The Saharan dust absorption results are likely to be representative of desert dust properties around the world, according to the researchers. So, more dust in the atmosphere will lower current estimates of warming temperatures in those areas. Remer has analyzed Asian dust that reached the Channel Islands off the southern California coast and found similar low levels of absorption. The researchers are now confident that desert dust absorbs far less radiation than previously thought, Kaufman said, because two independent methods and observations were used, and both measure the properties of dust as it is in the free atmosphere, not after collecting it into a measuring device. Particulate matter is smaller airborne bits of pollutants such as dirt, dust and soot.
Most particulate matter is created by the burning of coal, oil and gasoline.
Breathing particulate matter has been linked to health problems including asthma and other respiratory diseases. The new draft criteria for particulate matter incorporates revisions made in response to earlier public comments and a review by the Clean Air Scientific Advisory Committee of the first external review draft. It assesses scientific information about particulate matter that has become available since the 1996 criteria document was published. The draft includes assessments of human exposure, particulate matter monitoring measurement methods, numerous other papers generated by scientists in the EPA's research laboratories, and published research by U.S. and international scientists. The EPA will accept comments on the new information until July 12.