10 might be appropriate. Furthermore, the use pattern and the release scenario outlined in section 4 lead to the conclusion that Previous evaluations of mononitrophenols by nitrophenols emitted to surface waters will pose only a international bodies were not identified. minor risk to aquatic organisms. Information on international hazard classification There were no data available on the occurrence of and labelling for mononitrophenols is included in the nitrophenols in the terrestrial compartment. Therefore, an International Chemical Safety Card reproduced in this assessment of possible effects on organisms for this document. compartment could be conducted only with regard to the degradation of pesticides. For the insecticides mentioned in section 4 (parathion, parathion-methyl, carbofuran, phosalon, fluorodifen) and the herbicides 13. HUMAN HEALTH PROTECTION AND bifenox and nitrofen, predicted soil concentrations were EMERGENCY ACTION calculated from the maximum application rates (taken from Domsch, 1992) according to the EPPO (1993) guide- lines for environmental risk assessment of plant protec- Human health hazards, together with preventative tion products. Based on the relative molecular mass of and protective measures and first aid recommendations, the pesticides, the maximum concentration of nitrophe- are presented on the enclosed International Chemical nols in the top 5 cm of soil was calculated (worst case; Safety Card (ICSC 1342) reproduced in this document. one application). For pesticides that are applied at times when the soil is plant covered to a high degree, it is assumed that only half of the amount applied reaches the soil. Thus, the predicted environmental 14. CURRENT REGULATIONS, concentration (PEC) for the insecticides was reduced by GUIDELINES, AND STANDARDS 50%. Dividing the PECsoil by the lowest LC50 value for a terrestrial species gives the toxicity exposure ratio (TER).

The lowest LC50 value for earthworms (38 mg/kg body weight; see section 10.2) has to be corrected by a factor Information on national regulations, guidelines, of 2 because of the higher organic matter content in and standards is available from the International Register artificial soil compared with natural agricultural soil. The of Potentially Toxic Chemicals (IRPTC) legal file. following TERs were derived: The reader should be aware that regulatory deci- Insecticides Herbicides sions about chemicals taken in a certain country can be Parathion: 244 Bifenox: 131 fully understood only in the framework of the legislation Parathion-methyl: 557 Nitrofen: 18 of that country. The regulations and guidelines of all Carbofuran: 47 countries are subject to change and should always be Phosalon: 36 verified with appropriate regulatory authorities before Fluorodifen: 69 application.

According to the EPPO (1993) guidelines, the trig- ger value for concern is <10. Therefore, these pesticides are expected to pose only a minor risk to earthworms, even under a worst-case scenario. Furthermore, the herbicide nitrofen and the insecticides phosalon and fluorodifen are no longer manufactured or marketed for crop protection use.

23 MONONITROPHENOLS 1342 November 1998 CAS No: 25154-55-6 Nitrophenols (mixed isomers) RTECS No: Nitrophenols

UN No: 1663 C6H5O3N Molecular mass: 139.1

TYPES OF HAZARD/ ACUTE HAZARDS/SYMPTOMS PREVENTION FIRST AID/FIRE FIGHTING EXPOSURE

FIRE Combustible. Gives off irritating or NO open flames. Powder, water spray, foam, carbon toxic fumes (or gases) in a fire. dioxide.

EXPLOSION Finely dispersed particles form Prevent deposition of dust; closed In case of fire: keep drums, etc., explosive mixtures in air. system, dust explosion-proof cool by spraying with water. electrical equipment and lighting.

EXPOSURE PREVENT DISPERSION OF DUST! STRICT HYGIENE!

Inhalation Blue lips or finger nails. Blue skin. Local exhaust or breathing Fresh air, rest. Refer for medical Confusion. Convulsions. Cough. protection. attention. Dizziness. Headache. Nausea. Sore throat. Unconsciousness.

Skin MAY BE ABSORBED! Protective gloves. Protective Remove contaminated clothes. clothing. Rinse and then wash skin with water and soap. Refer for medical attention.

Eyes Redness. Pain. Safety goggles, or eye protection in First rinse with plenty of water for combination with breathing several minutes (remove contact protection. lenses if easily possible), then take to a doctor.

Ingestion Abdominal pain. Sore throat. Do not eat, drink, or smoke during Rinse mouth. Rest. Refer for Vomiting. (See Inhalation). work. medical attention.

SPILLAGE DISPOSAL PACKAGING & LABELLING

Sweep spilled substance into sealable containers. UN Hazard Class: 6.1 Do not transport with food and Carefully collect remainder, then remove to safe UN Pack Group: III feedstuffs. place. Do NOT let this chemical enter the environment. (Extra personal protection: P2 filter respirator for harmful particles).

EMERGENCY RESPONSE STORAGE

Separated from combustible and reducing substances, food and feedstuffs. Dry. Well closed.

Prepared in the context of cooperation between the International IPCS Programme on Chemical Safety and the European Commission International © IPCS 2000 Programme on Chemical Safety SEE IMPORTANT INFORMATION ON THE BACK. 1342 MONONITROPHENOLS

IMPORTANT DATA Physical State; Appearance Routes of exposure YELLOW CRYSTALS The substance can be absorbed into the body by inhalation of its aerosol, through the skin and by ingestion. Physical dangers Dust explosion possible if in powder or granular form, mixed Inhalation risk with air. Evaporation at 20°C is negligible; a harmful concentration of airborne particles can, however, be reached quickly. Chemical dangers May explode on heating. On combustion, forms nitrogen oxides. Effects of short-term exposure The substance decomposes on heating producing toxic fumes The substance irritates the eyes and the skin and the including nitrogen oxides. Reacts with strong oxidants. respiratory tract. The substance may cause effects on the blood, resulting in formation of methaemoglobin. The effects Occupational exposure limits may be delayed. Medical observation is indicated. TLV not established. Effects of long-term or repeated exposure Repeated or prolonged contact may cause skin sensitization.

