Academic journal article Environmental Health Perspectives

Use of Biomarkers to Indicate Exposure of Children to Organophosphate Pesticides: Implications for a Longitudinal Study of Children's Environmental Health

Academic journal article Environmental Health Perspectives

Use of Biomarkers to Indicate Exposure of Children to Organophosphate Pesticides: Implications for a Longitudinal Study of Children's Environmental Health

Article excerpt

Because of their history of widespread use in the United States and unknown long-term health effects, organophosphate pesticides (OPs) are being considered as a chemical class of interest in planning for the National Children's Study, a longitudinal study of children's environmental health. The availability and appropriate use of biomarkers to determine absorbed doses of environmental chemicals such as OPs are critical issues. Biomarkers of OP exposure are typically measured in blood and urine; however, postpartum meconium has been shown to be a promising matrix for assessing cumulative in utero exposure to the fetus, and studies are currently in progress to determine the utility of using saliva and amniotic fluid as matrices. In this article, we discuss the advantages and disadvantages of the currently available OP exposure monitoring methods (cholinesterase inhibition in blood, pesticides in blood, metabolites in urine and alternative matrices); study design issues for a large, long-term study of children's environmental health; and current research and future research needs. Because OPs are rapidly metabolized and excreted, the utility of one-time spot measurements of OP biomarkers is questionable unless background exposure levels are relatively stable over time or a specific time frame of interest for the study is identified and samples are collected accordingly. Biomarkers of OP exposure can be a valuable tool in epidemiology of children's environmental health, as long as they are applied and interpreted appropriately. Key words: biomarkers, blood, children, exposure, meconium, organophosphate, pesticides, study design, urine. Environ Health Perspect 111:1939-1946 (2003). doi:10.1289/ehp.6179 available via http://dx.doi.org/[Online 10 September 2003]

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The Children's Health Act of 2000 authorized the National Children's Study (NCS), a large, multiagency, long-term study of environmental influences on children's health and development (Children's Health Act 2000). The NCS will examine about 100,000 children across the United States and follow them during prenatal development, through birth and childhood, and into adulthood (Branum et al. 2003). The NCS Exposure to Chemical Agents Working Group has identified non-persistent pesticides, including synthetic pyrethroid and organophosphate pesticides (OPs), as chemical classes of study for potential adverse neurodevelopmental outcomes (National Children's Study 2001). The use of biomarkers to determine absorbed doses of environmental chemicals such as OPs is a critical issue for implementing the NCS.

OPs became widely used as the environmentally persistent organochlorine pesticides were banned in the 1970s. OPs gained popularity in the early 1980s because they were relatively inexpensive, readily available, less persistent in the environment, and less susceptible to pest resistance. OPs are used primarily in agriculture on crops, but are also used in residential settings for pest control and for public health protection against vector-borne diseases (Table 1). Approximately 60 million pounds of OPs are applied to U.S. crops annually; nonagricultural uses account for an additional 17 million pounds [U.S. Environmental Protection Agency (U.S. EPA) 1999]. A survey conducted for the U.S. EPA found that nearly half of U.S. households with a child younger than 5 years had a pesticide stored within reach of children (Whitmore et al. 1992). OPs account for about half of all insecticides used in the United States by amount sold. In outdoor settings, OPs are relatively nonpersistent because they are degraded by photochemical and microbiologic actions. However, when used indoors or as a part of structural treatments, these compounds can remain stable for extended periods of time (i.e., months to years; Fenske et al. 2000) and can remain potentially available for repeated exposure to both adults and children.

The safety of OPs has come under increasing scrutiny after the release of the National Research Council's (1993) report focusing on dietary pesticide exposure among infants and children. …

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