Peer Reviews of the Draft Dossier

Track A review : PeCB

PEER REVIEWS OF THE DRAFT DOSSIER Pentachlorobenzene

REVIEWER: Ingrid Hauzenberger

Summary: Introduction Pentachlorobenzene (PeCB) belongs to the group of chlorinated benzenes. Due to their risk profile PeCB is severely restricted or banned in many countries. Thus levels in the environment have decreased during the past years. However releases still occur from various sources (e.g. barrel burning of households, pesticide use). Monitoring data show that PeCB is present in all environmental media including humans and in remote areas.

Method The review evaluates critically the technical content of the proposal like in governmental documents and risk assessments. The risk profile was compared against the indicative numerical values given in EB 1998/2. In addition the submitted data in the proposal were assessed for their quality and completeness. The factors that had been taken into account for the conclusions on para. 2 a-b of EB 1998/2 were also recorded.

POP characteristics-Summary of dossier in terms of the guidance and indicative numerical values provided in Executive Body Decision 98/2 for:

Potential for long-range atmospheric transport: Based on the submitted data (vapour pressure, half-life, model calculation and monitoring data) it can be assumed, that PeCB is subject to LRAT. The indicative numerical values given in EB 1998/2 regarding vapour pressure and atmospheric half-life are fully met.

Toxicity and ecotoxicity: There is sufficient evidence that PeCB has a high (eco)toxic potential and can adversely effect human health and the environment. The requirement of EB 1998/2 with regard to toxicity is met.

Persistence: Based on the provided information PeCB exhibits a half-life in water > two months. Also in sediment PeCB is resistant to biodegradation. Under certain conditions PeCB might be degraded in soil. However all reported half-lives except one exceed the indicative numerical value given in EB 1998/2. It can be concluded that PeCB is persistent in the environment.

Bioaccumulation: The submitted data show that PeCB has a high bioaccumulation potential, which is substantiated by log Kow of around 5 and BCFs up to 260 000. Tests under suggested steady-state conditions and a field study gained BCF values on wet weight basis above the indicative numerical values of EB 1998/2. One BAF value determined in a Track A review : PeCB

terrestrial model species suggests an extremely high bioaccumulation potential.

Monitoring or equivalent scientific information suggesting long-range transboundary atmospheric transport Based on submitted monitoring data from remote regions it can be concluded that PeCB is susceptible to LRAT. Though environmental concentrations are declining PeCB can still be detected in sensitive areas such as the Arctic and in biota.

Sufficiency of the information to suggest that the substance is likely to have significant adverse human and/or environmental effects resulting from its long-range transboundary atmospheric transport – Human and wildlife are exposed to a cocktail of different contaminants in the environment including remote regions. Therefore it will be difficult to relate or predict effects to one single compound, especially if they have high hazard potentials. In this respect the PEC/PNEC approach is not a suitable tool to protect ecosystems in sensitive areas. PeCB exhibit persistent, bio -accumulative and toxic properties. Due to the widespread distribution of PeCB in the environment including remote regions, the occurrence in arctic top predators and the hazard potential, adverse effects on human health and the environment cannot be excluded.

Conclusions- The dossier is well prepared, updated and fulfils the requirements of EB decision 1998/2. However, data on human health could be more comprehensive.

Introduction A proposal on pentachlorobenzene (PeCB) prepared by the Netherlands was submitted on behalf of the European Commission to the UN ECE secretariat for consideration as a potential POP amending Annex I of the POP Protocol. According to the EB decision 1998/2 the proposal includes a risk profile, which addresses risks to human health and the environment associated with the uses and releases and a summary report on e.g. monitoring and degradation data. It further states that if the risk profile is deemed acceptable a technical review of the proposal shall be prepared. This technical review serves this purpose concerning the Track A review, which is limited to the evaluation of the proposal against the indicative numerical values according para 1. a-d and para 2. a-b of EB 1998/2. The review evaluates critically the technical content of the proposal like in governmental documents and risk assessments. The review evaluates critically the technical content of the proposal like in governmental documents and risk assessments. The review is based on the information contained in the dossier, an addendum to the dossier and the response to the comments to the dossier. As agreed additional information e.g. from open literature was only considered in critical cases or if more recent relevant information was available. The risk profile was compared against the indicative numerical values given in EB 1998/2. In addition the submitted data in the proposal were assessed for their quality and completeness. The factors that had been taken into account for the conclusions on para. 2 a-b of EB 1998/2 were also recorded. Track A review : PeCB

POP characteristics

a) Potential for long-range atmospheric transport (LRAT)

