Lung function and inflammatory responses in healthy young adults exposed to 0.06 ppm ozone for 6.6 hours

Abstract

Rationale: Exposure to ozone causes a decrease in spirometric lung function and an increase in airway inflammation in healthy young adults at concentrations as low as 0.08 ppm, close to the National Ambient Air Quality Standard for ground level ozone.

Objectives: To test whether airway effects occur below the current ozone standard and if they are more pronounced in potentially susceptible individuals, such as those deficient in the antioxidant gene glutathione S-transferase mu 1 (GSTM1).

Methods: Pulmonary function and subjective symptoms were measured in 59 healthy young adults (19-35 yr) immediately before and after exposure to 0.0 (clean air, CA) and 0.06 ppm ozone for 6.6 hours in a chamber while undergoing intermittent moderate exercise. The polymorphonuclear neutrophil (PMN) influx was measured in 24 subjects 16 to 18 hours postexposure.

Measurements and main results: Subjects experienced a significantly greater (P = 0.008) change in FEV(1) (± SE) immediately after exposure to 0.06 ppm ozone compared with CA (-1.71 ± 0.50% vs. -0.002 ± 0.46%). The decrement in FVC was also greater (P = 0.02) after ozone versus CA (-2.32 ± 0.41% vs. -1.13 ± 0.34%). Similarly, changes in %PMN were greater after ozone (54.0 ± 4.6%) than CA (38.3 ± 3.7%) exposure (P < 0.001). Symptom scores were not different between ozone versus CA. There were no significant differences in changes in FEV(1), FVC, and %PMN between subjects with GSTM1-positive and GSTM1-null genotypes.

Conclusions: Exposure of healthy young adults to 0.06 ppm ozone for 6.6 hours causes a significant decrement of FEV(1) and an increase in neutrophilic inflammation in the airways. GSTM1 genotype alone appears to have no significant role in modifying the effects.

Figures

Figure 1.

Percent changes in FEV1 and FVC after 6.6-hour exposure to clean air and 0.06 ppm ozone. (A, B) Group means (± SEM) and individual changes, respectively, for FEV1. (C, D) Group means (± SEM) and individual changes, respectively, for FVC.

Figure 2.

Clean air (CA) adjusted % changes (mean and 95% confidence interval) in (A) FEV1 and (B) FVC after ozone exposure for all subjects, and by sex and GSTM1 genotype. *P < 0.05; †0.05 < P < 0.1. F = females; GSTM1-n = glutathione S-transferase mu 1 null; GSTM1-p = glutathione S-transferase mu 1 positive; M = males; NS = not significant.

Figure 3.

% Polymorphonuclear neutrophils (PMN) changes in sputum samples after 6.6-hour exposure to clean air (CA) and 0.06 ppm ozone for (A) the group mean, and (B) each individual. Error bars represent standard error. %PMN is defined by neutrophil number as % of total cell counts in the sample. F = females; GSTM1-n = glutathione S-transferase mu 1 null; GSTM1-p = glutathione S-transferase mu 1 positive; M = males; NS = not significant.

Figure 4.

Clean air (CA) adjusted % changes in polymorphonuclear neutrophils (PMN) (mean and 95% confidence interval) after ozone exposure for all subjects, and by sex and GSTM1 genotype. *P < 0.05. F = females; GSTM1-n = glutathione S-transferase mu 1 null; GSTM1-p = glutathione S-transferase mu 1 positive; M = males; NS = not significant.