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COMPARISON OF FIELD MEASUREMENTS FROM A CHILDREN'S PESTICIDE STUDY AGAINST PREDICTIONS FROM A PHYSICALLY BASED PROBABILISTIC MODEL FOR ESTIMATING CHILDREN'S RESIDENTIAL EXPOSURE AND DOSE TO CHLORPYRIFOS
Citation:
Hore, P., V Zartarian, J. Xue, A H. Ozkaynak, D. Barr, L. Needham, N. G. Freeman, A. Roy, AND P. J. Lioy. COMPARISON OF FIELD MEASUREMENTS FROM A CHILDREN'S PESTICIDE STUDY AGAINST PREDICTIONS FROM A PHYSICALLY BASED PROBABILISTIC MODEL FOR ESTIMATING CHILDREN'S RESIDENTIAL EXPOSURE AND DOSE TO CHLORPYRIFOS. Presented at 11th Annual Meeting of the International Society of Exposure Analysis, Charleston, SC, November 4-8, 2001.
Impact/Purpose:
The primary objective of this research is to produce a documented version of the aggregate SHEDS-Pesticides model for conducting reliable probabilistic population assessments of human exposure and dose to environmental pollutants. SHEDS is being developed to help answer the following questions:
(1) What is the population distribution of exposure for a given cohort for existing scenarios or for proposed exposure reduction scenarios?
(2) What is the intensity, duration, frequency, and timing of exposures from different routes?
(3) What are the most critical media, routes, pathways, and factors contributing to exposures?
(4) What is the uncertainty associated with predictions of exposure for a population?
(5) How do modeled estimates compare to real-world data?
(6) What additional human exposure measurements are needed to reduce uncertainty in population estimates?
Description:
Semi-volatile pesticides, such as chlorpyrifos, can move about within a home environment after an application due to physical/chemical processes, resulting in concentration loadings in and on objects and surfaces. Children can be particularly susceptible to the effects of pesticides as they are still developing; consequently, it is useful to quantify children's exposure to a semi-volatile pesticide over time in a home environment post-application. Given the difficulties in quantifying aggregate exposure of children to pesticides in a home environment, models for predicting exposure can be employed using field collected data on activity patterns, environmental concentrations, exposure and dose. A physically-based-probabilistic-model referred to as the Residential Stochastic Human Exposure and Dose Simulation (Residential-SHEDS) model for pesticides has been developed by EPA's National Exposure Research Laboratory to help estimate children's aggregate exposure and dose to pesticides in the residential environment via dermal and non-dietary ingestion exposure routes. It is the intent of this paper to compare the results of a children's pesticide study with the estimates made by the Residential-SHEDS model.
Data gathered in New Jersey during the Children's Post-Pesticide Application Exposure Study (CPPAES) provides a unique set of results on micro-environmental and biological marker samples that are coupled with macro-and micro-activity data on individual children in homes. Residences with a child between the ages of 2-5 and that routinely apply pesticides were selected for CPPAES. On day-0, a crack and crevice application of chlorpyrifos was made by a licensed applicator to each home. Following the application, pesticide measurements were made on the indoor air and dust for a two-week period post-application (Days 1,2,3,5,7,9,11 post-application). Toys can act as potential sinks within homes and are accessible to the children. Therefore, indicator toys that were placed within the homes following the application were colllected sequentially throughout the sampling period and analyzed for their concentration of chlorpyrifos. Direct handrinse and handwipe samples were also collected from the children on each of the sampling days along with detailed records of the child's daily activities through the use of activity questionnaires. Furthermore, videotaped records of each child provided individual hand-to-mouth/object-to-mouth frequency data. Finally, urine samples were collected from the children each day and were analyzed for the chlorpyrifos metabolite. Results indicated that chlorpyrifos is present in the indoor environment throughout the sampling period. Levels in the air ranged from 43.0-351.4-ng m-3 reaching peak levels between days 0-2. Dust wipe concentrations ranged from 0.4-24.3-ng cm-2 with higher levels on days 1,2, and 3. Chlorpyrifos levels in the toys ranged from 245-966-ng/toy. Handrinse levels ranged from 0.23-7.08-ng cm-2. The micro-and macro-activity data and environmental concentrations described above are being used along with extant exposure factor data as input to the Residential-SHEDS model. The resulting model predictions compared against biomonitoring results described above will be presented.
This work has been funded in part by the United States Environmental Protection Agency under an EPA Technical Services Contract (Contract No. 0D-5227-NAEX) to the Environmental and Occupational Health Sciences Institute. It has been subjected to Agency review and approved for presentation and publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.