Airborne diazinon concentrations during and after outdoor spray application.

Airborne concentrations of the organophosphate pesticide diazinon were assessed using personal sampling on an applicator and area sampling at several locations within ornamental plant beds sprayed with the chemical. As part of field work testing a prototype pesticide monitor, diazinon was applied to azalea bushes, from a backpack sprayer, on two separate occasions. Personal and area sampling was used to measure concentrations during the application and over multiple time scales after the initial sampling. The area measurements indicated that diazinon concentrations during and immediately after application were similar to the consensus occupational exposure limit (OEL) of 10 mug/m(3) for airborne diazinon. Concentrations measured from personal samples worn by the applicator were 57-82% of the occupational limit during the application period. Therefore, an applicator and anyone else near ornamental plants being sprayed with diazinon should use personal protective equipment, including appropriate respiratory protection. Concentrations declined substantially with time during the subsequent 24-hr period. In 2006, the U.S. Environmental Protection Agency (EPA) set the restricted-entry interval (REI) after diazinon is applied to ornamental plants to 2 days, assuming only dermal exposures are relevant after spraying. However, the results of this study suggest that the health risks posed by estimated potential doses caused by inhalation exposures after spraying are of the same order of magnitude as the risks posed by potential dermal doses using the risk assessment methodology employed by EPA. Thus, EPA should not dismiss inhalation exposures when developing REIs for diazinon in the future.

Detection of organophosphate pesticides using a prototype liquid crystal monitor.

The precision and accuracy of a prototype wearable liquid crystal monitor (LCM) for the measurement of airborne organophosphate pesticide concentrations was explored in a series of laboratory experiments. LCM response to vapor-phase and aerosol diazinon was compared to concentrations obtained using a standard reference method (NIOSH 5600) at concentrations ranging from approximately 8 to 108 ppb (parts per billion) over durations of 2 to 80 hours. Temperature ( approximately 25, 30, and 35 degrees C) and relative humidity (15, 50, and 85%) were varied to estimate the effect of these factors on LCM performance. The LCM response to vapor phase pesticide exposure was linear for concentrations in the range of 8-20 ppb. At exposure concentrations above approximately 20 ppb, however, there was a decline in monitor response and measurement precision. Elevated temperatures improved diazinon vapor-only measurement precision, while increased relative humidity reduced LCM response at the extremes of tested temperatures. Compared to vapor-only exposures, the LCM was less sensitive to diazinon aerosol concentrations, but displayed reasonable precision over a relatively large range of exposures (29 to 1190 ppb-hr). Further efforts to characterize temperature and humidity effects and improve low-end sensitivity would likely provide a portable personal exposure monitor or environmental sensor for this widely used class of pesticides.