People worry about traffic pollution but most don’t even realize that some pollutants are at higher levels inside their cars than outside on the road.

 

Pollutant levels are higher inside because cars take in emissions from surrounding vehicles and recirculate them. Researchers have found that as much as half of the pollutants inside test cars come from the vehicles immediately ahead, especially if those vehicles are highly polluting, such as heavy-duty diesel trucks.

The lnternational Centre for Technology Assessment reviewed 23 studies and concluded that in-car pollution levels frequently reach unhealthy levels. The pollutants from petrol and especially diesel exhaust include volatile organic compounds such as benzene and formaldehyde (carcinogens), carbon monoxide (which interferes with the blood’s ability to transport oxygen), nitrogen oxides, and particulate matter (linked to increase death rates over long periods of exposure). Some of these are especially hazardous for people with respiratory problems or heart disease. But even in healthy people these compounds can affect heart rate and other cardiovascular functions, as well as increase markers for inflammation and blood clotting. Particulate matter can cause congestion, sinus and throat irritation, and chest discomfort; it can aggravate asthma. Some pollutants, such as benzene and toluene, can also cause drowsiness dizziness, nausea, and headaches in sensitive people.