PHYSICAL PROPERTIES

Boiling point: 194-279 Vapour pressure, Pa at 20°C: 0.0032 - 7 Melting point: 44-116°C Relative vapour density (air = 1): 4.81 Density: 1.5 g/cm3 Flash point: 169°C Solubility in water, g/100 ml: 0.13-1.2

ENVIRONMENTAL DATA The substance is toxic to aquatic organisms. Avoid release to the environment in circumstances different to normal use.

NOTES Depending on the degree of exposure, periodic medical examination is indicated. Specific treatment is necessary in case of poisoning with this substance; the appropriate means with instructions must be available.

ADDITIONAL INFORMATION

LEGAL NOTICE Neither the EC nor the IPCS nor any person acting on behalf of the EC or the IPCS is responsible for the use which might be made of this information

©IPCS 2000 Concise International Chemical Assessment Document 20

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Schoene K, Steinhanses J (1984) Comparative measurements of the Tseng S, Lin M (1994) Treatment of organic wastewater by anaerobic volatility in open systems. Schmallenberg, Fraunhofer Institute for biological fluidized bed reactor. Water science and technology, Toxicology and Aerosol Research (Report No. 10602024/7 Part II) (in 29:157–166. German). Urano K, Kato Z (1986) Evaluation of biodegradation ranks of priority Scholz N (1986) Development of test guidelines on marine species for organic compounds. Journal of hazardous materials, 13:147–159. ecotoxicological studies according to the chemicals act - Bryozota/Camptozoa. Berlin, Umweltbundesamt (Report No. Van Veld PA, Spain JC (1983) Degradation of selected xenobiotic 10603042/02) (in German). compounds in three types of aquatic test systems. Chemosphere, 12:1291–1305. Schwarzenbach RP, Stierli R, Folsom BR, Zeyer J (1988) Compound properties relevant for assessing the environmental partitioning of Vasilenko NM, Volodchenko VA, Baturina TS, Kolodub FA (1976) nitrophenols. Environmental science and technology, 22:83–92. Toxicological peculiarities of mononitrophenols with regard for their isomeric form. Farmakologiya i Toksikologiya, 39:718–721. Sewekow B (1983) Feasibility of test guidelines and evidence of the base-set testing according to the chemicals legislation. Muenchen, Vernot EH, MacEwen JD, Haun CC, Kinkead ER (1977) Acute toxicity Gesellschaft fuer Strahlen- und Umweltforschung (in German). and skin corrosion data for some organic and inorganic compounds and aqueous solutions. Toxicology and applied pharmacology, 42:417–423. Shimizu M, Yano E (1986) Mutagenicity of mono-nitrobenzene derivatives in the Ames test and rec assay. Mutation research, Verschueren K, ed. (1983) Handbook of environmental data on organic 170:11–22. chemicals, 2nd ed. New York, NY, Van Nostrand Reinhold Co.

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30 Mononitrophenols

APPENDIX 1 — 3-NITROPHENOL wastewater. From the available results, a slow mineralization of 3-nitrophenol under anaerobic conditions by adapted microorganisms can be expected. Identity and physical/chemical properties A soil sorption coefficient (Koc) of 52.83, determined by 3-Nitrophenol (CAS No. 554-84-7; 3-hydroxy-1- Boyd (1982), and the n-octanol/water partition coefficient (log nitrobenzene, m-nitrophenol) has the empirical formula C6H5NO3. Kow) of 2.0, reported by Hansch & Leo (1979), indicate a low to Its structural formula is shown below: moderate potential for soil sorption as well as for bioaccumulation.

OH Environmental levels

3-Nitrophenol was not detected in 27 samples of air (detection limit 8 ng/m3) in Japan in 1994 (Japan Environment Agency, 1995). It was not detected in 177 samples of Japanese surface waters (detection limits 0.04–10 :g/litre) or in 177 sediment samples (detection limits 0.002–0.8 :g/kg) in 1978, NO2 1979, and 1994 (Japan Environment Agency, 1979, 1980, 1995). 3-Nitrophenol was not detected in 129 fish samples (detection limits 0.005–0.2 :g/kg) in Japan in 1979 and 1994 (Japan Environment Agency, 1980, 1995). Physicochemical properties of 3-nitrophenol are given in Table A-1. Comparative kinetics and metabolism in laboratory animals and humans Table A-1: Physicochemical properties of 3-nitrophenol. Studies providing quantitative information on the absorption, metabolism, or elimination of 3-nitrophenol in Parameter Value humans were not identified. In addition, there is only very Molecular mass (g/mol) 139.11 limited information available for experimental animals. In rabbits given a single dose of 150–200 mg/kg body weight via Melting point (°C) 96–97 (1)(2) gavage, most of the applied dose (o80%) was excreted via the Boiling point (°C) 194 (1) urine within 24 h. About 68–86% was conjugated with glucuronic acid and sulfonic acid, whereas about 7–13% was Vapour pressure (kPa; 20 °C) 0.10 (3) reduced to aminophenols (Robinson et al., 1951). Skin in vitro Water solubility (g/litre; 25 °C) 13.5 (1) permeation was shown in several experiments (Huq et al., 1986; Jetzer et al., 1986; Ohkura et al., 1990). Although the n-Octanol/water partition coefficient 2.00 (4) information is limited, bioaccumulation of 3-nitrophenol in

