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Studies and Reports

  • Purdue M et al., Occupational exposure to organochlorine insecticides and cancer incidence in the Agricultural Health Study, Int J Cancer. 2007 Feb 1;120(3):642-9.
    • Abstract. "Organochlorine (OC) insecticides have been regulated as possible human carcinogens primarily on the basis of animal studies. However, the epidemiologic evidence is inconsistent. We investigated the relationship between cancer incidence and OC insecticide use among pesticide applicators enrolled in the Agricultural Health Study, a prospective cohort study of 57,311 licensed applicators in Iowa and North Carolina enrolled between 1993 and 1997. Information on ever use of 7 OC insecticides (aldrin, chlordane, DDT, dieldrin, heptachlor, lindane, toxaphene) was collected from a self-administered questionnaire at enrollment. Lifetime exposure-days to OC insecticides were calculated using additional data from a take-home questionnaire completed by 25,291 participants (44% of total). We found no clear evidence of an association between use of OC insecticides and incident cancers (N = 1,150) ascertained through December, 2002. When we focused on individual insecticides and structurally similar groups (aldrin and dieldrin; chlordane and heptachlor), significantly increased relative risks of some cancers were observed for use of some chemicals (rectal cancer and chlordane, lung cancer and dieldrin, non-Hodgkin lymphoma (NHL) and lindane, melanoma and toxaphene, leukemia and chlordane/heptachlor). Some significant decreased relative risks were also observed (colon cancer and aldrin; overall cancer and heptachlor). In conclusion, we did not observe any clear relationship between cancer risk and the use of OC insecticides. Our chemical-specific findings are based on small numbers and multiple comparisons, and should be interpreted with caution; however, some observed associations (lindane and NHL, chlordane/heptachlor and leukemia) are supported by previous evidence."
  • Colt J et al., Residential insecticide use and risk of non-Hodgkin's lymphoma, Cancer Epidemiol Biomarkers Prev. 2006 Feb;15(2):251-7.
    • Abstract. "Previous studies have linked non-Hodgkin's lymphoma (NHL) with occupational exposure to insecticides, but residential use is largely unexplored. In this population-based case-control study, we examined NHL risk and use of insecticides in the home and garden. We identified NHL cases, uninfected with HIV, diagnosed between 1998 and 2000 among women and men ages 20 to 74 years in Iowa and the metropolitan areas of Los Angeles, Detroit, and Seattle. Controls were selected using random digit dialing or Medicare files. Computer-assisted personal interviews (1,321 cases and 1,057 controls) elicited data on insecticide use at each home occupied since 1970. Insecticide levels were measured in dust taken from used vacuum cleaner bags (682 cases and 513 controls). We previously reported a positive association with dichlorodiphenyldichloroethylene levels in carpet dust residues. Here, we focus on insecticides that were commonly used after 1970, the time period covered by our questionnaire. People whose homes were treated for termites had elevated NHL risk (odds ratio, 1.3; 95% confidence interval, 1.0-1.6). Risk was modestly, although not significantly, elevated in all but one study center and in all sexes and races. The elevation in risk was restricted to people whose homes were treated before the 1988 chlordane ban. There was a significant trend of increasing risk with increasing levels of alpha-chlordane residues in dust (P(trend) = 0.04) and a marginally significant trend for gamma-chlordane (P(trend) = 0.06). We found no evidence of associations for insects overall, for specific types of insects other than termites, or for elevated residues of other insecticides. We concluded that chlordane treatment of homes for termites may increase residents' NHL risk."
    • Comment. The reported odds ratio is not statistically significant on the confidence interval.
  • Cocco P et al., Cancer mortality among men occupationally exposed to dichlorodiphenyltrichloroethane, Cancer Res. 2005 Oct 15;65(20):9588-94.
    • Abstract. " Several studies have evaluated cancer risk associated with occupational and environmental exposure to dichlorodiphenyltrichloroethane (DDT). Results are mixed. To further inquire into human carcinogenicity of DDT, we conducted a mortality follow-up study of 4,552 male workers, exposed to DDT during antimalarial operations in Sardinia, Italy, conducted in 1946 to 1950. Detailed information on DDT use during the operations provided the opportunity to develop individual estimates of average and cumulative exposure. Mortality of the cohort was first compared with that of the Sardinian population. Overall mortality in the cohort was about as expected, but there was a deficit for death from cardiovascular disease and a slight excess for nonmalignant respiratory diseases and lymphatic cancer among the unexposed subcohort. For internal comparisons, we used Poisson regression analysis to calculate relative risks of selected malignant and nonmalignant diseases with the unexposed subcohort as the reference. Cancer mortality was decreased among DDT-exposed workers, mainly due to a reduction in lung cancer deaths. Birth outside from the study area was a strong predictor of mortality from leukemia. Mortality from stomach cancer increased up to 2-fold in the highest quartile of cumulative exposure (relative risk, 2.0; 95% confidence interval, 0.9-4.4), but no exposure-response trend was observed. Risks of liver cancer, pancreatic cancer, and leukemia were not elevated among DDT-exposed workers. No effect of latency on risk estimates was observed over the 45 years of follow-up and within selected time windows. Adjusting risks by possible exposure to chlordane in the second part of the antimalarial operations did not change the results. In conclusion, we found little evidence for a link between occupational exposure to DDT and mortality from any of the cancers previously suggested to be associated."