EB 1998/2 considers for LRT the evidence that the substance has a vapour pressure below 1 000 Pa and an atmospheric half-life greater than two days. Or alternatively, monitoring data showing that the substance is found in remote regions. Based on the vapour pressure of around 2 Pa PeCB can be considered as semi- volatile. The Henry’s Law Constant confirms that volatilisation from surface water and moist soil can take place (HSDB, 2003). In the atmosphere PeCB might remain as a vapour and is susceptible to photooxidation at a very slow rate. The calculated atmospheric half-life is 45 to 467 days, but no further information explaining this wide range is given in the proposal. Monitoring data indicate that the wide distribution of PeCN in the northern hemispheric atmosphere is a result of the long atmospheric residence time. Monitoring and model data by EMEP also show the ability of PeCB (i.e. high calculated transport distance) to undergo LRAT. Conclusion: Based on the submitted data (vapour pressure, half-life, model calculation, monitoring data) it can be assumed, that PeCB is subject to LRAT. The indicative numerical values given in EB 1998/2 regarding vapour pressure and atmospheric half-life are fully met.

b) Persistence

The indicative numerical values for persistence according EB 1998/2 are half-life in water greater than two months, or half-life in soils or sediments greater than six months. Alternatively, evidence that the substance is otherwise sufficiently persistent to be of concern within the scope of the protocol. Abiotic degradation of PeCB was observed in a laboratory photolysis study using an organic solvent/water solution 1:9. However, based on the hydrophobic characteristic of the substance adsorption to suspended matter in the water column and transport to the sediment can be expected. Thus under field conditions susceptibility to photodegradation is likely to be limited. The proposal reported estimated half-lives for photodegradation of > six month. The degradation rate in sediment is low despite the occurrence of anaerobic conditions, which can favour reductive dechlorination. The dossier also pointed out, that occurrence of PeCB from metabolism of HCB is possible. The reported half-lives in soil under anaerobic conditions were several years. Laboratory soil studies indicate half-lives greater than six months. Information on HCB, which can also be of relevance, shows that under water saturation high rates of dechlorination are observed (Brahushi et al., 2004). In an agricultural field study the decrease of PeCB was partly attributed to volatilisation. Reported half-lives are 103 and 219 days. Conclusion: Based on the provided information PeCB exhibits a half-life in water > two months. Also in the sediment PeCB is resistant to biodegradation. In soil certain conditions may occur which favour PeCB degradation resulting in half-lives less than six months. However these applies only to one reported value in the proposal. All other reported half-lives in soil exceed the indicative numerical value given in EB 1998/2. Track A review : PeCB

c) Bio-accumulation

Indicators for bio-accumulation according EB 1998/2 are (i) a BCF or BAF greater than 5 000 or a log Kow greater than 5; or alternatively, if the bio-accumulation potential is significantly lower than (i) other factors, such as high toxicity of the substance, that make it of concern within the scope of the protocol. The proposal gives a good overview on the range of reported BCFs (from 1 800 to 260 000), which reflects different test designs and conditions as well as differences in expression of BCFs. Though the BCF related to lipid content enables good comparison of test results, regulatory bodies (e.g. EU, EPA) use trigger values based on BCF wet weight basis. Taking the comments from industry into consideration data and explanations for BCFs and log Kow have improved. However, detailed test conditions (e.g. lipid content of test species), if available at all, were not reported und could have contributed to a better interpretation of the reported values. The submitted data (including a field study) show that uptake of PeCB in aquatic species can result in very high BCF values. Furthermore an elimination half-live greater than 300 days for eels was found (WHO, 2004), which also flags the accumulation potential of this substance. US EPA (1998) used a BCF value of 8 314 to characterise the bioaccumulation potential of PeCB. A BAF of 401 000 was determined in a terrestrial species (E. andrei) (Government of Canada, 2003). The log Kow is around 5 (4.8 to 5.2, whereas 5 out of 7 measurements were slightly above 5) and indicates further the high potential for bioaccumulation. Conclusion: The submitted data show that PeCB has a high bioaccumulation potential, which is substantiated by a log Kow of around 5 and a range of BCF values from 1 800 up to 260 000. The high variation of BCF values is probably based on different expression of BCFs and test conditions. However, tests under suggested steady-state conditions and a field study reveal BCF values on wet weight basis above the indicative numerical values of EB 1998/2. One BAF value determined in a terrestrial model species suggests an extremely high bioaccumulation potential.

d) Toxicity and ecotoxicity

EB 1998/2 describes toxicity as adverse effects to human health and/or the environment. Ecotoxicity: The toxicity of chlorobenzenes to aquatic organisms increases with increasing chlorination partly due to increased uptake and bioaccumulation of higher chlorinated compounds (WHO, 2004). The proposal compiles acute and subchronic toxicity data for aquatic organism (algae, crustaceans and fish) from regulatory bodies and IPCS/WHO. Based on a LC50 of 250 µg/l in fish and a NOEC of 10 µg/l in crustaceans PeCB can be regarded as very toxic to aquatic organisms. PeCB is also toxic to algae (Sicko-Goad et al., 1989). No data were available on sediment dwelling organisms or other terrestrial species and wildlife. Human Health: The dossier recapitulates data from animal experiments with PeCB. The lowest LD50 value for acute toxicity (oral exposure, rats) was found to be 250 mg/kg bw. In a subchronic study a NOEC of 12,5 mg/kg was established. Negative results were obtained in Ames test, other mutagenicity tests with mammalian cells which were found to be negative (IRIS, Toxnet) were not mentioned in the proposal. The dossier points out that PeCB has been classified concerning carcinogenicity in Track A review : PeCB

