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A Longitudinal Approach of Assessing Urban and Suburban Children’s Exposure to Pyrethroid Pesticides

Environmental Health Prospectives - Lu C, Barr D, Pearson M, Bartell S, Bravo R
April 26, 2006

Pyrethroids, a group of synthetic insecticides, were manufactured in the 1970s
after the removal of organochlorine insecticides, such as DDT, from the consumer
market. The synthetic pyrethroids not only inherit the biological activity (ability to kill
insects) from their natural counterpart, pyrethrin, which is found in chrysanthemums, but
also improve their environmental stability. Pyrethroids are widely used in agriculture,
forest, textile industry, and public health programs worldwide (Heudorf and Angerer,
2001). With the phase-out of organophosphorus (OP) pesticide use in residential
environments in the U.S. (U.S. EPA 1998), the availability of pyrethroids for consumer
uses has increased since the late 1990s (U.S. EPA 2005).

Although individual pyrethroid insecticides share some common physical and
chemical properties as a group, unlike OP pesticides, their toxicological mechanisms vary
in mammals. Pyrethroid insecticides are subject for review as potential developmental
neurotoxicants because of their mode of action on voltage-sensitive sodium channels
(Shafer et al. 2005). In addition, permethrin, the most widely used pyrethroid insecticide,
is suspected as an endocrine disrupting chemical (Chen et al. 2002; Kakko et al. 2004;
Kim et al. 2004) and, along with fenvalerate, has been classified as a potential carcinogen
at high exposure levels (U.S. EPA 1989). Toxicological studies have also suggested that
pyrethroids have a suppressive effect on the immune system and may cause lymph node
and spleen damage (Repetto 1996).

Although pyrethroids have been sold in the U.S. consumer market for more than
30 years with the estimated annual use ranging from several thousands to a million
pounds (ATSDR 2003), very few studies have been conducted to quantitatively assess
human exposures to pyrethroids. Most of the relevant data were obtained from studies
conducted in Germany or in occupational settings (Hardt and Angerer 2003; Leng et al.
2003). Recently, the Center for Disease Control and Prevention reported urinary
pyrethroid metabolite levels for the U.S. population aged 6-59 years in the Third National
Report on Human Exposure to Environmental Chemicals, which is part of the National
Health and Nutrition Examination Survey (NHANES) conducted in 2001-2002 (CDC
2005). All of these studies were conducted cross-sectionally, and therefore, the results
only represent exposures over relatively short time periods.

The primary objective of this study was to establish a temporal profile of
pyrethroid exposure in a cohort of elementary school-aged children living in an
urban/suburban community using urinary pyrethroid metabolites as exposure biomarkers.
We also examined the relationship between pyrethroid exposure and children’s diets,
self-reported residential pyrethroid use, and age.

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