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Water quality criteria for hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)
REGULATORY
TOXICOLOGY
AND
PHARMACOLOGY
9, i47- 157 (1989)
Water Quality Criteria for Hexahydro-1,3,5trinitro-1,3,5-triazine (RDX)’ ELIZABETHL.ETNIER Chemical Hazard Evaluation Program, Information Research and Analysis Section, Health and Safety Research Division, Oak Ridge National Laboratory,2 Oak Ridge, Tennessee 37831-6050
Received April IO, 1988
The occurrence of the munitions compound hexahydro-l,3,5-trinitro-1,3,5-triazine (RDX) in groundwater surrounding Army ammunition plants may result in contamination of local drinking water supplies. RDX exerts its primary toxic effect in humans on the central nervous system, but also involves gastrointestinal and renal effects. Symptomatic effects following acute exposure include hyperirritability, nausea, vomiting, generalized epileptiform seizures, and prolonged postictal confusion and amnesia. Health effects data were analyzed for RDX, and although no controlled human studies exist concerning the acute or chronic toxic effects of exposure to RDX, sufficient animal toxicity data are available to derive an ambient water quality criterion for the protection of human health. This paper summarizes the available literature on metabolism of RDX and human and animal toxicity. Based on noncarcinogenic mammalian toxicity data, and following the methodologies of the U.S. Environmental Protection Agency, an ambient water quality criterion for the protection of human health of 103 &liter is proposed for ingestion of drinking water and aquatic foodstuffs. A criterion of 105 &liter is proposed for ingestion of drinking water alone.
INTRODUCTION The Chemical Effects Information Task Group-at Oak Ridge National Laboratory (ORNL) has evaluated available data on the human health effects of various munitions compounds and derived ambient water quality criteria for the protection of human health for these compounds using the latest U.S. Environmental Protection Agency (EPA) guidelines (USEPA, 1980). This project was funded by the U.S. Army Biomedical Research and Development Laboratory (USABRDL), Fort Detrick, Maryland. The munitions of interest to USABRDL are hexahydro-1,3,5-trinitro’ The U.S. Government’s right to retain a nonexclusive royalty-free license in and to the copyright covering this paper, for governmental purposes, is acknowledged. * Operated by Martin Marietta Energy Systems, Inc., under Contract Number DE-AC05-840R2 1400 with the U.S. Department of Energy. 147 0273-2300189 $3.00
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1,3,5-triazine (RDX), dinitrotoluene (DNT), trinitrotoluene (TNT), nitroglycerin, and white phosphorus. This article is the first in a series summarizing the results of the project. Hexahydro- 1,3,5-trinitro-1,3,5-triazine (CAS 12 l-82-4) is a white crystalline high explosive used predominantly by the military from 1940 to 1960. It is commonly known as RDX (British code name for research department explosive or royal demolition explosive). Other synonyms are hexolite, cyclonite, hexogen, and C-4 (Tatken and Lewis, 1983). During the 196Os, RDX was the third most important explosive from a tonnage viewpoint after TNT and nitrocellulose (Federoff and Sheffield, 1966). Production of RDX from 1969 to 197 1 averaged about 15 million pounds per month (Patterson et al., 1976). Current production of RDX is limited to Holston Army Ammunition Plant (AAP) in Kingston, Tennessee. Handling/packing operations using RDX still occur at several AAPs, and wastewaters resulting from the manufacture and loading of RDX may be discharged into the environment and represent a potential for aquatic pollution (Huff et al., 1975; Stilwell et al., 1977; Spanggord et al., 1980). Sediment deposits in settling ponds at these AAPs may also pose an environmental problem. Seepage into groundwater, and contamination of public drinking water supplies, has occurred at the Cornhusker AAP in Nebraska (Monnot et al., 1982) and is a concern for other waste disposal sites at Army installations. The Superfund Amendments and Reauthorization Act (SARA) of 1986 mandated that cleanup actions at all hazardous waste sites must be protective of human health and the environment and must comply with all requirements or standards established under any federal environmental law. However, to date, EPA has not established a water quality criterion for RDX, nor is it regulated under the Safe Drinking Water Act in the form of a maximum contaminant level (MCL) or maximum contaminant level goal (MCLG). The purpose of this project was to provide the Army with guidance for protection of water quality at U.S. Army installations in lieu of any available regulatory standards. The results of this study appear in their entirety in Etnier (1986), and this article briefly summarizes the information contained in that report. PHARMACOIUNETICS In humans and laboratory animals RDX is slowly absorbed from the gastrointestinal (GI) tract after ingestion (von Oettingen et al., 1949; Schneider et al., 1977) and also apparently from the lungs after inhalation (Hollander and Colbach, 1969; Ketel and Hughes, 1972); there is no clinical or experimental evidence of skin absorption. Schneider et al. ( 1977) reported a latent period of a few hours to 24 hr from administration of RDX in rats or miniature swine, respectively, to onset of toxic symptoms, with observed convulsions coincident with elevated levels of RDX in plasma. Similarly, symptoms of central nervous system (CNS) involvement and epileptiform seizure (generalized convulsions) occurred in a German shepherd dog 8-9 hr following ingestion of RDX (Berry et al., 1983). These results confirm the slow absorption of RDX from the GI tract. The latent period between RDX intake and the appearance of toxic manifestations in animals is consistent with that reported for humans following accidental or inten-
WATER
QUALITY
CRITERIA
FOR RDX
149
tional inhalation or ingestion of RDX (Barsotti and Crotti, 1949; Kaplan et al., 1965; Stone et al., 1969; Knepshield and Stone, 1972; Ketel and Hughes, 1972) and supports the conclusion that RDX is slowly absorbed from the GI tract. In laboratory animals RDX is metabolized primarily in the liver (Schneider et al., 1977) by microsomal enzymes (French et al., 1976; Bradley, 1977). Metabolism of RDX produces several kinds of one-carbon fragments: CO2 (Schneider et al., 1977) bicarbonate ion, and formic acid (Schneider et al., 1978, reporting unpublished observations of Anderson and Bradley). No larger intermediates have been identified. RDX does not accumulate appreciably in any tissue and is excreted primarily as metabolites in the urine or exhaled as carbon dioxide (Schneider et al., 1977, 1978).
HUMAN
TOXICITY
While no controlled human studies exist concerning the toxic effects of acute exposures to RDX, instances of accidental inhalation or ingestion of RDX by humans have been documented in the literature (Ketel and Hughes, 1972; Hollander and Colbach, 1969; Stone et al., 1969; Woody et al., 1986). No clinical descriptions of fatality from exposure to RDX have been reported in the literature, although several fatal cases have been mentioned by various authors (Sunderman, 1944; Vogel, 1952, as reported in Kaplan et al., 1965; Tsa and Lee, 1982, as reported in Woody et al., 1986). Sklyanskaya and Pozhariskii (1944) state that a number of cases of RDX poisoning, some fatal, appear in occupational records, although the original reference is not available to confirm a positive association with RDX. RDX exerts its primary toxic effect in humans on the central nervous system, but also involves GI and renal effects. Symptomatic effects following acute exposure include hyperirritability, nausea, vomiting, generalized epileptiform seizures, and prolonged postictal confusion and amnesia. These effects appeared to be completely reversible (Weigel, 1955; Stone et al., 1969; Ketel and Hughes, 1972; Path et al., 1980). Chronic RDX intoxication among workers in the munitions industry has been documented in several studies, exposure occurring mainly from inhalation of fine particles (Barsotti and Crotti, 1949; Vogel, 1952; Kaplan et al., 1965); because RDX is not particularly lipid soluble, skin absorption is very unlikely (Rosenblatt, 1980). Chronic intoxication in workers is characterized by epileptiform seizures (generalized convulsions) and unconsciousness. Convulsions may appear without warning or be preceded by 1 or 2 days of insomnia, restlessness, and irritability. Seizures are followed by temporary amnesia, disorientation, and asthenia (Barsotti and Crotti, 1949: Vogel, 1952; Kaplan et al., 1965).