(log Kow) organisms is not to be expected owing to the isomer’s rapid metabolism and excretion. Dissociation constant (pKa) (18 °C) 8.34 (2)

Conversion factors 1 mg/m3 = 0.173 ppmv Effects on laboratory mammals and in vitro test 3 1 ppmv = 5.78 mg/m systems

References: (1) Verschueren (1983); (2) Budavari et al. (1996); The oral LD50 of 3-nitrophenol is quoted to be $930 (3) HSDB (1998); (4) Hansch & Leo (1979) mg/kg body weight for rats (Vasilenko et al., 1976; Vernot et al., 1977) and $1070 mg/kg body weight for mice (Vasilenko et al., 1976; Vernot et al., 1977). Environmental transport, distribution, and transformation The available in vitro and in vivo genotoxicity studies on 3-nitrophenol are summarized in Table A-3. 3-Nitrophenol was Data on the abiotic degradation of 3-nitrophenol were not shown to be mutagenic in a rec-assay and gave inconsistent available. results in Salmonella/microsome assays. One study showed it to be non-mutagenic in the Salmonella typhimurium TA98 and Three studies on biotic degradation, summarized in TA100 strains, whereas another study showed mutagenicity in Table A-2, indicate the isomer to be inherently biodegradable both of these strains in both the presence and absence of in water under aerobic conditions. metabolic activation. In view of the conflicting results from Salmonella/microsome assays and the absence of any data on In tests on biotic degradation under anaerobic conditions clastogenicity, no conclusions can be made regarding the using sewage sludge and sludge from the primary anaerobic mutagenicity of 3-nitrophenol. stage of a municipal sewage treatment plant, respectively, initial 3-nitrophenol concentrations in the range of 96.5–579 mg/litre For 3-nitrophenol, there are no studies available were not degraded at all within 7–60 days (Wagner & concerning irritating or sensitizing effects, repeated exposure, Braeutigam, 1981; Battersby & Wilson, 1989). Boyd et al. reproductive and developmental toxicity, or effects on humans. (1983), however, found complete anaerobic removal of 50 mg/litre within 1 week of incubation. In this test, mineralization Effects on aquatic species was demonstrated only if the incubation period was extended to 10 weeks. Anaerobic degradation, even of high initial In tests performed on the toxicity of 3-nitrophenol to nitrophenol concentrations, was found by Tseng & Lin (1994), various aquatic organisms (see Table A-4), 3-nitrophenol who observed 90% removal of 3-nitrophenol (350–650 mg/litre) exhibited a moderate to high toxicity. in a biological fluidized bed reactor with three different kinds of

31 Concise International Chemical Assessment Document 20

Table A-2: Biotic degradation of 3-nitrophenol under aerobic conditions.

Concentration Additional Test duration Removal Test (mg/litre) carbon source (days) (%) Reference Tests on ready biodegradability MITI I 100 no 14 0 Gerike & Fischer (1979); Urano & Kato (1986)

Tests on inherent biodegradability Batch test, aerated 200 CODa no 5 95 Pitter (1976)

Respirometric test 300 yes 10 44 Kayser et al. (1994) a COD = chemical oxygen demand.

Table A-3: Genotoxicity of 3-nitrophenol in vitro and in vivo.

Results a Without With Concentration metabolic metabolic Species (test system) End-point range activation activation Remarks References In vitro studies Bacillus subtilis H17, Recombinatio 0.01–5 + 0 positive at $0.5 Shimizu & M45 n assay mg/plate mg/plate Yano (1986) Salmonella Reverse 0.01–5 ! ! Shimizu & typhimurium TA1535, mutations mg/plate Yano (1986) TA1537, TA1538 Salmonella Reverse 0.1–5 mg/plate + + Study in Japanese Kawai et al. typhimurium TA98, mutations (data taken from (1987) TA100 tables) Salmonella Reverse 0.01–5 ! ! Suzuki et al. (1983) Suzuki et al. typhimurium TA98, mutations mg/plate also tested both (1983); Shimizu TA100 strains in the pres- & Yano (1986) ence of norharman, which also gave negative results

In vivo studies Drosophila SLRL assay via feed (5000 Foureman et al. melanogaster ppm) or injec- (1994) tion (1200 ppm) a !, negative; +, positive; 0, not tested.

Table A-4: Aquatic toxicity of 3-nitrophenol.

Species Effective concentration (test method/end-point) (mg/litre) Reference Bacteria Pseudomonas putida (cell multiplication inhibition 16-h MICa: 7.0 Bringmann & Kuehn (1977) test)

Protozoa Entosiphon sulcatum (cell multiplication inhibition 72-h MIC: 0.97 Bringmann (1978); Bringmann et al. test) (1980)

Algae

Scenedesmus subspicatus 6-h EC50: 6.21 Kramer et al. (1986) Chlorella vulgaris (cell multiplication inhibition test)

Invertebrates

Moina macrocopa (acute) (immobilization) 3-h LC50: 1.7 Yoshioka et al. (1985)

Fish

Cyprinus carpio (static) 96-h LC50: 17.5 Lang et al. (1996) a MIC = minimum inhibitory concentration.

