But now a new study conducted by an international team of researchers is suggesting that laboratory rats who were exposed to the highly polluted air of Beijing, for three to eight weeks, also gained weight along with having cardio-respiratory problems.
To reach their findings, the research team put pregnant rats, along with their young, in two compartments. One was open to the outdoor air of Beijing and the other included an air filter that removed most of the air pollution.
Both sets of rats were fed the same diet throughout the experiments.
The researchers found that the pregnant rats who breathed the polluted air after only 19 days had heavier lungs and livers along with increased tissue inflammation.
“Since chronic inflammation is recognized 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 the study’s senior author Junfeng “Jim” Zhang, of Duke University in Nashville, TN in a press release.
Compared to those who breathed filtered air, the researchers also found that the air pollution breathing rats also had 50 percent higher levels of LDL (bad) cholesterol; 46 percent higher triglycerides; 97 percent higher total cholesterol and a higher level of insulin resistance. Having a high insulin resistance level can set the stage for Type 2 diabetes.
The research team said that the baby rats displayed comparable results to their mothers, who lived under identical conditions in the same compartments.
For example, an eight week old female rat exposed to air pollution was 10% heavier and a male 18% heavier than those who breathed filtered air.
Since the researchers found that the detrimental effects of air pollution was more noticeable at eight weeks than at three weeks, the study suggests longstanding exposure to high levels of air pollution may be essential to produce the kinds of physiological changes that lead to obesity.