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Environmental Health Perspectives (EHP) is a monthly journal of peer-reviewed research and news on the impact of the environment on human health. EHP is published by the National Institute of Environmental Health Sciences and its content is free online. Print issues are available by paid subscription.DISCLAIMER
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Comparative Toxicogenomics Database (CTD)

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Environmental Health Perspectives Volume 111, Number 9, July 2003 Open Access
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Assessing Human Exposure to Phthalates Using Monoesters and Their Oxidized Metabolites as Biomarkers

Dana B. Barr, Manori J. Silva, Kayoko Kato, John A. Reidy, Nicole A. Malek, Donald Hurtz, Melissa Sadowski, Larry L. Needham, and Antonia M. Calafat

Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA

Abstract

Phthalates are a group of industrial chemicals with many commercial uses, such as solvents, additives, and plasticizers. For example, di-(2-ethylhexyl) phthalate (DEHP) is added in varying amounts to certain plastics, such as polyvinyl chloride, to increase their flexibility. In humans, phthalates are metabolized to their respective monoesters, conjugated, and eliminated. However, despite the high production and use of DEHP, we have recently found that the urinary levels of the DEHP metabolite mono-(2-ethylhexyl) phthalate (MEHP) in 2,541 persons in the United States were lower than we anticipated, especially when compared with urinary metabolite levels of other commonly used phthalates. This finding raised questions about the sensitivity of this biomarker for assessing DEHP exposure. We explored the utility of two other DEHP metabolites, mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP) and mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) , as additional DEHP biomarkers. These metabolites are formed by oxidative metabolism of MEHP. In urine from 62 people, both the range and the mean urinary levels of MEOHP and MEHHP were on average 4-fold higher than those of MEHP ; the mean of the individual ratios of MEHHP/MEOHP, MEHHP/MEHP, and MEOHP/MEHP were 1.4, 8.2, and 5.9, respectively. These data suggest that MEOHP and MEHHP are more sensitive biomarkers of exposure to DEHP than is MEHP. These findings also suggest a predominant human metabolic route for DEHP hydrolysis to MEHP followed by oxidation of MEHP ; they also imply that a similar mechanism may be relevant for other high-molecular-weight phthalates, such as di-n-octyl, di-isononyl, and di-isodecyl phthalates. Key words: , , , , . Environ Health Perspect 111:1148-1151 (2003) .
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