CHLORDANE EXPLANATION Chlordane was evaluated for acceptable daily intake by the Joint Meeting in 1963, and reviewed in 1970, 1977, and 1982 (Annex 1, FAO/WHO, 1964, 1965a, 1968a, 1971a, 1978a, and 1983a). Toxicological monographs were prepared in 1963, 1965, and 1967 (Annex 1, FAO/WHO, 1971b, 1978b, and 1983b). The 1982 Joint Meeting required submission of a study of at least 90 days' duration in rats, using oxychlordane, and the results of the long-term studies then on-going in Japan. Submission of human monitoring data pertinent to oxychlordane and trans-nonachlor was considered desirable. These and other studies are summarized in this monograph addendum. EVALUATION FOR ACCEPTABLE INTAKE Biochemical aspects Absorption, distribution, and excretion In a comparative study, groups of three male Sprague-Dawley rats and three male C57 BL/6 JX mice received single oral doses of 14C-cis-chlordane in corn oil (0-2 ml) and were sacrificed at intervals over the ensuing week. Faeces and urine were collected at 12-hour intervals for three days and at 24-hour intervals thereafter, and blood was collected at sacrifice. The 14C-cis-chlordane was absorbed more quickly by rats than mice; peak blood radioactivity occurred after two hours in rats (81 mg/ml) and after eight hours in mice (112 mg/ml). The rate of dissipation of these peak levels was also faster in rats than in mice since, after 24 hours, 41% and 76% of peak levels remained in rats and mice, respectively. The proportions of peak radioactivity remaining in liver at this time were 11% and 19% in rats and mice, respectively. Although there was significant individual variability among mice, the elimination of radioactivity in urine and faeces was initially higher in mice than rats. After three days, the cumulative faecal excretion was 83% in both species, although urinary excretion remained lower in rats. The results of this study indicate significant quantitative differences in the absorption, distribution, and excretion of cis-chlordane in rats and mice (Ewing et al., 1985). Toxicological studies Special study on cardiovascular effects Groups of three male and three female baboons received technical chlordane (0, 0.1, or 1.0 mg/kg b.w.) in a diet enriched in saturated fat and cholesterol for 24 months. There were no significant effects on the weight gain of treated animals. No significant effects of treatment were found on the development of atherosclerosis, on the lipid composition of the aortic intima, or on serum lipid or lipoprotein concentrations. Similarly, there were no treatment-related effects on the activities of mitochondrial enzymes of the heart or liver. Only the high-dose chlordane treatment induced hepatic cytochrome P-450 activity. No consistent haematological effects or behavioural alterations were observed. Chlordane exposure had no apparent effect on blood lipoproteins, arteries, or cardiac muscle of the baboon (McGill et al., 1979). Special study on inhalational toxicity Rats Groups of 35 male and 35 female Wistar (Crl:(WI) BR) albino rats were exposed for eight hours per day, five days per week, to nominal atmospheric concentrations of 0, 0.1, 1.0, or 10.0 µg/1 technical chlordane for 13 weeks, and then sacrificed. Recovery groups of nine males and nine females were held for 13 weeks after exposure before sacrifice. There were no clinical signs or deaths related to chlordane exposure. Some high-dose males and females appeared to become more sensitive to touch during the study, especially the females. There were no treatment-related effects on food or water consumption or on body-weight gain. Ophthalmoscopy findings were unremarkable. Apparent treatment-related findings were leucocytosis, cholesterolaemia, and elevation of serum glutamate dehydrogenase in the early part of the study. There was a dose-related increase in cytochrome-P450 levels at termination of exposure, which persisted for 10-11 days thereafter. At necropsy, increased liver weight in the high-dose groups was accompanied by centrilobular enlargement of hepatocytes. Kidney weights were increased in mid- and high-dose males at week nine and in the high-dose groups at week 14. There was a tendency for increased thyroid weight in exposed groups (Hardy et al., 1984). Monkeys An inhalation study was conducted with Macaca irus monkeys using the same exposure regime as in the rat study just described. Thus, groups of six male and six female monkeys were exposed to mean atmospheric chlordane concentrations of 0, 0.1, 1.0, or 10 µg/l for eight hours daily, five days per week, for 13 weeks. There were no effects or clinical signs due to chlordane exposure; food consumption and body-weight gain were unaffected. Rectal temperatures were found to be slightly increased during exposure, especially in the mid- and high-dose groups. Ophthalmoscopy showed no treatment-related effects. No adverse effects were found on pulmonary