EXPLOSIVES 409 CHIMIA 2004, 58, No. 6

Chimia 58 (2004) 409–413 © Schweizerische Chemische Gesellschaft ISSN 0009–4293

Toxicity and Degradation of

Hans Stucki*

Abstract: Safety regulations about handling energetic materials deal mostly with the protection of man against ex- plosions. Explosives contain many components with toxic hazards where protection measures are necessary or a replacement by other substances should be considered. Not only the well-known toxins like aromatic nitro com- pounds, nitrosamines, mercury, and lead are important, but also hazardous burning and detonation products and metabolites arising in the environment need serious control. Residues of organic nitro compounds and nitrates in the environment show, influenced by the microbiology, slow degradation reactions. Recently developed com- pounds have to be investigated to assess toxicity risks and possible endocrine effects.

Keywords: Degradation · Energetic materials · Environmental impact · Explosives · Toxicity

1. Introduction 2. Toxic Aspects in Manufacturing Safety and Health (NIOSH) the DNTs are noted; TNT presents a lesser cancer risk Several explosives and the components in First of all, the safety procedures of the and is not on the list [1]. The DNTs nor- mixtures show toxic effects and chemical industry have to be observed when mally are more toxic for mammals than are impacting the environment. We can find manufacturing explosive substances. In ad- TNT, but TNT is a stronger toxin for fishes. acute toxicity, chronic infection, and the dition, the regulations dealing with the safe- Table 1 shows some toxic and carcinogenic risk for cancer when there is contact with ty and the protection of the workers against data of TNT and DNTs. the products over a prolonged period. In the possible explosions have to be followed. The toxic effects of TNT include blood environment, some explosives and their changes, cyanosis, methaemoglobinaemia burning residues can be persistent for very 2.1. Toxicity of Glycerol Trinitrate and toxic hepatitis. Contamination is possi- long times, others slowly decompose. (Nitroglycerine) ble by inhalation, ingestion and skin ab- These are the reasons why the workers Glycerol trinitrate (nitroglycerine) is sorption. Vaporization of melted TNT and in the explosives industry and people in used in medicine as a vasodilator. In case of dust at the workplace have to be avoided. contact with such materials have to take an attack of angina pectoris a nitroglycerine The other organic high explosives like care when manufacturing, handling, or capsule is placed under the tongue. This cyclotrimethylenetrinitramine (RDX), cy- using these products. The problems of helps dilate blood vessels and more blood clotetramethylenetetranitramine (HMX), the residues in the environment and the can reach the heart. and pentaerythritol tetranitrate (PETN) possible risks for man, animals and nature Nevertheless human beings have to be have lower vapor pressures and the toxic have to be clarified seriously. protected against chronic exposure to nitro- effects are of less importance. glycerine. This substance is usually ab- sorbed through the skin and by inhalation. 2.3. Mercury Fulminate Nitroglycerine can produce methaemoglo- The primary explosive mercury fulmi- binaemia and the body develops a tolerance nate was the product mainly used in earlier to this substance. Withdrawal from frequent times for percussion caps and as a detona- exposure to nitroglycerine may cause se- tor. In Swiss munitions production it was vere headaches. replaced by lead compounds and other products between 1950 and 1960, because 2.2. TNT and Other Aromatic Nitro many workers in the production plants Compounds showed health problems connected with The toxicity of aromatic nitro com- mercury. In modern explosives the mercury pounds is of great importance because of is no longer a problem. their wide distribution in munitions: 2,4,6- Low level poisoning with mercury leads trinitrotoluene (TNT) is present in bombs to fatigue, headaches, lack of concentra- and shells and dinitrotoluene (DNT) is used tion, hair loss until ultimately the central

*Correspondence: Dr. H. Stucki as an energetic additive in propellants. Not nervous system is attacked and brain and armasuisse only contact with the original substances liver are damaged. Science and Technology but also the natural impurities and the de- Feuerwerkerstrasse 39 composition products has to be controlled 2.4. Diphenylamine and CH-3602 Thun Tel.: +41 33 228 29 44 since these represent compounds with high- Nitrosamines Fax: +41 33 228 46 01 er toxic potentials. In the list of Diphenylamine (DPA) is often used as a E-Mail: [email protected] the US National Institute of Occupational stabilizer in nitrocellulose propellants. Af- EXPLOSIVES 410 CHIMIA 2004, 58, No. 6

