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AGRICULTURAL HEALTH STUDY/PESTICIDE EXPOSURE STUDY: STATUS UPDATE AND PRELIMINARY RESULTS
Citation:
Thomas, K W. AGRICULTURAL HEALTH STUDY/PESTICIDE EXPOSURE STUDY: STATUS UPDATE AND PRELIMINARY RESULTS. Presented at North Carolina Field Station Advisory Panel Meeting, Raleigh, NC, November 13, 2002.
Impact/Purpose:
The primary goal of the AHS Pesticide Exposure Study (AHS/PES) is to measure exposure to applied pesticides for a subset of the cohort of private pesticide applicators and to provide data to evaluate exposure algorithms developed for exposure classification in the study cohort.
Description:
The Agricultural Health Study (AHS) is a prospective epidemiological study of pesticide applicators and their spouses in Iowa and North Carolina. Exposure to 2,4-D or chlorpyrifos is being measured for a subset of applicators in the AHS Pesticide Exposure Study to assess exposure classification procedures. Applicators were selected based on specific application methods and use of personal protective equipment that would place them into one of eight exposure scenarios. Potential exposures are measured on one day of pesticide mixing, loading, and application (MLA) using dermal patch, hand wipe, and personal air samples. Urinary biomarker levels are measured in pre-and post-application samples from each applicator and from participating spouses and children. Questionnaires and observations of MLA activities provide information about work practices, use of protective equipment, and hygiene. A total of 108 field monitoring visits were performed in Iowa and North Carolina from 2000 through 2002. This included field monitoring visits to 24 North Carolina farmers. Although 112 North Carolina farmers consented to participate during 2001 and 2002, field monitoring visits were completed for only 24 farmers. In many cases farmers made decisions not to apply one of the target chemicals; this was particularly true in 2002 when drought conditions were cited as the reason that the target chemicals were not being used. North Carolina farmers were monitored in 7 of the 8 exposure scenarios. Applications to wheat, corn, tobacco, sweet potatoes, peanuts, sod, Bermuda Grass, hay, pasture, and fencerow weeds were monitored in North Carolina. Products containing 2,4-D were used in 17 of the monitored North Carolina applications (89 overall), products containing chlorpyrifos were used 6 times in North Carolina (18 overall). One North Carolina applicator made a last-moment decision not to use a 2,4-D product in combination with an atrazine product. His dermal patch, handwipe, and air samples were analyzed for atrazine but his urine samples were not analyzed. Urine samples were collected from 11 North Carolina spouses (48 overall). Urine samples were collected from three North Carolina children (12 overall).
Preliminary urinary biomarker measurement results were examined for 71 applicator monitoring events completed in Iowa and North Carolina 2000 and 2001. Urine samples were collected from 35 spouses and 10 children during this period. For 59 monitored spray applications of products containing 2,4-D, the concentration in the applicators' first post-application urine sample ranged from 1.6 to 1040 ug/L. For 28 of the 29 spouses of these applicators the post-application urine 2,4-D concentrations ranged from < 1 to 14 ug/L; one spouse working with the applicator had a post-application concentration of 59 ug/L. Urinary 2,4-D concentrations for eight children ranged from 1.2 to 5.9 ug/L. For the 12 monitored applications of products containing chlorpyrifos (including three liquid spray applications and nine granular product applications) the concentration of the metabolite trichloropyridinol (TCP) in the applicators' first post-application urine samples ranged from 4.6 to 17 ug/L. TCP concentrations for chlorpyrifos applicator spouses (n=5) and children (n=2) ranged from 2.8 to 8.3 ug/L. The Spearman correlation between the pesticide applicators' second post-application urine samples and the spouses post application urine sample was 0.55 (p=0.0006, n=35); the correlation between the applicator and children was 0.22 (p=0.53, n=10).
A preliminary examination in the differences in post-application urinary biomarker concentrations between the eight exposure scenarios was performed. Mean applicator urinary concentrations ranged from 9 +/- 5 ug/L (n=5) for a granular product application scenario, and up to 200 +/- 310 ug/L (n=18) for a hand-spray application scenario. Mean ratios of urinary concentration to the amount of active ingredient applied ranged from 0.3 +/- 0.1 (n=5) to 330 +/- 610 (n=18). The Spearman correlation between 71 applicator post-application urine concentrations and the AHS algorithm-derived exposure intensity scores for the eight exposure scenarios was 0.43 (p=0.0002). The Spearman correlation for the ratio of concentration to amount of active ingredient applied was 0.76 (p<0.0001).
Preliminary results for North Carolina dermal patch, and handwipe, and air samples will be presented.
Analyses of the data produced in the AHS/PES will continue as measurement results from the 2002 season become available. Dermal and air sampling data will allow more direct assessment of potential differences in exposures from specific, observed activities. These data will also be used to examine specific exposure pathways and specific work practices. Results from the AHS/PES will be used to assess how AHS exposure algorithms and questionnaires can be refined to improve exposure classification in the epidemiological study. Fact sheets summarizing the study results and conclusions will be prepared for distribution in agricultural communities of Iowa and North Carolina.
This work has been funded in part by the U.S. Environmental Protection Agency. It has been subjected to Agency review and approved for publication. Mention of trade names of commercial products does not constitute endorsement or recommendation for use.