Spatio-temporal variation of outdoor and indoor pesticide air concentrations in homes near agricultural fields

Previous research has shown that many current-use pesticides can be detected in air around application areas. Environmental exposure to pesticides may cause adverse health effects, necessitating accurate assessment of outdoor and indoor air concentrations for people living close to spraying sites. We evaluated outdoor and indoor air concentrations of different pesticides, as well as factors influencing spatial and temporal variations. We collected outdoor air samples at 58 homes located within 250 m of bulb fields and 15 control homes located further than 500 m from any agricultural field. Outdoor air sampling following a pesticide spray event was performed 24-h a day for 7 consecutive days. Two full day samples were collected at the same locations during a non-use period. In homes located within 50 m from agricultural fields (N = 18), indoor air was also sampled for the first 24 h after field spraying. Samples were analysed for a total of 46 pesticides and degradation products. From these, 11 were actively used on nearby fields, 3 were used in bulb disinfection and 6 were degradation products. Compared to non-use periods, pesticides concentrations were 5–10 times higher in outdoor air during application periods. Similar concentration differences were observed between exposed homes and controls both during pesticide use and non-use period. For 14 pesticides, there were moderate correlations (spearman > 0.4–0.7) between outdoor and indoor air concentrations. Wind direction, evapotranspiration and agricultural area surrounding a home were the most important determinants of air concentration of the applied pesticides. This study provides strong evidence suggesting that environmental exposure to pesticides via air is not limited to the day of application and may occur year-round. The concentrations appeared higher during the use period. Factors influencing the local fate of pesticides in air may differ significantly between compounds.