ACUTE
ANIMAL
TOXICITY
As in man, CNS excitation is the most prominent acute effect of RDX animals. Other toxic manifestations include gasping and labored breathing.
in most
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ELIZABETH
L. ETNIER
Table 1 summarizes RDX lethality data for various species and routes of exposure. Oral LDSo values for RDX range from 44 to 300 mg/kg in the rat, indicating that RDX is moderately to highly toxic. Oral LDso values for the same species may differ among laboratories depending on the physical form of the RDX and on the vehicle used to suspend or dissolve it (Schneider et al., 1977). The route of administration may also influence acute toxicity (Sunderman, 1944). In addition, there may be sex differences in response to RDX treatment (Levine et al., 198 1; Cholakis et al., 1980; Dilley et al., 1978). In an attempt to ascertain whether RDX was affecting the CNS, an early study (Sunderman, 1944) found that administration of Nembutal, an antispasmodic drug, prevented convulsions and death in rats, and that decerebrated rats exhibited no convulsive symptoms after intraperitoneal injection of a dose of 100 mg/kg RDX (lethal in untreated rats). Studies evaluating the neurobehavioral toxicity of acute RDX exposure in rats found a dose-related response in schedule-controlled behavior, flavor-aversion conditioning, motor activity, and landing footspread at 12.5 mg/kg (McPhail et al., 1984, 1985). SUBCHRONIC
AND
CHRONIC
ANIMAL
TOXICITY
Subchronic and chronic RDX toxicity tests have been performed to determine the mechanism of RDX toxicity and to establish no-effect dose levels. Pathological changes following subchronic and chronic exposure to RDX are generally nonspecific and consist of congestion in various organs, swelling and degeneration of renal tubular epithelium, fatty degeneration of the liver, and areas of hyaline degeneration of heart muscle (Sunderman, 1944; von Oettingen et ul., 1949; Litton Bionetics, Inc., 1974; Cholakis et al., 1980; Levine et al., 198 1). No pathological changes have been noted in the brain (von Oettingen et al., 1949; Sunderman, 1944). Litton Bionetics, Inc. (1974) studied the subchronic toxicity of RDX in rhesus monkeys. Doses of 0,O. 1, 1, and 10 mg/kg/day RDX in an aqueous solution of methylcellulose were administered orally 7 days a week for 13 weeks (90 days). Test and control groups consisted of six monkeys (combined sex); due to the small sample size no statistical analysis was performed. Five monkeys in the 10 mg/kg/day dose group exhibited signs of CNS disturbance on 12 occasions after 2-3 months exposure, usually involving tonic convulsions. Recovery was complete in all but one monkey which was euthanatized. Except for frequent episodes of vomiting, no other clinical signs of toxicity were observed in any of the dose groups. Increases in numbers of degenerate or necrotic megakaryocytes in bone marrow sections were observed, as well as increased amounts of iron-positive material in liver cord cytoplasm, both occurring in the high-dose group. The toxicological significance of these findings was not known. The no-observed-effect level (NOEL) was 1.O mg/kg/day. Subchronic (12 week) exposure of rats to 2.5, 6.5, or 12.5 mg/kg/day RDX was found to induce time- and dose-related, biphasic changes in brain monoamine oxidase, cholinesterase, and oxygen uptake. None of these effects were found in rats dosed with 0.3 mg/kg/day; thus this level is reported as a NOEL (Brown, 1975). Chronic studies evaluated the toxicity of 0.3, 1.5, 8.0, or 40.0 mg/kg/day RDX [contaminated with 3 to 10% octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine
WATER
QUALITY
CRITERIA
TABLE
151
FOR RDX
1
RDX” LETHALITYDATA Species Rat
Route/vehicle Oral/saffron oil Oral/saffron oil Oral/diet Oral/diet Oral/DMSO or saline slurry Oral/methyl cellulosepolysorbate 80 Oral/diet
Mouse
Reference 44 70 (immature male) 50-75 (immature female) 50 (LD,‘-fasted) 75 (LDLo-nonfasted) 100
Sunderman ( 1944) Sunderman (1944) Schneider et al. ( 1977)
I 18 (combined sexes)
Cholakis et al. ( 1980)
153
Kaczorowski and Syrowatka ( 1960) as reported in Chem. .4bstr. von Oettingen et al. (1949) Schneider et al. ( 1977) Sunderman ( 1944)
Oral/gum acacia
200
Oral/coarse powder Intraperitoneal/saline solution Oral/aqueous solution
300 25 wLo)
Oral/corn oil
<75 (immature male) 86 (immature female) 80 (combined sexes)
Oral/methyl cellulosepolysorbate 80 Intravenous/DMSO
500
19
Cat
Oral/linseed oil
100 WXo)
Rabbit
Oral/linseed oil
500
18WLO)
Guinea pig
Intravenous/saline solution Intravenous/DMSO
25
Dog
Intravenous/DMSO
40 (LD,ood)
WLO)
0 RDX = hexahydro-1,3,5-trinitro-1,3,5-triazine. b Except as otherwise noted. c LDu, = the lowest dose at which mortality was observed. dLD,m = the dose at which 100% mortality occurred.
