Longitudinal Assessment of Chlorpyrifos Exposure in Farmers and Residents of an Italian Alpine Region

The aim of this study was to obtain a longitudinal evaluation of the exposure to chlorpyrifos (CP) and chlorpyrifos-methyl (CPM) in agricultural workers in South Tyrol and in a residential group living in the same area. CP and CPM are widely used pesticides in agriculture. Biological monitoring of CP and CPM exposure in humans can be achieved by analyzing urinary levels of 3,5,6-trichloro-2-pyridinol (TCPy). TCPy a metabolite of CP and CPM which is produced by a two-step metabolic transformation. Between May 14th, 2014 and March 16th, 2015 we conducted a longitudinal study on 28 farmers actively working in spray pesticide treatment and 43 non-farmers living in the same agricultural area of South Tyrol (Italy). Urine samples were collected at two time points: during the pesticide treatment period and in a temporally distant season that should guarantee metabolite clearance. We developed and validated a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination of urinary TCPy levels. During the treatment season, both farmers and residents showed higher TCPy levels (median = 6.8 and 6.73 ug/g creatinine, respectively) than during the non-treatment season (median = 2.54 and 3.22 ug/g creatinine, respectively), suggesting a similar effect of the pesticide spraying on both groups. However, the observed TCPy levels resulted in a daily CP and CPM intake well below the limits recommended by FAO/WHO. During the non-treatment season, non-farmers showed higher TCPy levels values than farmers, suggesting the existence of TCPy of other unmeasured sources of exposure not considered in this study. This suggests that, for a comprehensive evaluation of the risks associated with TCPy exposure, additional sources should be identified in addition to CP and CPM pesticides.