Roughly one-third of the US population may be at an increased risk of developing health problems resulting from exposure to polluted air containing fine particulates. The tiny size of these pollutants allows them to travel deep into the lungs or other organs, potentially causing damage. In a new study, the specific effects of exposure to fine particulates on occurrence of inflammation, insulin resistance and obesity has been examined. These conditions are not only harmful themselves but are also risk factors for the development of type 2 diabetes.

In the study, young male C57BL/6 mice were exposed to polluted air containing ∼111 μg per m3 of fine particulate matter, a pollution level similar to those that can be found in urban areas of the US. Mice were exposed to the polluted air for 6 h per day, 5 days a week, for 10 weeks, beginning when they were 3 weeks old. This time frame roughly correlates with toddlerhood to late adolescence in humans.

Credit: Lee Pettet

Mice exposed to the polluted air experienced a greater accumulation of abdominal and subcutaneous fat, higher blood sugar levels, increased insulin resistance and higher levels of TNF-α, a molecule associated with inflammation, than did mice supplied with clean air (Arterioscler. Thromb. Vasc. Biol. 30, 2518–2527; 2010). These results suggest that exposure to polluted air alone can induce metabolic dysfunction and contribute to obesity and proinflammatory conditions. In a press release, Sanjay Rajagopalan (The Ohio State University, Columbus), a leader of the research group, stated, “[t]hese findings suggest that fine particulate pollution exposure...may lead to an increase in fat cell size and number, and also have a proinflammatory effect.”

Qinghua Sun, another study leader, added, “[t]his is one of the first, if not the first, study to show that these fine particulates directly cause inflammation and changes in fat cells, both of which increase the risk for type 2 diabetes.”

It isn't known whether the effects of exposure to fine particulates are reversible or whether they are sustained during adult life, even if exposure ends. “In a real-world scenario, it would be very difficult to escape from the pervasive influence of dirty air, an influence that begins very early in life,” said Sun.

The group has planned a human study that will take place in Beijing, China, in which the incidence of metabolic syndrome and insulin resistance will be tracked in participants wearing personal monitors to measure their exposure to pollution.