(CNN) Even when air pollution is at levels below air quality guidelines and regulatory limits, it can still pose a hazard to public health, a new study finds.

In a 30-year analysis of 652 cities in 24 countries and regions on six continents, researchers found that increases in air pollution were linked to increases in related deaths. The study, published Wednesday in the New England Journal of Medicine, was one of the largest international studies to look at the short-term impact of pollution as a cause of death, the researchers said.

The analysis of air pollution data from 1986 through 2015 found there were increases in total deaths linked to exposure to inhalable particles and fine particles. The deaths were from cardiovascular and respiratory problems.

Particle pollution is the mix of solid and liquid droplets in the air, according to the US Environmental Protection Agency. It can come in the form of dirt, dust, soot or smoke. It comes from coal- and natural gas-fired plants, cars, agriculture, unpaved roads and construction sites.

With higher levels of pollution, the faster people are dying, said Chris Griffiths, a professor of primary care at Queen Mary University of London.