To evaluate whether acute effects of ozone, nitrogen dioxide, and particulates with mass median diameter less than 10 micro m could be attenuated by antioxidant vitamin supplementation, we conducted a randomized trial using a double-blinded design. Children with asthma (n = 158) who were residents of Mexico City were randomly given a daily supplement of vitamins (50 mg/day of vitamin E and 250 mg/day of vitamin C) or a placebo and were followed from October 1998 to April 2000. Pulmonary function tests were carried out twice a week in the morning. During the follow-up observation period, the mean 1-hour maximum ozone level was 102 ppb (SD = 47), and the mean 24-hour average PM(10) level was 56.7 micro g/m(3) (SD = 27.4). In children with moderate and severe asthma, ozone levels 1 day before spirometry were inversely associated significantly with forced expiratory flow (FEF(25-75)) (-13.32 ml/second/10 ppb; p = 0.000), FEV(1) (-4.59 ml/10 ppb; p = 0.036), and peak expiratory flow (PEF) (-15.01 ml/second/10 ppb; p = 0.04) in the placebo group after adjusting for potential confounding factors. No association between ozone and lung functions was observed in the supplement group. We observed significant differences in lung function decrements between groups for FEF(25-75) and PEF. Our results suggest that supplementation with antioxidants might modulate the impact of ozone exposure on the small airways of children with moderate to severe asthma.
In an effort to improve risk assessments for ozone (O3) we compared the incorporation of inhaled oxygen-18-labeled O3 (18O3) into the lungs of humans and laboratory rats. Cells and fluids obtainable through bronchoalveolar lavage (BAL) were examined after exposure to 18O3 to determine whether excess 18O concentrations (presumed to be reaction products of 18O3) could be detected and equated to the O3 dose to the lung. Three O3 effect measurements (increased BAL protein and neutrophils and decreased BAL macrophages) were also made in subjects or animals exposed in parallel to determine whether there was a correspondence between dose and effect measurements. Eight human male volunteers 18 to 35 yr of age were exposed to 18O3 (0.4 ppm for 2 h) with 15-min alternating periods of heavy treadmill exercise and rest. Rats (F344) were exposed identically, except without exercise. 18O3 was generated directly from pure 18O2. BAL cells and centrifugally separable surfactant material were freeze-dried and analyzed by mass spectrometer for excess 18O. Results showed that the exercising humans had four- to fivefold higher 18O concentrations in all of their BAL constituents than did the rats. The humans also had significant increases in all of the effects markers after 0.4 ppm O3, whereas the rats did not. Rats that were exposed to higher concentrations of 18O3 (2.0 ppm) had levels of 18O in BAL that were more comparable to but still lower than those of exercising humans. Changes in all of the effects markers in these rats were comparable or higher than in exercising humans.(ABSTRACT TRUNCATED AT 250 WORDS)
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