Objectives In developed countries, poultry are raised in totally confined buildings in which workers are exposed to indoor airborne contaminants. A prospective study was conducted to investigate the relationship between workers' respiratory health and airborne contaminants during the life cycle of broiler and layer flocks.

Methods Seventeen layer and 16 broiler operations were chosen within a 200 km radius of Edmonton. An attempt was made to visit each broiler operation twice during the winter and summer seasons in the early and later periods of the 6-week production cycle and visit each layer operation three times during the early, middle and later periods of the 40-week production cycle.

Results In broiler operations, respirable particle counts, total dust and endotoxin concentrations, and ammonia levels increased with flock age, while mean endotoxin load (EU/mg) decreased in the winter and summer seasons. Increases in dust and endotoxin concentrations in the winter season were not statistically significance. Mean endotoxin concentration increased and mean dust concentration and ammonia level decreased with flock age in layer operations, although not all these changes were statistically significant. Mean across-shift decrements in FEV₁ and FVC increased with flock age among workers from layer operations. Endotoxin concentration was significantly associated with across-shift changes in FEV₁ among workers in layer operations.

Conclusion In our study, changes in lung function appear more closely associated with changes in endotoxin than other contaminants. Changes in indoor environmental conditions occurring in poultry barns which are dependent on the flock age may affect workers' health in poultry operations.