Obesity risks rise with exposure to air pollution: Study
The findings further add to a limited body of evidence that suggests air pollution is a risk factor for childhood obesity. Data that are available have shown that early-life exposure to airborne pollution either increases susceptibility to diet-induced weight gain in adulthood or increases insulin resistance and inflammation.
However, no data have directly supported a link between air pollution and non-diet-induced weight increases.
Study criteria and results
The study, conducted by scientists from the Chinese Research Academy of Environmental Sciences in Beijing, and Duke University in North Carolina, used pregnant rats and their offspring as the animal model.
These subjects were placed in one of two conditions - one exposed to outdoor Beijing air and the other containing an air filter that removed most of the air pollution particles.
The scientists observed the rats for 19 days and found the lungs and livers of the pregnant rats exposed to the polluted air had gained weight and exhibited increased tissue inflammation. These rats also had 50% higher LDL cholesterol; 46% higher triglycerides; and 97% higher total cholesterol.
In addition, their insulin resistance level was higher than their clean air-breathing counterparts. The rat’s offspring also exhibited similar changes having being kept in the same conditions as their mothers.
An interesting finding, noted by the researchers, was these effects were less pronounced after eight weeks, where female and male rats exposed to the pollution were 10% and 18% heavier, respectively, than those exposed to clean air.
Junfeng "Jim" Zhang, a professor of global and environmental health at Duke University and a senior author of the paper, suggested long-term exposure was required in order for the inflammatory and metabolic responses that ultimately increased body weight to have a long-term effect.
"Since chronic inflammation is recognised as a factor contributing to obesity and since metabolic diseases such as diabetes and obesity are closely related, our findings provide clear evidence that chronic exposure to air pollution increases the risk for developing obesity," said Junfeng Zhang from Duke University.
"If translated and verified in humans, these findings will support the urgent need to reduce air pollution, given the growing burden of obesity in today's highly polluted world," said Zhang.
Air pollution and health
The link between air pollution and numerous health conditions has long been the focus of a number of studies. Beijing is a city that has long been troubled by air pollution levels that the air quality index (AQI) has recorded as between 34-199 (Particle Pollution (PM2.5)) in 2015. The World Health Organisation, recommends a safe exposure level of 25.
Air pollution is associated with significant adverse health effects including increased cardiovascular morbidity and mortality. One study, found that air pollution could induce considerable oxidative stress and systemic inflammation in mice and contribute to the progression of atherosclerosis.
Another study seemed to find similar results to Zhang’s study discovering that early-life exposure to high levels of a certain type of air pollution was a risk factor for the development of insulin resistance, adiposity, and inflammation.
Source: Journal of the Federation of American Societies for Experimental Biology (FASEB)
Published online ahead of print, DOI: 10.1096/fj.201500142
"Chronic Exposure to Air Pollution Particles Increases the Risk of Obesity and Metabolic Syndrome: Findings from a Natural Experiment in Beijing,"
Authors: Yongjie Wei, Junfeng (Jim) Zhang, Zhigang Li, Andrew Gow, Kian Fan Chung, Min Hu, Zhongsheng Sun, Limin Zeng, Tong Zhu, Guang Jia, Xiaoqian Li, Marlyn Duarte, Xiaoyan Tang
