Academic journal article Environmental Health Perspectives

Estimating Pesticide Exposure from Dietary Intake and Organic Food Choices: The Multi-Ethnic Study of Atherosclerosis (MESA)

Academic journal article Environmental Health Perspectives

Estimating Pesticide Exposure from Dietary Intake and Organic Food Choices: The Multi-Ethnic Study of Atherosclerosis (MESA)

Article excerpt

Introduction

Organophosphate pesticides (OPs) have been the most commonly used insecticides in the United States for more than three decades. After the passage of the Food Quality Protection Act of 1996, which required food tolerance decisions to consider cumulative and aggregate risk (Food Quality Protection Act 1996), the U.S. Environmental Protection Agency (EPA) conducted chemical-specific risk reassessments of all OPs. These reassessments resulted in substantial reductions in OP use, including the elimination of many agricultural and nearly all residential uses of OPs (Clune et al. 2012). Despite these reductions, OPs remain the primary form of insect control in American agriculture, with > 33 million pounds applied in 2007 (Grube et al. 2011). According to data from the National Health and Nutrition Examination Survey (NHANES) from 2003 to 2004, OP exposure is prevalent; metabolites of OPs were detected in the urine of > 75% of the U.S. population (Barr et al. 2011).

The U.S. EPA's 2006 Cumulative Risk Assessment for OPs determined that the primary route of exposure in the general U.S. population is through diet (U.S. EPA 2006). Studies show that consumption of an organic diet--consisting of food grown without the use of most synthetic pesticides, including OPs--can lead to a substantial and immediate reduction in OP exposure, with metabolite levels dropping below limits of detection immediately after the introduction of organic diets (Lu et al. 2006, 2008). Concentrations of urinary OP metabolites in children consuming organic diets are consistently below limits of detection (Curl et al. 2003; Lu et al. 2006, 2008).

Many studies of OP exposure have used urinary biomarkers to estimate dose. However, OP biomarkers have significant limitations as exposure assessment tools. OP metabolites have short half-lives, only representing exposures over approximately 2 days prior to sample collection (Garfitt et al. 2002; Griffin et al. 1999; Kwong 2002), and within-individual measurements are highly variable (Attfield et al. 2014; Griffith et al. 2011; Kissel et al. 2005). Further, OP metabolites can be found, preformed, in food items and in the environment (Lu et al. 2005; Quiros-Alcala et al. 2012; Zhang X et al. 2008). If these metabolites are excreted unchanged, as has been shown in experimental studies (Forsberg et al. 2011; Timchalk et al. 2007), exposures based on urinary biomarker levels may be overestimated. Dialkylphosphate metabolites (DAPs) are common by-products of the metabolism of most OPs and are frequently used as OP biomarkers; as described by Bravo et al. (2004), six DAPs can be used to represent combined exposure to at least 28 OPs. Because individual OPs can vary in toxicity by as much as 6,000fold (U.S. EPA 2006), this lack of specificity limits the utility of DAPs in risk assessment. For all of these reasons, the oft-used urinary biomarkers do not provide a gold standard for OP exposure assessment, particularly for estimation of long-term exposure. A better measure is one that would accurately quantify exposure to specific parent compounds of known toxicity and would reflect typical, rather than acute, exposures.

We assessed long-term dietary OP exposure in a cohort of 4,466 participants by combining self-reported information on typical dietary intake with average residue levels in those items from a national database. We further assessed the relationship between these estimates and urinary DAP concentrations in a subset of participants with conventional diets (n = 480). This analysis of intermethod comparability was intended as a check on the face validity of our estimates. In a second subset of participants (n = 240), we investigated the association between self-reported organic produce consumption habits and urinary DAP levels.

Methods

Study population. The Multi-Ethnic Study of Atherosclerosis (MESA) was initiated in 1999 to investigate the progression of subclinical cardiovascular disease among 6,814 participants from six metropolitan areas: Baltimore, Maryland; Chicago, Illinois; Forsyth County, North Carolina; Los Angeles County, California; New York, New York; and St. …

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