32 Mononitrophenols

APPENDIX 2 — SOURCE DOCUMENTS APPENDIX 3 — CICAD PEER REVIEW

BUA (1992): BUA-Stoffbericht 2- und 4- The draft CICAD on mononitrophenols was sent for review to institutions and organizations identified by IPCS after contact Nitrophenol. Beratergremium fuer with IPCS national Contact Points and Participating Institutions, Umweltrelevante Altstoffe. Weinheim, VCH as well as to identified experts. Comments were received from: VerlagsGmbH (Report No. 75; February 1992) Federal Institute for Health Protection of Consumers & For the BUA review process, the company that is in charge Veterinary Medicine, Berlin, Germany of writing the report (usually the largest producer in Germany) prepares a draft report using literature from an extensive Gesellschaft Deutscher Chemiker, Frankfurt, Germany literature search as well as internal company studies. This draft is subject to a peer review during several readings of a working Institute of Occupational Medicine, Chinese Academy of group consisting of representatives from government agencies, Preventive Medicine, Ministry of Health, Beijing, People’s the scientific community, and industry. Republic of China

The English translation of BUA Report No. 75 (BUA Institute of Terrestrial Ecology, Huntingdon, United Report 2- and 4-Nitrophenol. GDCh-Advisory Committee on Kingdom Existing Chemicals of Environmental Relevance. Stuttgart, Hirzel Verlag [February 1992]) was released in 1993. Joint Food Safety and Standards Group, Department of Health, London, United Kingdom

National Institute of Health Sciences, Tokyo, Japan ATSDR (1992): Toxicological profile for nitrophenols: 2- and 4-nitrophenol. Atlanta, GA, National Institute of Public Health, Prague, Czech US Department of Health and Human Services, Republic Public Health Service, Agency for Toxic United States Department of Health and Human Services Substances and Disease Registry (Report No. (National Institute of Environmental Health Sciences, TP-91/23) Research Triangle Park), USA

Copies of the ATSDR Toxicological profile for United States Environmental Protection Agency (National nitrophenols: 2- and 4-nitrophenol (ATSDR, 1992) may be Center for Environmental Assessment, Washington, DC; obtained from the: Region VIII), USA

Agency for Toxic Substances and Disease Registry World Health Organization/International Programme on Division of Toxicology Chemical Safety, Montreal, Canada 1600 Clifton Road, E-29 Atlanta, Georgia 30333 USA

Initial drafts of the Toxicology profile for nitrophenols: 2- and 4-nitrophenol were reviewed by scientists from the Agency for Toxic Substances and Disease Registry, the US Centers for Disease Control, the US National Toxicology Program, and other federal agencies. The document was also reviewed by an expert panel of nongovernmental reviewers, consisting of the following members:

Dr Martin Alexander, Cornell University Dr Gary Booth, Brigham Young University Dr Samuel Cohen, University of Nebraska Medical Center Dr Loren Koller, Oregon State University Dr Frederick Oehme, Kansas State University

33 Concise International Chemical Assessment Document 20

APPENDIX 4 — CICAD FINAL REVIEW Dr M. Sweeney, Document Development Branch, National Institute for Occupational Safety and Health, Cincinnati, OH, BOARD USA

Washington, DC, USA, 8–11 December 1998 Dr K. Ziegler-Skylakakis, GSF-Forschungszentrum für Umwelt und Gesundheit GmbH, Institut für Toxikologie, Oberschleissheim, Germany Members

Dr T. Berzins, National Chemicals Inspectorate (KEMI), Solna, Secretariat Sweden (Vice-Chairperson) Dr M. Baril, Institut de Recherches en Santé et Sécurité du Mr R. Cary, Toxicology Unit, Health Directorate, Health and Travail du Québec (IRSST), Montreal, Quebec, Canada Safety Executive, Bootle, Merseyside, United Kingdom (Rapporteur) Dr H. Galal-Gorchev, Chevy Chase, MD, USA

Dr S. Dobson, Institute of Terrestrial Ecology, Monks Wood, Ms M. Godden, Health and Safety Executive, Bootle, Abbots Ripton, Huntingdon, Cambridgeshire, United Kingdom Merseyside, United Kingdom

Dr O. Faroon, Agency for Toxic Substances and Disease Dr R.G. Liteplo, Environmental Health Directorate, Health Registry, Centers for Disease Control and Prevention, Atlanta, Canada, Ottawa, Ontario, Canada GA, USA Ms L. Regis, Programme for the Promotion of Chemical Safety, Dr G. Foureman, National Center for Environmental Assessment, World Health Organization, Geneva, Switzerland US Environmental Protection Agency, Research Triangle Park, NC, USA Mr A. Strawson, Health and Safety Executive, London, United Kingdom Dr H. Gibb, National Center for Environmental Assessment, US Environmental Protection Agency, Washington, DC, USA Dr P. Toft, Programme for the Promotion of Chemical Safety, (Chairperson) World Health Organization, Geneva, Switzerland

Dr R.F. Hertel, Federal Institute for Health Protection of Consumers & Veterinary Medicine, Berlin, Germany

Dr I. Mangelsdorf, Documentation and Assessment of Chemicals, Fraunhofer Institute for Toxicology and Aerosol Research, Hanover, Germany

Dr A. Nishikawa, Division of Pathology, National Institute of Health Sciences, Tokyo, Japan

Dr E.V. Ohanian, Office of Water/Office of Science and Technology, Health and Ecological Criteria Division, US Environmental Protection Agency, Washington, DC, USA

Dr J. Sekizawa, Division of Chem-Bio Informatics, National Institute of Health Sciences, Tokyo, Japan

Professor P. Yao, Institute of Occupational Medicine, Chinese Academy of Preventive Medicine, Ministry of Health, Beijing, People’s Republic of China

Observers

Dr K. Austin, National Center for Environmental Assessment, US Environmental Protection Agency, Washington, DC, USA

Dr I. Daly (ICCA representative), Regulatory and Technical Associates, Lebanon, NJ, USA

Ms K.L. Lang (CEFIC, European Chemical Industry Council, representative), Shell International, London, United Kingdom

