The study, published recently by Emissions Analytics, a U.K.-based emissions testing firm, found that under normal driving conditions, particulate emissions from tires are an eye-popping 1,850 times greater than from a tailpipe of a gas-powered car.
The U.S. Environmental Protection Agency defines particulate matter as "solid particles and liquid droplets found in the air" that are "so small that they can be inhaled and cause serious health problems." Some are small enough to enter deep into the lungs and even soak into the bloodstream.