Lehman et al. (1965) Dilley et al. (1978)
Sklyanskaya and Pozhariskii ( 1944) as reported in Kaplan et al. ( 1965) Dilley et al. ( 1978) Cholakis et al. ( 1980) McNamara et al. (1974) Sklyanskaya and Pozhariskii ( 1944) as reported in Kaplan et al. ( 1965) Sklyanskaya and Pozhariskii ( 1944) as reported in Kaplan et al. ( 1965) Sunderman ( 1944) McNamara et al. (1974) McNamara et al. (1974)
152
ELIZABETH
L. ETNIER
(HMX)] administered continuously in the diet of Fischer 344 rats for 2 years. The major toxic effects of RDX were reported to include anemia with secondary splenic lesions, hepatotoxicity, possible CNS involvement, cataracts, and urogenital lesions. Statistically significant reductions in mean survival time were reported for males at all but the lowest dose level, and for females at 40 mg/kg/day. Based on observations of adverse effects in rats, the authors report a NOEL under the conditions of their study of 0.3 mg/kg/day (Levine et al., 1983). In contrast to the results of Levine et al. (1983), Hart (1976) in an earlier study with Charles River Sprague-Dawley rats found that dietary RDX at a level of 0, 1.O, 3.1, or 10 mg/kg/day for 2 years resulted in no evidence of toxicity. One hundred male and female rats per dose group were treated and examined for various clinical endpoints. Hematology, blood chemistry, urinalysis, gross necropsies, organ weights, and histopathological examination resulted in no significantevidence of RDX toxicity. In addition, there was no significant incidence of neoplasms in 16 tissues examined when compared with controls. The discrepancy between these results may be explained by the difference in physical form of RDX administered and in the method of suspension (Schneider et al., 1977). In another study evaluating the chronic toxicity and carcinogenicity of RDX (contaminated with 3 to 10% HMX) in B6C3Fl hybrid mice, the major toxic effects observed after 2 years included hepatotoxicity, possible CNS involvement, and testicular degeneration seen at 35 and 100 mg/kg/day doses (Levine et al., 1984). A possible treatment-related elevation in serum triglyceride levels was observed in female mice at 35 mg/kg/day, and elevated serum cholesterol levels were also observed in female mice at 35 mg/kg/day, and possibly at 7 mg/kg/day. Based on these observations, a NOEL of 1.5 mg/kg/day was reported. The possible carcinogenicity of RDX is suggested by this study. However, the absence of an adequate dose-response curve, the high mortality rate recorded at the highest concentration tested, and contamination with HMX, as well as the absence of any other supporting data, preclude the development of a carcinogenic-based risk assessment for humans based on this data. Furthermore, no evidence of carcinogenicity was apparent in a 24-month rat study performed in the same laboratory with the same mixture of RDX/HMX (Levine et al., 1983). No evidence of genotoxicity or developmental/reproductive toxicity was found in various short- and long-term studies (Simmon et al., 1977; Stilwell et al., 1977; Cotruvo et al., 1977; Dilley et al., 1978; Cholakis et al., 1980; Isbister et al., 1984). PREVIOUSLY
RECOMMENDED
CRITERIA
The threshold limit value (TLV) for RDX recommended by the ACGIH (1980) is 1.5 mg/m3, followed by the notation “skin” indicating the possibility of cutaneous absorption. However, a review of the literature indicates no evidence of skin absorption, which is supported by its low lipid solubility. The TLV value was based on the analogy of RDX to TNT, and the observation that concentrations of RDX below 1.5 mg/m3 do not cause occupational injury (Hyatt and Milligan, 1953, as reported in Stokinger, 1982). The short-term exposure limit (STEL) is 3 mg/m3 (ACGIH, 1980). OSHA has adopted the ACGIH limit of 1.5 mg/m3 (Stokinger, 1982); the USSR has a maximum acceptable concentration (MAC) of 1 mg/m3 (ILO, 1983).
WATER
QUALITY
CRITERIA
FOR
153
RDX
USABRDL calculated an interim standard of 0.03 mg/liter for protection of human health (Dacre, 1980; U.S. Army, 1982, 1983) based on the NOEL of 1.O mg/kg/ day reported in the 90-day feeding study in monkeys (Litton Bionetics, Inc. 1974), a bioconcentration factor of 4.2 (Sullivan et al., 1979), a fish ingestion rate of 0.0187 kg/day, and an uncertainty factor of 1000. This value of 1000 was selected in the absence of valid long-term human or animal data, as recommended by USEPA guidelines (USEPA, 1980). The data of Litton Bionetics, Inc. ( 1974) were rejected in this evaluation for several reasons: the exposure period was subchronic (90 days) rather than chronic; too few animals were studied to allow for a statistical analysis of results; and, the study has been superseded by the more recent, chronic study of Levine et al. ( 1983). DERIVATION
OF AMBIENT
WATER
QUALITY
CRITERION
There are insufficient carcinogenicity data from human or animal tests to derive a water quality criterion based on the nonthreshold low-dose extrapolation procedure. There are also no human studies suitable for estimating a NOEL. Therefore, data for calculating a human health criterion are based on the long-term chronic toxicity study in rats administered RDX in the diet at concentrations of 0.3, 1.5, 8.0, or 40.0 mg/kg/day RDX (Levine et al., 1983). In the study of Levine et al. (1983), RDX at 40 mg/kg/day was lethal to 68% of the males and 36% of the females during the 2-year treatment period, and statistically significant reductions (P < 0.05) in mean survival time were observed for both sexes. At this level, anemia consisting of reduced hematocrit, hemoglobin, and red blood cells was observed in both sexes; thrombocytosis, hypoglycemia, hypocholesterolemia, and reductions in serum triglyceride were apparent; statistically significant increases in the number of cataracts in females were found, increased liver, kidney, and adrenal weights were reported for both sexes; and significant reductions in testes weights were observed. The dose of 40 mg/kg/day appears to be a well-defined “frankeffect level.” A significant decrease in mean survival time (6%) in males at the 1.5 mg/kg/day dose level was also seen, as well as enlarged prostate accompanied by spermatic granuloma and suppurative inflammation, and increased levels of a hemosiderin-like pigment deposited in the spleen (a secondary response to a hemolytictype anemia). No evidence of carcinogenicity was reported in this study. Based on the observation of adverse effects seen at 1.5 mg/kg/day, the authors report a NOEL under the conditions reported in their study of 0.3 mg/kg/day. It should be pointed out that the RDX administered in the study was contaminated with 3 to 10% HMX, and it is not known to what extent this may have affected the results of the experiment. Brown ( 1975) found RDX to induce time- and dose-related, biphasic, changes in brain monoamine oxidase, cholinesterase, and oxygen uptake in rats during subchronic ( 12 week) oral feeding studies. Based on his results, Brown also reported 0.3 mg/kg/day as a NOEL. The methodology outlined by the USEPA for estimation of a water quality criterion for protection of human health (USEPA, 1980) has been used for derivation of a water quality criterion for RDX. Using the NOEL of 0.3 mg/kg/day reported by
154
ELIZABETH
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Levine et al. ( 1983), and an uncertainty factor of 100, an acceptable daily intake for a 70-kg human is calculated to be 0.2 1 mg/day: AD1 (mg/day) =
70 kg X NOEL (mg/kg/day) uncertainty factor
’
The uncertainty factor of 100 was selected because the results are from valid longterm feeding studies on experimental animals in which a well-defined LOAEL and NOEL exist. The uncertainty factor of 100 is designed to account for extrapolation of animal data to human data and to account for sensitive subpopulations (USEPA, 1987). The equation for calculating the human health criterion for RDX given an AD1 is c=
AD1 - (DT + IN) 2 liters/day + (0.0065 kg/day X 1 liter/kg
X BCF) ’
where C AD1 DT IN 2 liters 0.0065 BCF 1 liter/kg
= water quality criterion, mg/liter; = acceptable daily intake, 0.2 1 mg/day; = dietary nonfish intake, assumed to be 0 mg/day; = inhalation intake, assumed to be 0 mg/day; = daily water intake; = daily dietary fish intake, kg/day; = bioconcentration factor, assumed to be 4.7 (Bentley et al., 1977); = unit conversion factor.
