Exposure-response relationships for work-related sensitization in workers exposed to rat urinary allergens: Results from a pooled study

Background: Recent studies in a few industries have shown that the likeliho od of IgE-mediated sensitization increases with increasing exposure. The sh ape of the exposure-response relationships and modification by age, sex, an d smoking habit has hardly been studied. Objective: The purpose of this study was to determine exposure sensitizatio n relationships for rat sensitization and to evaluate the influence of atop y, smoking habits, and sex. Methods: Data from 3 cross-sectional studies in The Netherlands, the United Kingdom, and Sweden were used and involved 1062 animal laboratory workers. Selection criteria were harmonized, and this resulted in a study populatio n of 650 animal laboratory workers (60.6% female) with less than 4 years of exposure. Air allergen levels were assessed previously and converted on th e basis of an interlaboratory allergen analysis comparison. Available sera were analyzed for the presence of specific antibodies against common allerg ens (house dust mite, cat, dog, and grass and birch pollen) and work-relate d allergens (rat and mouse urinary proteins). Questionnaire items on work-r elated respiratory symptoms, hours worked with rats per week, job performed , smoking habits, and sex were used in this analysis Results: The prevalence of work-related sensitization to rat urinary allerg ens (IgE >0.7 KU/L) was 9.7% (n = 63), Thirty-six of the sensitized workers had work-related symptoms (asthma or rhinitis). Two hundred forty-eight wo rkers (38.2%) mere atopic (defined as specific IgE to 1 of the common aller gens), The sensitization rate increased with increasing air allergen exposu re. Atopic workers exposed to low levels of allergen had a more than 3-fold increased sensitization risk compared with nonexposed atopic workers. For atopic subjects, the risk increased little with increasing exposure, wherea s for nonatopic subjects, a steadily increasing risk was observed. Smoking and sex did not modify the sensitization risk. Conclusion: Rat urinary allergen-sensitization risk increased with increasi ng exposure intensity. Workers who mere atopic had a clearly elevated sensi tization risk at Low allergen exposure levels.