Your address may be harming your health. New research has found that living close to a major road in middle age can increase your risk of asthma by about 50 per cent compared with those who live further away.

A study published in the European Respiratory Journal found Australians aged 45-50 who lived less than 200 metres from a major road had a 50 per cent higher risk of asthma, wheeze and lower lung function over a five-year period than those who lived more than 200 metres from a major road.

The study found that the increased risk was despite Australia's relatively low safe nitrogen dioxide (NO2) limit of 30 parts per billion per year. The highest reading was just 23.

The results have prompted researchers to urge governments to reduce NO2 emissions by diverting vehicles, particularly trucks, from major roads and/or regulating to further reduce vehicle emissions.

Lead author Dr Gayan Bowatte, from the University of Melbourne, says the study found that despite our relatively low air pollution levels compared to developing South East Asian countries, they are still associated with increased risk of asthma and poor lung function in adults.

Dr Bowatte says governments need to investigate ways of reducing emissions on busy roads, particularly trucks using diesel.

"Diesel is much more harmful than petrol because of the composition of the fuel," he says. "When it burns, diesel produces more pollutants."

Led by researchers at the University of Melbourne's Allergy and Lung Health Unit and the Centre for Air Quality and Health Research and Evaluation (CAR), the study monitored traffic-related air pollution, known as TRAP, exposure over five years.

One of only a few studies to investigate the long-term health effects of air pollution, it surveyed about 700 participants from the Tasmanian Longitudinal Health Study when they were aged 45 and 50. Although the Tasmanian Health Study started in Tasmania, study participants are now living across the country in Tasmania, Victoria, New South Wales and Queensland.

Until now, the most evidence of traffic-related air pollution's impact on adult respiratory problems has come from short-term cross-sectional research. Related research has also tended to focus on children. This study sought to establish more robust measures using longitudinal data from an established cohort study. Results were adjusted so that socioeconomic status was not a factor.

The project defined major roads using Australian transport hierarchy codes supplied by the Public Sector Mapping Agencies. State classifications vary slightly but usually include highways, freeways and arterial roads that link major metropolitan activity centres.

In Victoria, they included freeways and arterial roads that provide a principal route for people and goods. This could include roads connecting major regions, population centres, metropolitan activity centres and transport terminals.

Researchers defined asthma as taking asthma medication or having asthma or wheezy breathing within the last 12 months. Wheeze included wheezing or whistling in the chest without having had a cold over that period.

"Asthma in adults is a common and important public health problem," say the authors.

"It is a heterogeneous disease that may appear at any age and shows variable activity over time."

Study supervisor, Professor Shyamali Dharmage, of the Melbourne School of Population and Global Health, says it is now up to authorities to act. In the meantime, people living close to major roads should talk to their GP about the possibility of respiratory problems being related to their address.

Professor Dharmage says that due to Australia's relatively low pollution levels compared to many other countries, these residents may not realise that it does not take much to cause health problems.

"They should be aware that they are at a higher risk," she says. "We have underestimated the health effects because of our low pollution levels. The message is it's not a problem that can be ignored."

The research, which has prompted Dr Bowatte to further study whether these asthma symptoms persist and/or cause new cases over time, comes at a time of increasing awareness about environmental links to various health conditions.

"The rapidly increasing prevalence of asthma after the second half of the twentieth century strongly suggests that environmental exposures play a major role," the researchers write.

"In particular, the role of traffic-related air pollution exposures in exacerbating or causing asthma has attracted substantial interest.

"Our study adds to the existing body of evidence that even relatively low levels of TRAP exposure are associated with asthma and poor lung function in adults."

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