Air Concentrations of TDI and Total Reactive Isocyanate Group in Three Flexible Polyurethane Manufacturing Facilities

Abstract

In-depth industrial hygiene surveys were conducted in two large facilities manufacturing molded flexible foam and one facility manufacturing and finishing flexible slab foam. These surveys were performed to support a retrospective, cohort, mortality study of workers that were potentially exposed to toluene diisocyanate (TDI).

The air sample results show that isocyanate concentrations differed from plant to plant and were probably dependent on the operations performed, engineering controls, and the physical layout of the plant. In the two molded foam facilities, many of the personal exposures were above 35 μg/m³, as had been recommended by the National Institute for Occupational Safety and Health (NIOSH). As expected, pouring line workers were generally more exposed than finishing workers. However, thermal degradation of foam can release toxic substances, including TDI, into the air. This was found to occur in some of the finishing operations, resulting in elevated air concentrations of TDI. Throughout the facilities, the concentration of the 2, 6-isomer was found usually to be at least as great as the 2, 4-isomer. Total reactive isocyanate group (TRIG) was determined using NIOSH Method 5505. Although this method (now withdrawn) could not be used to quantitate TRIG, the results provide clues to its formation and control.

The data in this article are considered in regard to the practicing industrial hygienist who must collect and interpret isocyanate exposure data in the flexible polyurethane foam manufacturing industry.