Exposure to traffic-related pollution early in life linked to childhood asthma

Exposure in infancy to nitrogen dioxide (NO2), a component of motor vehicle air pollution, has been found to be strongly associated with later development of childhood asthma, according to a team led by UCSF scientists.

The researchers said their findings indicate that air pollution might, in fact, be a cause of the disease.

In the study, the largest to date of air pollution exposure and asthma risk in minority children in the United States, the team found that for every five parts per billion increase in NO2 exposure during the first year of life, there was a 17 percent increase in the risk of developing asthma later in life.

The study involved 3,343 Latino and 977 African American participants.

"Many previous studies have shown an obvious link between traffic-related pollution and childhood asthma, but this has never been thoroughly looked at before in an all-minority population," said lead author Katherine K. Nishimura, MPH, a graduate student in the laboratory of senior author Esteban G. Burchard, MD, MPH, a UCSF professor of bioengineering and therapeutic sciences and medicine and director of the UCSF Center for Genes, Environment and Health.

What made the current study different from previous research, said Nishimura, was that the scientists looked retrospectively at the study participants' exposure to air pollution in early childhood, before they developed asthma. Children who developed asthma before this exposure period were excluded.

Study co-author John R. Balmes, MD, of UC San Francisco and UC Berkeley, pointed out that a previous study of children living in southern California showed that living and attending school close to major roadways was associated with an increased risk of new-onset asthma.

"Together with our findings, this makes for strong evidence that reducing children's exposure to traffic emissions can prevent some cases of asthma," said Balmes.

The study is reported online currently in the American Journal of Respiratory and Critical Care Medicine ahead of print publication.