An observational study of the potential exposures of preschool children to pentachlorophenol, bisphenol-A, and nonylphenol at home and daycare☆
Introduction
Young children are likely to be more vulnerable than adults to chemical exposures as a result of their immature organ systems, their rapid physical development, their higher ventilation and metabolic rates, their greater surface-to-volume ratios, and their activities. Therefore, low levels of chronic exposure to some chemicals in their environments may eventually lead to adverse health effects in children.
The Children's Total Exposure to Persistent Pesticides and Other Persistent Organic Pollutants (CTEPP), study, conducted in 2000 and 2001 in the states of North Carolina (NC) and Ohio (OH), investigated the exposures of 257 preschool children and their primary caregivers to a variety of anthropogenic organic chemicals that were likely to be found at low levels in their everyday environments (Wilson et al., 2004). There were four primary goals for the CTEPP study: (1) to measure the concentrations of more than 50 selected organic chemicals in multimedia samples collected at the homes and daycare centers of preschool children, ages , (2) to determine the distributions of children's characteristics, activities, and locations that contributed to their exposures, (3) to estimate the children's aggregate exposures to the chemicals in their everyday environments, and (4) to evaluate the contributions of each route of exposure to the aggregate exposures. This paper provides results for phenols relative to the first, third, and fourth objectives of the overall CTEPP study.
In the CTEPP study, children and their primary caregivers were recruited randomly from households in six randomly selected NC counties, and in the second phase, from six randomly selected OH counties, to allow collection of exposure information from two different geographical regions in the US. Details of the study design, recruitment, and sampling methods for CTEPP, and data from two CTEPP prepilot studies have been published (Wilson et al., 2001, Wilson et al., 2003, Wilson et al., 2004). A comprehensive description and details of the CTEPP study and the study findings are published in the study report (Morgan et al., 2004).
Among the more than 50 chemicals analyzed in environmental and personal media were three phenols: pentachlorophenol (PCP), bisphenol-A [2,2-bis(4-hydroxyphenyl)propane], and nonylphenol (4-n-nonylphenol). These phenols were targeted because they are widely used, they have been found extensively in the environment, and PCP has been found in urine samples from the US population (CDC, 2005).
PCP is a chlorinated hydrocarbon insecticide and fungicide, which was produced and used in the US in large quantities (50 million pounds in 1977, 35 million pounds in 1985). It has been used as an herbicide, a termiticide and an antimicrobial agent; in adhesives, paints, paper coating, food cans and storage containers, leather tanning, pulp and paper production; and in disinfectants (ATSDR, 2001; IPCS, 2003). PCP has not been available for use by the general public since the early 1980s, and its registration was canceled in 1998 by the USEPA for all uses except as a wood preservative, to protect timber from wood-boring insects and fungal rot (Fisher, 1991). PCP was found in 10% or more of the urine samples collected from a national sample of the US population in 1999–2000, including children ages 6–11 (CDC, 2005).
Bisphenol-A (BPA) is an industrial chemical, which serves as a precursor for a variety of compounds found in materials such as polycarbonate plastics and epoxy resins. As a result, it can be found in a variety of products to which consumers can be exposed, including food and beverage containers, household appliances, sports equipment, paints, dental sealants, and others (Kamrin, 2004). Of particular concern is the possible human exposure to BPA that may occur when it leaches out of plastic food and drink containers, and from dental prostheses and sealants. BPA is a likely weak endocrine-disrupting compound (Ashby et al., 2004; Gould et al., 1998; Herath et al., 2004; Kawato, 2004; Kitamura et al., 2005; MacLusky et al., 2005; Nishizawa et al., 2005; Olea et al., 1996; Pflieger-Bruss et al., 2004; Quiros et al., 2005; Schonfelder et al., 2004; Steinmetz et al., 1998; Takeuchi et al., 2004). Recently published urinary concentration data in an adult human reference population suggest that US residents may be widely exposed to BPA (Calafat et al., 2005). BPA was found in 95% of the adult urine samples examined in the latter study, at concentrations greater than 0.1 μg/L.
Nonylphenol (NP) and its ethoxylates are used widely as surfactants in industrial and household cleaners and in processing of textiles, paints and coatings, pulp and paper, and agricultural chemicals (Shaw and McCully, 2002). NP is also a likely endocrine-disrupting compound. This phenol was found in >51% of the adult urine samples in the Calafat study cited above.
This paper presents the findings of the CTEPP study on the participating children's exposures to the above three phenols at their homes and daycare centers. The concentrations of the phenols in the sampled media and estimates of the children's potential exposures and potential absorbed doses resulting from intake through the inhalation, dietary ingestion, and indirect ingestion routes of exposure are presented.
Section snippets
Participants
Children, ages , who were toilet-trained and not currently breast-fed, and their primary caregivers were recruited randomly from eligible households and child daycare centers in six NC counties, and in the second phase of the study, in six OH counties. Approximately half the children attended child daycare centers at least 25 h/wk. Participants were selected from several categories to allow comparisons between home and daycare settings, between urban and rural locations, and between
Concentrations and exposures
Shown in Table 1 are the percentages of BPA and PCP that were detected in each medium and the distributions of the concentrations of these two phenols. Data are given in the table for those phenols and media having measurable values for more than 5% of the samples. Both BPA and PCP were detected in all environmental and personal media, with the exception of urine, which was not analyzed for BPA. BPA was detected in more than 50% of the indoor air, hard floor surface wipe, food preparation
Acknowledgments
The authors thank profusely the Battelle human exposure research group, and the Battelle field, laboratory, and statistical analysis staff for their many contributions to the design, implementation, and interpretation of the CTEPP study. Special thanks go to Marielle Brinkman for her design and careful oversight of the CTEPP database. Many others contributed substantially to this study, including Christopher Lyu, Joshua Finegold, Kelley Hand, and Ying-Liang Chou, and other members of the field
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This research was funded by the US Environmental Protection Agency through Contract 68-D-99-011 to Battelle Memorial Institute. The human subjects research described in this paper was reviewed and approved by the Institutional Review Board of Battelle, and by the US Environmental Protection Agency Office of Human Subjects Research Protection.