A team of researchers who just finished analyzing 20 years of data from locales around Los Angeles said that particulate matter less than 2.5 micrometers in diameter poses the greatest risk of causing early death as it can penetrate deep into the lungs and sometimes even enter the bloodstream. Such particles are often found in smoke, vehicle exhaust, industrial emissions, and haze. The researchers also tracked ozone pollution, but found no link between ozone levels and mortality. The researchers found that for each increase of 10 micrograms per cubic meter ([micro]g/[m.sup.3]) of fine particles in the neighborhood's air, the risk of death from any cause rose by 11 to 17 percent. Ischemic heart disease mortality risks rose by 25 to 39 percent for the 10 [micro]g/[m.sup.3] increase in air pollution.