The effect of pre-exposure to 0.12 ppm of ozone on exercise-induced asthma

The health effects of exercising in air pollution

The health benefits of exercise are well known. Many of the most accessible forms of exercise, such as walking, cycling, and running often occur outdoors. This means that exercising outdoors may increase exposure to urban air pollution. Regular exercise plays a key role in improving some of the physiologic mechanisms and health outcomes that air pollution exposure may exacerbate. This problem presents an interesting challenge of balancing the beneficial effects of exercise along with the detrimental effects of air pollution upon health. This article summarizes the pulmonary, cardiovascular, cognitive, and systemic health effects of exposure to particulate matter, ozone, and carbon monoxide during exercise. It also summarizes how air pollution exposure affects maximal oxygen consumption and exercise performance. This article highlights ways in which exercisers could mitigate the adverse health effects of air pollution exposure during exercise and draws attention to the potential importance of land use planning in selecting exercise facilities.

Exercise-induced bronchospasm in children: effects of asthma severity

The prevalence of exercise-induced bronchospasm (EIB) in asthmatic individuals has been reported to vary from 40% to 90%. There are, however, few studies addressing the effects of asthma severity on airway responsiveness to exercise. The purpose of the present study was to investigate the effects of asthma severity on EIB in children. We studied 164 children classified as having intermittent (n = 63), mild persistent (n = 30), moderate persistent (n = 40), and severe persistent asthma (n = 31) according to the Global Initiative for Asthma classification. Subjects exercised for 6 min on a cycle ergometer at 80% of their maximum heart rate, and spirometry was performed before and 5, 10, and 20 min after exercise challenge. The prevalence of EIB in children with moderate or severe persistent asthma was significantly greater than in children with intermittent asthma (p < 0.001). EIB-positive children with intermittent asthma exhibited smaller changes in FEV1 than children in the other three groups (p < 0.001). There was no significant relationship between baseline FEV1 and the decline in FEV1 after exercise. We conclude that the prevalence of EIB is greater in children with more severe asthma, and that the intensity of response to exercise is not consistently related to the clinical severity of asthma.

Mechanisms of pollution-induced airway disease: in vivo studies

Several studies have investigated the effects of ozone, sulphur dioxide (SO2), and nitrogen dioxide (NO2) on lung function in normal and asthmatic subjects. Decreased lung function has been observed with ozone levels as low as 0.15 ppm-this effect is concentration dependent and is exacerbated by exercise. A number of lines of evidence suggest that the effect on lung function is mediated, at least in part, by neural mechanisms. In both normals and asthmatics, ozone has been shown to induce neutrophilic inflammation, with increased levels of several inflammatory mediators, including prostaglandin E2. However, in normal subjects, none of the markers of inflammation correlate with changes in lung function. The lung function changes in asthmatics may be associated with inflammatory effects; alternatively, ozone may prime the airways for an increased response to subsequently inhaled allergen. Indeed, an influx of both polymorphonucleocytes and eosinophils has been observed in asthmatic patients after ozone exposure. It has been suggested that the effect of ozone on classic allergen-induced bronchoconstriction may be more significant than any direct effect of this pollutant in asthmatics. SO2 does not appear to affect lung function in normal subjects, but may induce bronchoconstriction in asthmatics. Nasal breathing, which is often impaired in asthmatics, reduces the pulmonary effects of SO2, since this water-soluble gas is absorbed by the nasal mucosa. NO2 may also influence lung function in asthmatics, but further research is warranted. SO2 and NO2 alone do not seem to have a priming effect in asthmatics, but a combination of these two gases has resulted in a heightened sensitivity to subsequently inhaled allergen.