Using boundary layer theory to improve the accuracy of air release factors in environmental exposure estimations

A realistic release estimation is key when assessing whether the use of a chemical can be considered environmentally safe. For practically all industrial, professional, and consumer use patterns, air emission measurements are absent or available for only one or, at best, a handful of volatile chemicals. When such empirical data are used in the release estimation of other chemicals, environmental risks will be underpredicted for more volatile chemicals or unnecessarily overpredicted for less volatile chemicals. This short communication describes a pragmatic method to extrapolate release rates between chemicals with different physicochemical properties used under similar conditions. This method, which is is based on boundary layer theory and has been confirmed with empirical data, is applicable to evaporative release from liquids and semisolids. To demonstrate the value and ease of use of the boundary layer theory-based method in improving environmental risk assessments, we used this method to generate vapor pressure specific air release factors for hydrocarbons used as industrial laboratory reagents.