Diisocyanate-exposed auto body shop workers: a one-year follow-up

Diisocyanates currently are the most commonly identified cause of occupational asthma in industrialized countries. Auto body shops, a common hexamethylene diisocyanate (HDI) exposure setting, are difficult to study due to their small size and episodic exposures.

A 1-year follow-up was undertaken as an adjunct to the cross-sectional SPRAY study (Survey of Painters & Repairers of Auto bodies by Yale) to investigate the effects of HDI on auto body shop workers over time and whether or not the healthy worker effect may exist in this industry.

Forty-eight workers from seven shops were re-contacted. Thirty-four subjects who stayed at the same shop and 11 who left their original shop participated. No statistically significant changes in physiology, symptoms, and immunologic responses from baseline to follow-up were noted. However, significant differences between those who left the shops and those who stayed were noted. Those who left were younger, less experienced in the industry, and more likely to have a history of asthma (23 vs. 3%; P < 0.05), bronchial hyper-responsiveness (23 vs. 9%), HDI-specific IgG (64 vs. 29%; P < 0.05), and HDI-specific proliferation (S.I. 2.0 vs. 1.3; P < 0.05).

The differences in workers who stayed at their shop compared to those who left, combined with the low asthma prevalence and high job turnover rate, all suggest that a healthy worker effect may exist in the auto body industry, and may in part account for the low prevalence of asthma noted in SPRAY and other cross-sectional studies of diisocyante workers.