Ms K. Roberts (ICCA representative), Chemical Self-funded Technical Advocacy and Research (CHEMSTAR), Chemical Manufacturers Association, Arlington, VA, USA

Dr W. Snellings (ICCA representative), Union Carbide Corporation, Danbury, CN, USA

34 Mononitrophenols

RÉSUMÉ D’ORIENTATION l’atmosphère et qu’il ne passe sans doute qu’en quantité négligeable de l’eau à l’air selon ce processus. On constate un enrichissement en 2-nitrophénol de la phase Ce CICAD relatif aux isomères en position 2-, 3- et aqueuse des nuages; en revanche, dans la phase 4- du nitrophénol a été préparé par l’Institut Fraunhofer gazeuse, la proportion de 4-nitrophénol est plus de recherche en toxicologie et sur les aérosols de importante qu’on pourrait le penser en fonction des Hanovre (Allemagne). Il est basé sur des mises au point données physico-chimiques, par suite d’une importante rédigées par le Comité consultatif allemand sur les fixation du composé sur les particules. Compte tenu de produits chimiques qui posent un problème écologique leur solubilité dans l’eau et de leur concentration dans la (BUA, 1992) et par l’US Agency for Toxic Substances phase gazeuse, on peut s’attendre à ce que les and Disease Registry (ATSDR, 1992) afin d’évaluer les nitrophénols présents dans l’atmosphère se déposent effets potentiels du 2- et du 4-nitrophénol sur par voie humide sur la surface du sol et de l’eau. La l’environnement et la santé humaine. Les données prises principale voie de transformation du 2-nitrophénol en compte dans ces mises au point vont jusqu’en 1992. présent dans l’atmosphère est vraisemblablement sa Une recherche bibliographique exhaustive a été effectuée nitration rapide en 2,4-dinitrophénol, le 4-nitrophénol en 1998 sur plusieurs bases de données afin de relever étant quant à lui en majeure partie fixé aux particules les références intéressantes sur le 2- et le 4-nitrophénol aéroportées et donc disponible en petites quantités publiées après celles qui figurent dans les documents de seulement pour des réactions photochimiques. La base et d’obtenir toutes celles qui contiennent des majeure partie du 4-nitrophénol devrait d’ailleurs données utiles sur le 3-nitrophénol. On a trouvé très peu disparaître de l’atmosphère en se déposant soit par voie de données sur cet isomère, ce qui rend impossible une sèche, soit par voie humide. Il ne semble pas que les véritable évaluation. Les données concernant cet nitrophénols contribuent directement à la dégradation de isomère sont donc récapitulées à l’appendice 1. On la couche d’ozone stratosphérique ni au réchauffement trouvera à l’appendice 2 des indications sur le mode général de la planète. Soumis à une photodécomposition d’examen par des pairs ainsi que sur les sources en milieu aqueux, le 4-nitrophénol a une demi-vie qui documentaires utilisées. Les renseignements concernant peut aller de 2,8 à 13,7 jours selon les mesures. Les l’examen du CICAD par des pairs font l’objet de l’appen- nombreuses études consacrées à la biodégradation du 2- dice 3. Ce CICAD a été approuvé en tant qu’évaluation et du 4-nitrophénol montrent que ces deux isomères sont internationale lors de la réunion du Comité d’évaluation intrinsèquement biodégradables dans l’eau en aérobiose. finale qui s’est tenue à Washington du 8 au 11 décembre La minéralisation des nitrophénols en anaérobiose exige 1998. La liste des participants à cette réunion figure à à l’évidence une importante adaptation des populations l’appendice 4. La fiche d’information internationale sur la microbiennes. sécurité chimique (ICSC No 1342) relative au mélange d’isomères du nitrophénol, établie par le Programme La valeur du coefficient de sorption par les international sur la sécurité chimique (IPCS, 1998) est particules du sol (Koc), qui se situe entre 44 et 530, également reproduite dans ce document. indique que le potentiel de sorption est faible à modéré. Les nitrophénols qui passent dans le sol vont vraisem- Les isomères du nitrophénol sont des solides blablement subir une biodégradation aérobie. Il ne solubles dans l’eau qui sont légèrement acides dans ce devrait y avoir infiltration dans les eaux souterraines que solvant par suite de leur dissociation. Les isomères 2- et lorsque les conditions ne sont pas favorables à une bio- 4- sont utilisés comme intermédiaires dans la synthèse dégradation. Pour le 2- et le 4-nitrophénol, la mesure du d’un certain nombre d’insecticides organophosphorés et facteur de bioconcentration donne des valeurs allant de de composés à usage médical. Lorsqu’ils passent dans 11 à 76, ce qui indique un faible potentiel de bioconcen- l’environnement, c’est principalement par suite tration. d’émissions dans l’eau, l’air et le sol provenant de sources diffuses comme la circulation automobile ou la On connaît plutôt mal le profil toxicologique du 2- décomposition par photolyse ou hydrolyse de certains et du 4-nitrophénol. Lorsqu’il est administré à des insecticides. Le dépôt par voie sèche ou humide de animaux de laboratoire par voie orale, intraveineuse ou nitrophénols présents dans l’atmosphère constitue un intrapéritonéale, le 4-nitrophénol est en majeure partie apport supplémentaire dans l’hydrosphère et la géo- excrété dans les urines en l’espace de 24 à 48 h sous sphère. La formation photo-oxydative du 2- et du 4- forme de glucuronide ou de sulfo-conjugué, une faible nitrophénol dans l’atmosphère est encore débattue. partie seulement passant dans les matières fécale ou restant inchangée. On a montré que la proportion de Les données disponibles montrent que le 2-nitro- glucuronide et de sulfo-conjugués variait selon les phénol ne devrait se volatiliser que lentement dans espèces. Après administration par voie orale à des

