Air Pollution (IMAGE) Intermountain Medical Center Caption Even the briefest increase in airborne fine particulate matter PM2.5, pollution-causing particles that are about 3% of the diameter of human hair, is associated with the development of acute lower respiratory infection (ALRI) in young children, according to newly published research. Credit Intermountain Medical Center Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.