  • Cantor.l K et al., Risk of non-Hodgkin's lymphoma and prediagnostic serum organochlorines: beta-hexachlorocyclohexane, chlordane/heptachlor-related compounds, dieldrin, and hexachlorobenzene, Environ Health Perspect. 2003 Feb;111(2):179-83.
    • Abstract. "Increases in non-Hodgkin's lymphoma (NHL) incidence and mortality rates during the past few decades remain largely unexplained. Studies suggest that organochlorine pesticides may contribute to an increased risk of NHL. In 1974, serum samples were obtained from 25,802 participants in the Campaign Against Cancer and Stroke in Washington County, Maryland (USA), and cryopreserved for future study. We measured prediagnostic levels of chlordane, lindane (gamma-hexachlorocyclohexane), beta-hexachlorocyclohexane, transnonachlor, heptachlor, heptachlor epoxide, oxychlordane, dieldrin, and hexachlorobenzene in serum samples of 74 cases of NHL and 147 matched controls. Previously, we found an association between NHL and serum levels of total PCBs (polychlorinated biphenyls), but not DDT (dichlorodiphenyltrichloroethane) and related compounds. In this instance, there was no evidence of an association between NHL risk and serum levels of any of the individual lipid- and recovery-corrected organochlorines that we evaluated, nor of the summed chlordane-related compounds (transnonachlor, heptachlor, heptachlor epoxide, oxychlordane). These findings do not support the hypothesis that the organochlorine compounds included in this study are strongly linked to the development of NHL. The possibility of a weak association cannot be excluded by these data."
  • Zheng T et al., Oxychlordane and trans-nonachlor in breast adipose tissue and risk of female breast cancer, J Epidemiol Biostat. 2000;5(3):153-60.
    • Conclusion. "We found no significantly increased risk of breast cancer associated with breast adipose-tissue levels of OCD or TNC; this is consistent with recent epidemiological studies, indicating that environmental exposure to organochlorine compounds does not have an overall significant impact on breast-cancer risk."
  • Kamble S et al., Exposure of applicators and residents to chlordane and heptachlor when used for subterranean termite control, Arch Environ Contam Toxicol. 1992 Apr;22(3):253-9.
    • Abstract. "Research was conducted to assess dermal and respiratory exposure to applicators from chlordane and heptachlor used for subterranean termite control and exposure to residents of treated homes. Dermal exposure of 29 applicators was evaluated by using gauze pads attached to outer and inner clothing at selected body regions. Respiratory exposure of applicators was monitored with personnel-type air samplers worn during application periods. Air samplers were equipped with polyurethane foam plugs to trap airborne chlordane and heptachlor. Exposure of residents was measured by sampling ambient air of 19 homes treated with the termiticides. Electric air samplers equipped with foam plugs were used to monitor ambient air from the basement, the kitchen, and one bedroom at: 24 h prior to termiticide application, during application, and post-application at 24 h, 1 wk, and monthly for 6 mo. Applicator dermal exposure was estimated based on exposure rates to each body region. Respiratory exposure was estimated based on termiticide concentrations in the air and on the ventilation rate of a person doing light work. Residents' exposure was estimated based on the amount of termiticide present in ambient air. Results indicated that applicator exposure rates to chlordane and heptachlor were 2.54 and 1.88 micrograms/kg/h, respectively. Residents were exposed to less than 0.69 and 2.86 micrograms/m3 of chlordane and heptachlor, respectively. During this research, the application of termiticide containing chlordane and heptachlor posed minimal risk in terms of acute exposure to either the applicators or the residents of the treated homes."
  • MacMahon B et al., A second follow-up of mortality in a cohort of pesticide applicators, J Occup Med. 1988 May;30(5):429-32.
    • Abstract. "A cohort of 16,124 male pesticide applicators was matched with Social Security Administration and National Death Index (NDI) files through December 31, 1984. In all, 1,082 deaths were ascertained, and death certificates were obtained for 994 (92%). The standardized mortality ratio (SMR) for all causes of death was 98. Although a number of specific causes of death showed SMRs significantly below 100, only one category of cause of death showed a significantly elevated SMR--cancer of the lung, with an SMR of 135. Termite control operators (TCO)--the group with the greatest likelihood of exposure to chlordane and heptachlor--had an SMR for lung cancer of 97, compared with 158 for other pesticide operators. The excess of lung cancer in the non-TCO workers was limited to operators employed as such for less than five years."
  • Blisard K et al., The investigation of alleged insecticide toxicity: a case involving chlordane exposure, multiple sclerosis, and peripheral neuropathy, J Forensic Sci. 1986 Oct;31(4):1499-504.
    • Abstract. "A man with no previous medical problems had two documented exposures to an insecticide containing the organophosphorous compounds chlordane and heptachlor. Six months to one year later, he began to experience neurological symptoms which progressed until his death. At autopsy, his brain showed classic findings of multiple sclerosis, and he had a severe peripheral neuropathy. Review of the literature indicates that the findings are not compatible with chlordane toxicity. Some of the factors to be used in determining the casual relationship between toxic exposure and disease processes are discussed."
