Michael G. Costello

Modeled Comparisons of Health Risks Posed by Fluorinated Solvents in a Workplace Spill Scenario

The purpose of this study was to illustrate how available physical-chemical exposure models can be used to compare potential risks and define risk management measures for non-routine exposure events, such as spills, leaks, or process upset conditions. A two-zone physical-chemical model was used to quantify and compare the potential exposure risks from five fluorinated solvents used in the manufacturing of electronic materials during an anticipated spill scenario. A 1-l spill scenario in a room measuring 2.74 m (9 ft) high by 3.66 m (12 ft) wide by 9.14 m (30 ft) long was constructed for modeling exposures using The Two-zone Model with An Exponentially Decreasing Contaminant in available freeware IH MOD (a PC based program available from the American Industrial Hygiene Association). This treatment was followed by using the results from an experimental chamber study in which the evaporation rates and vapor concentrations of the five fluorinated solvents were measured under realistic conditions and then compared to exposure model outputs. The breathing zone concentration/time profiles predicted for the five solvents were compared to their exposure limits to estimate the relative risk. This information was used to help define operationally sufficient risk management options for the safe handling of spills in laboratories, warehouses, or manufacturing facilities. The model indicated that each solvent presented very different risk profiles for the same 1-l liquid spill scenario. Potential exposure concentrations relative to short-term exposure limit (15 min) and Ceiling (C) exposure limit available for some of the solvents are predicted to be exceeded within a few minutes in the area near the spill and in the far field. In addition, the model showed that near-field concentrations for one solvent exceeded the published LC-50 (the concentration predicted to cause 50% mortality in the test animals), which indicates a very high degree of risk for this material in similar scenarios. Given the speed of evaporation during these spills for the materials tested in this study, donning personal protective equipment in the area may not be a viable option and short-term evacuation of the area immediately surrounding the spill would appear to be a practical risk management response.