Parents seeking to minimize health risks for their children, including those that have yet to be born, will be interested in the findings of a new study conducted by Columbia University.

According to the study’s findings, the effects of air pollution on unborn children still in the womb are more likely to result in obesity later in life as compared to children born in areas with little to no air pollution.

In particular, the researchers discovered that unborn children exposed to high levels of pollutants called polycyclic aromatic hydrocarbons (or PAHs) were 1.8 times more likely to become obese by age 5 than unborn children exposed to minimal levels of these chemicals. The obesity risk increased to 2.3 times the normal rate by the time the children reached age 7.

2.4 Pounds of Excess Body Fat by Age 7, Study Says

During the study, researchers examined approximately 700 Dominican and African American pregnant women in New York City. The female subjects lived primarily in low-income areas of the South Bronx and Manhattan. None of the women smoked cigarettes, which could influence the levels of pollutants in their bodies.

All of the women that participated in the study were required to wear special backpacks designed to measure levels of PAHs in the surrounding environment. The backpacks were worn on two separate days during the third trimester of pregnancy.

Following the data-collection stage of the study and the births of all the children involved, the researchers followed up with 422 of the children through age 5 and 341 children through age 7.

After aggregating the data and measuring the body mass indexes of the children using their weight and height, the researchers determined that 25% of the children were obese by the time they turned 7 years of age. The evidence suggests that obesity becomes more likely over time, since roughly 21% of the children were obese by the time they reached the age of 5.

The researchers also discovered that obesity risk rose commensurate with PAH exposure levels. In other words, mothers exposed to the highest levels of PAHs during pregnancy were also the most likely to have obese children. Children born to these mothers averaged an extra 2.4 pounds of body fat by the time they turned 7.

The researchers said that they’re confident in their findings given that they accounted for a number of factors that influence childhood obesity, such as household income, proximity to busy roads, overall community economic health and the health and weight of the pregnant mothers themselves. At the same time, the researchers cautioned that their study only detected a link of association, not necessarily one of causation. In other words, PAH exposure wasn’t necessarily the main factor influencing childhood obesity in the subject pool, and more research will be needed to confirm the link.

What are Polycyclic Aromatic Hydrocarbons?

PAHs are actually very common. They’re air pollutants released through a number of combustion processes, including the burning of gas, oil, diesel, coal and even cigarettes. However, Andrew Rundle, an epidemiology professor and one of the chief researchers behind the study conducted by Mailman School of Public Health at Columbia University, said that some fuels release higher levels of PAHs than other fuels when burned.

In fact, efforts are currently underway in New York City to upgrade oil furnaces to reduce their emissions. Since diesel fuel is another major source of PAHs, New York City is also attempting to reduce the number of diesel buses operating on city streets.

Unfortunately, the researchers in this study had no way of measuring the levels of PAHs to which the children were exposed after being born. The researchers admitted that post-birth exposure may be partially or even solely responsible for the apparent link between pollution and obesity.

PAH exposure may increase the risk of obesity because PAHs are known to disrupt the cellular processes that break down fat. In fact, animal studies have indicated that mice gain body weight after being exposed to PAHs.

Are PAHs the Main Culprit Behind Childhood Obesity?

No. According to the researchers, childhood obesity is still primarily caused by a lack of exercise and diets containing too much sugar and fat. At the same time, the researchers believe that their study strongly indicates that body processes such as metabolism and hormone function can be influenced by chemical pollutant exposure, subsequently increasing obesity risk.

Dr. Rundle said that while all parents and soon-to-be-parents should be conscious of pollution levels in their immediate environments, those who lack the time to exercise or the financial resources to purchase healthy food should be most concerned with the study’s findings.

Approximately one year ago, the American Lung Association released a report listing the most polluted cities in America, as well as the cleanest cities. Five of the top six most-polluted cities are located in California, with Los Angeles and nearby Bakersfield topping the list.

Air Pollution Effects on Children: The Bottom Line

A newly published study provided by researchers at Columbia University indicates that children are more likely to become obese when they’re exposed to high levels of pollutants called polycyclic aromatic hydrocarbons (PAHs) in the womb.

The researchers determined that obesity chances increase in accordance with exposure levels. Other factors such as diet and exercise are still the primary contributing factors to obesity, however.

The full text of the study can be found in the American Journal of Epidemiology.