Using the methodology of the USEPA (1980), and the above equations, an ambient water quality criterion for the protection of human health and sensitive populations of 103 pg/liter is calculated for RDX following ingestion of drinking water and aquatic foodstuffs. An adjusted water quality criterion of 105 &liter for consump tion of drinking water alone may be more appropriately utilized for situations in which contaminated groundwater at hazardous waste sites may be a potential source of drinking water. This criterion is based on more realistic exposure conditions following groundwater contamination, i.e., exclusion of aquatic organism ingestion as an exposure pathway. Although the water quality criterion for RDX has not yet been officially approved by the U.S. Army Surgeon General or by EPA, it will provide some guidance to individuals attempting to preserve water quality in order to protect human health. For example, the criterion for RDX was used to set discharge limits for NPDES permits allowing discharge of RDX-contaminated groundwater into a creek near the Cornhusker AAP in Grand Island, Nebraska. Based on the water quality criterion calculated for USABRDL, Nebraska State Health and EPA officials stated that the permit discharge levels should pose no threat to humans (Lincoln Star, 1985). REFERENCES American Conference of Governmental Industrial Hygienists ACGIH (1980). Documentation Threshold Limit Values, 4th ed., p. 115. Cincinnati, OH.
of the
WATER
QUALITY
CRITERIA
155
FOR RDX
BARSO~I, M., AND CROTTI, G. (1949). Epileptic attacks as manifestations of industrial intoxication caused by trimethylenetrinitroamine (T.,). Med. Lav. 40, 107- 112. BENTLEY, R. E., DEAN, J. W., ELLS, S. J., HOLLISTER, T. A., LEBLANC, G. A., SAUTER, S., AND SLEIGHT, B. H. (1977). Laboratory Evaluation ofthe Toxicity of RDX to Aquatic Organisms. Final Report. AD A06 1 730. EC&G Bionomics, Wareham, MA. DAMD 17-74-C-4 10 1. BERRY, A. P., ARBUCKLE, J. B. R., AND NICOL, J. ( 1983). Cyclonite poisoning in a dog. Vet. Rec. 113, 449. BRADLEY, S. L. (1977). The role of the mixed function oxidases in the metabolism of cyclotrimethylenetrinitramine (RDX). Master Abstr. 15(l), 133. BROWN, D. (1975). The Acute and Chronic Biochemical and Behavioral Eflects of Cyclotrimethylenetriamine. AD-A0244 15/2. Maryland University School of Pharmacy, Baltimore, MD. CHOLAKIS, J. M., WONG, L. C. K., VANGOETHEM, D. L., MINOR, J., SHORT, R., SPRINZ, H., AND ELLIS, H. V. (1980). Mammalian Toxicological Evaluation of RDX Final Report, AD A09253 1. Midwest Research Inst., Kansas City, MO. DAMDl7-78-C-8027. COTRUVO, J. A., SIMMON, V. F., AND SPANGGORD, R. J. (1977). Investigation of mutagenic effects of products of ozonation reactions in water. Ann. N. Y. Acad. Sci. 298, 124- 140. DACRE, J. C. ( 1980). Recommended Interim Environmental Criteria for SixMunitions Compounds. Memorandum Report. U.S. Army Medical Bioengineering Research and Development Laboratory, Fort Detrick, MD. DILLEY, J. V., TYSON, C. A., AND NEWELL, G. W. (1978). Mammalian Toxicological Evaluation of TNT Wastewaters, Vol. 2, Acute and Subacute Mammalian Toxicity of TNT and LAP Wastewaters. Report. SRI International, Menlo Park, CA. DAMDl7-76-C-6050. ETNIER, E. L. (1986). Water Quality Criteria for Hexahydro-1,3,5-trinitro-1,3.5-triazine (RDX). Final Report. U.S. Army Medical Bioengineering Research and Development Laboratory, Oak Ridge National Laboratory, Oak Ridge, TN. ORNL-6 178 (ADA 169506). FEDEROFF, B. T., AND SHEFFIELD, 0. E. (1966). HMX and RDX. In Encyclopedia of Explosives and Related Items, Vol. 3, pp. C605-C630. Picatinny Arsenal, Dover, NJ. FRENCH,J. E., BRADLEY, S. L., SCHNEIDER, N. R., AND ANDERSEN, M. E. (1976). Cyclotrimethylenetrinitramine induced ultrastructural changes in rat liver and kidney. Toxicol. Appl. Pharmacol. 37( 1), 122. HART, E. R. (1976). Two-year Feeding Study in Rats. Final Report, AD A04016 1. Litton Bionetics Inc., Kensington, MD. NOOO14-73-C-0162, NR202-043. HOLLANDER, A. I., AND COLBACH, E. M. (1969). Composition C-4 induced seizures: A report of five cases. Mil. Med. 134(13), 1529-1530. HUFF, B. L., DUCKERT, W. D., BARDING, P. G., WHEELER, J. H., AND HOGAN, T. M. (1975). Aquatic FieldSurveys at Radford, Holston, Volunteer, andMilan Army Ammunition Plants, Vol. 4. Milan. Final Report, AD-A024 194. Wapora, Inc., Washington, DC. DAMDl7-74-C-4138. International Labour Office IL0 (1983). Encyclopedia of Occupational Health and Safety (L. Parmeggiani, Ed.), Vols. l-2, p. 807. McGraw-Hill, New York. ISBISTER,J. D., ANSPACH, G. L., KITCHENS, J. F., AND DOYLE, R. C. (1984). Composting for decontamination of soils containing explosives. Microbiologica (Bologna) 7,47-73. KAPLAN, A. S.. BERGHOUT, C. F., AND PECZENIK, A. (1965). Human intoxication from RDX. Arch. Environ.
Health
10,877-883.
KACZOROWSKI, T., AND SYROWATKA, T. (1960). Toxicology of hexogen. Rocz. Panstw. Zakl. Hig. 11, 373-378. As reported in Chem. Abstr. 55,17,998c (1961). KETEL, W. B., AND HUGHES, J. R. (1972). Toxic encephalopathy with seizures secondary to ingestion of composition C-4: a clinical and electroencephalographic study. Neurology 22(8), 87 l-876. KNEPSHIELD, J. H., AND STONE, W. J. (1972). Toxic effects following ingestion of C-4 plastic explosive. In Drug Abuse (W. Keup, Ed.), Chap. 3. Thomas, Springfield, IL. LEHMANN, P. A., CARWNA, L., FAVARI, L., et al. (1979). Determination of the median lethal dose of trimethylene-trinitramine in rats. Bol. Estud. Med. Biol. (Mexico) 30(8), 298. LEVINE, B. S., FUREDI, E. H., GORDON, D. E., BURNS, J. M., AND LISH, P. M. (198 1). Thirteen Week Oral (Diet) TNT/RDX
Toxicity mixtures
Study of Trinitrotoluene (TNT), Hexahydro-1,3,5-trinitro-X,3.5-triazine in the Fischer 344 Rat. Report, AD A108 447. IIT Research
(RDX),
and
Institute, Chicago, IL.
DAMD 17-79-C-9 120 and DAMD 17-79-C-9 16 1. LEVINE, B. S., FUREDI, Chronic Mammalian
E. M., Rat, Toxicological
V. S., GORDON, Eflects ofRDX.
D. E., AND LISH, P. M. ( 1983). Determination of the Twenty-four Month Chronic Toxicity/Carcinogenic-
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ity Study of Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in the Fischer 344 Rat. Final Report. Contract No. DAMDl7-79-C-9 16 1. IITRI Project No. L6 12 1, Study No. 6. U.S. Army Medical Research and Development Command, Ft. Detrick, MD (draft copy). LEVINE, B. S., FUREDI, E. M., SAGARTZ, J. M., RAC, V. S., AND LISH, P. M. (1984). Determination of the Chronic Mammalian Toxicological Eflects ity Study of Hexahydro-1,3,5-trinitro-1,3,5-triazine
ofRDX.
Twenty-four Month Chronic Toxicify/Carcinogenic(RDX) in the B6C3FI Hybrid Mouse. Phase
VI.
