5.2 Exhaust is bad for your heart. A CNET News article reported that the artery walls of people living within 100 meters of a highway thicken more than twice as fast as the average person’s. Researchers used ultrasound to measure the carotid artery wall thickness of 1483 people living near freeways in the Los Angeles area. The artery wall thickness among those living within 100 meters of a highway increased by 5.5 micrometers (roughly 1/20th the thickness of a human hair) each year during the three-year study, which is more than twice the progression observed in participants who did not live within this distance of a highway.