Table 1. Toxicity and carcinogenic data of TNT and DNTs and extended environment of the site of combustion. Property 2,4,6-trinitro 2,4-dinitro 2,6-dinitro toluene (TNT) toluene toluene 3.3. Lead Dust in Indoor Shooting Ranges LD for rat 800–1300 mg/kg 268–650 mg/kg 177–795 mg/kg 50 The layout of ventilation systems in lethal dose, 50% kill closed shooting ranges is normally calcu-

LC50 for fish 2.4 mg/l 35.5 mg/l 19.8 mg/l lated to remove the carbon monoxide re- lethal concentration, 50% kill sulting from the incomplete burning of the propellants. Measuring the actual toxins in Carcinogenic class (D) possible possible unambiguous the air often shows that lead dust exceeds carcinogen (B2) carcinogen (B2) carcinogen (B1) the limits. The decomposition of lead sty- TDI = Tolerable Daily 0.05 µg 0.2 µg 0.0002 µg phnate and other lead compounds in the Intake per kg weight (D) percussion caps is responsible for the high lead emissions. Intensive shooting with pis- Equivalent factor for long-term 1 5 150 tols can result in a lead concentration in the exposure (TNT = 1) (D) air of more than 1 mg/m3. Most countries limit the long-term occupational exposure Permissible Exposure Limit 1.5 1.5 1.5 3 (mg/m3 in air) US-OSHA to 0.1 mg/m . This is the reason why lead-free primary mixtures like SINTOX® exist today and ammunition for pistols without lead in the percussion caps is available. Another ter long storage N-nitroso-DPA is detected, taining perchloronaphthalene as organic source for lead dust is the bullet. The sur- formed by the decomposition products of chlorine compound. The complete formula- face of the bullet must be protected, so that the nitrocellulose and the DPA. The ni- tion is listed in Table 2. The first small scale lead cannot be eroded in the gun. The com- trosamines have been described as a widely use and burning of this mixture for the cam- plete replacement of lead in the bullet ad- acting and potent group of and ouflage of military objects showed good re- versely influences the precision in shooting the US Occupational Safety and Health Ad- sults. On alpine pastureland in the central and leads to technical problems. ministration (OSHA) has classified these parts of Switzerland, large quantities of this chemicals as carcinogens [1]. They decom- product were burned off. After the tests pose and have an effect on the DNA in or- cows and other animals fell sick in these 4. Environmental Impact by ganisms. The aromatic nitroso compounds regions. 15’000 cows were involved in Explosives seem to be less dangerous as a cancer risk this environmental disaster – an ‘alpine than the aliphatic compounds. Nevertheless, Seveso’. 4.1. Mercury Residues at Old persons handling such products must be se- The perchloronaphthalene used in 1940 Shooting Ranges riously protected against any contact [2]. was of technical grade with a chlorine con- Analysis of the mercury content of the There are new efforts in the industry to tent of 62–64%, corresponding to a hexa- soil of old gun shooting ranges shows con- eliminate the DPA as a stabilizer in the chloronaphthalene. Other impurities in this centrations of 2–8 ppm of mercury at the lo- field of the explosives. One substitute product are unknown. The mechanism of cations where the guns were placed [4]. which is discussed, is triphenylamine in the formation of the highly toxic products This contamination is restricted to the sur- which formation of N-nitroso compounds has not been investigated and the com- face and to a layer of 20–40 cm in depth and is not possible. pounds could not be analyzed at that time, covers an area of few square meters. The but we can assume that the low burning limits for mercury contamination of the temperature facilitated the formation of soil, for instance in Switzerland at 0.5 ppm, 3. Toxicity Problems in the Use of chloro dioxins, similar to the toxins of are clearly exceeded. The contamination is Explosives Seveso. the result of the use of mercury fulminate before 1960 and it remains for a very long 3.1. Perchloronaphthalene Smoke 3.2. Current Smoke Compositions time. In 1940 the Swiss army introduced a At the present time, the most common- At old munitions demolition sites in the new smoke-generating composition, con- ly used main compounds in smoke produc- alpine regions, where the disposal of muni- ing mixtures are red phosphorous, zinc tions and explosives was carried out by compounds and PVC powders. Hexa- open burning and open detonation in the Table 2. Components of the hazardous perchlo- chloroethane (HC) as a further organic years before 1995, the mercury concentra- ronaphthalene smoke mixture used in 1940 in chlorine compound is used in mixtures tions of the soil reaches barely the limits, Switzerland abroad. These HC mixtures are able to pro- but the contaminated areas cover a surface Component Percentage [%] duce hexachlorobenzene in yields of ap- with a diameter of some hundred meters proximately 0.5% [3]. Practically all organ- [3]. Perchloronaphthalene 38 ic chlorine compounds produce traces of chloro dioxins, when burning occurs at low 4.2. Organic Explosives in the Zn and ZnO 25 temperatures. Environment Another problem when burning off red In some areas of military firing ranges Calcium silicide 6 phosphorous is the formation and conden- and in the central areas of former munitions Ammonium perchlorate 15 sation of small quantities of toxic white demolition grounds we can find residues of phosphorous, a risk for animals and man. various explosives in the soil. One source Ammonium chloride 15 Zinc as a current component in the smokes is incomplete detonation or deflagration, is slightly toxic and impacts the immediate which leads to fine or coarse explosive par- EXPLOSIVES 411 CHIMIA 2004, 58, No. 6

