Babies and toddlers who live within 400 m of a source of diesel exhaust have double the risk for persistent allergic cough by the age of 3 years, compared to infants who live further away.

If babies are exposed to high levels of indoor allergens, such as paint, household chemicals, and carpentry, this risk is more than 4-fold higher.

The findings of a study showing the link were reported here this week at the Academy of Allergy, Asthma & Immunology 2008 Annual Meeting by Patrick H. Ryan, PhD, an epidemiologist from the University of Cincinnati, Ohio, and coordinator of the Cincinnati Childhood Allergy and Air Pollution Study.

“The timing of exposure and the mechanism of exposure are key” in the development of allergic wheeze and asthma in childhood, Dr. Ryan told meeting attendees.


Dr. Ryan’s team sampled dust samples in the homes, day cares, and other indoor environments where the infants spent a significant amount of time. They measured endotoxins and allergens and measured air quality —in particular diesel exhaust particles — in the homes of 792 newborns living within 400 m of interstate highways.

In this analysis, the investigators followed 624 infants through age 3 years, conducting physical assessments and measuring blood samples at 6, 12, 24, and 36 months.


Dr. Ryan reported that exposure to high levels of diesel exhaust had an increased risk for persistent allergic wheezing at age 3 years. Exposure did not increase risk for persistent nonallergic wheezing.

“The combination of the particles and the endotoxin create a chronic inflammatory condition,” he said. The findings were supported by elevated IgE levels in the exposed children, indicating an allergic immune response.

Dr. Busse said the findings indicate the importance of the environment in the incidence of asthma and the importance of educating the public as to the causes, symptoms, and proper treatment of asthma, a disease that is sharply increasing in prevalence.