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Air Attack

  • 14/01/2002

Air Attack Air Pollution aggravates asthma. Industrial smog (sulphur dioxide particulate complex) and photochemical smog (ozone and nitrogen oxides) are known to be triggers of mass asthma attacks. Yet the causal relationship is complex.

Asthmatics are the most sensitive group in a community, that is, they suffer the most at lower levels. Long-term exposure to even low concentrations of particulate matter in air results in increased rates of bronchitis and reduced lung function. Ozone reduces lung function in a continuum, that is, higher the concentration, longer the duration of exposure, greater the effect. Though scientific studies have found a wide range of sensitivity to sulphur dioxide among both healthy people and those with asthma, says World Health Organisation (WHO), even concentrations as low as one part per million (ppm) can trigger an attack. These studies also show that sulphur dioxide has continuous exposure-response relationships without any clear safe level, it points out.

Though research on asthma is yet to reach a consensus on the exact mechanism and the quantum of effect of these pollutants at different levels of concentration, most studies acknowledge that air pollution triggers violent asthma attacks in pre-sensitised atopic and normal individuals.

Although asthma prevalence is higher in industrialised countries, the direct role of air pollution has been questioned by some studies. While a study of two German cities showed that asthma and allergy were significantly more prevalent in the western city of Munich with its heavy automobile traffic, as compared to Leipzig in the east, which has heavy industrial pollution, a study by the Centers for Disease Control and Prevention (CDC) shows that lesser use of automobiles in Atlanta during the 1996 Summer Olympics led to improved air quality and a large decrease in childhood emergency room visits and hospitalisations for asthma.

A study done in 1986-92 in Barcelona, Helsinki, Paris and London during 1982-92 showed a significant increase in the number of the reported cases of asthma with the rise in the air pollutant levels. Cases for adult asthma increased with the increase in the nitrogen dioxide levels whereas the sulphur dioxide levels affected children.

Another study confirms that air pollution levels affect the children more than it does adults. The prevalence of asthma in schoolchildren has been increasing gradually in Taiwan. High levels of nitrogen dioxide, ozone, carbon monoxide, air-borne dust particles and total suspended particulate were significantly related to 8-29 per cent increase in the asthma risk. A World Bank study states that in Delhi, one out of 10 children aged 5-16 suffers from bronchial asthma, which is caused in part by air pollution.

Thus, even though there persists an uncertainty on whether air pollution causes asthma, there is a wide consensus that it aggravates the disease. Reason enough to operate on the precautionary principle and reduce levels of air pollutants and exposure to them.

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