35 Concise International Chemical Assessment Document 20 lapins, le 4-nitrophénol est réduit en p-aminophénol et sur des mammifères, il n’est pas possible de savoir si le subit aussi une transformation en glucuronide et sulfo- pouvoir mutagène de cet isomère peut s’exprimer in vivo. conjugués. Les données tirées des études in vivo et in vitro donnent une indication sur la résorption du 4- Chez la souris l’application cutanée de 4-nitro- nitrophénol par la voie transcutanée. En revanche, les phénol pendant une durée de 78 semaines n’a pas donné données concernant le 2-nitrophénol sont très limitées. d’indices d’effets cancérogènes. Dans une autre étude Quoi qu'il en soit, on peut considérer, en se basant sur sur la souris, qui présentait toutefois un certain nombre les données disponibles, que les deux isomères ont un d’insuffisances, on n’a pas non plus observé de tumeurs métabolisme comparable. Le 2- et le 4-nitrophénol ne cutanées après application cutanée de ces deux isomères devraient pas s’accumuler dans l’organisme en raison de pendant 12 semaines. Aucune étude de cancérogénicité leur métabolisation et de leur excrétion rapides. utilisant la voie orale ou respiratoire n’était disponible.

Les études de toxicité aiguë montrent que le 4- Les données relatives au 4-nitrophénol ne révèlent nitrophénol a un effet nocif après ingestion et qu’il est aucun effet indésirable sur la reproduction ou le plus toxique que le 2-nitrophénol. Chez des chats, on a développement qui soit statistiquement significatif après constaté une augmentation du taux de méthémoglobine exposition de rats et de souris par voie orale ou cutanée. liée à la dose après ingestion de 2-nitrophénol; la même Après administration par voie orale de 2-nitrophénol à constatation a été faite chez des rats après inhalation de des rats, on a constaté dans la progéniture des animaux 4-nitrophénol. Une exposition répétée à du 4-nitrophénol des effets indésirables sur le développement, mais a montré que la formation de méthémoglobine est l’effet seulement aux doses toxiques pour les mères. On n’a le plus déterminant d’une exposition par la voie toutefois pas recherché la présence de malformations respiratoire et cela vaut sans doute aussi pour la voie internes. orale. Parmi les autres effets observés, on peut citer un moindre gain de poids, une modification du poids des La base de données relative au 2-nitrophénol est organes, une dégénérescence graisseuse du foie et des extrêmement limitée et celle qui concerne le 4-nitrophénol anomalies hématologiques. Il n’a pas été possible de est insuffisante pour qu’on puisse en tirer une valeur dégager une véritable relation dose-réponse ni de fiable de la NO(A)EL. Il est donc impossible de fixer pour déterminer de manière fiable la dose sans effet (nocif) l’instant une valeur pour la dose journalière tolérable observable (NO(A)EL) correspondant à ces effets. (DJT) ou pour la concentration tolérable (CT) de ces deux isomères. Le 2-nitrophénol est légèrement irritant pour la peau mais il n’irrite pas la muqueuse oculaire. Le test de D’après les résultats des études toxicologiques Buehler montre que le composé n’a pas non plus d’effet valables effectuées sur divers organismes aquatiques , sensibilisateur. En s’appuyant sur des études valables on peut considérer que ces deux nitrophénols sont effectuées sur l’animal, on peut conclure que le 4- modérément à fortement toxiques pour la vie aquatique. nitrophénol a par contre une légère action irritante sur la La concentration sans effet la plus faible qui ait été peau et les yeux. Un test de maximalisation sur le cobaye obtenue lors d’études de longue durée sur des a montré que le 4-nitrophénol avait également une légère organismes d’eau douce (Scenedesmus subspicatus, action sensibilisatrice. Chez l’homme, on ne peut exclure EC50 à 96 h : 0,39 mg de 2-nitrophénol/litre; Entosiphon une légère sensibilisation après un contact avec le sulcatum, concentration minimale inhibitrice à 72 h ou composé, d’autant plus que la pose d’un timbre cutané CMI : 0,83 mg de 4-nitrophénol/l) était 40 à 50 fois plus chez des ouvriers pouvant avoir été en contact avec du forte que la valeur maximale obtenue dans un bassin 4-nitrophénol a permis de constater une telle fluvial d’Asie situé dans une zone très industrialisée et sensibilisation. densément peuplée (respectivement 0,0072 mg/l et 0,019 mg/l). Par conséquent, malgré la biodégradation et la Aucun des deux isomères n’a fait l’objet décomposition photochimique, les nitrophénols d’épreuves de génotoxicité suffisamment complètes. déversés dans l’eau peuvent présenter un certain risque S’agissant du 2-nitrophénol, les données sont insuf- pour les organismes aquatiques sensibles, notamment fisantes pour que l’on puisse tirer la moindre conclusion dans des eaux superficielles où les conditions ne sont concernant une mutagénicité éventuelle. Dans le cas du pas favorables à ces deux modes d’élimination. 4-nitrophénol, les études de mutagénicité sont plus Cependant, compte tenu de leurs usages et de leurs nombreuses, mais le compte rendu en est parfois possibilités de libération dans l’environnement, ces deux insuffisant. On est fondé à penser que ce composé est nitrophénols ne présentent qu’un risque mineur pour les susceptible de provoquer des aberrations chromoso- organismes aquatiques. miques in vitro. Faute d’études de mutagénicité in vivo

36 Mononitrophenols

Les données disponibles indiquent que la toxicité potentielle de ces nitrophénols est modérée dans l’envi- ronnement terrestre. Le calcul du rapport d’exposition toxique (TER) des nitrophénols provenant de la décom- position de certains pesticides montre que, dans ce milieu, le risque reste faible pour la faune et la flore, même dans la pire des hypothèses.

