By Chris Richard
Studies have linked air pollution exposure, especially exposure to pollution from congested roadways, with serious health conditions ranging from asthma, to heart disease, to cancer, to low birth weight.
Now a research team at the University of Southern California’s Keck School of Medicine has received funding to investigate whether children living near busy roadways are more prone to obesity.
The National Institute of Environmental Health Sciences and the federal Environmental Protection Agency recently awarded $7.8 million to the medical school’s Southern California Children’s Environmental Health Center to fund research by over the next five years.
Scientists will conduct new studies and analyze existing data on whether and how roadway pollution may make children obese. They’ll also study metabolic abnormalities linked to air pollution from roads that might increase the risk of Type 2 diabetes.
Rob McConnell, professor of preventive medicine at Keck, will oversee the new investigations. He said the research proposal grew out of an earlier study on how the built environment might induce obesity.
For the past decade or so, scientists have looked into correlations between recreation and exercise opportunities and comparative leanness or heaviness.
Children who attend schools with recreation programs or live in a neighborhood with a sidewalk, where it’s easy to walk around, do tend to be a little more lean, McConnell said.
“The common wisdom is that we’ve got an epidemic of obesity and diabetes because we eat a lot of unhealthy foods and we don’t get any exercise. I think that’s certainly a big part of the explanation, but I think it’s more complicated that what we’ve thought,” he said.
Some three years ago, McConnell participated in a study that found a correlation between heavier children and higher traffic density around their homes. Not only were the children who were exposed to a lot of traffic fatter, but the more traffic they had in their neighborhoods, the more quickly they packed on pounds.
Researchers surmised that parents might be reluctant to send their children out to play in a neighborhood where going outside was unpleasant and possibly dangerous. So McConnell and his colleagues expected to find the kids who got the least exercise gained the most weight.
However, the data didn’t match that hypothesis. There wasn’t the strong correlation between fat and a sedentary life that researchers had expected to see. The exercise records were spotty, but still, it was puzzling.
Around the same time as McConnell's study, researchers at Ohio State University published research in which they had fed mice a high-fat diet and made them breathe polluted air. The mice developed a resistance to insulin and gained abdominal fat quickly, both reactions that match animal models for diabetes.
McConnell said he remained intrigued by the mismatch between weight and exercise in his study, and he thought the Ohio State research held the key to an explanation.
Later, other researchers found a correlation between prenatal exposure to urban pollution and higher obesity rates among children, and the Ohio State team’s follow-up investigations on their mouse study reinforced the link between fat and a polluted atmosphere.
So it does appear true that where the overweight kids live has a big influence on whether or not they grow fat. But there’s probably more to the story than exercise opportunity. There are increasing indications that the air the children breathe plays a significant role too, McConnell said.
His team will examine the records for 12,000 children who have been followed from elementary school through high school graduation as part of the USC Children’s Health Study, checking their exposure to air pollution against obesity. Researchers will give 200 obese children MRI exams, checking to see whether their body fat has concentrated around their abdominal organs, as it did with the mice in the Ohio study. Such fat buildups are increasingly believed to be a key risk factor for diabetes, McConnell said. He said the team also will test blood and fat samples for signs of inflammatory and pre-diabetic characteristics found in the mouse studies. Finally, an animal study will try exposing the test subjects to air pollution at different points in their lives – for example, before and after birth. The goal there will be to identify a point where exposure has the greatest impact, McConnell said.
“Over the next five years, I think we have a great opportunity to nail down what’s going on by looking at it from a variety of different levels,” he said.
McConnell also has been a leader in research showing how roadway air pollution may cause asthma.
“We don’t need a lot of additional reasons to control air pollution, but I think understanding the true burdens associated with it probably helps policy makers decide what to do,” McConnell said.