function (blood gases, lung function, and pulmonary ventilation parameters). No consistent treatment-related effects on haematological, serum biochemical, or urinalysis parameters were found. At necropsy, there were no significant macroscopic pathological changes in any group, although treatment-group mean liver and thyroid weights were greater than controls. No histopathological findings were related to chlordane exposure (Hardy et al., 1984). Special study on promotion of hepatic neoplasia In the initiation phase, groups of 40 male B6C3F1 hybrid mice received diethyl nitrosamine (0 or 200 ppm) in their drinking water for 14 weeks. After four weeks' recovery on basal diet, the groups received one of the following compounds in their diet for a further 25 weeks, as the promotion phase: technical chlordane (25 or 50 ppm), technical heptochlor (5 or 10 ppm), DDT (50 ppm), or N-2-fluorenyl- acetamide (150 ppm). In addition, some groups received the chemicals before diethyl nitrosamine, to determine possible syncarcinogenic effects. Randomly-selected mice from several of the groups were sacrificed at weeks 14, 18, 26, and 34, and the remainder upon completion of exposure. Prior to the interim kills (and at termination with 8-10 mice), mice received s.c. injections of iron dextran (12.5 mg iron/100 gm b.w.) to produce hepatic siderosis for the subsequent delineation of iron-excluding lesions. Diethylnitrosamine initiation was indicated by the presence of altered hepatic foci displaying abnormal alkaline phosphatase, adenosine triphosphatase, glucose-6-phosphatase, gamma-glutamyl transpeptidase, or iron accumulation in varying degrees. Abnormalities of glucose-6-phosphatase were most marked. Neoplasia was not observed at this stage. At termination, most exposed animals exhibited reduced body-weight gain, especially those in the high-dose chlordane and heptochlor groups. Liver weights were increased in mice in those groups which received diethyl nitrosamine followed by chlordane and heptochlor, but not in animals in those groups receiving only chlordane or heptochlor. While the number of hepatic foci found at week 43 was less than that found 12 or 20 weeks after cessation of exposure in mice given diethylnitrosamine alone, the number and size of foci were increased by chlordane or heptochlor exposure in initiated mice. N-2-Fluorenylacetamide increased the number, but not the size, of hepatic foci in initiated mice, but exposure to DDT, chlordane, heptochlor, or N-2-fluorenylacetamide alone did not increase the number of foci compared to untreated controls. Diethylnitrosamine produced squamous cell papillomas and carcinomas in the forestomach and pulmonary adenomas in treated mice. The incidence of hepatic neoplasms was particularly increased by treatment with diethyl nitrosamine (40%) compared to untreated controls (11%). Feeding of chlordane, heptochlor, DDT, or N-2-fluorenylacetamide further increased not only the incidence of hepatic neoplasms (to 66-85%), but also the multiplicity of liver neoplasms. In each case the number of adenomas exceeded that of adenocarcinomas. Mice given the higher doses of chlordane, heptochlor, or N-2-fluorenylacetamide alone had the same incidence of hepatic neoplasms as the controls, although the chlordane and heptochlor treatment included hepatocyte hypertrophy with nuclear enlargement. Chlordane, heptochlor, and DDT also increased the severity of cystic changes found in the livers of all mice previously treated with diethyl nitrosamine. Administration of the test chemicals in reverse sequence did not increase the incidence of liver neoplasms over that of controls. The results of this study indicate that chlordane, heptochlor, and DDT induce hepatocellular foci and enhance the development of hepatocellular adenomas and adenocarcinomas in mice pre-treated with diethylnitrosamine. However, the promotional effect seemed to be specific to the liver (Williams and Numoto, 1984). Long-term studies Mice In a combined chronic toxicity and carcinogenicity study, groups of 80 male and 80 female Charles River ICR:SPF mice were fed technical chlordane at dietary concentrations of 0, 1, 5, or 12.5 ppm for 104 weeks. An interim sacrifice of eight mice of each sex was conducted at week 52. Chlordane had no apparent effect on the clinical condition of the treated mice, and their mortality was unaffected. No consistent influences on body-weight gain, food consumption, or food-conversion efficiency were observed during treatment. Urinalysis and full haematological examination, performed at weeks 52 and 104, were unremarkable. There was a tendency for increased serum aspartate aminotransferase and alanine aminotransferase among the mid- and high-dose groups. Similarly, gamma-glutamyl transpeptidase values were elevated among some high-dose females at 52 weeks. At terminal sacrifice there was a dose-related increase in hepatic size and