Spatio-temporal variation in pesticides air concentrations from homes near agricultural fields

Background Pesticides enter the atmosphere mainly through spray drift, volatilization and erosion. Exposure to these compounds may cause adverse health effects, therefore being important to accurately assess exposure for people living close to spraying sites. We collected air samples to evaluate presence, levels and distributions of different pesticides. Methods We deployed active samplers to collect outdoor air in 58 homes located within 250m from bulb fields and in 16 homes located further than 500m from any agricultural field (controls). We sampled during pesticides use periods, with 7 consecutive daily measurements following a spray event. two day samples were collected in the same homes during non-use periods. Indoor air was sampled for the first 24h after field spraying, in homes located within 50m from agricultural fields (n=18). We analysed a total of 46 pesticides and concentrations were determined using liquid chromatograph coupled to LC-MS/MS. Results During use period, 5 to 10 times higher concentrations were found for pesticides applied on bulbs as compared to non-use periods. We observed similar exposure contrasts when we compared concentrations between exposed homes and controls. We observed a significant decrease in concentrations with increasing buffer distance for 64% of the pesticides that were applied in fields located within 250m from the studied homes. For 82% of the pesticides, there was a moderate correlation (spearman > 0.4 - 0.7) between outdoor and indoor concentrations. Finally, some of the detected pesticides (n=11) were not sprayed during the sampling period.Conclusions Concentrations were higher closer to fields than further away. There is evidence that exposure to pesticides via air can also be bound to previous applications, and, although higher during use period, occurs also during the non-use period. Moderate, but not strong, correlations between outdoor and indoor air concentrations might be an indication of indoor sources and sinks of pesticides.