Health Risk Assessment and Biomarkers of Chlorpyrifos in Rice Farmers

Abstract

The purpose of this study was to assess health risk and cholinesterase levels due
to chlorpyrifos exposure among rice farmers in Phatthalung Province. The 31 study subjects used chlorpyrifos insecticides. Air samples were collected in the breathing zone of the rice farmers using OSHA (Occupational Safety and Health Administration) versatile sampler (OVS-2) tubes, containing a glass fiber filter and two sections of XAD-2 adsorbent, following NIOSH method no. 5600. The accuracy, precision and detection limit of this method were also tested.
Blood samples were collected and questionnaires were also administered by interviewers. Results revealed that the limit of detection of the method was 0.1 μg/tube. The percent recoveries of the method ranged from 99.20% to 102.83% with coefficients of variation of less than 7.00% for chlopyrifos concentrations of 1-3 μg/tube. The average occupational chlorpyifos exposure among rice farmers was 0.062 ± 0.092 mg/m3. Thirty subjects (96.8%) had been exposed to chlorpyrifos concentrations less than the TLV-TWA of 0.1 mg/m3 recommended by the American Conference of Governmental Industrial Hygienists (ACGIH). Many farmers had developed signs and symptoms, sweating (80.7%), chest tightness (32.3%), vomiting (25.8%) and blurred vision (35.5%). A high correlation coefficient was found between chlorpyrifos exposure and levels of cholinesterase in blood (r=0.872; p=0.01). The estimated daily intake of chlorpyrifos exposure through inhalation was 0.004 mg/ kg-day. The risk of exposure to chlorpyrifos was not acceptible (HQ ≥ 1).