Chlorpyrifos is one of the most extensively used insecticides in China. The distribution and residues of chlorpyrifos in a paddy environment were characterized under field and laboratory conditions. The half-lives of chlorpyrifos in the two conditions were 0.9–3.8 days（field） and 2.8–10.3 days（laboratory）, respectively. The initial distribution of chlorpyrifos followed the increasing order of water 〈 straw 〈 soil, and soil was characterized as the major absorber. The ultimate residues in rice grain were below the maximum residue limit（MRL） with a harvest interval of 14 days. The chronic exposure for chlorpyrifos was rather low compared to the acceptable daily intake（ADI = 0.01 mg/kg bw） due to rice consumption. The chronic exposure risk from chlorpyrifos in rice grain was 5.90% and 1.30% ADI from field and laboratory results respectively. Concerning the acute dietary exposure,intake estimated for the highest chlorpyrifos level did not exceed the acute reference dose（ARf D = 0.1 mg/kg bw）. The estimated short-term intakes（ESTIs） were 0.78% and 0.25% of the ARf D for chlorpyrifos. The results showed that the use of chlorpyrifos in rice paddies was fairly safe for consumption of rice grain by consumers.
Yan FuFeifei LiuChenglin ZhaoYing ZhaoYihua LiuGuonian Zhu
