Academic journal article Environmental Health Perspectives

Urinary Concentrations of 2,4-Dichlorophenol and 2,5-Dichlorophenol in the U.S. Population (National Health and Nutrition Examination Survey, 2003-2010): Trends and Predictors

Academic journal article Environmental Health Perspectives

Urinary Concentrations of 2,4-Dichlorophenol and 2,5-Dichlorophenol in the U.S. Population (National Health and Nutrition Examination Survey, 2003-2010): Trends and Predictors

Article excerpt

Introduction

2,5-Dichlorophenol (2,5-DCP) is a major metabolite of 1,4-dichlorobenzene (1,4-D), which has been used as a chemical intermediate for the manufacture of dyes and pharmaceutical and agricultural products, as a moth repellent, and as a space deodorant for industrial and indoor home applications [Hazardous Substances Data Bank (HSDB) 2014; International Programme on Chemical Safety (IPCS) 1989]. 2,4-Dichlorophenol (2,4-DCP) is primarily used in the production of phenoxy acid herbicides such as 2,4-diphenoxyacetic acid (2,4-D) and for the synthesis of pharmaceuticals and antiseptics (HSDB 2014). 2,4-DCP can also enter the environment as a degradation product of triclosan, an antimicrobial agent (Canosa et al. 2005), and both 2,4-DCP and 2,5-DCP are by-products of the chlorination of municipal drinking water and industrial waste water (HSDB 2014). The U.S. Environmental Protection Agency (EPA 2002) considers dichlorophenols (DCPs) to be hazardous pollutants. General population exposure to DCPs and their precursors can occur through industrial and indoor air pollution, diet, and the use of pesticides and consumer products (HSDB 2014).

Chlorinated phenols are toxic for a wide range of wildlife organisms and humans (Hsiao et al. 2009; IPCS 1989; Takahashi et al. 2011). In 1987, the International Agency for Research on Cancer (IARC) classified 1,4-D as a carcinogen in animals [IARC 1999; National Toxicology Program (NTP) 2011]. The Agency for Toxic Substances and Disease Registry (ATSDR) and IARC have classified 1,4-D as a suspected human carcinogen (ATSDR 2006; IARC 1999). Because of the potential adverse health effects upon exposure to these DCPs or their precursors (Buttke et al. 2012; Chevrier et al. 2012; Hsiao et al. 2009; Jerschow et al. 2012; Philippat et al. 2012; Twum and Wei 2011; Wolff et al. 2008), assessing the prevalence of human exposure to these compounds is warranted.

Like many nonpersistent chemicals, DCPs or their precursors can be metabolized rapidly via phase I (e.g., oxidation) or phase II (i.e., conjugation) biotransformations and eliminated in urine. The urinary concentrations of total (free plus conjugated) species of DCPs have been used as exposure biomarkers (Hill et al. 1995; Hissink et al. 1997). Urinary concentrations of 2,4-DCP and 2,5-DCP in the general U.S. population have been measured as part of the National Health and Nutrition Examination Survey (NHANES), conducted by the Centers for Disease Control and Prevention (CDC 2012). In the present study, we examined data from NHANES 2003-2004, 2005-2006, 2007-2008, and 2009-2010 cycles (CDC 2012) to evaluate exposure trends during this 8-year period and to evaluate potential differences in urinary concentrations by race/ethnicity, age, sex, and income. Because housing-related environmental hazards may affect health (CDC 2011a), we therefore also examined housing type as a predictor of the urinary concentrations of DCPs.

Materials and Methods

Urine samples analyzed for 2,4-DCP and 2,5-DCP were obtained from 10,426 participants [greater than or equal to] 6 years of age from NHANES 20032010. The CDC's National Center for Health Statistics Institutional Review Board reviewed and approved the NHANES study protocol. All participants gave informed written consent; parents or guardians provided consent for participants < 18 years of age (CDC 2006b). We quantified the urinary concentrations of 2,4-DCP and 2,5-DCP by online solid-phase extraction coupled to isotope dilution-high performance liquid chromatography-tandem mass spectrometry (Ye et al. 2005). The limit of detection (LOD) for 2,4-DCP was 0.2 [micro]g/L for all four surveys; the LOD for 2,5-DCP was 0.1 [micro]g/L for NHANES 2003-2004 and 0.2 [micro]g/L (NHANES 2005-2010) (CDC 2012). Details of the analytical procedures used are available to the public on the NHANES website (CDC 2006a).

For statistical analyses, we used SAS (version 9. …

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