Study objectives: Acute exposure to the air in swine
confinement units causes bronchial hyperresponsiveness and inflammation
of the airways. This study was performed to assess the longitudinal
development of bronchial responsiveness in pig farmers and to establish
Methods: A cohort of
171 pig farmers was followed over a 3-year period. Bronchial
responsiveness was assessed by a histamine provocation test. Long-term
average exposure to inhalable dust and endotoxin was determined by
personal monitoring in summer and winter, using data on farm
characteristics and activities. Time-weighted average (TWA) personal
exposure to ammonia was measured. Data on farm characteristics were
gathered in the same period.
Results: Mean increase in
responsiveness was 2.52 doubling concentrations of histamine for a 10%
decrease in FEV1 and 1.36 doubling concentrations for a
20% decrease in FEV1. Long-term average exposure to dust
was 2.63 mg/m3 and to endotoxin was 105 ng/m3.
TWA exposure to ammonia was 1.60 mg/m3. After adjusting for
age and smoking behavior, long-term average exposure to inhalable dust
was associated with increases in bronchial responsiveness expressed as
steps for provocative concentration causing 10% fall in
FEV1. TWA exposure to ammonia, use of wood shavings as
bedding, and automated dry feeding were associated with increases in
responsiveness expressed as steps for provocative concentration causing
a 20% fall in FEV1.
Exposure to dust and ammonia in pig farms contributes to chronic
inflammation of the airways and should be reduced.