The number of people killed or disabled by certain heart problems caused by exposure to air pollution has risen significantly since 1990: 31% worldwide, according to a study published Wednesday in the Journal of the American Heart Association.Particle pollution is specifically to blame, the researchers say. Also called PM2.5 or particulate matter pollution, it's the mix of solid and liquid droplets floating in the air, according to the U.S. Environmental Protection Agency. It can come in the form of dirt, dust, soot or smoke. Particulate pollution comes from coal- and natural gas-fired plants. Cars, agriculture, unpaved roads, construction sites and wildfires can also create it.Video above: Particle pollution is affecting Americans' health across the U.S., a report saysParticle pollution is particularly deadly. PM2.5 is so tiny — 1/20th of a width of a human hair — that you can't see it, and it can travel past your body's usual defenses. Instead of being breathed out when you exhale, it can get stuck in your lungs or go into your bloodstream.The particles cause irritation and inflammation and can lead to respiratory problems. Research has found that long-term exposure to particle pollution can cause cancer, dementia, depression, breathing problems and a variety of heart problems.For the new study, researchers analyzed nearly 30 years of death and disability data from a research set called the Global Burden of Disease 2019, which provides an estimation of how many people there are in 204 countries and includes information about mortality and disability due to exposure to particle matter pollution.The data tracked two heart-related problems: strokes and ischemic heart disease, a condition in which the heart can't get enough blood and oxygen, largely because of plaque buildup in the arteries.Video below: Look out for these health issues caused by poor air qualityThe researchers found that the total number of premature deaths and years of heart disease-related disability that can be attributed to particle pollution exposure rose from 2.6 million in 1990 to 3.5 million in 2019. There was a 36.7% decline in premature deaths alone in that time period – but that wasn't all good news."The declines in deaths may be considered positive news, as they indicate improvements in health care, air pollution control measures and access to treatment. However, the increase in disability-adjusted life years suggests that although fewer people were dying from cardiovascular disease, more people were living with disability," said study co-author Dr. Farshad Farzadfar, a professor of medicine in the Non-Communicable Diseases Research Center of the Endocrinology and Metabolism Research Institute at Tehran University of Medical Sciences in Iran.Men were much more likely to die from particle pollution exposure than women, the study found. Richer countries had the lowest number of lost years of life due to this pollution, but they also had the highest number of people who lived with heart-related disability.Heart problems due to pollution will probably continue to increase as global temperatures rise, experts say. Earlier research has found that a person's risk of a fatal heart attack may double in a heat wave and on days in which pollution levels are higher.Many countries have created laws and incentives to reduce air pollution, but almost the entire global population breathes air that exceeds World Health Organization air quality limits, and the number of "very unhealthy" and "hazardous" air quality days has grown over the years, in large part because of the climate crisis. In 2011 in the U.S. alone, exposure to this kind of pollution resulted in 107,000 extra premature deaths for all causes, not just heart problems, research has shown.