Final Report. Contract No, DAMD 17-79-C-9 16 1. IITRI Project No. L6 12 1, Study No. 7. U.S. Army Medical Research and Development Command, Fort Detrick, MD (draft copy). Lincoln Star (1985). “Officials say discharge plan won’t cause health problems,” p. 15. Lincoln, Nebraska, July 27. Litton Bionetics, Inc. (1974). Subacute Toxicity ofRDXand TNT in Monkeys. AD-A044650/0. Kensington, MD. MACPHAIL, R. C. (1984). Neurotoxicity of Cyclotrimethylenetrinitramine (RDX). Progress Report to U.S. Army Medical Bioengineering Research and Development Laboratory, Project Order No. 28 13. October 16. MACPHAIL, R. C. (1985). Neurotoxicity of Cyciotrimethyfenetrinitramine (RDX). Progress Report to U.S. Army Medical Bioengineering Research and Development Laboratory, Project Order No. 28 13. February 1. MCNAMARA, B. P., AVERILL, H. P., OWENS, E. J., CALLAHAN, J. F., FAIRCHILD, D. G., CINCHTA, H. P., RENGSTORFF, R. H., AND BISKUP, D. K. (1974). The ToxicoZogy of Cyclotrimethylenetrinitramine (RDX) and Cyclotetramethylenetetranitramine hexanone, andAcetone. Technical Report,
(HMX)
Solutions
in Dimethylsulhoxide
(DMSO),
Cyclo-
AD-780010. Edgewood Arsenal, Aberdeen Proving Ground,
MD. MONNOT, D., KENNEDY, D., CIRA, D., AND STARKEY, D. (1982). Cornhusker Army Ammunition Plant. Final Report prepared for Comhusker Army Ammunition Plant, Grand Island, NE, and for Commander, U.S. Army Toxic and Hazardous Materials Agency, Aberdeen Proving Ground, MD. Envirodyne Engineers, Inc., St. Louis, MO, August 1982. Report DRX-AS-CR-82155. PACH, J., GROSZEK, B., BOGUSZ, M., et al. (1980). Acute forced poisoning with explosives. Arch. Med. Sadowej. Kryminol. 30(4), 32 l-325. PATTERSON, J., SHAPIRA, I. N., BROWN, J., DUCKERT, W., AND POLSON, J. (1976). State-of-the-Art: Military Explosives and Propellants Production Industry, Vols. 1-3. EPA-600/2-76-213a-c. U.S. Environmental Protection Agency. ROSENBLATT, D. H. ( 1980). Toxicology of explosives and other propellants In Encyclopedia of Explosives and Related Items (S. M. Kaye, Ed.) Vol. 9, pp. T235-T298. U.S. Army Armament Research and Development Command, Dover, NJ. SCHNEIDER, N. R., BRADLEY, S. L., AND ANDERSEN, M. E. (1977). Toxicology of cyciotrimethylenetrinitramine: Distribution and metabolism in the rat and the miniature swine. Toxicol. Appl. Pharmacol. 39(3), 531-541. SCHNEIDER, N. R., BRADLEY, S. L., AND ANDERSEN, M. E. (1978). The distribution and metabolism of cyclotrimethylenetrinitramine (RDX) in the rat after subchronic administration. Toxicol. Appl. Pharmacol.
46( l), 163-172.
SIMMON, V. F., SPANGGORD, R. J., ECKFORD, S. L., AND MCCLUNG, V. (1977). Mutagenicity of Some Munitions Wastewater Chemicals and Chlorine Test Kit Reagents. Final Report, AD-AO57680/1. SRI
International, Menlo Park, CA. SKLYANSKAYA, R. M., AND POZHARISKII, F. I. (1945). Toxicity of hexogen. Farmakol. Toksikol. 7,4347 (1944); Chem. Abstr. 39,3073 (1945). SPANGGORD, R. J., MILL, T., CHOU, T.-W., MABEY, W. R., AND SMITH, J. H. (1980). EnvironmentalFate Studies
on Certain
Munition
Wastewater
Constituents-Phase
II, Laboratory
Studies.
Final
Report,
AD-A099 256. SRI International, Menlo Park, CA. STILwELL, J. M., FISCHER, M. A., MARGARD, W. L., MATTHEWS, M. C., AND STANFORD, T. B. (1977). Toxicological
Investigations
of Pilot
Treatment
Plant
Wastewaters
at Holston
Army
Ammunition
Plant.
Final Report, AD AO426O 1. Battelle Columbus Laboratories, Columbus OH. DAMD 17-74-C-4 123. STOKINGER, H. E. (1982). Aliphatic nitro compounds, nitrates, nitrites. In Patty’s Industrial Hygiene and Toxicology (G. D. Clayton and F. E. Clayton, Eds.), pp. 4 14 l-4208. Wiley, New York.
WATER
QUALITY
CRITERIA
FOR RDX
157
STONE, W. J., PALETTA, T. L., HEIMAN, E. M., BRUCE, J. I., AND JSNEPSHIELD,J. H. (1969). Toxic effects following ingestion of C-4 plastic explosive. Arch. Intern. Med. 124,726-730. SULLIVAN, J. H., JR., PUTNAM, H. D., KEIRN, M. A., PRUITT, B. C., JR., NICHOLS, J. C., AND MCCLAVE, J. T. (1979). A Summary and Evaluation of Aquatic Environmental Data in Relation to Establishing Water Quality Criteria for Munitions-Unique Compounds, Part 4, RDX and HMX. Final Report, ADA087 683. Water and Air Research, Inc., Gainesville, FL. DAMD-77-C-7027. SUNDERMAN, F. W. (1944). Hazards to the Health of Individuals Working with RDX(B), Report OSRD No. 4 174. National Defense Research Committee of the Office of Scientific Research and Development. TATKEN, R. L., AND LEWIS, R. J. (1983). Registry of Toxic Eficts of Chemical Substances, 198 l- 1982 ed., Vol. 3, p. 800. U.S. Department ofHealth and Human Services, National Institute for Occupational Safety and Health, Cincinnati, OH. U.S. Army (1982). Environmental Criteria for Explosives in Drinking Water, Letter dated 17 November 1982. Office of the Surgeon General. U.S. Army (1983). Environmental Criteria for Explosives in Drinking Water, Letter dated 17 February 1983. Office of the Surgeon General. USEPA (1980). Guidelines and methodology used in the preparation of health effectsassessment chapters ofthe Consent Decree Water Quality Criteria. Fed. Regist. 45,79347-79357. USEPA (1987). Integrated Risk Information System. Supportive Documentation. Vol. 1. Office of Health and Environmental Assessment, U.S. Environmental Protection Agency. EPA/600/8-86/032a. VOGEL, W. (1952). Hexogen poisoning in human beings. Zentralbl. Arbeitsmed. Arbeitsschutz 1, 5 l-54 (195 1); abstracted Ind. Hyg. Digest 16,29. VON OETTINGEN, W. F., DONAHUE, D. D., YAGODA, H., MONACO, A. R., AND HARRIS, M. R. (1949). Toxicity and potential dangers of cyclotrimethylenetrinitramine (RDX). J. Ind. Hyg. Toxicol. 31, 2 l31. WEIGEL. K. (1955). An explosive as a new rodenticide. Seifen Oele Fette Wachse 81,95-96. WOODY, R. C., KEARNS, G. L., BREWSTER,M. A., TURLEY, C. P., LAKE, R. S., AND SHARP, G. B. ( 1986). The neurotoxicity of cyclotrimethylenetrinitramine (RDX) in a child: A clinical and pharmacokinetic evaluation. Clinic. Toxicol. 24(4), 305-3 19.
