Student Research: Wenjie Zhu
Many studies have shown that there are serious risks associated with pesticides such as cancer, reproductive problems, organ damage, and endocrine and/or immune system dysfunction. In recent years, there is a growing concern about the pesticide residues exposure due to the indiscriminate use of pesticides in China. One essential component of exposure assessment is to identify exposure level (concentration) of residues; another is knowledge of where the farmers spend their time and their exposure duration. Thus time-location information can be linked with residue concentration data to produce exposure estimates for farmers.
This study was aimed to determine time-location patterns of Organophosphate (OP) pesticide users among Chinese farmers by employing a novel Global Positioning System (GPS) instrument suitable for time-location tracking and to estimate the OP pesticides exposure level by combination of Graphic Information System (GIS) maps and measurements of pesticide residues on crops. GIS maps can be used to visually show location distribution of subjects monitored. Compared to traditional time-location analysis from interviews or diaries, we expected to get more reliable human exposure assessment by employing GPS/GIS technology.
This project was carried out in the Xichang, Sichuan Province where the pesticides were extensively used since August 2003, and was completed in November 2003. Prior to conducting the study, the Sichuan CDC-Institutional Review Board reviewed the written protocols and approved the project. A five-page, Chinese language questionnaire with consent form, eliciting data on pesticide use, health information and work practice was administered at the enrollment for 100 farmers. The overall participation rate was 97% for the questionnaire and all these potentially exposed subjects agreed to participate this study voluntarily.
A total of 24 volunteer farmers sprayed a single OP, dimethoate, on their garlic crops over a period of about 1~2.5 hrs depending on their field areas. They also were asked to wear GPS instruments for approximately 8 hours based on the consideration of local weather conditions, and the number of available GPS instruments at that time. The investigators from the University of Washington processed the incoming time-location data. Leaf samples were collected to test for exposure to dimethoate at about 2-hr after spraying and were returned to the lab in the Sichuan University for analysis. Blank leaf samples also were collected and analyzed for quality control purposes. To date, analysis of the samples we collected is still in progress.