Traffic air pollution near school associated with onset of asthma.

Jul 07, 2010

McConnell, R, T Islam, K Shankardass, M Jerrett, F Lurmann, J Gauderman, E Avol, N Kuenzli, L Yao, J Peters and K Berhane. 2010. Childhood incident asthma and traffic-related air pollution at home and school. Environmental Health Perspectives http://dx.doi.org/10.1289/ehp.0901232.

Synopsis by Patrick H. Ryan

The risk for developing asthma increases in children who are exposed to traffic-related air pollution at school.

Children who breathe traffic-related air pollution at school are more likely to develop asthma, even after taking into account levels of air pollution at their homes, report researchers in the journal Environmental Health Perspectives.

This study adds to the small, but growing, body of research implicating traffic-related air pollution in the development of asthma. In addition, this study suggests that places away from home where children spend time play an important role in their health.

Asthma is one of the most common childhood diseases in the United States. Rates among school-aged children continue to rise, leading to increased absences, more health care and lower quality of life. Asthma is a lung disease with symptoms that include wheezing, coughing, shortness of breath and difficulty breathing.

Public schools in urban areas of the United States are frequently located near streets with heavy traffic flow. The close proximity to freeways and busy roads may result in increased exposure to traffic-related air pollution. Prior studies show that children attending these schools have higher rates of asthma.

But, it is not known if the traffic-related pollution would contribute to the onset of asthma in children without the respiratory disease. To find out, researchers from the University of Southern California followed almost 2,500 asthma-free children beginning when they were younger than 6 years old and just entering either kindergarten or first grade. The children were from 45 different schools in 13  communities in Southern California.

Outdoor  traffic-related air pollutants – including particulate pollutants, nitrogen dioxide (NO2) and ozone – were measured continuously at central neighborhood locations during the three-year study. The child's exposure to traffic-related pollution at home and school were estimated. Family health history, housing, smoking and other personal information was gatherered from questionnaires given at the study's start and once a year after that. Children with asthma or wheezing at the start of the study were not included in this analysis.

During the study, 120 children developed asthma.

Interestingly, the risk of developing asthma increased by about the same amount – about 50 percent – for exposures at school and at home, even though less time is spent at school.

Weather may play a bigger role than other studies have shown. The results were strongest when weather was combined with traffic volume and closeness to busy streets.

Exposure at school may be higher because of deeper, more frequent breathing during exercise and recess. Also, schools may have higher pollution levels in mornings – when winter-time air inversions may keep pollution at ground level – and evenings when buses and cars congregate to drop off and pick up kids.