Relationship between exposure duration and sulfur dioxide-induced bronchoconstriction in asthmatic subjects
The purpose of the study was to determine the shortest duration of exposure to 1.0 ppm sulfur dioxide (SO/sub 2/) sufficient to induce bronchoconstriction significantly greater than that observed with exposure to clean air (CA) in exercising SO/sub 2/ sensitive asthmatics. Asymptomatic, nonmedicated, male asthmatics (n=12) with airway hyperresponsiveness to both methacholine and SO/sub 2/ were exposed in a chamber (20/sup 0/C, 40% relative humidity) for 0.0, 0.5, 1.0, 2.0 and 5.0 min to both CA and 1.0 ppm SO/sub 2/ on separate days (10 exposures). Just prior to each exposure, subjects walked on a treadmill in CA for 5 min at a predetermined speed/elevation to elicit a target ventilation of about 40 L/min. i.e., a brisk pace up a slight incline. After this walk, subjects rapidly entered adjoining exposure chamber containing either CA or SO/sub 2/ and immediately walked at the same speed/elevation for the specified exposure duration. Subjects then rapidly exited the chamber. Postexposure SRaw and symptom ratings increased with increased exposure duration in SO/sub 2/; pstexposure SRaw also was increased with increased exposure duration in CA but to a lesser extent. After adjusting for the CA response, significantly greater SO/sub 2/ induced bronchoconstriction was observed for the 2.0 and 5.0 min exposures as indicated by substantially greater increases in SRaw and substantially higher ratings of respiratory symptoms. The authors conclude that with the above exposure conditions, on average, SO/sub 2/ sensitivie asthamtics exhibit significant brochoconstriction at exposure durations of 2.0 min or more.
- Research Organization:
- Environmental Protection Agency, Research Triangle Park, NC (USA). Health Effects Research Lab.
- OSTI ID:
- 7070235
- Report Number(s):
- PB-88-219761/XAB; EPA-600/J-88/018
- Resource Relation:
- Other Information: Pub. in American Industrial Hygiene Association Jnl., Vol. 49, No. 1, 38-47(1988)
- Country of Publication:
- United States
- Language:
- English
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SULFUR DIOXIDE
BIOLOGICAL EFFECTS
ASTHMA
INHALATION
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