Objectives: The objective of the study was to determine whether swine farmers continuously exposed to the farming environment react differently to acute exposure than previously unexposed nonfarmers.
Methods: Nine healthy nonfarmers, not previously exposed to a farming environment, and eight swine farmers were exposed in a swine confinement building for 3 hours while weighing pigs. Lung function measurements, methacholine challenge tests, and nasal lavages were performed before and after the exposure. Blood samples were drawn repeatedly during the exposure day. Differential cell counts and cytokine levels were analyzed in the nasal lavage fluid and blood.
Results: The exposure levels were the same in both groups. Bronchial responsiveness to methacholine increased by a median of 4.0 (25th-75th percentiles 2.2-10.1 among the nonfarmers) and 0.7 (25th-75th percentiles 0.01-3.5 among the farmers) doubled concentration steps. The median serum levels of interleukin-6 increased from 3.8 (25th-75th percentiles <3-5.8) ng/l to 23.7 (25th-75th percentiles 11.6-41.6) ng/l among the nonfarmers and from <3 to 3.8 (25th-75th percentiles 3.1-11.6) ng/l among the swine farmers after the exposure. Swine dust exposure induced a ninefold increase in the total cell counts in the nasal lavage fluid of the nonfarmers, but no significant increase among the swine farmers.
Conclusions: The exposure altered lung function and bronchial responsiveness, as well as cell number and cytokines in blood and nasal lavage fluid in previously unexposed nonfarming subjects, whereas only minor alterations were found in the farmers. This finding suggests possible adaptation mechanisms in chronically exposed swine farmers.