Prevalence of symptoms, sensitization to rats, and airborne exposure to major rat allergen (Rat n 1) and to endotoxin in rat-exposed workers: a cross-sectional study

OBJECTIVE: To analyse the relation between airborne exposure to major rat allergen and to endotoxins in exclusively rat-exposed workers and the prevalence of rat-related symptoms and sensitization. METHODS: A total of 113 workers answered a standardized questionnaire on their atopy status, occupational exposure to rats, and possible work-related symptoms. Specific IgE against rat urinary proteins (RUP) was measured for 73 subjects. Individual airborne exposure to Rat n 1 and endotoxin were determined with static (n = 256) samplings. Rat n 1 was measured with enzyme-linked immunosorbent assay (ELISA) and endotoxin by the Limulus method. RESULTS: Forty-four of 113 subjects (38.9%) reported at least one rat-related symptom: asthma (4.4%), rhinitis (34%) and conjunctivitis (16%). Twelve per cent were sensitized to RUP (specific IgE > 0.35 KU/L). But only 30.8% of all symptomatic subjects were sensitized to rat allergens. Airborne Rat n 1 levels were not related to symptoms in workers. Symptomatic patients not sensitized to rats were exposed to higher endotoxin levels, but airborne exposure to endotoxins did not significantly protect against or increase sensitization to RUP or rat-related symptoms. CONCLUSION: Most symptomatic workers were not sensitized to rat allergen; but no significant relation between rat-related symptoms and endotoxin levels was found. This suggests that more studies are needed to determine causes other than rat allergens or endotoxins that may be responsible for symptoms in rat-exposed workers.