Table 3. Environmental behavior of explosives methyl-N,2,4,6,-tetranitroaniline. The concentrations of dissolved mate- Explosive Solubility in water Distribution: Adsorbance at Volatility, Hc rials, caused by the low solubilities and ab-

[mg/l, 20 °C] water/organic silicate, Kd [l/kg] (Henry const.) sorbance effects, never can reach danger- carbon log Koc [atm m3mole–1] ous levels in the soil and in water, if we discount the sites with mines, unexploded TNT 130 3.2 21’500 1.1 10–8 shells, and large pieces of unburnt or un-

–9 exploded explosives. The original state of PETN 43 (25 °C) 3.4 – 1.07 10 these lost objects after a period of 30–40 RDX 70 0.9–2.4 1.2 1.96 10–11 years in the soil or in the water is still vis- ible. It seems that not only the low solu- Tetryl 75 1.7–3.5 5.8 2.79 10–11 bility of these materials is responsible for the low concentrations found. The metal 2-ADNT 2800 0.4 2’900 – covers, the added wax and polymers, and 4-ADNT poorly soluble 1.0 125 – the large crystals of the cast TNT all seem to delay the speed of dissolution.

5.2. Degradation of TNT ticles in the surroundings. Another source plosives are used. The products used here All organic explosives and their of explosives are unexploded shells, which are mixtures of inorganic nitrates and chlo- residues show degradation in the water and penetrated into the ground without detonat- rates with mineral oils, paraffins and emul- in the soil, influenced by microorganisms, ing. Such unexploded shells are hard to de- gators as additives. The water solubility of light, oxygen and reducing chemicals. tect and to dispose of. some components is high and explosives Many investigations regarding the decom- Dumping waste ammunition in the sea residues impact the environment faster and position of TNT molecules in the environ- was common in many countries. Swiss mil- will degrade in shorter time. ment were executed and many degradation itary used lakes for the disposal of waste products are known [7–10]. Another source materials. This activity was discontinued in for the knowledge about the explosives and 1964 because of the introduction of a new 5. Degradation of Explosives in the the formation of metabolites in the environ- law concerning the protection of water. In Environment ment is the large amount of analytical data Switzerland, Lake Thun is the most affect- of soil and water samples, generated by the ed lake with an estimated amount of 3’000 5.1. Behavior of Explosives control analyses of sites with dangerous tons of deposited ammunition. The amount Military organic explosives normally waste residues or polluted by explosives of TNT, as the main organic explosive, is have a low solubility in water. The decom- [11]. estimated to be 500 tons. The degradation position of such materials needs a long Scheme 1 presents the postulated of the material and the liberation of chemi- time. TNT decomposition yields amino scheme for TNT degradation under aerobic cal substances are expected to be very slow compounds, which is why the two most conditions like in the water of a clear lake. [7]. An analysis of the water of Lake Thun commonly found compounds, 2-amino 4,6- In Lake Thun and in the uppermost layers was carried out, TNT and its metabolites DNT (2-ADNT) and 4-amino 2,6-DNT (4- of the sediments at the bottom of this lake could not be found within detection limits ADNT) are included in the considerations. the oxygen content of the water is dominant of 1–20 ng/l [5]. The environmental behavior, listed in sev- and the degradation seems to be aerobic. The situation is different at mining sites eral papers [6–8] is partly described in Degradation begins with the formation of and tunnel construction sites where civil ex- Table 3. Tetryl is the abbreviation of N- hydroxylamino compounds, which then

Scheme 1. Biological degradation of TNT in water under aerobic conditions [8][9]. a) and b) with high TNT concentrations, c) low TNT concentrations and corresponds to the situation in Lake Thun. A thick line indicates the main path. The most important end product is expected to be 2,4-diamino-6- nitro-toluene. EXPLOSIVES 412 CHIMIA 2004, 58, No. 6