37 Concise International Chemical Assessment Document 20

RESUMEN DE ORIENTACIÓN Con los datos disponibles sólo cabe esperar una volatilización lenta desde el agua hacia el aire para el 2- nitrofenol y no significativa para el 4-nitrofenol. El 2- Preparó el presente CICAD sobre los isómeros 2-, nitrofenol se enriquece en la fase líquida de las nubes, 3- y 4-nitrofenol el Instituto Fraunhofer de Toxicología y mientras que es posible encontrar más 4-nitrofenol del de Investigación sobre los Aerosoles de Hannover, previsto a partir de los datos fisicoquímicos en la fase Alemania. Se basa en los exámenes compilados por el gaseosa de las nubes, debido a una amplia unión a Comité Consultivo Alemán sobre las Sustancias partículas. Habida cuenta de la solubilidad en agua y la Químicas Importantes para el Medio Ambiente (BUA, presencia prevista en la fase de vapor, cabe esperar una 1992) y la Agencia para el Registro de Sustancias deposición húmeda de nitrofenoles del aire en las aguas Tóxicas y Enfermedades de los Estados Unidos superficiales y en el suelo. La vía principal de trans- (ATSDR, 1992) para evaluar los efectos potenciales del formación del 2-nitrofenol emitido a la troposfera debe 2- y el 4-nitrofenol en el medio ambiente y en el ser ser la nitración rápida a 2,4-dinitrofenol, mientras que se humano. En estos exámenes se incluyeron los datos supone que la mayor parte del 4-nitrofenol suspendido identificados hasta 1992. En 1998 se realizó una en el aire se encuentra unido a partículas y, por con- búsqueda bibliográfica amplia de varias bases de datos siguiente, disponible solamente en menor cantidad para para identificar todas las referencias importantes reacciones fotoquímicas. La mayor parte del 4-nitrofenol relativas al 2- y el 4-nitrofenol publicadas con del aire debe precipitar por deposición húmeda y seca. posterioridad a las que figuran en los documentos No se considera que los nitrofenoles contribuyan originales y para conocer todas las referencias con datos directamente al agotamiento de la capa de ozono pertinentes sobre el isómero 3-nitrofenol. La información estratosférico o al calentamiento mundial. La semivida obtenida sobre el 3-nitrofenol fue muy escasa, lo que medida para la descomposición fotoquímica del 4- impide una evaluación válida. En consecuencia, los nitrofenol en agua osciló entre 2,8 y 13,7 días. Numero- datos sobre este isómero se resumen en el apéndice 1. La sos estudios sobre la biodegradación del 2- y el 4- información relativa al carácter del examen colegiado y a nitrofenol indican que los isómeros son inherentemente la disponibilidad de los documentos originales figura en biodegradables en agua en condiciones aerobias. La el apéndice 2. La información sobre el examen colegiado mineralización de los nitrofenoles en condiciones de este CICAD se presenta en el apéndice 3. Este CICAD anaerobias requiere evidentemente una amplia adap- se aprobó como evaluación internacional en una reunión tación de las comunidades microbianas. de la Junta de Evaluación Final celebrada en Washington, DC, Estados Unidos, los días 8-11 de Los coeficientes de sorción en el suelo (Koc) diciembre de 1998. La lista de participantes en esta medidos del orden de 44-530 indican un potencial de reunión figura en el apéndice 4. La Ficha internacional de bajo a moderado para la sorción en el suelo. Los seguridad química (ICSC 1342) para las mezclas de nitrofenoles liberados al suelo se deben biodescomponer isómeros de nitrofenoles, preparada por el Programa en condiciones aerobias. Cabe prever filtración hacia el Internacional de Seguridad de las Sustancias Químicas agua freática sólo en condiciones desfavorables para la (IPCS, 1998), también se reproduce en el presente biodegradación. Para el 2- y el 4-nitrofenol, los factores documento. de bioconcentración medidos de 11 a 76 ponen de manifiesto un potencial bajo de bioacumulación. Los isómeros del nitrofenol son sólidos hidro- solubles con una acidez moderada en agua debido a la Se dispone sólo de información limitada relativa a disociación. El 2-nitrofenol y el 4-nitrofenol se utilizan los perfiles toxicológicos del 2- y el 4-nitrofenol. Los como intermediarios en la síntesis de diversos animales experimentales a los que se administró 4- plaguicidas órganofosforados y algunos productos nitrofenol por vía oral, intravenosa o intraperitoneal médicos. La liberación en el medio ambiente se produce excretaron la mayor parte de la dosis aplicada por vía fundamentalmente por emisiones en el aire, el agua y el urinaria en un plazo de 24-48 horas en forma de conju- suelo a partir de fuentes difusas, como el tráfico de gados de glucurónidos y sulfatos, mientras que por las vehículos y la degradación hidrolítica y fotolítica de los heces se excretaron solamente cantidades muy respectivos plaguicidas. También se produce liberación pequeñas, o bien como 4-nitrofenol inalterado. Se en la hidrosfera y la geosfera a partir de la atmósfera observó que los porcentajes de conjugados de debido a la deposición seca y húmeda de nitrofenoles glucurónidos y sulfatos eran dependientes de la especie suspendidos en el aire. La formación fotooxidativa de 2- y de la dosis. Tras la administración oral a conejos, el 4- y 4-nitrofenol en la atmósfera es todavía objeto de nitrofenol sufre una reducción a p-aminofenol, así como estudio. una glucuronización y sulfatación. Los datos disponibles de estudios in vivo e in vitro dan una idea

