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American Academy of Allergy, Asthma & Immunology Annual Meeting
February 25, 2013
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Airborne chemicals linked to immune dysfunction, asthma

Children with increased exposure to polycyclic aromatic hydrocarbons in air pollution reportedly had increased incidence of certain immune system effects and asthma, according to research presented at the 2013 Annual Meeting of the American Academy of Allergy, Asthma & Immunology.

Polycyclic aromatic hydrocarbons (PAHs) are found naturally in the environment, but also can be created when substances such as coal, oil and gas are burned but not completely combusted. Exposure to PAHs can occur through a variety of ways, including vehicle exhaust fumes, wildfires, wood-burning stoves, fossil fuel combustion, barbecued meats and cigarette smoke.

“We already know that immunoglobulin E (IgE) plays a role in asthma development and increased IgE levels result when asthmatics are exposed to triggers like pollutants,” senior study researcher Kari Nadeau, MD, PhD, FAAAAI, of Stanford University School of Medicine, said in a press release. “There is also growing evidence that regulatory T cells, which are a specific kind of cell that modulates the immune system, play an important role in inhibiting allergic sensitization and IgE production after exposure to an allergen. Regulatory T-cell numbers are reduced in patients with asthma.”

To assess the effects of PAH exposure on the immune system and the occurrence of new asthma cases, Nadeau and other researchers from Stanford University and the University of California, Berkeley, studied a sample of children from Fresno, Calif., a city known for its high levels of PAH in the air. A total of 332 children aged 10 to 18 years were given questionnaires and tested for lung function.

Total IgE levels were measured for 153 children enrolled in the study and regulatory T cells separated from blood samples. Researchers found higher levels of PAH exposure were linked to increased total IgE levels, and significantly weakened regulatory T-cell function also was observed in those children exposed to higher amounts of PAH.

Researchers said the study results yielded an unexpected discovery: an apparent association between PAH exposure accumulated during the previous 3 months and the diagnosis of asthma. An asthma diagnosis also appeared to be correlated with total IgE levels, according to the findings.

“Further research needs to be done, but what we can hypothesize from our pediatric sample is that exposure to high PAH quantities may be having an effect at the molecular level, possibly leading to new cases of asthma,” Nadeau said.

For more information:

Walker AI. Abstract #197. Presented at: 2013 Annual Meeting of the AAAAI; Feb. 22-26, 2013; San Antonio.

Disclosure: Nadeau reports no relevant financial disclosures.