Ambient air pollution and the lungs: what do clinicians need to know?

Educational aims

1. To provide physicians with knowledge of the common ambient air pollutants and their adverse effects on human lungs.

2. To emphasise the fact that neonates, children and adults with pre-existing lung diseases are a susceptible population that need to be protected from the harmful effects of ambient air pollution.

3. To educate physicians about the role of oxidative stress in mediating the harmful effects of ambient air pollution, and the consequences that individuals with inherent defects in antioxidant defence genes may be more vulnerable to the harmful effects.

4. To provide physicians with current knowledge on the available dietary and drug sources of antioxidants which have the potential to enhance lung defence mechanisms against the harmful effects of air pollution.

5. To encourage physicians to act as advocates to help reduce the levels of ambient air pollutants and to conduct research that will not only identify susceptible individuals by conducting genetic studies, but will also help in developing interventions that will reduce the harmful effects of ambient air pollutants.

Summary Ozone, oxides of nitrogen, sulphur dioxide and particulate matter are the important ambient air pollutants associated with adverse health effects. A large number of ambient air pollutants have been isolated from the fetal cord blood indicating that babies are exposed to air pollutants even before they are born. Children and the elderly are most susceptible to the harmful effects of ambient air pollutants. High levels of ambient air pollutants are associated with increased incidence or worsening of asthma and increased risk of developing allergic diseases, respiratory symptoms and respiratory tract infections. Mortality rates also increase in individuals with pre-existing cardiorespiratory diseases. The underlying mechanism for the harmful effects is the generation of oxidative stress which induces a strong respiratory as well as systemic inflammatory response. Individuals with genetic defects in enzymes associated with antioxidant defences seem to be particularly vulnerable to the harmful effects of air pollutants. Supplementation with antioxidants such as N-acetyl cysteine and sulforaphene has shown some protective effects in preliminary studies. High doses of vitamin C and vitamin E have shown some benefit in genetically susceptible asthmatic children. Physicians should play an important role in advocating to governments for a reduction in ambient air pollutants using innovative strategies and stricter legislation. Clearly more research is required to better understand intervention strategies to reduce morbidity and mortality due to ambient air pollutants, but in the meantime, the least we can do is to supplement diets with rich sources of antioxidants.