Scheme 2. Biological degradation of TNT in water under anaerobic conditions [8][10]. A thick line indicates the main path. The most important tempo- rary products are expected to be mono-, di- and triamino toluene. form partial or complete amino com- they may have endocrine effects on wildlife munitions manufacturing. These residues pounds. These are stable for a limited time and man. come from the disposal of explosive wastes only; afterwards complete mineralization A report of the European Community and from acid used in the nitration process. takes place. [13], listing 147 candidates, includes the More than 50 years after contamination Anaerobic conditions are dominant in a compound 4-nitro toluene as a compound ended, TNT, its by-products and degrada- soil containing a high level of organic com- suspected to be potentially hormone-active. tion products are detectable in the soil and pounds, or in the deeper parts of sediments Additionally a WWF publication, dealing in the water [11]. Methods for a clean up of at the bottom of lakes and also when soil with the risks of artificial fragrances such soils are washing, thermal treatment or with contamination of explosives is remedi- [14] names the two aromatic nitro com- removal. Another method of decontamina- ated by composting methods. The anaero- pounds musk xylene and musk ketone, which tion, tested in the lab and in pilot plants, is bic situation is showed in Scheme 2. This are used as low-cost artificial musk fra- composting. The soil, containing low con- degradation seems to be similar for observ- grances, as endocrine-disrupting chemicals. centrations of explosives, is mixed with or- ing stable intermediate amines and for a The widely used explosives and their ganic materials like hay, grass, leaves, horse judgment of the toxic risks. degradation products need special exami- manure, and garden soil. At reaction tem- The reaction can start only when the nation concerning effects as endocrine dis- peratures of 60–80 °C, the explosives TNT, substances are in a fine distribution in the ruptors. In a first investigation a mixture RDX and HMX present in concentrations soil or dissolved in water. The first step of containing TNT, 2,6-DNT, 2,6-diamino-4- of 1%, disappeared completely within 10 TNT degradation is the reduction of a nitro nitrotoluene, 2,4-diamino-6-nitrotoluene, weeks [18][19]. This degradation occurs group to a hydroxylamino group. The influ- PETN, RDX and other energetic com- only when the explosives are finely distrib- ence of oxygen leads to the production of pounds was checked for hormone activity. uted; the problem of mines, unexploded intermediate azoxy compounds, followed The two employed test methods were: a shells and large pieces of unexploded or un- by the formation of amines. The resulting yeast oestrogen screen (Routledge and burnt explosives in the ground cannot be products with a certain stability can be ana- Sumpter) [15] and a yeast androgen screen solved by this method. lyzed. They are mono-, di-, and tri-amino (Purvis et al.) [16]. In these two assays not nitrotoluenes, formed in both cases, with only the estrogenic and androgenic activity 6.2. Thermal Destruction Plants and without the influence of oxygen. of the explosives, but also the anti-estro- In the period of 1990 to 2000 various in- The following degradation period, with genic and anti-androgenic activities were cineration plants for an ecological disposal the loss of nitrogen, formation of phenols, investigated. In none of these tests was an of energetic waste materials were con- and then complete decomposition and min- endocrine disrupting potential of the explo- structed. The disposal of ammunition and eralization, leading to CO2 and H2O, is less sives found [17]. This is a first indication explosives can be carried out with legal explored. that the examined explosives do not act as compliance in such plants. At the same endocrine disruptors via estrogen – or an- time, the NATO states, Switzerland and 5.3. Toxic and Endocrine Risks drogen receptors. Nevertheless we have to other nations did not allow destruction or Experiments of TNT with monkey, complete analysis of the range of explosive disposal of these materials by open burning mouse and rat showed paternal effects on compounds and metabolites and testing and open detonation. the testes, epididymis, sperm duct [12], but will continue in the near future. The most