"A health hazard evaluation at a facility that manufactured refrigerated tractor trailers (reefers) for the trucking industry was reviewed. The study was conducted by NIOSH and focused on exposures to diisocyanates in the polyurethane foaming areas of the facility, and on the risk of asthma among exposed workers. A two component polyurethane foam system was used to insulate the walls, ceiling, floor, and doors of the reefer. Component-A of this system consisted of 40 to 50% 4,4'-diphenylmethane-diisocyanate (101688) (MDI) and 50 to 60% of MDI based polyisocyanate. Component-B contained a mixture of polyether polyols, surfactants, catalysts, and blowing agents. A cross sectional study was designed to determine whether workers exposed to MDI had respiratory symptoms and pulmonary function decrements consistent with occupational asthma, and whether there was any relationship between the presence of antibodies to MDI/human-serum-albumin (HSA) and a worker's exposure or disease status. The study cohort included 18 workers from the foaming and painting areas of the facility, divided into exposed and nonexposed groups. Six of the nine in the exposed group had elevated immunoglobulin (Ig)-G antibodies specific for the MDI/HSA conjugate. Two were symptomatic and had a decreased forced expiratory volume for one second forced vital capacity ratio indicative of possible asthma. The six with elevated IgG to MDI/HSA also exhibited antibody responses to the other diisocyanate/HSA antigens. None of the MDI exposed workers demonstrated increased diisocyanate specific IgE antibodies when compared to nonexposed workers or to nonexposed laboratory controls. No definitive cases of occupational asthma were documented. The authors conclude that serum concentrations of MDI specific IgG appear to be a moderately sensitive biological marker of MDI exposure, but not an indicator of occupational asthma. Workers with IgG antibodies specific for one diisocyanate/HSA conjugate exhibited cross reactivity to antigens prepared with the other diisocyanates."

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