A new study printed in the European Respiratory Journal claims that 14 percent of chronic childhood asthma is caused by exposure to traffic pollution. The study, conducted in 10 European cities, challenges the accepted belief that traffic pollution merely triggers pre-existing asthma symptoms.
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The researchers used a method known as population-attributable fractions to assess the impact of near-road traffic pollution. This calculates the proportional reduction in disease or death that would occur if exposure to a risk factor were reduced to a lower level.
The new research used data from existing epidemiological studies which found that children exposed to higher levels of near-road traffic-related pollution also had higher rates of asthma, even when taking into account a range of other relevant factors such as passive smoking or socioeconomic factors.
The researchers aimed to take these findings further and estimate how many asthma cases could be avoided if exposure was removed.
The results found that 14% of asthma cases across the 10 cities could be attributed to near-road traffic pollution. The findings also take into account differences in the health of the overall population in different cities.
“Air pollution has previously been seen to trigger symptoms but this is the first time we have estimated the percentage of cases that might not have occurred if Europeans had not been exposed to road traffic pollution,” said Dr. Laura Perez, the lead author of the study, to Science Daily. “In light of all the existing epidemiological studies showing that road-traffic contributes to the onset of the disease in children, we must consider these results to improve policy making and urban planning.”
A previous study by scientists at Columbia University found that neighborhood differences in rates of childhood asthma could be explained by the amount of pollution in the neighborhoods. According to the study’s senior author, Matthew Perzanowski, the “study adds to the evidence that further public health interventions on oil and truck emissions standards and the use of dirty oil may be warranted.”
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In New York City, where the study was conducted, asthma among school-age children ranges from a low of 3% to a high of 19% depending on the neighborhood, and even children growing up within walking distance of each other can have 2- to 3-fold differences in risk for asthma. Helping explain these disparities, the researchers found that levels of airborne black carbon, which mostly comes from incomplete combustion sources like diesel trucks and oil furnaces, were high in homes of children with asthma. They also reported elevated levels of black carbon within homes in neighborhoods with high asthma prevalence and high densities of truck routes and homes burning low-grade or “dirty” heating oil.