Fatty foods and lazy lifestyles might not be the only factors contributing to the obesity epidemic. A new study points a finger at air pollution.
The research, conducted by the Columbia University Center for Children's Environmental Health, pegs the obesity rate of New York City children at 25 percent (compared to a national average of 17 percent). Sure, fast-food joints are on just about every corner in the Big Apple, but what also abound are PAHs (polycyclic aromatic hydrocarbons). And it is the exposure of pregnant women to this common urban air pollutant that may be priming their children for a fat future.
The burning of coal, diesel, oil and gas, and other organic substances such as tobacco releases PAHs into the air. In cities, trucks and buses are the worst PAH polluters as they typically run on diesel fuel. The 8-year study monitored 702 non-smoking mothers living in northern Manhattan and the South Bronx.
Previous research at the center indicates that PAHs pose a number of hazards. In addition to obesity, prenatal exposure to PAHs can negatively affect childhood IQs and is linked to anxiety, depression, and attention problems in young children. The pollutants are also known carcinogens and have been shown to disrupt the body's endocrine system, which is instrumental in regulating mood, growth and development, metabolism, sexual function, and reproductive processes.
So is it the PAHs' effect on the endocrine system and metabolism that leads to obesity? Possibly. According to studies on mice, PAH exposure causes gains in fat mass. Corroborating evidence from cell culture studies have shown PAHs can prevent normal lipolysis, the process by which fat cells shed lipids and shrink in size.
These earlier studies correlate well with the findings from the new "street-science" study, which was published earlier this month in the American Journal of Epidemiology. Over the course of two days during their third trimester, the mothers wore a small backpack equipped to continually sample the surrounding air. At night, they placed the monitors at their bedsides. What the researchers found was that children born of women exposed to high levels of PAHs during pregnancy were nearly twice as likely (1.79 times) to be obese at age 5 and more than twice as likely (2.26 times) to be obese by age 7, compared with children of mothers with lower exposure levels. On average, the 7 year olds whose mothers had been exposed to PAHs the most had 2.4 pounds more fat mass than the kids of mothers with the least exposure.
"Obesity is a complex disease with multiple risk factors,” says Andrew G. Rundle, lead author and professor of epidemiology at Columbia's Mailman School of Public Health. “For many people who don't have the resources to buy healthy food or don't have the time to exercise, prenatal exposure to air pollution may tip the scales, making them even more susceptible to obesity."
Interestingly, though obesity clusters among poorer families -- and New York City has big pockets of poverty -- Rundle finds that the obesity risk from PAHs is not influenced by household income or neighborhood poverty.
But obesity rates are higher among African American and Hispanic children, and Rundle notes: "So while NYC has many advantages in terms of walkability and parks, it also has many residents traditionally thought to be at higher risk."
Fortunately, there are ways to reduce the impact of PAHs on your community. As stated above, certain fuels release more of the pollutants than others. So working with your city or town to require trucks, buses, and building furnaces to switch to cleaner fuels or be equipped with the latest emission controls could make a big difference. Such efforts by community action groups in New York City to take diesel buses off the streets and retrofit oil furnaces so they burn cleaner fuel have successfully improved air quality in their neighborhoods.
Many cities and towns have also passed anti-idling rules that prohibit trucks and buses from running their engines while stopped for more than a few minutes. NYC allows authorities to issue idling summonses, appearance tickets, and violation notices as well as gives citizens the ability to report truck violations. Getting your community to do the same would be a good start to help put the quality of the air you breathe into the hands of those it affects most.
Cleaner air, just like healthier diet and access to parks and recreation areas, is our ticket to smarter, healthier, and more productive lives for our children.