Air and Surface Chlorpyrifos Residues following Residential Broadcast and Aerosol Pesticide Applications

Ambient air at three different heights and surface chlorpyrifos residues were measured for 7 days following broadcast (Dursban) and total release aerosol (K-RID) chlorpyrifos applications for flea control in four dormitory rooms. All rooms were ventilated with forced air for 30 min immediately following applications. One room of each type was then maintained with no ventilation, while the other rooms were ventilated by forced air for an additional 4 h and by ambient air on subsequent study days. Peak air concentrations of 118 μg/m 3 (broadcast) and 82 μg/m 3 (aerosol) were measured at 4−12 h postapplication. Concentrations decreased rapidly over the first 4 days post-application and remained low (1 μg/m 3 ) and relatively constant on days 5−7. Forced air ventilation reduced air concentrations only transiently in the broadcast room, and subsequent ambient air ventilation had little effect. In the aerosol room, however, ventilation decreased air concentrations substantially. Broadcast applications resulted in 7.5 times more total deposited chlorpyrifos on carpets than aerosol applications; however, dislodgeable residues on carpets were only 2-fold greater. Chlorpyrifos residues deposited on nontarget surfaces (e.g., furniture) by aerosol applications were 140−500 times greater than by broadcast applications. The estimated total absorbed chlorpyrifos doses for broadcast and aerosol applications (12−33 μg/kg) were near the no observable effect level (NOEL, 30 μg/kg) on day 1 but not on the remaining days. Future studies should measure airborne particulates and assess residue dislodgeability from nontarget surfaces, as these pathways are likely contributors to human exposure. Accurate estimates of exposure in these environments will also require detailed analysis of human activities.