California's urban, transportation policies contribute to children's asthma.

Nov 30, 2012

Perez, L, F Lurmann, J Wilson, M Pastor, SJ Brandt, N Künzli and R McConnell. 2012. Near-roadway pollution and childhood asthma: Implications for developing “Win-Win” compact urban development and clean vehicle strategies. Environmental Health Perspectives

Synopsis by Kai Zhang

California's effort to reverse urban sprawl and encourage denser development may mean more children will live closer to polluted high-traffic areas. A new study estimates that near-road air pollution is at least partially responsible for 8 percent of childhood asthma cases in Los Angeles County. The authors reported that their findings "suggest that there are large and previously unappreciated public health consequences of air pollution" in metropolitan areas and that "compact urban development strategies should be coupled with policies to reduce near-roadway pollution exposure."

In California, urban planning policies designed to reduce vehicle emissions and limit urban sprawl encourage people to build and live closer to transit centers. That way, they can use their cars less and public transportation more. But people then live closer to major roads and higher air pollution levels, which can be unhealthy.

Now, a study of children's asthma in Los Angeles County finds that may be true. The results suggest the number and severity of health impacts from living less than a football field away from high-traffic roads have been underestimated.

By comparing health data with how far residents live from heavy-traffic roads, the researchers figure around 27,000 – or about 8 percent – of the total childhood asthma cases in the county are at least partly due to exposures from living near busy streets. In addition, a larger percentage of the children experience symptoms serious enough to send them to the hospital.

Lowering traffic-related air pollution in these transportation-centric areas could reduce the children’s respiratory problems, the study's authors suggest.

This is the first study to examine the impact of what is called compact urban development from the perspective of reducing health burdens of roadway air pollution. The state-mandated policies attempt to integrate land use and transportation planning in order to reduce urban sprawl and slow vehicle emissions. The policies do not consider health effects of near-roadway air pollution.

Traffic on roads has significantly increased in the United States during the past 20 years. In many cities, vehicle emissions have become one of the dominant sources of air pollutants, including carbon monoxide, carbon dioxide, volatile organic compounds, hydrocarbons, nitrogen oxides and particulate matter (PM).

Traffic-related air pollution is associated with respiratory, cardiovascular and other chronic health problems in adults and children. While air pollution can trigger asthma attacks, the underlying mechanism is not well understood.

People with asthma have a hard time breathing. Allergens, pollution, cigarette smoke and general poor air quality can trigger mild to severe asthma symptoms, including wheezing, shortness of breath and coughing. The disease – which can affect quality of life – has increased in the United States by 75 percent since 1980, according to the California Environmental Protection Agency.

Living close to busy roads poses a significant public health threat because concentrations of traffic-related pollutants are higher near high-traffic areas. The levels fall off sharply away from the highways. An estimated 11 percent of U.S. households are within 100 meters (about 110 yards) of a four-lane highway.

In this study, investigators compared the number of asthma cases and asthma exacerbations in children younger than 18 in Los Angles County during 2007. They looked at three scenarios linked to exposures to near-road air pollution and regional urban air pollution.

Exposures to near-road pollution were estimated with dispersion models of residential proximity to a major road while exposures to the regional air pollutants nitrogen dioxide and ozone were estimated using data from the U.S. Environmental Protection Agency. Data from the Children's Health Study were used to link population data to pollution data and find the associations between children's asthma and air pollution.

The researchers estimated, among 2.5 million children in Los Angeles County, about 17.8 percent of those lived within 75 meters – about 82 yards – of busy roads.

When looking at childhood asthma, the researchers found that around 27,100 cases of childhood asthma – about 8 percent of the total number of kids with asthma – were caused by near-road pollution within 75 meters (about 80 yards) of a busy highway. If the number of children living within 75 meters of a major road rose by 3.6 percent, an additional 5,900 asthma cases would be attributable to near-roadway pollution.

They also found that near-road pollution disproportionately had a greater impact on the more severe asthma symptoms. These often lead to more serious health problems that need more medical care, for example, emergency room visits and hospital admissions.

The study suggests that near-road air pollution is a factor in children's asthma and should be considered in urban planning policies meant to reduce urban sprawl and traffic-related air pollution. Smarter strategies will be needed to limit urban sprawl and reduce health burdens of near-road air pollution at the same time.

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