Academic journal article Environmental Health Perspectives

Characterizing Exposures to Nonpersistent Pesticides during Pregnancy and Early Childhood in the National Children's Study: A Review of Monitoring and Measurement Methodologies

Academic journal article Environmental Health Perspectives

Characterizing Exposures to Nonpersistent Pesticides during Pregnancy and Early Childhood in the National Children's Study: A Review of Monitoring and Measurement Methodologies

Article excerpt

The National Children's Study is a proposed longitudinal cohort study to evaluate the relationships between children's health and the environment. Enrollment is estimated to begin in September 2005, and 100,000 children will be followed from preconception or early pregnancy until adulthood. Among multiple health outcomes, the study is proposing to investigate whether pre- and/or postnatal exposures to nonpersistent pesticides increase the risk of poor performance on neurobehavioral and cognitive exams during infancy and early childhood. Characterization of exposures will be challenging. Nonpersistent pesticides include many chemicals with biologic half-lives on the order of hours or days. Exposures can occur through multiple pathways (e.g., food and residential or agriculture pesticide use) and by multiple routes (inhalation, ingestion, dermal). Effects may depend on the developmental stage when exposure occurs. Sequential sampling is likely to be required and may involve a combination of environmental and biologic monitoring as well as collection of questionnaire data. In this article we review measurements that can be used to characterize exposures. These include biologic markers, personal and indoor air sampling techniques, collection of dust, surface and dermal wipe samples, and dietary assessment tools. Criteria for sample selection will necessitate evaluation of the time frame of exposure captured by the measurement in relationship to critical windows of susceptibility, the cost and validity of the measurements, participant burden, and variability in exposure routes across populations and at different age periods. Key words: biomonitoring, early childhood, environment, exposure assessment, in utero, National Children's Study, pesticides. doi:10.1289/ehp.7769 available via http://dx.doi.org/[Online 12 May 2005]

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Pesticide use is widespread in the United States. A billion pounds or more of conventional pesticides are used annually, and 85% of households store at least one pesticide in their homes (Adgate et al. 2000; Kiely et al. 2004). Approximately 78% of conventional pesticide use is for agriculture, 10% is used in the home and garden, and the remainder is for government, commercial building, and industrial use. Recent biologic monitoring studies indicate that pesticide exposures are ubiquitous, including among women of childbearing age, pregnant women, children, and fetuses (Adgate et al. 2001; Barr et al. 2004; Berkowitz et al. 2003; Bradman et al. 2003; Lu et al. 2000; Whyatt and Barr 2001; Whyatt et al. 2003). To test the hypothesis that exposures to nonpersistent pesticides in utero and postnatally increase the risk of poor performance on neurobehavioral and cognitive examinations, the National Children's Study (NCS) will need to characterize exposures to a broad array of pesticides. The Exposure to Chemical Agents and Development and Behavior 2002 Interworking Group to the NCS, for example, has recommended that this hypothesis focus on current-use neurotoxic insecticides, including organophosphates (OPs), carbamates, pyrethroids, and nicotinoids, and additionally consider other current-use pesticides.

Exposure assessment will be challenging. Nonpersistent pesticides do not accumulate in the body and are generally excreted within hours and days, often via water-soluble metabolites in urine. Biologic exposure markers tend to reflect low-level, transient exposures that are highly variable. Further, the pesticides often degrade rapidly in the ambient environment. Although persistence in the indoor environment appears longer (Gurunathan et al. 1998; Lewis et al. 1994; Whyatt et al. 2004a), indoor levels can be highly variable depending on use patterns. Pesticide exposures can also vary by season (Berkowitz et al. 2003; Whyatt et al. 2003), and exposures can occur through multiple pathways and routes. Diet may be a significant source for some children (Clayton et al. 2003). Dermal exposure and non-intentional ingestion as well as inhalation may all be important routes for pesticides used in the home (Clayton et al. …

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