Occupational asthma risk from exposures to toluene diisocyanate: A review and risk assessment

BackgroundToluene Diisocyanate (TDI) is a known respiratory sensitizer linked to occupational asthma (OA). To better manage worker risks, an appropriate characterization of the TDI-OA dose-risk relationship is needed. MethodsThe literature was reviewed for data suitable for dose-response modeling. Previous study data were fit to models to derive prospective occupational exposure limits (OELs), using benchmark dose (BMD) and low-dose extrapolation approaches. ResultsData on eight TDI-exposed populations were suitable for analysis. There were 118 OA cases in a population contributing 13590 person-years. The BMD-based OEL was 0.4ppb. The OEL based on low-dose extrapolation to working lifetime extra risk of 1/1000 was 0.3ppb. ConclusionsThis study synthesized epidemiologic data to characterize the TDI-OA dose-risk relationship. This approach yielded prospective OEL estimates below recent recommendations by the American Conference of Governmental Industrial Hygienists, but given significant study limitations, this should be interpreted with caution. Confirmatory research is needed.