Exposure to high endotoxin concentration increases wheezing prevalence among laboratory animal workers: a cross-sectional study.

BACKGROUND: Endotoxin from Gram-negative bacteria are found in different concentrations in dust and on the ground of laboratories dealing with small animals and animal houses. METHODS: Cross-sectional study performed in workplaces of two universities. Dust samples were collected from laboratories and animal facilities housing rats, mice, guinea pigs, rabbits or hamsters and analyzed by the "Limulus amebocyte lysate" (LAL) method. We also sampled workplaces without animals. The concentrations of endotoxin detected in the workplaces were tested for association with wheezing in the last 12 months, asthma defined by self-reported diagnosis and asthma confirmed by bronchial hyperresponsiveness (BHR) to mannitol. RESULTS: Dust samples were obtained at 145 workplaces, 92 with exposure to animals and 53 with no exposure. Exposed group comprised 412 subjects and non-exposed group comprised 339 subjects. Animal-exposed workplaces had higher concentrations of endotoxin, median of 34.2 endotoxin units (EU) per mg of dust (interquartile range, 12.6-65.4), as compared to the non-exposed group, median of 10.2 EU/mg of dust (interquartile range, 2.6-22.2) (p < 0.001). The high concentration of endotoxin (above whole sample median, 20.4 EU/mg) was associated with increased wheezing prevalence (p < 0.001), i.e., 61 % of workers exposed to high endotoxin concentration reported wheezing in the last 12 months compared to 29 % of workers exposed to low endotoxin concentration. The concentration of endotoxin was not associated with asthma report or with BHR confirmed asthma. CONCLUSION: Exposure to endotoxin is associated with a higher prevalence of wheezing, but not with asthma as defined by the mannitol bronchial challenge test or by self-reported asthma. Preventive measures are necessary for these workers.

Study of risk factors for atopic sensitization, asthma, and bronchial hyperresponsiveness in animal laboratory workers.

OBJECTIVES: The aim of this estudy was to investigate the influence of allergen exposure levels and other risk factors for allergic sensitization, asthma, and bronchial hyperresponsiveness (BHR) in workers exposed to laboratory animals. METHODS: This was a cross-sectional study performed at two universities, 123 workplaces with 737 subjects. Dust samples were collected from laboratories and animal facilities housing rats, mice, guinea pigs, rabbits, or hamsters and analyzed by enzyme-linked immunosorbent assay (ELISA) to measure allergen concentrations. We also sampled workplaces without animals. Asthma was defined by both symptoms and BHR to mannitol. The concentrations of allergens were tested for association with a skin prick test, respiratory symptoms, spirometry data, and BHR. This multivariate analysis was performed by using Poisson regression to estimate the relative risk (RR) for the exposed group. RESULTS: Our sample comprised students and workers, with 336 subjects in the nonexposed group and 401 subjects in the exposed group. Sixty-nine subjects (17%) had positive results in the skin prick test for animal allergens in the exposed group; in the nonexposed group, 10 subjects had positive results (3%) (p<0.001). Exposure to laboratory animals over 2.8 years was associated with atopic sensitization (RR=1.85; 95% confidence interval: 1.09-3.15; p=0.02). Allergen concentration was not associated with sensitization, asthma, or BHR. CONCLUSION: Exposure to laboratory animals was associated with atopic sensitization. However, we did not find a cutoff allergen concentration that increased the risk for sensitization. Duration of exposure seems to be more relevant to sensitization than concentration of allergens in dust.