MATHERIALS AND METHODS
The research design of this study is a cross-sectional study. Sisa Krabue sub-district, Ongkharak district, Nakhon Nayok province, Thailand, was purposively selected because it is occupied by the largest number of agriculturists as well as contains the most rice paddies in the District [8]. Based on sample size calculated by using the formula for the sample size for the mean [9], target populations were divided into two groups; farmer group (n=35) and non-farmer group (n=35). Inclusion criteria for the farmer group were rice farmers, both male and female, aged 18 to 59. They were all growing rice, applying organophosphate (OP) pesticides in paddy areas, as well as loading, mixing, or/and spraying a day (24 hours) before blood collection. Inclusion criteria for the non-farmer group were non-rice farmers, both male and female, aged 18 to 59. They were all non-daily farm workers, had no contact with pesticide application within three months both from their household or planting. Those with a history of liver failure, cardiovascular disease, taking anti-malarial drugs, malnutrition, and taking amphetamine, were excluded. The representatives were recruited as subjects from each house (one subject per household). The simple random sampling was done by drawing in accordance with the criteria is used to get target number of sample (70 subjects).