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RELIABILITY OF BIOMARKERS OF PESTICIDE EXPOSURE AMONG CHILDREN AND ADULTS IN CTEPP OHIO
Citation:
EGEGHY, P. P., M. K. MORGAN, C. W. CROGHAN, AND RELIABILITY OF BIOMARKERS OF PESTICIDE EXPOSURE AMONG CHILDREN AND ADULTS IN CTEPP OHIO. Presented at International Society for Exposure Analysis Conference, Tucson, AZ, October 30 - November 03, 2005.
Impact/Purpose:
The objectives for this task are to
Compile results and important findings from NERL-sponsored children's exposure studies;
Determine which pathways produce the greatest contribution to aggregate exposure among children for specific classes of pesticides;
Identify and quantify the factors that influence pesticide exposures among children;
Develop input parameters (e.g. multimedia pesticide distributions, exposure factor data) for exposure and dose models for assessing aggregate exposures and cumulative risks;
Evaluate exposure and dose models, including algorithms for estimating route-specific exposures, against real world data; and
Identify additional data gaps for modeling aggregate exposure and dose.
Description:
Urinary biomarkers offer the potential for providing an efficient tool for exposure classification by reflecting the aggregate of all exposure routes. Substantial variability observed in urinary pesticide metabolite concentrations over short periods of time, however, has cast some doubt on their usefulness. Greater attention to the within- and between-person variation in biomarker concentrations can provide insight into the reliability of a single measurement in representing a longer-term mean, and can improve the effectiveness of measurement efforts. The reliability of urinary biomarkers of pesticide exposure was investigated in a subsample from the Children's Total Exposure to Persistent Pesticides and Other Persistent Organic Pollutants (CTEPP) study. A series of up to six spot urine samples (including first morning voids) collected over a 48-h monitoring period from 15 Ohio preschool children and their adult caregivers was analyzed by GC/MS for several biomarkers, including the non-specific pyrethroid metabolite 3-phenoxybenzoic acid (3-PBA) and the somewhat specific chlorpyrifos metabolite 3,5,6-trichloro-2-pyridinol (TCPy). The Intraclass Correlation Coefficient (ICC), the ratio of the between-person component of variance to the total variance (sum of the within- and between-person components), was used to make inferences regarding the reliability of a single spot sample in representing a 48-h average. Measurements of 3-PBA from children were more reliable than those from adults, with ICCs of 0.69 and 0.52, respectively. Conversely, measurements of TCPy from children were less reliable than those from adults, with ICCs of 0.44 and 0.67, respectively. The ICCs for 3-PBA from children and TCPy from adults indicate good reliability, with a single measurement adequately representing the mean. Adjustment of values by specific gravity did not meaningfully change the ICCs. These results suggest that the consistency of urinary metabolite concentrations over relatively short periods of time may be dependent on both the metabolite and the study population.