Group V (inadequate data for evaluation). Data from rat and monkey metabolism studies, Engst et al. (1976) and Rozman et al. (1979) where pentachlorophenol (classified as B2, probable human carcinogen) was found to be one major metabolite of pentachlorobenzene are missing in the proposal. Pentachlorophenol has also been identified in the urine of rabbits administered pentachlorobenzene (Kohli et al., 1976). In the adapted dossier another toxicity study from NTP with rats and mice was included. NOELs for histological lesions in the liver in rats were found to be 33 ppm for male rats and 330 ppm for female rats, whereas the NOEL for histological lesions in female mice was 100 ppm and no NOEL could be determined for male mice. Blood abnormalities were reported as well. From the reviewers point of view several important findings were not mentioned in the proposal. The organs most affected by exposure with PeCB were beside the liver the kidneys in rats, with male rats being more sensitive. Thyroid gland effects also occurred in rats, though they were observed in the 1000 and 2000 ppm dose group only. From the ethical point of view the term “epidemiologic studies” should be used instead of the term “human studies” in the proposal. Conclusion: There is sufficient evidence that PeCB has a high (eco)toxic potential and can adversely effect human health and the environment. The requirement of EB 1998/2 with regard to toxicity is met.

Release to the environment a) Environmental levels The proposal reported monitoring data in different media: air (including precipitation), sediment, soil and biota (mosses, mussel, blubber, fish, bird and bear) focusing on remote regions. Data on PeCB levels in seawater were obtained by Strachan et al. (2001) who investigated PeCB concentrations in the Bering and Chukchi Sea. Industry provided additional information on herring gull eggs, sediment and suspended matter from the Great Lakes and Niagara river. Data demonstrated that PeCB concentrations declined steadily in this region. A trend which is confirmed by other monitoring data, mainly obtained from industrial regions (HSDB, 2003). Recently more data has become available for remote areas. According to Government of Canada (2003) peak chlorobenzenes (PeCB and HCB) concentrations in northern lake sediments also dated back to the late 1970s and 1980s. Nevertheless PeCB still occur in environmental media and biota in remote regions. Monitoring data could not show a declining trend for Σchlorobenzenes in polar bears (Verreault et al., 2005). However, only the sum of chlorobenzenes including PeCB was reported. Concentrations of PeCB were elevated in bottom sediments from harbours of northern Norway and the Kola Peninsula compared to previous reports for background areas at offshore locations (de March et al., 1998 in AMAP, 2004). However these concentrations could also originate from arctic local sources. b) Levels in humans and biota compared to effect levels PeCB is detected in environmental media as well as in biota. PeCB has also been detected in human adipose tissue and human milk (e.g. Smeds and Saukko, 2001). Currently there is no adequate scientific tool available to estimate risks arising from substances, which show persistent, bioaccumulative and toxic properties. In this respect the PEC/PNEC approach is not a suitable tool to protect sensitive areas such as the Arctic. Ecotoxicity data were also limited for such a comparison (no effect data for sediment-dwelling or soil-born organisms, birds or wildlife are available). Track A review : PeCB

Compared to the high aquatic toxicity, levels in some arctic species were also relative high. However, due to the fact that contamination of human and environment is not restricted to PeCB it is difficult to relate effects to this special compound. As it is shown in polar bears (Verrault et al., 2005) exposure occurs through a suite of chlorinated hydrocarbons, including organochlorine pesticides and by products, polychlorinated biphenyls and metabolites of these compounds. Several classes of compounds like heavy metals, PBDE, PFOS which were not investigated in this study also contribute to the body burden of polar bears and other species of remote regions, including marine mammals as it is shown in other publications. Such compounds can alter biological functions and behaviour in several ways and can contribute to a reduced fitness and/or more severe effects. Therefore any effort should be taken to reduce body burden and environmental concentrations to chlorinated hydrocarbon contaminants. Taking into consideration the arguments above this is in contradiction to the statement of industry, which claimed that insufficient evidence for significant exposure to biota in remote regions exsists.

Conclusion PeCB can be characterised as persistent, toxic and bioaccumulative. Though emissions from PeCB have been effectively reduced this compound can still be found in environmental media and biota including humans. PeCB has recently been detected in a variety of arctic species including top predators. Organisms and humans are exposed to a cocktail of different contaminants. Ecotoxicity effect data are limited and synergistic effects are difficult to predict. Therefore any effort should be taken to reduce body burden and environmental concentrations of these contaminants. According to the risk profile of PeCB adverse effects to humans and the environment including remote areas cannot be excluded. The dossier is well prepared, updated and fulfils the requirements of EB decision 1998/2. However, data on human health could be more comprehensive.

Acknowledgment Special thanks to Dr. Maria Uhl for her cooperation and review of the human health part.

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