Effects of Ozone on the Respiratory Health, Allergic Sensitization, and Cellular Immune System in Children

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Abstract
To investigate the lasting effects of high ozone concentrations under environmental conditions, we examined the respiratory health, pulmonary function, bronchial hyperresponsiveness to methacholine, allergic sensitization, and lymphocyte subpopulations of 10- to 14-yr-old children. A total of 218 children recruited from an area with high ozone concentrations (Group A) were tested against 281 children coming from an area with low ozone concentrations (Group B). As to subjective complaints, categorized as “usually cough with or without phlegm,” “breathlessness,” and “susceptibility to chest colds,” there was no difference between the two groups. The lung function parameters were similar, but in Group A subjects' bronchial hyperresponsiveness occurred more frequently and was found to be more severe than in Group B (29.4 versus 19.9%, p < 0.02; PD20 2,100 ± 87 versus 2,350 ± 58 µg, p < 0.05). In both groups the number of children who had been suffering from allergic diseases and sensitization to aeroallergens, found by means of the skin test, was the same. Comparison of the total IgE levels showed no difference at all between the two groups. As far as the white blood cells are concerned, the total and differential cell count was the same, whereas lymphocyte subpopulations showed readily recognizable changes. In Group A subjects the absolute and relative numbers of T-helper cells (OKT4+) had decreased and those of T-suppressor cells (OKT8+) had increased, which resulted in a significantly low helper/suppressor cell index (OKT4+/OKT8+: 1.44 ± 0.45 versus 1.75 ± 0.57, p < 0.0001); moreover, the absolute and relative numbers of natural killer cells (OKNK+) dropped significantly (p < 0.001 and p < 0.0001). These findings suggest that long-term exposure to high ozone concentrations may lead to persistent bronchial hyperresponsiveness and subclinical effects on lymphocyte subpopulations in children.

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