CHILDREN exposed to traffic pollution are more likely to suffer from coughing, wheezing, asthma and allergic rhinitis, according to two huge studies in Germany and Taiwan. The findings suggest that vehicle fumes can sensitise children鈥檚 airways to the agents that trigger allergies and inflammation.
Numerous studies attest to the deadly effects of traffic pollution, with the very fine particles called particulates blamed for tens of thousands of premature deaths each year. But the question of whether traffic pollution is partly to blame for the rise in allergies and asthma worldwide is controversial, as some studies have found no link at all. Although epidemiological studies can only reveal associations rather than causes, the latest studies are significant because of their sheer size.
In Taiwan, a team examined the effects of traffic fumes on more than 300,000 pupils aged 12 to 15 at 800 schools throughout the country. 鈥淭hat鈥檚 almost every middle school in the country,鈥� says Yueliang Leon Guo of the National Cheng Kung University in Tainan, who led the project.
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The children all attended schools within 2 kilometres of 55 air monitoring stations. From the monitoring data, and from questionnaires sent to family doctors and parents, Leon Guo estimates that children exposed to the heaviest traffic pollution (mainly carbon monoxide and nitrogen oxides) are 16 per cent more likely to develop allergic rhinitis 鈥� conditions like hay fever that result in blocked or runny noses and sneezing fits.
鈥淥ur study shows that people living in busy traffic will have most problems with allergic rhinitis,鈥� says Leon Guo. Exposure to air pollutants in early life can induce changes in either immunity or responsiveness to allergens in the nose, he thinks.
Another team looked at the effects of pollutants and traffic density on 4000 children in Munich. High traffic exposure is associated with coughing, asthma and wheezing in all children, conclude Thomas Nicolai and Erika von Mutius at Munich鈥檚 University Children鈥檚 Hospital.
Children living within 50 metres of busy roads have nearly twice the risk of asthma symptoms, the team found. They are also 1.6 times more likely to suffer from coughing and wheezing, and are 17 to 56 per cent more susceptible to allergies, depending on the allergen (European Respiratory Journal, vol 21, p 956 and p 964).
The two studies suggest that traffic pollution can sometimes cause asthma, rather than just triggering attacks.