relative and absolute liver weight in treated males; treated females exhibited less of an increase in hepatic weight, especially at the highest dose. Increased incidences of liver nodules were found in mid- and high-dose groups, especially in male mice. Histopathological lesions corresponding to the above changes were found. In males, hepatocellular swelling, with associated changes to hepatic cords and hepatocytes, increased in incidence from week 52 at the high dose and from week 79 at the mid dose. Hepatocellular fatty degeneration occurred at the high dose, while hepatocellular necrosis was increased in incidence in the mid- and high-dose groups at terminal sacrifice. There were increased incidences of hepatocellular adenomas and haemangiomas in the high-dose males at termination. Female mice exhibited a dose-related increase in the incidence of hepatocellular swelling, with a tendency for hepatocellular necrosis in only the high-dose group. The incidence of hepatic tumours in female mice was not increased by treatment. The results of this study indicate a no-observed-effect level of 1 ppm (Ihui et al., 1983a). Rats Groups of 80 male and 80 female F-344 SPF rats were fed technical chlordane in the diet at 0, 1, 5, or 25 ppm for 130 weeks before sacrifice. Interim sacrifices of groups of eight males and nine females were conducted at 26 and 52 weeks for pathological investigation. Treatment with chlordane produced no clinical signs of toxicity and had no effect on mortality. Body weights, food consumption, and food-conversion efficiency of treated animals were not consistently different from controls. Urinalysis of sample groups of eight male and eight female rats were unaffected by treatment after 26 and 52 weeks; however, all groups exhibited proteinuria and haematuria at week 130. Haematological and biochemical parameters, including serum hepatic enzyme levels (aspartate and alanine aminotransferases, gamma-glutamyl transpeptidase, and alkaline phosphatase), were not influenced by treatment. Serum bilirubin levels were increased in mid- and high-dose male groups at termination. At necropsy significant increases in absolute and relative liver weights in treated groups, as compared with controls, were noted; absolute hepatic weights were increased in high-dose females at 26 and 52 weeks and in mid- and high-dose males at 130 weeks, while relative liver weights were significantly increased in both high-dose groups. Histopathological examination revealed a significantly-increased incidence of hepatocellular swelling centered on hepatic nodules in male and female high-dose rats and in some mid- and low-dose males, towards the end of the study. There was also an increased incidence of diffuse hepatocellular necrosis in some high- and some low-dose male rats dying after week 79, but this lesion was not found at terminal sacrifice. High-dose male rats also had an increased incidence of hepatocellular adenomas. The incidences of mammary fibroadenoma and adenoma were increased in treated females but not in a dose-related manner. A no-effect level of 1 ppm was indicated by this study (Ihui et al., 1983b). Observations in humans Clinical and epidemiological studies of chlordane exposure in man have been reviewed (IARC, 1979; IPCS, 1984). Additional studies are reviewed here. Table 1 summarizes surveys of blood concentrations of workers engaged in chlordane manufacture. Table 1. Human blood chlordane concentrations in workers engaged in chlordane manufacture Blood chlordane concentration (ppb) Number of Year workers Range Mean 1975 50 0.7-32.0 6.6 1976 135 0.1-29.4 3.3 1979 109 0.8-76.9 11.2 Adipose tissue concentrations ranged from 900-6400 ppm with an average concentration of 4067 ppm. Atmospheric concentrations in the plant typically range from 10-550 µg/m3, although higher concentrations may occur in certain areas. Significant surface residues also contribute to exposure. Blood concentrations of chlordane and heptochlor and their metabolites ranged from 0-75 ppb (mean 1.5 ppb) among 411 pest-control operators (Khasawinah, 1986). A survey of 567 randomly-selected serum samples collected from citrus field workers found blood oxychlordane, heptochlor epoxide, and trans-nonachlor concentrations, where detected, ranging from 0.2-2.9 ppb (Griffith & Duncan, 1985). A recent survey of 22 male and 21 female volunteer Japanese city dwellers has found the chlordane derivatives oxychlordane and trans- nonachlor to be the main terminal residues in blood at concentrations ranging from 0.18 - 1.16 mg/ml. A significant correlation was noted between the concentrations of trans-nonachlor and oxychlordane, between trans-chlordane and cis-chlordane, and between trans-chlordane and cis-nonachlor. Dietary exposure seemed to be the main source of the residues, although termite treatment of dwellings remained a possible exposure source in some cases (Wariishi et al., 