TOXICOLOGY
AND
PHARMACOLOGY
9, i47- 157 (1989)
Water Quality Criteria for Hexahydro-1,3,5trinitro-1,3,5-triazine (RDX)’ ELIZABETHL.ETNIER Chemical Hazard Evaluation Program, Information Research and Analysis Section, Health and Safety Research Division, Oak Ridge National Laboratory,2 Oak Ridge, Tennessee 37831-6050
Received April IO, 1988
The occurrence of the munitions compound hexahydro-l,3,5-trinitro-1,3,5-triazine (RDX) in groundwater surrounding Army ammunition plants may result in contamination of local drinking water supplies. RDX exerts its primary toxic effect in humans on the central nervous system, but also involves gastrointestinal and renal effects. Symptomatic effects following acute exposure include hyperirritability, nausea, vomiting, generalized epileptiform seizures, and prolonged postictal confusion and amnesia. Health effects data were analyzed for RDX, and although no controlled human studies exist concerning the acute or chronic toxic effects of exposure to RDX, sufficient animal toxicity data are available to derive an ambient water quality criterion for the protection of human health. This paper summarizes the available literature on metabolism of RDX and human and animal toxicity. Based on noncarcinogenic mammalian toxicity data, and following the methodologies of the U.S. Environmental Protection Agency, an ambient water quality criterion for the protection of human health of 103 &liter is proposed for ingestion of drinking water and aquatic foodstuffs. A criterion of 105 &liter is proposed for ingestion of drinking water alone.
INTRODUCTION The Chemical Effects Information Task Group-at Oak Ridge National Laboratory (ORNL) has evaluated available data on the human health effects of various munitions compounds and derived ambient water quality criteria for the protection of human health for these compounds using the latest U.S. Environmental Protection Agency (EPA) guidelines (USEPA, 1980). This project was funded by the U.S. Army Biomedical Research and Development Laboratory (USABRDL), Fort Detrick, Maryland. The munitions of interest to USABRDL are hexahydro-1,3,5-trinitro’ The U.S. Government’s right to retain a nonexclusive royalty-free license in and to the copyright covering this paper, for governmental purposes, is acknowledged. * Operated by Martin Marietta Energy Systems, Inc., under Contract Number DE-AC05-840R2 1400 with the U.S. Department of Energy. 147 0273-2300189 $3.00
148
ELIZABETH
L. ETNIER
1,3,5-triazine (RDX), dinitrotoluene (DNT), trinitrotoluene (TNT), nitroglycerin, and white phosphorus. This article is the first in a series summarizing the results of the project. Hexahydro- 1,3,5-trinitro-1,3,5-triazine (CAS 12 l-82-4) is a white crystalline high explosive used predominantly by the military from 1940 to 1960. It is commonly known as RDX (British code name for research department explosive or royal demolition explosive). Other synonyms are hexolite, cyclonite, hexogen, and C-4 (Tatken and Lewis, 1983). During the 196Os, RDX was the third most important explosive from a tonnage viewpoint after TNT and nitrocellulose (Federoff and Sheffield, 1966). Production of RDX from 1969 to 197 1 averaged about 15 million pounds per month (Patterson et al., 1976). Current production of RDX is limited to Holston Army Ammunition Plant (AAP) in Kingston, Tennessee. Handling/packing operations using RDX still occur at several AAPs, and wastewaters resulting from the manufacture and loading of RDX may be discharged into the environment and represent a potential for aquatic pollution (Huff et al., 1975; Stilwell et al., 1977; Spanggord et al., 1980). Sediment deposits in settling ponds at these AAPs may also pose an environmental problem. Seepage into groundwater, and contamination of public drinking water supplies, has occurred at the Cornhusker AAP in Nebraska (Monnot et al., 1982) and is a concern for other waste disposal sites at Army installations. The Superfund Amendments and Reauthorization Act (SARA) of 1986 mandated that cleanup actions at all hazardous waste sites must be protective of human health and the environment and must comply with all requirements or standards established under any federal environmental law. However, to date, EPA has not established a water quality criterion for RDX, nor is it regulated under the Safe Drinking Water Act in the form of a maximum contaminant level (MCL) or maximum contaminant level goal (MCLG). The purpose of this project was to provide the Army with guidance for protection of water quality at U.S. Army installations in lieu of any available regulatory standards. The results of this study appear in their entirety in Etnier (1986), and this article briefly summarizes the information contained in that report. PHARMACOIUNETICS In humans and laboratory animals RDX is slowly absorbed from the gastrointestinal (GI) tract after ingestion (von Oettingen et al., 1949; Schneider et al., 1977) and also apparently from the lungs after inhalation (Hollander and Colbach, 1969; Ketel and Hughes, 1972); there is no clinical or experimental evidence of skin absorption. Schneider et al. ( 1977) reported a latent period of a few hours to 24 hr from administration of RDX in rats or miniature swine, respectively, to onset of toxic symptoms, with observed convulsions coincident with elevated levels of RDX in plasma. Similarly, symptoms of central nervous system (CNS) involvement and epileptiform seizure (generalized convulsions) occurred in a German shepherd dog 8-9 hr following ingestion of RDX (Berry et al., 1983). These results confirm the slow absorption of RDX from the GI tract. The latent period between RDX intake and the appearance of toxic manifestations in animals is consistent with that reported for humans following accidental or inten-
WATER
QUALITY
CRITERIA
FOR RDX
149
tional inhalation or ingestion of RDX (Barsotti and Crotti, 1949; Kaplan et al., 1965; Stone et al., 1969; Knepshield and Stone, 1972; Ketel and Hughes, 1972) and supports the conclusion that RDX is slowly absorbed from the GI tract. In laboratory animals RDX is metabolized primarily in the liver (Schneider et al., 1977) by microsomal enzymes (French et al., 1976; Bradley, 1977). Metabolism of RDX produces several kinds of one-carbon fragments: CO2 (Schneider et al., 1977) bicarbonate ion, and formic acid (Schneider et al., 1978, reporting unpublished observations of Anderson and Bradley). No larger intermediates have been identified. RDX does not accumulate appreciably in any tissue and is excreted primarily as metabolites in the urine or exhaled as carbon dioxide (Schneider et al., 1977, 1978).
HUMAN
TOXICITY
While no controlled human studies exist concerning the toxic effects of acute exposures to RDX, instances of accidental inhalation or ingestion of RDX by humans have been documented in the literature (Ketel and Hughes, 1972; Hollander and Colbach, 1969; Stone et al., 1969; Woody et al., 1986). No clinical descriptions of fatality from exposure to RDX have been reported in the literature, although several fatal cases have been mentioned by various authors (Sunderman, 1944; Vogel, 1952, as reported in Kaplan et al., 1965; Tsa and Lee, 1982, as reported in Woody et al., 1986). Sklyanskaya and Pozhariskii (1944) state that a number of cases of RDX poisoning, some fatal, appear in occupational records, although the original reference is not available to confirm a positive association with RDX. RDX exerts its primary toxic effect in humans on the central nervous system, but also involves GI and renal effects. Symptomatic effects following acute exposure include hyperirritability, nausea, vomiting, generalized epileptiform seizures, and prolonged postictal confusion and amnesia. These effects appeared to be completely reversible (Weigel, 1955; Stone et al., 1969; Ketel and Hughes, 1972; Path et al., 1980). Chronic RDX intoxication among workers in the munitions industry has been documented in several studies, exposure occurring mainly from inhalation of fine particles (Barsotti and Crotti, 1949; Vogel, 1952; Kaplan et al., 1965); because RDX is not particularly lipid soluble, skin absorption is very unlikely (Rosenblatt, 1980). Chronic intoxication in workers is characterized by epileptiform seizures (generalized convulsions) and unconsciousness. Convulsions may appear without warning or be preceded by 1 or 2 days of insomnia, restlessness, and irritability. Seizures are followed by temporary amnesia, disorientation, and asthenia (Barsotti and Crotti, 1949: Vogel, 1952; Kaplan et al., 1965).
