Cancer Incidence among Pesticide Applicators Exposed to Dicamba in the Agricultural Health Study

Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20852, USA.
Environmental Health Perspectives (Impact Factor: 7.98). 11/2006; 114(10):1521-6. DOI: 10.1289/ehp.9204
Source: PubMed


Dicamba is an herbicide commonly applied to crops in the United States and abroad. We evaluated cancer incidence among pesticide applicators exposed to dicamba in the Agricultural Health Study, a prospective cohort of licensed pesticide applicators in North Carolina and Iowa.
Detailed pesticide exposure information was obtained through a self-administered questionnaire completed from 1993 to 1997. Cancer incidence was followed through 31 December 2002 by linkage to state cancer registries. We used Poisson regression to estimate rate ratios and 95% confidence intervals for cancer subtypes by tertiles of dicamba exposure. Two dicamba exposure metrics were used: lifetime exposure days and intensity-weighted lifetime exposure days (lifetime days x intensity score).
A total of 41,969 applicators were included in the analysis, and 22,036 (52.5%) reported ever using dicamba. Exposure was not associated with overall cancer incidence nor were there strong associations with any specific type of cancer. When the reference group comprised low-exposed applicators, we observed a positive trend in risk between lifetime exposure days and lung cancer (p = 0.02), but none of the individual point estimates was significantly elevated. We also observed significant trends of increasing risk for colon cancer for both lifetime exposure days and intensity-weighted lifetime days, although these results are largely due to elevated risk at the highest exposure level. There was no apparent risk for non-Hodgkin lymphoma.
Although associations between exposure and lung and colon cancer were observed, we did not find clear evidence for an association between dicamba exposure and cancer risk.

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Available from: Michael C Alavanja
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    • "Findings for pesticides and other agricultural exposures and cancer include several aspects of prostate cancer (family history, aggressive prostate cancer, genetic polymorphisms) [Alavanja et al., 2003; Koutros et al., 2011, 2013], contact with farm animals [Beane et al., 2012], monoclonal gammopathy of undetermined significance [Landgren et al., 2009], telomere length [Hou et al., 2013], and childhood cancer among children of pesticide applicators [Flower et al., 2004]. Many individual pesticides have been evaluated for cancer risk in human studies, some for the first time in the AHS, including atrazine [Beane et al., 2011], glyphosate [De Roos et al., 2005], diazinon [Beane et al., 2005], pendimethalin [Hou et al., 2006], metolachlor [Rusiecki et al., 2006], dicamba [Samanic et al., 2006], fonofos [Mahajan et al., 2006], organochlorine pesticides [Purdue et al., 2007], malathion [Bonner et al., 2007], dichlorvos [Koutros et al., 2008], permethrin [Rusiecki et al., 2009], metribuzin [Delancey et al., 2009], coumaphos [Christensen et al., 2010], and terbufos [Bonner et al., 2010]. "
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    ABSTRACT: Prospective cohorts have played a major role in understanding the contribution of diet, physical activity, medical conditions, and genes to the development of many diseases, but have not been widely used for occupational exposures. Studies in agriculture are an exception. We draw upon our experience using this design to study agricultural workers to identify conditions that might foster use of prospective cohorts to study other occupational settings. Prospective cohort studies are perceived by many as the strongest epidemiologic design. It allows updating of information on exposure and other factors, collection of biologic samples before disease diagnosis for biomarker studies, assessment of effect modification by genes, lifestyle, and other occupational exposures, and evaluation of a wide range of health outcomes. Increased use of prospective cohorts would be beneficial in identifying hazardous exposures in the workplace. Occupational epidemiologists should seek opportunities to initiate prospective cohorts to investigate high priority, occupational exposures. Am. J. Ind. Med. 58:113–122, 2015.
    Full-text · Article · Feb 2015 · American Journal of Industrial Medicine
    • "Exposure to Phenoxy herbicides or contaminants of phenoxy herbicides furans, dioxin, pendimethlin and metolachlor excess lung cancer death were observed in a cohort of employees from four manufacturing plants in Germany (Becher et al., 1996; Hou et al., 2006; Rusiecki et al., 2006). An association was also observed for dicamba, dieldrin and carbofuran exposure and occurrence of lung cancer (Samanic et al., 2006; Purdue et al., 2007; Bonner et al., 2005). "
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    ABSTRACT: The occurrence of cancer in human is strongly associated with chronic exposure to various pesticides. Users may be exposed to pesticides through different ways, such as inhalation (absorption through the lungs) dermal contact (absorption through the skin or eyes) or ingestion (through the mouth). The pesticides such as, arsenic pesticides, dicamba, dieldrin, carbofuran, carbamate, organophosphate, phenyoxyaceticacid, furans, dioxin, pendimethlin and metolachlor are associated with lung cancer. Chronic exposure of dioxin, herbicides, maneb/mancozeb, parathion and carbaryl are extensively associated with the development of melanoma. Similarly the occurrence of prostate cancer is linked with organochlorine, triazine and organophosphates. Pancreatic cancer can be caused by chronic exposure to DDT, DDD ethylan, pendimethalin and overall organochlorine pesticides while breast cancer is strongly linked with organochlorines. This mini review focuses some of the commonly used pesticides and its association with the development of various forms of cancers.
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    • "This possibility is supported by the fact that Alavanja et al. (2003) did not observe an association between metolachlor and lung cancer among applicators exposed for 116–457 LDs. Finally, increased risks of colon cancer observed in chemical specific analyses for dicamba (Samanic et al. 2006) and trifluralin (Kang et al. 2008) do not agree with findings reported in cancer-specific analyses (Lee et al. 2007b). However, analyses for dicamba and trifluralin were limited to ever/never exposure classification in the study by Lee et al. (2007b), whereas Samanic et al. (2006) and Kang et al. (2008) reported increased RRs for colon cancer when exposures were analyzed according to intensity-weighted exposure days. "
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    ABSTRACT: We reviewed epidemiologic evidence related to occupational pesticide exposures and cancer incidence in the Agricultural Health Study (AHS) cohort. Studies were identified from the AHS publication list available at as well as through a Medline/PubMed database search in March 2009. We also examined citation lists. Findings related to lifetime-days and/or intensity-weighted lifetime-days of pesticide use are the primary focus of this review, because these measures allow for the evaluation of potential exposure-response relationships. We reviewed 28 studies; most of the 32 pesticides examined were not strongly associated with cancer incidence in pesticide applicators. Increased rate ratios (or odds ratios) and positive exposure-response patterns were reported for 12 pesticides currently registered in Canada and/or the United States (alachlor, aldicarb, carbaryl, chlorpyrifos, diazinon, dicamba, S-ethyl-N,N-dipropylthiocarbamate, imazethapyr, metolachlor, pendimethalin, permethrin, trifluralin). However, estimates of association for specific cancers were often imprecise because of small numbers of exposed cases, and clear monotonic exposure-response patterns were not always apparent. Exposure misclassification is also a concern in the AHS and may limit the analysis of exposure-response patterns. Epidemiologic evidence outside the AHS remains limited with respect to most of the observed associations, but animal toxicity data support the biological plausibility of relationships observed for alachlor, carbaryl, metolachlor, pendimethalin, permethrin, and trifluralin. Continued follow-up is needed to clarify associations reported to date. In particular, further evaluation of registered pesticides is warranted.
    Full-text · Article · May 2010 · Environmental Health Perspectives
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