Residential pesticide exposure and neuroblastoma

Health Effects of Chronic Pesticide Exposure: Cancer and Neurotoxicity

Pesticides are widely used in agricultural and other settings, resulting in continuing human exposure. Epidemiologic studies indicate that, despite premarket animal testing, current exposures are associated with risks to human health. In this review, we describe the routes of pesticide exposures occurring today, and summarize and evaluate the epidemiologic studies of pesticide-related carcinogenicity and neurotoxicity in adults. Better understanding of the patterns of exposure, the underlying variability within the human population, and the links between the animal toxicology data and human health effects will improve the evaluation of the risks to human health posed by pesticides. Improving epidemiology studies and integrating this information with toxicology data will allow the human health risks of pesticide exposure to be more accurately judged by public health policy makers.

Farm Childrenʼs Exposure to Herbicides

BACKGROUND

Pesticide exposure has been associated with various childhood cancers. However, most studies rely on questionnaires, with few using biologic measures of dose. This study was designed to measure herbicide exposure directly in children of farm applicators, and to compare these results with exposure imputed from questionnaire information.

METHODS

Two consecutive 24-hour urine samples were collected from 92 children of Ontario farm applicators who used the herbicides 2,4-D (2,4-dichlorophenoxyacetic acid) or MCPA (4-chloro-2-methylphenoxyacetic acid) for the first time during 1996. The farm applicator completed questionnaires describing his pesticide-handling practices as well as the child's location during the various stages of handling these pesticides.

RESULTS

Approximately 30% of the children on farms using these herbicides had detectable concentrations in their urine, with maximum values of 100 microg/L for 2,4-D and 45 microg/L for MCPA. Children with higher levels were more likely to be boys and to have parents who also had higher mean urinary concentrations. The sensitivity and specificity of a simple indicator of use were 47% and 72%, respectively, for 2,4-D, and 91% and 30%, respectively, for MCPA, using the biomonitoring data as the gold standard.

CONCLUSIONS

Information on living on a farm, or on living on a farm where a specific pesticide is used, is not enough to classify children's exposures. Given this potential for misclassification, we urge incorporation of biomonitoring studies in subsets of children at least to estimate the extent of misclassification.

Questionnaire assessment of nonoccupational pesticide exposure in epidemiologic studies of cancer

Pesticides have been examined in epidemiologic studies as environmental risk factors for cancer, in part, due to the identification of carcinogenic properties of some of these chemicals using animal models. Although the majority of these epidemiologic studies have focused on occupational pesticide exposure, nonoccupational pesticide exposure has also been investigated. The objective of this paper is to review the methodological issues of nonoccupational pesticide exposure assessment, including identifying the methods that have been used to assess self-reported nonoccupational pesticide exposure in epidemiologic studies of cancer, and discussing the strengths and limitations of the current methodology as well as possible enhancements that could be incorporated into future investigations. Issues of exposure assessment that will be reviewed include specificity, recall, and characteristics of pesticide exposure. Additionally, sources of nonoccupational pesticide exposure other than residential will be briefly reviewed.