1986). Results of a large-scale human monitoring programme indicated that the general U.S. population is exposed to relatively low levels of trans-nonachlor and oxychlordane. Blood concentrations were determined in approximately 21,000 individuals aged 12-74 years during the period 1976-1980. In only 4.4% of the general population were quantifiable levels of trans-nonachlor (median 1.4 ppb; range 1-17 ppb) found; the proportion of population subgroups that were exposed increased with increasing age. Some 2.5% of the population had quantifiable oxychlordane (median 1.7 ppb, range 1-23 ppb) or heptochlor epoxide (median 1.7 ppb, range 1-23 ppb) in the blood (Murphy and Harvey, 1985). A follow-up prospective mortality study of workers occupationally exposed to chlordane during manufacture during the period January 1946 to June 1985 has been reported. The study examined the rates of overall mortality, cerebrovascular deaths, and cancer mortality in 800 employees with at least three months' exposure, in relation to standard mortality ratios. Chlordane exposure was ranked by consideration with the results of blood oxychlordane concentrations previously determined. Compared to other employees, production workers had less overall mortality, with lower standard mortality ratios for both heart disease and cancer. However, they did experience an apparent, although not statistically significant, mortality excess from cerebrovascular accident and trauma. Twenty cerebrovascular deaths occurred among 176 deaths, when 11.7 were to be expected. This excess cerebrovascular mortality occurred in one occupational subgroup with high pesticide exposure and in another with low exposure. The apparent excess of cerebrovascular mortality contrasts with the observed overall deficit of cardiovascular disease. In comparison to the U.S. male population, overall cancer mortality was slightly reduced in production workers and was at the expected level for others. No type of cancer consistently occurred and there seemed to be an inverse relationship between cancer mortality and length of employment. The results of this study do not suggest any association between occupational exposure to chlordane and human mortality or cancer incidence (Shindell and Ulrich, 1986). A further follow-up study of the mortality of pesticide applicators has been conducted. Termite-control operators with a high probability of exposure to chlordane and hepatochlor were identified among a cohort of 16,126 male pesticide applicators employed in the period January 1968 to September 30, 1981. Although ascertainment was incomplete, the overall number of deaths among the cohort and the termite-control operators was less than expected. No single cause of death was significantly elevated, although the incidences of cancers of the lung, skin, and bladder were each slightly increased among the cohort, rather than the termite-control operators. Thus, there was no apparent association between chlordane exposure and increased mortality or human cancer in this study (McMahon et al., 1986). COMMENTS A comparative study of absorption, distribution, and excretion of orally-administered cis-chlordane (alpha-chlordane) in rats and mice indicated significant qualitative differences. It remains uncertain, however, whether one of these species is a better animal model for humans than the other. As previously noted, there has been uncertainty over the potential for chlordane, and to a lesser extent, heptochlor and/or their metabolites, to accumulate in tissues. The presence of trans-nonachlor and oxychlordane in human milk and adipose tissue has been previously recognized (IPCS, 1984). The 1982 JMPR noted the significant differences in the metabolism of chlordane by rats and humans, but was concerned that metabolites such as trans-nonachlor could accumulate in human tissues. Recent human data suggest the presence of low blood levels of cis- and trans-oxychlordane and cis- and trans-nonachlor and their metabolites in the general population. These studies do not indicate that either trans-nonachlor or oxychlordane are accumulating in human tissues to a significant extent. Hence, the need for further study with oxychlordane in rats has been superseded. An inhalation study indicates that the monkey, Macaca irus, is less susceptible to chlordane toxicity than rats. A study in baboons did not indicate that low dietary levels of chlordane adversely influenced serum lipoprotein or cholesterol levels, or the development of atherosclerosis. The recent chronic feeding study in rats has confirmed and extended the results of previous studies. Proliferative lesions in the liver were seen at a significant level at 25 ppm in male rats. Hepatic changes, suggestive of an adaptive response, occurred at lower doses, but these were not considered to represent an adverse toxicological effect. A further chronic feeding study has again confirmed