Air Pollutants Up Asthma Risk in Obese Children

Asthma may be more likely to develop in obese young children in association with greater exposure to polycyclic aromatic hydrocarbons (PAH), according to a new study that found obese children exposed to high levels of air pollutants were nearly 3 times as likely to have asthma as nonobese children.

“We previously have shown that repeated high exposure to PAH air pollution during the prenatal period and early childhood is associated with asthma in young children. Reducing indoor and outdoor PAH air pollution may help to diminish the risk of developing asthma for young children,” senior author Rachel Miller, MD, Professor of Medicine (in Pediatrics) and Environmental Health Sciences and Chief of Pediatric Allergy and Immunology at Columbia University Medical Center in New York, told ConsultantLive.

Exposure to traffic-related air pollutants, including PAHs from traffic emissions and other combustion sources, and childhood obesity have been implicated as risk factors for asthma. Since 1980, the percentage of American children who are obese has nearly tripled and childhood asthma rates have more than doubled.

Dr Miller and colleagues followed 311 children in predominantly Dominican and African American neighborhoods of New York City. They monitored indoor air in each child’s home for 2 weeks at age 5 or 6 years to measure exposure to PAHs. The child’s height and weight were measured and respiratory questionnaires were administered. In all, 20% of the children were found to have asthma and 20% were categorized as obese based on body mass index.

High PAH exposure was associated with asthma only among obese children. A 2- to 3-fold increase in asthma risk was seen among obese children exposed to high levels of the PAH chemicals 1-methylphenanthrene and 9-methylphenanthrene, respectively. Exposure to PAH or obesity alone did not predict asthma.

A better understanding of the risk factors opens the door to more targeted interventions. “We may be able to bring down childhood asthma rates by reducing sources of indoor emissions, such as gas cooking, space heating, burning incense or candles, environmental tobacco smoke, or encouraging the use of cleaner heating sources,” said Dr Miller, who is also co-deputy director of the Columbia Center for Children's Environmental Health at Columbia's Mailman School of Public Health. “Or we could implement an age-appropriate diet and increase vigorous physical activity.”

The mechanism behind how obesity may magnify the effects of these air pollutants, placing children at greater risk for asthma, is not well understood. “One possible explanation is that the sedentary lifestyle of obese children could result in more time spent indoors, thereby increasing their exposure to indoor PAH. Also, rapid breathing frequency may lead obese children to be exposed to a greater dose of asthma-promoting PAH, compared to non-obese children,” Dr Miller said.

Dr Miller recommends that primary care physicians continue to inform the parents of young patients with asthma about the importance of treating obesity and overweight syndromes in children and to review with families possible sources of indoor emissions of pollutants.

The researchers published their results in the January 2014 issue of Environmental Research.