important part of an incinera- only with relatively high quantities of the tion plant is a rotary kiln incinerator with a explosive applied. The organic explosives thick-walled steel tube or an other robust contaminating the environment show most- 6. Disposal of Organic Explosives oven. After that follows a high-temperature ly no toxic effects, because of the low solu- secondary combustor. The gas stream is then bility, the low tendency of enrichment in bi- 6.1. Remediation of Contaminated cooled, washed and filtered; additionally a ological cycles and degradation in nature. Soil NOx removal tower is needed and mercury- Recently many chemicals impacting the en- Soil and groundwater contamination by containing materials require carbon black vironment are under discussion because TNT has resulted from TNT production and filters. The preparation of the explosive ma- EXPLOSIVES 413 CHIMIA 2004, 58, No. 6 terial, the subdivision into small parts is ex- Report of Eidg. Forschungsanstalt Wä- stances for further evaluation of their role in pensive. Dangerous rockets and hazardous denswil, CH, 2003. endocrine disruption’, Final report 2000. munitions are often cut in parts with the re- [6] R. Haas, ‘Stoffdatenblätter wichtiger [14] ‘ Fragrances’, WWF Pub- quired size by abrasive water jet equipment. Explosivstoffe’, Auszug aus UBA-Texten lication, 2000. 26/96, Umweltbundesamt, Berlin, D, 1996. [15] E.J. Routledge, J.P. Sumpter, ‘Estrogenic Acknowledgments [7] H. Stucki, ‘Die Munitionsmaterialien in Activity of Surfactants and Some of Their den Thunersee-Deponien und ihr toxi- Degradation Products Assessed Using a The author thanks all who have contributed sches und endokrines Potential’, Gruppe Recombinant Yeast Screen’, Environ. Tox- to this work. Special thanks to Mrs. Sonia Rüstung FS 261, Thun, CH, Report Nr. icol. Chem. 1996, 15(3), 241–248. Rodriguez Bares, Eidg. Forschungsanstalt 1723, 2003. [16] I.J. Purvis, D. Chotai, C.W. Dykes, D.B. Wädenswil, for literature search, analytical [8] S. Rodriguez Bares, T. Poiger, M.D. Lubahn, F.S. French, E.M. Wilson, A.N. work and drawing the schemes, Mrs. Nina Müller, H.P. Kohler, ‘Gewässerbelastung Hobden, ‘Androgen-Inducible Expression Schweigert, EAWAG Dübendorf, for testing durch Sprengstoffe im Thunersee’, Report System for Saccharomyces cerevisiae’, the hormone activity of explosives, Peter of Eidg. Forschungsanstalt, Wädenswil, Gene 1991, 106(1), 35–42. Mäder and Beat Berger for review of the paper CH, 2003. [17] N. Schweigert, ‘Oekotoxikologische Un- and Hansruedi Bircher for supporting this proj- [9] S. McFarlan, ‘2,4,6-Trinitrotoluene tersuchung der Sprengstoff-Proben ect. Graphical Pathway Map’, The University Thunersee’, Report of Swiss Federal Insti- of Minnesota Biocatalysis/Biodegradation tute for Environmental Science and Tech- Received: March 30, 2004 Database, http://umbbd.ahc.umn.edu/, nology (EAWAG), Dübendorf, CH, Dec. 2002. 2003. [1] ‘Carcinogen List’, National Institute for [10] S. McFarlan, G. Yao, ‘Anaerobic Trinitro- [18] D.L. Kaplan, A.M. Kaplan, ‘Thermophilic Occupational Safety and Health, NIOSH, toluene Pathway Map’, The University of biotransformation of 2,4,6-trinitrotoluene http://www.cdc.gov/niosh/npotocca.html, Minnesota Biocatalysis/Biodegradation under simulated composting conditions’, update 2002. Database, http://umbbd.ahc.umn.edu/, Appl. Environ. Microbiol. 1982, 44, [2] Houben-Weyl, ‘Methoden der organi- 2002. 757–760. schen Chemie’, Bd. E 16a / Teil 2, 1990. [11] H. Holland, ‘Erfahrungen aus der Bestim- [19] K.A. Feller, ‘Biologischer Abbau von [3] H. Stucki, ‘Environmental Contamination mung von sprengstoffspezifischen Schad- Trinitrotoluol’, Proc. 23rd Intern. Ann. of Explosive Ordnance Disposal’, 12th stoffen in Boden- und Wasserproben’, Conf. of ICT, Karlsruhe, D, 1992,pp IRSAG Conference, MOD Abbey Wood, CPM-Seminar: Bewertung von spreng- 33–1–11. Bristol, UK, 2000. stoffspezifischen Schadstoffen auf Rüs- [4] ‘Schadstoffbelastung des Bodens bei tungs- und militärischen Standorten, Schiessanlagen’, Kant. Amt für Bonn, D, 1994. Umweltschutz Solothurn, CH, Bericht [12] ‘2,4,6-Trinitrotoluene, The Registry of Jan. 1994. Toxic Effects of Chemical Substances’, [5] S. Rodriguez Bares, H.R. Buser, T. Poiger, NIOSH (US), update 2002. M.D. Müller, H.P. Kohler, ‘Gewässerbe- [13] European Commission DG ENV, ‘Towards lastung durch Sprengstoffe im Thunersee’, the establishment of a priority list of sub-