the liver as the target organ for chlordane toxicity in mice. Liver tumours occurred in male mice at 12.5 ppm, but significant hepatic changes were seen at lower doses. Chlordane seems to act as a tumour promoter in the mouse liver. Additional epidemiological data from two mortality studies of occupationally-exposed individuals do not suggest that chlordane exposure adversely affects the mortality or development of cardiovascular diseases or cancer. However, the value of these data is limited by relatively small group-sizes and uncertainty of duration and degree of exposure. The temporary ADI was converted to an ADI at a lower level. TOXICOLOGICAL EVALUATION LEVEL CAUSING NO TOXICOLOGICAL EFFECT Mice: 1 ppm in the diet, equal to 0.12 mg/kg b.w./day. Dogs: 3 mg/kg in the diet, equal to 0.075 mg/kg b.w./day. Rats: 1 ppm in the diet, equivalent to 0.05 mg/kg b.w./day. ESTIMATE OF ACCEPTABLE DAILY INTAKE IN MAN 0-0.0005 mg/kg b.w. FURTHER WORK OR INFORMATION STUDIES WHICH WILL PROVIDE INFORMATION VALUABLE FOR THE CONTINUED EVALUATION OF THE COMPOUND Further human monitoring data. Investigation of the promotional activity of chlordane on the diethylnitrosamine-induced liver tumours in a species other than the mouse, with special emphasis on cytochrome P-450 induction. REFERENCES Ewing, A.D., Kadry, A.M., & Dorough, H.W., 1985. Comparative disposition and elimination of chlordane in rats and mice. Toxicology Letters, 26, 233-239. Griffith, J. & Duncan, R.C., 1985. Serum organochlordane residues in Florida citrus workers compared to the National Health and Nutrition Examination Survey sample. Bull. Environ. Contam. Toxicol., 35, 411-417. Hardy, C.J., Clark, G.C., Street, A.E., Read, L.E., Gopinath, C., Gregson, R.L., & Down, W.H., 1984. Chlordane, a 90-day inhalation toxicity study in the rat and monkey. Unpublished report by Huntingdon Research Centre, Huntingdon, Cambridgeshire, England. Submitted to WHO by Velsicol Chemical Corp., Chicago, IL, USA. IARC, 1979. IARC monographs on the evaluation of the carcinogenic risk of chemicals to man: some halogenated hydrocarbons. Chlordane. International Agency for Research on Cancer, Lyon, Volume 20, pp. 45-65. IPCS, 1984. Chlordane, Environmental Health Criteria No 34. International Programme on Chemical Safety, WHO, Geneva. Ihui, S., Hayakawa, T. Yonemura, T., Takamura, F., Takahashi, Y., & Yamazaki, K., 1983a. Twenty-four month chronic toxicity and tumourigenicity test in mice by chlordane technical. Unpublished report by Research Institute for Animal Science in Biochemistry and Toxicology. Submitted to WHO by Velsicol Chemical Corp., Chicago, IL, USA. Ihui, S., Hayakawa, T., Yonemura, T., Takamura, F., Takahashi, Y., & Hashizume, M., 1983b. Thirty-month chronic toxicity and tumourigenicity test in rats with chlordane technical. Unpublished report by Research Institute for Animal Science in Biochemistry and Toxicology. Submitted to WHO by Velsicol Chemical Corp., Chicago, IL, USA. Khasawinah, A.M., 1986. Plant workers and pest control operators exposure to chlordane and heptachlor. Unpublished report. Submitted to WHO by Velsicol Chemical Corp., Chicago, IL, USA McGill, H., Mott, G.E., Kruski, A.W., Montiel, M.M., Stavinoha, W.B., Coelho, A.M., Carey, K.D., & McMahan, C.A., 1979. Pilot study of the effects of pesticides on blood lipoproteins, arteries and cardiac muscle of baboons. Unpublished report by University of Texas Health Science Center and Southwest Foundation for Research and Education. Submitted to WHO by Velsicol Chemical Corp., Chicago, IL, USA McMahon, B., Wang, H., & Monson, R., 1986. A second follow-up of mortality in a cohort of pesticide applicators. Unpublished report. Submitted to WHO by Velsicol Chemical Corp., Chicago, IL, USA Murphy, R. & Harvey, C., 1985. Residues and metabolites of selected persistent halogenated hydrocarbons in blood specimens from a general population survey. Environmental Health Perspectives, 60, 115-120. Shindell, S. & Ulrich, S., 1986. Mortality of workers employed in the manufacture of chlordane: An update. J. Occup. Med., In Press. Wariishi, M., Suzuki, Y., & Nishiyama, K., 1986. Chlordane residues in normal human blood. Bull. Environ. Toxicol., 36, 635-643. Williams, G.M. & Numoto, S., 1984. Promotion of mouse liver neoplasms by the organochlorine pesticides chlordane and heptachlor in comparison to dichlorodiphenyltrichloroethane. Carcinogenesis, 5, 1689-1696.
See Also: Toxicological Abbreviations Chlordane (EHC 34, 1984) Chlordane (HSG 13, 1988) Chlordane (PIM 574) Chlordane (FAO Meeting Report PL/1965/10/1) Chlordane (FAO/PL:1967/M/11/1) Chlordane (FAO/PL:1969/M/17/1) Chlordane (AGP:1970/M/12/1) Chlordane (WHO Pesticide Residues Series 2) Chlordane (WHO Pesticide Residues Series 4) Chlordane (Pesticide residues in food: 1977 evaluations) Chlordane (Pesticide residues in food: 1982 evaluations) Chlordane (Pesticide residues in food: 1984 evaluations)