Estimating the time-varying emission rate of peracetic acid.

The use of peracetic acid (PAA) as a general disinfectant has seen increasing usage in recent years, and although it is a strong irritant, exposure monitoring for PAA may often be difficult due to relatively high costs and the potential for interferences by other co-occurring chemicals such as hydrogen peroxide. These issues with exposure monitoring make modeling a potentially useful tool in exposure assessment of PAA if model parameters can be accurately determined. This study estimates the time-varying mass emission rate of PAA for use in exposure modeling by using the small spill model and examines the effect of various environmental conditions on the PAA evaporation rate, including surface roughness/substrate, general ventilation rate, and local wind speed. The relatively high evaporation rate constant (1.18 min-1) determined did not vary significantly with these parameters, suggesting it is applicable across a wide range of common environmental conditions. In addition, in a controlled chamber setting, the first-order decay rate constant for PAA in air was determined to be 0.5 h-1. The corresponding half-life of 83 min is approximately 4 times longer than previous estimates. This decay rate should be accounted for in future modeling and exposure assessments. To evaluate the estimated evaporation rate, trials were conducted in a highly controlled exposure chamber using conditions similar to those found in healthcare settings to compare predicted modeled concentrations to those made by a real-time detection instrument, SafeCide 2.0 (ChemDAQ, Inc.). The results of the trials indicate that the evaporation rate constant and well-mixed room model perform well in predicting the concentration of PAA over a range of conditions. Moreover, the modeling results and measured concentrations across all trials indicate a high potential for overexposure to PAA. Therefore, exposure controls must be adequate when considering the use of PAA as a general disinfectant.