Occupational asthma exposure-response relationships

There is little information on exposure-response relationships for the induction of asthma. There are several explanations for this. Estimates of workers chemical exposure are needed, which usually require a sampling survey of representative current exposures and assessment of past exposure. Making use of measurements made to document compliance with regulations is rarely sufficient because such measurements generally focus only on those jobs and tasks likely to cause violations of occupational standards. 

Many cross-sectional surveys report no or weak exposure-response relationships or even an inverse relationship for which survivor bias is the most probable explanation. For example, in a survey of a workforce exposed to tetrachlorophthalic anhydride (TCPA) carried out by the authors, all the cases affected in an epidemic of occupational asthma had left the factory before it was possible to carry out a survey (Venables et al., 1985a). In this survey, conclusions could be drawn by studying specific IgE against TCPA. However, reliable tests for specific IgE antibody are not available for all chemical respiratory allergens. 

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