Diesel Exhaust Exposure Early in Life Doubles Asthma Risk

Martha Kerr

March 21, 2008

March 21, 2008 (Philadelphia) — Infants younger than 1 year who live within 400 m of a source of diesel exhaust have double the risk for persistent allergic wheeze by the age of 3 years than infants who live farther away. If the living environment also has a high risk for indoor allergens, 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, with an odds ratio (OR) of 2.1 (95% confidence interval [CI], 1.0 – 4.3). Exposure did not increase risk for persistent nonallergic wheezing.

If infants were also exposed to high levels of endotoxin, risk was significantly higher, with an OR for wheeze of 4.1 (95% CI, 1.5 – 11.7), an OR of 3.4 for persistent allergic wheeze (95% CI, 0.8 – 14.1), and an OR of 4.1 for persistent nonallergic wheeze (95%, CI, 0.9 – 17.8).

"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. Ryan presented his findings during a session moderated by William W. Busse, MD, chairman of the Department of Medicine at the University of Wisconsin, Madison, and past president of the American Academy of Allergy, Asthma & Immunology.

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.

Neither Dr. Ryan nor Dr. Busse has disclosed any relevant financial relationships.

Academy of Allergy, Asthma & Immunology 2008 Annual Meeting: Abstract 252. Presented March 15, 2008.

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