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ADULT AND CHILDREN'S EXPOSURE TO 2,4-D FROM MULTIPLE SOURCES AND PATHWAYS
Citation:
MORGAN, M. K., L. S. SHELDON, K. W. THOMAS, P. P. EGEGHY, C. W. CROGHAN, P. A. JONES, J. C. Chuang, AND N. K. WILSON. ADULT AND CHILDREN'S EXPOSURE TO 2,4-D FROM MULTIPLE SOURCES AND PATHWAYS. Journal of Exposure Science and Environmental Epidemiology . Nature Publishing Group, London, Uk, 18(5):486-494, (2008).
Impact/Purpose:
The National Exposure Research Laboratory’s (NERL) Human Exposure and Atmospheric Sciences Division (HEASD) conducts research in support of EPA’s mission to protect human health and the environment. HEASD’s research program supports Goal 1 (Clean Air) and Goal 4 (Healthy People) of EPA’s strategic plan. More specifically, our division conducts research to characterize the movement of pollutants from the source to contact with humans. Our multidisciplinary research program produces Methods, Measurements, and Models to identify relationships between and characterize processes that link source emissions, environmental concentrations, human exposures, and target-tissue dose. The impact of these tools are improved regulatory programs and policies for EPA.
Description:
In this study, we investigated the 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide exposures of 135 preschool-aged children and their adult caregivers at 135 homes in North Carolina (NC) and Ohio (OH). Participants were randomly recruited from six NC and six OH counties. Monitoring was performed over a 48-h period at the participants’ homes. Environmental samples included soil, outdoor air, indoor air, and carpet dust. Personal samples collected by the adult caregivers concerning themselves and their children consisted of solid food, liquid food, hand wipe, and spot urine samples. All samples were analyzed for 2,4-D (free acid form) by gas chromatography/mass spectrometry. 2,4-D was detected in all types of environmental samples but the most often in carpet dust samples, with detection frequencies of 83% and 98% in NC and OH, respectively. The median level of 2,4-D in the carpet dust samples was about three times higher in OH homes compared to NC homes (156 vs. 47.5 ng/g , p<0.0002). For personal samples, 2,4-D was more frequently detected in the hand wipe samples from OH participants (> 48%) than from NC participants (< 9%). Hand wipe levels at the 95th percentile were about five times higher for OH children (0.1 ng/cm2) and adults (0.03 ng/cm2) than for the NC children (0.02 ng/cm2) and adults (<0.005 ng/cm2). 2,4-D was detected in greater than 85% of the child and adult urine samples in both states. The median urinary 2,4-D concentration was more than twice as high for OH children compared to NC children (1.2 vs. 0.5 ng/mL, p<0.0001); however, the median concentration was identical at 0.7 ng/mL for both NC and OH adults. The intraclass correlation coefficient of reliability ( r) for an individual’s urinary 2,4-D measurements, estimated from the unadjusted (0.31 to 0.62) and specific gravity-adjusted (0.37 to 0.73) 3 values, were somewhat low for each group in this study. The variability in urinary 2,4-D measurements over the 48-h period for both children and adults in NC and OH suggests that several spot samples were needed to adequately assess these participants’ exposures to 2,4-D in residential settings. Results from this study showed that children and their adult caregivers in NC and OH were likely exposed to 2,4-D through several pathways at their homes. In addition, our findings suggest that the OH children may have been exposed to higher levels of 2,4-D through the dermal and nondietary routes of exposure than the NC children and the NC and OH adults.
