Effect of Exposure to Low Levels of Ozone on the Response to Inhaled Allergen in Allergic Asthmatic Patients

¹ From the Department of Medicine, Baylor College of Medicine, Houston, TX
² From the Department of Medicine, University of Toronto
³ From the Gage Occupational and Environmental Health Unit, Toronto, Ontario, Canada
⁴ From the Department of Preventive Medicine and Biostatistics, University of Toronto

Susan M. Tarlo, MBBS, FCCP, The Toronto Hospital, Western Division, EC4-009, 399 Bathurst Street, Toronto, Ontario M5T 2S8, Canada; email susan.tarlo{at}utoronto.ca

Study objectives: In a previous study published by our group, six out of nine subjects with mild allergic asthma were shown to have an enhanced response to allergen challenge following a 1-h exposure in an 0.8-m³ exposure chamber (modified from a body plethysmograph) to an average of 120 parts per billion (ppb) ozone at rest. Other studies failed to confirm this effect. In the present study, using a similar design, we reexamined this effect using a larger group of asthmatics and a larger chamber allowing minimal fluctuations in ozone levels during exposures.

Design: Prospective, randomized single-blinded crossover study.

Setting: Pulmonary function laboratory equipped with an exposure chamber.

Subjects: Fifteen subjects had mild allergic asthma; 9 men and 6 women; the mean (SD) age was 32.5 (10) years; FEV₁ was 3.4 (0.8) L; baseline methacholine provocation concentration causing a 20% fall in FEV₁ was (PC₂₀) 3.28 (4.1) mg/mL.

Interventions: Each participant was exposed, at rest, on 1 day to filtered air and on another day to ozone (mean level=120 ppb) in a larger exposure chamber than the one used in our first study with less variability in ozone level (110 to 130 vs 85 to 175 ppb) using a random, single-blinded design. After each exposure, the subject was challenged with allergen (nine with grass pollen extract and six with ragweed extract) and allergen PC₁₅ was measured.

Results: Ozone preexposure did not affect allergen PC₁₅ when compared with clean air preexposure (allergen PC₁₅ dilution 1/114 vs 1/119, respectively). Ozone vs air preexposure resulted in an allergen PC₁₅ that was lower in five subjects, higher in six, and unchanged (within one doubling dose) in four.

Conclusions: At this low level with less variability and lower peaks than our previous study, ozone had no significant effect on airway allergen responsivess.

Key Words: allergen • allergen challenge • asthma • ozone

Submitted on December 4, 1997
Accepted on March 17, 1998

This article has been cited by other articles:

				L. L. Chen, I. B. Tager, D. B. Peden, D. L. Christian, R. E. Ferrando, B. S. Welch, and J. R. Balmes Effect of Ozone Exposure on Airway Responses to Inhaled Allergen in Asthmatic Subjects Chest, June 1, 2004; 125(6): 2328 - 2335. [Abstract] [Full Text] [PDF]

				J. F. Gent, E. W. Triche, T. R. Holford, K. Belanger, M. B. Bracken, W. S. Beckett, and B. P. Leaderer Association of Low-Level Ozone and Fine Particles With Respiratory Symptoms in Children With Asthma JAMA, October 8, 2003; 290(14): 1859 - 1867. [Abstract] [Full Text] [PDF]

				I. M. NDUKWU, E. T. NAURECKAS, C. MAXWELL, M. WALDMAN, and A. R. LEFF Relationship of Cellular Transmigration and Airway Response after Allergen Challenge Am. J. Respir. Crit. Care Med., November 1, 1999; 160(5): 1516 - 1524. [Abstract] [Full Text]