Background: Workers in the poultry industry have increased frequencies of respiratory health problems. The aim of the present study was to investigate acute health effects from exposure in poultry houses and to compare the health effects observed in a cage rearing system and the alternative "cage-less" rearing system for laying hens.
Methods: Thirty-four subjects were exposed for 3 hr in confined poultry houses. The subjects were randomized into three groups: one was exposed in a building with a cage rearing system and the two other groups were exposed in buildings with a cage-less system, with either young hens and fresh bedding material or with older hens and old bedding material.
Results: Inhalable dust levels were approximately 4 mg/m3 in the buildings with the cage-less system and 2 mg/m3 in the building with cage rearing system; the endotoxin concentration was approximately 100 ng/m3 in both systems. Bronchial responsiveness to methacholine increased approximately fivefold in all groups following exposure. The concentration of the proinflammatory cytokine interleukin-6 (IL-6) increased in nasal lavage fluid and in peripheral blood as a result of the exposure. The number of leukocytes in peripheral blood increased only in the groups exposed among loose laying hens.
Conclusion: In the present study, we have demonstrated among previously non-exposed subjects, that 3-hr exposure in confined buildings for egg production induces an acute inflammatory reaction in the upper airways and increased bronchial responsiveness. There is a tendency towards stronger reactions in the groups exposed in the buildings with loose housing for laying hens.