Longitudinal Investigation of Dietary Exposure to Selected Pesticides

Article excerpt

Between September 1995 and September 1996, 4-day composite duplicate plate samples (379 solid food samples and 303 beverage samples) were obtained from a stratified random sample of 75 individuals in Maryland and analyzed for the presence of 10 pesticides. Samples were collected in each of six approximately equally spaced cycles as part of a larger pilot investigation of longitudinal exposure to pesticides and other elements. Chlorpyrifos was detected in 38.3% of the solid food samples, malathion in 75.2%, and p,p'-DDE in 21.4%. Other pesticides were detected in less than 10% of the solid food samples. Pesticide residues were not detected in duplicate beverage samples. In solid food samples, the mean concentration of chlorpyrifos was 0.7 (SD 1.7) [micro]g/kg, 1.8 (2.1) for malathion, and 0.2 (0.6) for p,p'-DDE. The detection rate and mean concentration of chlorpyrifos, malathion, and p,p'-DDE varied by a factor of 2-3 among sampling cycles and significantly according to results from several statistical analyses. Co-occurrence of chlorpyrifos and malathion in solid food samples was found relatively frequently and also varied with time. Pesticides were detected in food samples with greatest frequency in spring and summer months and with lowest frequency in winter months. These results support the hypothesis that 4-day average exposure to chlorpyrifos and malathion varies over time for this population mean and for individual members of the population and that correlation between exposures to these two organophosphate pesticides can occur. The measurements of pesticide levels in duplicate plate samples presented here can be used to evaluate and set parameters for dietary exposure models. Key words: chlorpyrifos, p,p'-DDE, duplicate plate, food contamination, malathion, pesticide contamination, pesticide exposure. Environ Health Perspect 109:145-150 (2001). [Online 24 January 2001]

http://ehpnet1.niehs.nih.gov/docs/2001/ 109p145-150macintosh/abstract.html

Passed into law in 1996, the U.S. Food Quality Protection Act (FQPA) requires a more comprehensive assessment than ever before of pesticide exposure, dose, and effects (1,2). In particular, the FQPA requires pesticide risk assessments to consider exposure to potentially sensitive subgroups in the population, coincident dietary and nondietary (i.e., aggregate) exposure, and contemporaneous multichemical (i.e., cumulative) exposure. These issues also are important to epidemiological studies designed to evaluate the associations between selected human health outcomes and pesticide exposure (3-5).

Traditional dietary exposure assessments for pesticides are based on food consumption data from population-based surveys and pesticide levels observed in food samples collected for surveillance monitoring or in a market-basket design (6-13). The utility of this approach is limited by incomplete information on the accuracy of the market-basket methodology, interindividual variability of dietary pesticide exposure, temporal aspects of dietary pesticide exposure, and cumulative pesticide exposure through food. In this paper, we present the results of an investigation of these issues for seven organochlorine insecticides, two organophosphorous insecticides, and one triazine herbicide. The objectives of the study were to a) determine pesticide levels in short-term composite food samples; b) evaluate variability in pesticide occurrence and levels by time of year; c) evaluate variability in pesticide occurrence and levels among individuals; and d) describe co-occurrence of multiple pesticides in short-term food samples. The data presented here are the product of a pilot investigation of temporal variation in human exposure to selected contaminants in multiple media--the National Human Exposure Assessment Survey in Maryland (NHEXAS-Maryland).

Methodology

Study population. A stratified probability sample of 80 individuals older than 10 years of age was selected from four contiguous counties in Maryland that compose the Baltimore metropolitan statistical area. …