An on-board air filtration system developed specifically for school buses reduces exposure to vehicular pollutants by up to 88 percent, according to a study by researchers at the UCLA Fielding School of Public Health. The high-efficiency cabin air, or HECA, system could help protect the 25 million American children who commute on school buses nearly every day. Children are more susceptible to air pollution than adults because they breathe more quickly and their immune and cardiovascular systems are still developing, said Yifang Zhu, the study’s senior author and an associate professor in the department of environmental health sciences.