They studied 348 people, testing their blood pressure, weight, and other factors.
More than half of the study participants were considered obese.
People living in the smoggiest areas were found to have higher systolic blood pressure and higher pulse pressure, with the effect greatest among those who were obese.
Researchers say society needs to address the combined health threat of obesity and air pollution, noting that smog only makes things worse for those with obesity related conditions such as high blood pressure or diabetes.
The findings were published in the October 16th online edition of the Journal of Epidemiology and Community Health.