  • Shindell S and Ulrich S, Mortality of workers employed in the manufacture of chlordane: an update, J Occup Med. 1986 Jul;28(7):497-501.
    • Abstract. "A prospective mortality study was conducted of the 800 employees who worked 3 months or more during the period January 1946 through June 1985, in the only plant in the US where the termiticide chlordane has been produced. The study covers the entire period of chlordane production to date and includes 7,347 person-years of employment at the chlordane plant and 21,585.5 person-years of follow-up since commencement of employment. All but three former employees considered to be alive at the end of the study period were either contacted directly or were identified as alive by a variety of reliable sources. Death certificates were obtained for 161 of the 181 decedents and reliable causes of death were reported for an additional 11 cases. Overall death rate was slightly less than expected but not to the level of statistical significance. Production workers with higher pesticide blood levels had lower standardized mortality ratios for cancer than nonproduction employees, and there appears to be an inverse relationship of cancer mortality to length of employment. An unexplained excess of cerebrovascular deaths was observed, offset by a lesser degree of cardiovascular deaths."
  • Ditraglia D et al., Mortality study of workers employed at organochlorine pesticide manufacturing plants, Scand J Work Environ Health. 1981;7 Suppl 4:140-6.
    • Abstract. "A retrospective cohort study was conducted to examine the mortality of workers employed in the manufacture of the chlorinated hydrocarbon pesticides, chlordane, heptachlor, dichloro-diphenyl-trichloro-ethane (DDT) and aldrin/dieldrin/endrin. Four manufacturing plants were selected for study, and each cohort included all workers employed for at least six months prior to January 1964. The entire study group totaled approximately 2,100 individuals. Vital status ascertainment for these cohorts ranged from 90 to 97% complete; the cut-off date for follow-up was 31 December 1976. In general there were too few deaths in this study on which to draw any meaningful conclusions. The standardized mortality ratio (SMR) for all causes in each cohort was below the expected level (100) and ranged from 66 to 82, probably a reflection of the "healthy worker effect." For "all malignant neoplasms" the SMRs ranged from 68 to 91 and for respiratory cancer from 55 to 132. In the aldrin/dieldrin/endrin cohort observed deaths due to pneumonia and "other respiratory diseases" were significantly above the expected number of deaths. For several other specific cancer sites (stomach in plant 1, esophagus, rectum, liver and lymphatic/hematopoietic system in plant 3), the observed deaths were more than the expected number and should be examined in more detail. It is recommended that these cohorts be followed for several more years and the mortality patterns be reexamined."
  • Wang H and MacMahon B, Mortality of pesticide applicators, J Occup Med. 1979 Nov;21(11):741-4.
    • Abstract. "Information has been obtained on a cohort of professional pesticide applicators which will be followed prospectively. The cohort consists of 16,126 males employed for three months or more between 1967 and 1976 by any of three nationwide pest control companies. Deaths which occurred between 1967 and 1976 were reported by the Social Security Administration as a result of a search of its records. Overall, 311 deaths were ascertained, giving a standardized mortality ration (SMR) of 84. SMRs were over 100 for three causes of death--cancer of the lung (115), cancer of the skin (173) and cancer of the bladder (277). The confidence intervals of two of these ratios include 100, and the observed numbers therefore do not differ significantly from those expected. For bladder cancer the excess is on the border of statistical significance (p less than 0.05). The excess of deaths from lung cancer was not seen for applicators classified as termite control operators, a group more likely to be exposed to chlordane and heptachlor. There were significantly low SMRs for cancer of the digestive organs (46) and for other diseases of the digestive (55) and respiratory (29) systems. Deaths from cerebrovascular disease were also less than expected, though not significantly so."
  • Wang H and MacMahon B, Mortality of workers employed in the manufacture of chlordane and heptachlor, J Occup Med. 1979 Nov;21(11):745-8.
    • Abstract. "A retrospective mortality study has been carried out on workers employed in the manufacture of chlordane and heptachlor between 1946 and 1976. The study group was comprised of 1403 white males who worked for more than three months at either of the two plants in the United States now producing these compounds. Information on deaths among terminated employees was obtained from the Social Security Administration and supplemented by information collected by another investigator by individual follow-up. There were 113 deaths observed in the group, compared to 157 expected, giving a standardized mortality ratio (SMR) of 72. There was no overall excess of deaths from cancer, even among workers followed twenty or more years after entry into the occupation. There was one death from liver cancer. An excess of deaths from lung cancer (12 observed, 9.0 expected) was not statistically significant and was not distributed by duration of exposure or of latency in any pattern suggesting an etiologic role for chlordane-heptachlor exposure. Although diseases of the circulatory system as a whole showed fewer deaths than expected (SMR 83), there was a statistically significant excess of deaths from cerebrovascular disease (17 observed, 9.3 expected). This excess was not related to duration of exposure or latency and occurred exclusively after termination of employment."
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