ACUTE
ANIMAL
TOXICITY
As in man, CNS excitation is the most prominent acute effect of RDX animals. Other toxic manifestations include gasping and labored breathing.
in most
150
ELIZABETH
L. ETNIER
Table 1 summarizes RDX lethality data for various species and routes of exposure. Oral LDSo values for RDX range from 44 to 300 mg/kg in the rat, indicating that RDX is moderately to highly toxic. Oral LDso values for the same species may differ among laboratories depending on the physical form of the RDX and on the vehicle used to suspend or dissolve it (Schneider et al., 1977). The route of administration may also influence acute toxicity (Sunderman, 1944). In addition, there may be sex differences in response to RDX treatment (Levine et al., 198 1; Cholakis et al., 1980; Dilley et al., 1978). In an attempt to ascertain whether RDX was affecting the CNS, an early study (Sunderman, 1944) found that administration of Nembutal, an antispasmodic drug, prevented convulsions and death in rats, and that decerebrated rats exhibited no convulsive symptoms after intraperitoneal injection of a dose of 100 mg/kg RDX (lethal in untreated rats). Studies evaluating the neurobehavioral toxicity of acute RDX exposure in rats found a dose-related response in schedule-controlled behavior, flavor-aversion conditioning, motor activity, and landing footspread at 12.5 mg/kg (McPhail et al., 1984, 1985). SUBCHRONIC
AND
CHRONIC
ANIMAL
TOXICITY
Subchronic and chronic RDX toxicity tests have been performed to determine the mechanism of RDX toxicity and to establish no-effect dose levels. Pathological changes following subchronic and chronic exposure to RDX are generally nonspecific and consist of congestion in various organs, swelling and degeneration of renal tubular epithelium, fatty degeneration of the liver, and areas of hyaline degeneration of heart muscle (Sunderman, 1944; von Oettingen et ul., 1949; Litton Bionetics, Inc., 1974; Cholakis et al., 1980; Levine et al., 198 1). No pathological changes have been noted in the brain (von Oettingen et al., 1949; Sunderman, 1944). Litton Bionetics, Inc. (1974) studied the subchronic toxicity of RDX in rhesus monkeys. Doses of 0,O. 1, 1, and 10 mg/kg/day RDX in an aqueous solution of methylcellulose were administered orally 7 days a week for 13 weeks (90 days). Test and control groups consisted of six monkeys (combined sex); due to the small sample size no statistical analysis was performed. Five monkeys in the 10 mg/kg/day dose group exhibited signs of CNS disturbance on 12 occasions after 2-3 months exposure, usually involving tonic convulsions. Recovery was complete in all but one monkey which was euthanatized. Except for frequent episodes of vomiting, no other clinical signs of toxicity were observed in any of the dose groups. Increases in numbers of degenerate or necrotic megakaryocytes in bone marrow sections were observed, as well as increased amounts of iron-positive material in liver cord cytoplasm, both occurring in the high-dose group. The toxicological significance of these findings was not known. The no-observed-effect level (NOEL) was 1.O mg/kg/day. Subchronic (12 week) exposure of rats to 2.5, 6.5, or 12.5 mg/kg/day RDX was found to induce time- and dose-related, biphasic changes in brain monoamine oxidase, cholinesterase, and oxygen uptake. None of these effects were found in rats dosed with 0.3 mg/kg/day; thus this level is reported as a NOEL (Brown, 1975). Chronic studies evaluated the toxicity of 0.3, 1.5, 8.0, or 40.0 mg/kg/day RDX [contaminated with 3 to 10% octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine
WATER
QUALITY
CRITERIA
TABLE
151
FOR RDX
1
RDX” LETHALITYDATA Species Rat
Route/vehicle Oral/saffron oil Oral/saffron oil Oral/diet Oral/diet Oral/DMSO or saline slurry Oral/methyl cellulosepolysorbate 80 Oral/diet
Mouse
Reference 44 70 (immature male) 50-75 (immature female) 50 (LD,‘-fasted) 75 (LDLo-nonfasted) 100
Sunderman ( 1944) Sunderman (1944) Schneider et al. ( 1977)
I 18 (combined sexes)
Cholakis et al. ( 1980)
153
Kaczorowski and Syrowatka ( 1960) as reported in Chem. .4bstr. von Oettingen et al. (1949) Schneider et al. ( 1977) Sunderman ( 1944)
Oral/gum acacia
200
Oral/coarse powder Intraperitoneal/saline solution Oral/aqueous solution
300 25 wLo)
Oral/corn oil
<75 (immature male) 86 (immature female) 80 (combined sexes)
Oral/methyl cellulosepolysorbate 80 Intravenous/DMSO
500
19
Cat
Oral/linseed oil
100 WXo)
Rabbit
Oral/linseed oil
500
18WLO)
Guinea pig
Intravenous/saline solution Intravenous/DMSO
25
Dog
Intravenous/DMSO
40 (LD,ood)
WLO)
0 RDX = hexahydro-1,3,5-trinitro-1,3,5-triazine. b Except as otherwise noted. c LDu, = the lowest dose at which mortality was observed. dLD,m = the dose at which 100% mortality occurred.
Lehman et al. (1965) Dilley et al. (1978)
Sklyanskaya and Pozhariskii ( 1944) as reported in Kaplan et al. ( 1965) Dilley et al. ( 1978) Cholakis et al. ( 1980) McNamara et al. (1974) Sklyanskaya and Pozhariskii ( 1944) as reported in Kaplan et al. ( 1965) Sklyanskaya and Pozhariskii ( 1944) as reported in Kaplan et al. ( 1965) Sunderman ( 1944) McNamara et al. (1974) McNamara et al. (1974)
152
ELIZABETH
L. ETNIER
(HMX)] administered continuously in the diet of Fischer 344 rats for 2 years. The major toxic effects of RDX were reported to include anemia with secondary splenic lesions, hepatotoxicity, possible CNS involvement, cataracts, and urogenital lesions. Statistically significant reductions in mean survival time were reported for males at all but the lowest dose level, and for females at 40 mg/kg/day. Based on observations of adverse effects in rats, the authors report a NOEL under the conditions of their study of 0.3 mg/kg/day (Levine et al., 1983). In contrast to the results of Levine et al. (1983), Hart (1976) in an earlier study with Charles River Sprague-Dawley rats found that dietary RDX at a level of 0, 1.O, 3.1, or 10 mg/kg/day for 2 years resulted in no evidence of toxicity. One hundred male and female rats per dose group were treated and examined for various clinical endpoints. Hematology, blood chemistry, urinalysis, gross necropsies, organ weights, and histopathological examination resulted in no significantevidence of RDX toxicity. In addition, there was no significant incidence of neoplasms in 16 tissues examined when compared with controls. The discrepancy between these results may be explained by the difference in physical form of RDX administered and in the method of suspension (Schneider et al., 1977). In another study evaluating the chronic toxicity and carcinogenicity of RDX (contaminated with 3 to 10% HMX) in B6C3Fl hybrid mice, the major toxic effects observed after 2 years included hepatotoxicity, possible CNS involvement, and testicular degeneration seen at 35 and 100 mg/kg/day doses (Levine et al., 1984). A possible treatment-related elevation in serum triglyceride levels was observed in female mice at 35 mg/kg/day, and elevated serum cholesterol levels were also observed in female mice at 35 mg/kg/day, and possibly at 7 mg/kg/day. Based on these observations, a NOEL of 1.5 mg/kg/day was reported. The possible carcinogenicity of RDX is suggested by this study. However, the absence of an adequate dose-response curve, the high mortality rate recorded at the highest concentration tested, and contamination with HMX, as well as the absence of any other supporting data, preclude the development of a carcinogenic-based risk assessment for humans based on this data. Furthermore, no evidence of carcinogenicity was apparent in a 24-month rat study performed in the same laboratory with the same mixture of RDX/HMX (Levine et al., 1983). No evidence of genotoxicity or developmental/reproductive toxicity was found in various short- and long-term studies (Simmon et al., 1977; Stilwell et al., 1977; Cotruvo et al., 1977; Dilley et al., 1978; Cholakis et al., 1980; Isbister et al., 1984). PREVIOUSLY
RECOMMENDED
CRITERIA
The threshold limit value (TLV) for RDX recommended by the ACGIH (1980) is 1.5 mg/m3, followed by the notation “skin” indicating the possibility of cutaneous absorption. However, a review of the literature indicates no evidence of skin absorption, which is supported by its low lipid solubility. The TLV value was based on the analogy of RDX to TNT, and the observation that concentrations of RDX below 1.5 mg/m3 do not cause occupational injury (Hyatt and Milligan, 1953, as reported in Stokinger, 1982). The short-term exposure limit (STEL) is 3 mg/m3 (ACGIH, 1980). OSHA has adopted the ACGIH limit of 1.5 mg/m3 (Stokinger, 1982); the USSR has a maximum acceptable concentration (MAC) of 1 mg/m3 (ILO, 1983).
