Risk behaviors for hypertension—like eating a high-salt diet and smoking—may now include exposure to air pollution.

Recently the scientific community has been abuzz about blood pressure, one of the most powerful contributors to heart disease. Doctors are actively debating how low blood pressure should go in order to protect against heart attacks and stroke, and researchers are focusing on what people can do to keep their levels healthy.

Now, in a new study published in the journal Hypertension, scientists report on an unexpected connection to blood pressure: air pollution. The Chinese researchers, led by Yuanyuan Cai from Sun Yat-Sen University, analyzed all available studies involving air pollution and blood pressure and found that people exposed to high levels of pollutants, including ozone, carbon monoxide, nitrogen oxide and sulfur dioxide, were more likely to have high blood pressure—readings above 140 mm Hg for the first number in the ratio—than those exposed to lower amounts of pollutants. Exposure to particulates, the tiny, hard-to-see particles of pollutants circulating the air, also contribute to higher blood pressures.

The effect held for both short-term and long-term exposure to the pollution, and the increased risk of hypertension remained strong even after the researchers adjusted for other factors that could contribute to elevated blood pressure, including a history of heart problems and higher BMI.

More research is needed, as the findings are the first to look at both short-term and more lasting effects of pollution on blood pressure. It’s not clear yet, for example, whether people who already have hypertension will experience even higher elevations if they live in polluted areas. The scientists are also planning to investigate further the connection between particulate matter and risk of hypertension.

But Dr. Martha Daviglus, professor of medicine at the University of Chicago and spokesperson for the American Heart Association, says the results should serve as a warning to policy makers who may not take the health effects of pollution seriously enough. The findings should start a conversation about how legislators and regulators can start to improve air quality and potentially lead to better health for people, she says. In the meantime, doctors can “remind the population about the dangers of hypertension by advising them to lower the salt in their meals, cook in a healthier way and exercise.” On top of that, Daviglus adds, it might be a good idea to limit exposure to air pollutants by not going outside on days with high levels of pollution.