(CNN)Short-term exposure to air pollution is linked to a higher risk of sudden heart problems, especially among older people, according to a study published Monday.
The study, published in the journal The Lancet, indicates that even low levels of air pollution can increase the likelihood of cardiac arrest. Study researchers at The University of Sydney say there is an "urgent need to reassess" international guidelines on air quality.
The research is believed to be the largest of its kind to date, according to the study's authors. They looked at data from emergency medical responses in Japan over a two-year period, as well as the country's records on air pollution involving particulate matter.
Particulate matter, or particulate pollution, is a mix of solid and liquid airborne droplets, according to the Environmental Protection Agency. The particles, made up of dust, dirt, soot or smoke, originate from construction sites, unpaved roads, fields, smokestacks or fires, and can contain different chemicals. But most particles are a mix of pollutants from power plant, industrial and vehicle emissions.
The study focused on PM2.5, or tiny particulate matter, which can move deep into the lungs when inhaled and from there into the bloodstream.