A new report says that even short-term exposure to major air pollutants increases the risk of heart attack. In an analysis of more than 100 studies conducted worldwide, researchers from the Paris Cardiovascular Research Center found that increased exposure to pollutants — including fine particles, coarse particles, nitrogen dioxide, carbon monoxide, and sulfur dioxide — consistently increased the health risks after even short-term exposure, or less than seven days. While the risk from pollutant exposure was relatively small, compared with factors such as high blood pressure, the number of people breathing these pollutants worldwide is so large that a sizable number of people are at risk, the study said. In the case of fine particles, the researchers found that heart attacks increased 2.5 percent for every incremental increase in pollution levels. In other words, if fine particle levels reached 10 micrograms per cubic meter in one city, and 20 micrograms in another, the rate of heart attacks would be 2.5 percent greater in the second city, according to the study, published in the Journal of the American Medical Association. Most of the pollutants are associated with the burning of fossil fuels for transportation or industry. In a separate study, MIT researchers found that air pollution associated with China’s steep industrial growth caused health care costs to jump from $22 billion in 1975 to $112 billion in 2005.