WATER
QUALITY
CRITERIA
FOR
153
RDX
USABRDL calculated an interim standard of 0.03 mg/liter for protection of human health (Dacre, 1980; U.S. Army, 1982, 1983) based on the NOEL of 1.O mg/kg/ day reported in the 90-day feeding study in monkeys (Litton Bionetics, Inc. 1974), a bioconcentration factor of 4.2 (Sullivan et al., 1979), a fish ingestion rate of 0.0187 kg/day, and an uncertainty factor of 1000. This value of 1000 was selected in the absence of valid long-term human or animal data, as recommended by USEPA guidelines (USEPA, 1980). The data of Litton Bionetics, Inc. ( 1974) were rejected in this evaluation for several reasons: the exposure period was subchronic (90 days) rather than chronic; too few animals were studied to allow for a statistical analysis of results; and, the study has been superseded by the more recent, chronic study of Levine et al. ( 1983). DERIVATION
OF AMBIENT
WATER
QUALITY
CRITERION
There are insufficient carcinogenicity data from human or animal tests to derive a water quality criterion based on the nonthreshold low-dose extrapolation procedure. There are also no human studies suitable for estimating a NOEL. Therefore, data for calculating a human health criterion are based on the long-term chronic toxicity study in rats administered RDX in the diet at concentrations of 0.3, 1.5, 8.0, or 40.0 mg/kg/day RDX (Levine et al., 1983). In the study of Levine et al. (1983), RDX at 40 mg/kg/day was lethal to 68% of the males and 36% of the females during the 2-year treatment period, and statistically significant reductions (P < 0.05) in mean survival time were observed for both sexes. At this level, anemia consisting of reduced hematocrit, hemoglobin, and red blood cells was observed in both sexes; thrombocytosis, hypoglycemia, hypocholesterolemia, and reductions in serum triglyceride were apparent; statistically significant increases in the number of cataracts in females were found, increased liver, kidney, and adrenal weights were reported for both sexes; and significant reductions in testes weights were observed. The dose of 40 mg/kg/day appears to be a well-defined “frankeffect level.” A significant decrease in mean survival time (6%) in males at the 1.5 mg/kg/day dose level was also seen, as well as enlarged prostate accompanied by spermatic granuloma and suppurative inflammation, and increased levels of a hemosiderin-like pigment deposited in the spleen (a secondary response to a hemolytictype anemia). No evidence of carcinogenicity was reported in this study. Based on the observation of adverse effects seen at 1.5 mg/kg/day, the authors report a NOEL under the conditions reported in their study of 0.3 mg/kg/day. It should be pointed out that the RDX administered in the study was contaminated with 3 to 10% HMX, and it is not known to what extent this may have affected the results of the experiment. Brown ( 1975) found RDX to induce time- and dose-related, biphasic, changes in brain monoamine oxidase, cholinesterase, and oxygen uptake in rats during subchronic ( 12 week) oral feeding studies. Based on his results, Brown also reported 0.3 mg/kg/day as a NOEL. The methodology outlined by the USEPA for estimation of a water quality criterion for protection of human health (USEPA, 1980) has been used for derivation of a water quality criterion for RDX. Using the NOEL of 0.3 mg/kg/day reported by
154
ELIZABETH
L. ETNIER
Levine et al. ( 1983), and an uncertainty factor of 100, an acceptable daily intake for a 70-kg human is calculated to be 0.2 1 mg/day: AD1 (mg/day) =
70 kg X NOEL (mg/kg/day) uncertainty factor
’
The uncertainty factor of 100 was selected because the results are from valid longterm feeding studies on experimental animals in which a well-defined LOAEL and NOEL exist. The uncertainty factor of 100 is designed to account for extrapolation of animal data to human data and to account for sensitive subpopulations (USEPA, 1987). The equation for calculating the human health criterion for RDX given an AD1 is c=
AD1 - (DT + IN) 2 liters/day + (0.0065 kg/day X 1 liter/kg
X BCF) ’
where C AD1 DT IN 2 liters 0.0065 BCF 1 liter/kg
= water quality criterion, mg/liter; = acceptable daily intake, 0.2 1 mg/day; = dietary nonfish intake, assumed to be 0 mg/day; = inhalation intake, assumed to be 0 mg/day; = daily water intake; = daily dietary fish intake, kg/day; = bioconcentration factor, assumed to be 4.7 (Bentley et al., 1977); = unit conversion factor.
Using the methodology of the USEPA (1980), and the above equations, an ambient water quality criterion for the protection of human health and sensitive populations of 103 pg/liter is calculated for RDX following ingestion of drinking water and aquatic foodstuffs. An adjusted water quality criterion of 105 &liter for consump tion of drinking water alone may be more appropriately utilized for situations in which contaminated groundwater at hazardous waste sites may be a potential source of drinking water. This criterion is based on more realistic exposure conditions following groundwater contamination, i.e., exclusion of aquatic organism ingestion as an exposure pathway. Although the water quality criterion for RDX has not yet been officially approved by the U.S. Army Surgeon General or by EPA, it will provide some guidance to individuals attempting to preserve water quality in order to protect human health. For example, the criterion for RDX was used to set discharge limits for NPDES permits allowing discharge of RDX-contaminated groundwater into a creek near the Cornhusker AAP in Grand Island, Nebraska. Based on the water quality criterion calculated for USABRDL, Nebraska State Health and EPA officials stated that the permit discharge levels should pose no threat to humans (Lincoln Star, 1985). REFERENCES American Conference of Governmental Industrial Hygienists ACGIH (1980). Documentation Threshold Limit Values, 4th ed., p. 115. Cincinnati, OH.
of the
WATER
QUALITY
CRITERIA
155
FOR RDX
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