38 Mononitrophenols de la absorción cutánea del 4-nitrofenol. Los datos para carcinogénicos. En otro estudio con ratones, que tiene el 2-nitrofenol son muy limitados. Sin embargo, teniendo varias limitaciones, no se detectaron tumores cutáneos cuenta los datos disponibles, se supone que se produce tras la aplicación en la piel de 2- ó 4-nitrofenol durante 12 una transformación metabólica comparable. No cabe semanas. Para ninguno de los isómeros había estudios prever bioacumulación de 2- y 4-nitrofenol en los de carcinogenicidad utilizando la vía oral o la inhalación. organismos debido a la rapidez de su metabolismo y excreción. Los datos disponibles para el 4-nitrofenol no pusieron de manifiesto efectos específicos o estadística- En estudios de toxicidad aguda, el 4-nitrofenol es mente significativos de toxicidad reproductiva o del perjudicial tras la absorción oral, y se observó que era desarrollo tras la administración cutánea u oral a ratas y más tóxico que el 2-nitrofenol. Se detectó un aumento en ratones. En un estudio de administración por vía oral a la formación de metahemoglobina dependiente de la ratas, el 2-nitrofenol indujo efectos en el desarrollo de la dosis en gatos tras la exposición oral al 2-nitrofenol y en camada sólo con dosis que también producían toxicidad ratas tras la exposición por inhalación al 4-nitrofenol. materna. Sin embargo, en estos estudios no se examin- Después de una exposición repetida al 4-nitrofenol, se aron los fetos para investigar malformaciones internas. observó la formación de metahemoglobina como el efecto final más importante de la exposición por La base de datos para el 2-nitrofenol es inhalación, y se considera que esto es aplicable también enormemente limitada y la relativa al 4-nitrofenol es a la exposición oral. Otros efectos observados fueron la insuficiente para deducir valores fidedignos de la reducción del aumento del peso corporal, diferencias en (NO(A)EL). Por consiguiente, es imposible determinar en el peso de los órganos, degeneración adiposa focal del este momento la ingesta diaria tolerable o las hígado y cambios hematológicos. Para esos efectos no concentraciones tolerables para el 2- ó el 4-nitrofenol. fue posible determinar una relación clara dosis-respuesta o concentraciones sin efectos (adversos) observados De los resultados disponibles de pruebas válidas (NO(A)EL) fidedignas. sobre la toxicidad del 2-y el 4-nitrofenol para diversos organismos acuáticos, los nitrofenoles se pueden El 2-nitrofenol es ligeramente irritante para la piel, clasificar como sustancias con una toxicidad entre pero no para los ojos. En una prueba de Buehler no se moderada y alta en el compartimento acuático. Las observó efecto sensibilizador. Tomando como base los concentraciones más bajas con efectos obtenidas en estudios válidos con animales experimentales, se supone estudios crónicos con organismos de agua dulce que el 4-nitrofenol tiene efectos irritantes en la piel y los (Scenedesmus subspicatus, CE50: 0,39 mg de 2-nitro- ojos. En una prueba de maximización en cobayas, se fenol/litro a las 96 h; Entosiphon sulcatum, concentra- observó que el 4-nitrofenol era ligeramente sensibili- ción inhibitoria mínima a las 72 horas: 83 mg de 4- zante. En el ser humano no se puede excluir una posible nitrofenol/litro) fueron 40-50 veces superiores a los sensibilización tras el contacto con 4-nitrofenol, niveles máximos determinados en una cuenca fluvial especialmente teniendo en cuenta que se ha observado asiática densamente poblada y muy industrializada sensibilización cutánea en pruebas de parche en (0,0072 mg de 2-nitrofenol/litro y 0,019 mg de 4-nitro- trabajadores de fábricas que podían haber estado fenol/litro). Por consiguiente, a pesar de la descomposi- expuestos al 4-nitrofenol. ción biótica y fotoquímica, los nitrofenoles emitidos al agua pueden representar algún peligro para los organis- No se ha sometido a pruebas completas de mos acuáticos sensibles, particularmente en las condici- genotoxicidad ninguno de los dos isómeros del ones de las aguas superficiales que no favorecen ambas nitrofenol. Los datos disponibles sobre el 2-nitrofenol vías de eliminación. Habida cuenta de sus pautas de uso son insuficientes para poder sacar conclusiones acerca y sus características de liberación, probablemente los de su posible mutagenicidad. Hay más estudios de nitrofenoles plantean sólo un pequeño riesgo para los mutagenicidad para el 4-nitrofenol, aunque algunos se organismos acuáticos. notificaron de manera inadecuada. Hay pruebas que parecen indicar que el 4-nitrofenol puede producir Los datos disponibles indican solamente una aberraciones cromosómicas in vitro. En ausencia de toxicidad potencial moderada de los nitrofenoles en el estudios de mutagenicidad in vivo en mamíferos, no es medio ambiente terrestre. A partir de los cálculos de la posible llegar a la conclusión de si se expresa o no in razón exposición-toxicidad de los nitrofenoles a partir de vivo el potencial mutagénico del 4-nitrofenol. la degradación de plaguicidas, sólo cabe esperar un pequeño riesgo para los organismos en este comparti- Tras la aplicación cutánea de 4-nitrofenol a mento, incluso en el peor de los casos. ratones durante 78 semanas no se observaron efectos

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