A Quarter of Cars on Road Produce Most of the Pollution

By monitoring traffic in downtown Toronto, scientists found that 25 percent of the cars they measured produced 95 percent of the total particulates.

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That beat-up junker in your neighbor’s driveway is likely to produce more pollution during a long day’s commute than some newer vehicles emit driving cross country.

A new study out of Canada has tried to quantify the pollution gap. By monitoring traffic in downtown Toronto, scientists found that 25 percent of the cars they measured produced 95 percent of the total particulates and 93 percent of the carbon monoxide.

The University of Toronto researchers made on-the-spot measurements of the exhaust from 100,000 vehicles driving past air sampling probes set up on one of Toronto’s busiest roads. They confirmed that a relatively small number of older or badly tuned vehicles produced the vast majority of harmful emissions. A quarter of the vehicles they measured produced:

  • 95 percent of black carbon, the particulates often linked to lung disease
  • 93 percent of carbon monoxide; and
  • 76 percent of benzene, toluene, and other volatile organic compounds known to be carcinogens.

The researchers also confirmed that automotive pollution is particularly severe near freeways and other high-traffic roads. But it also found that emissions spread farther than previously known. Those living or working as much as 900 feet downwind from a highway can be exposed to twice the pollution of those further away.

Prior studies had estimated that the worst pollution was generally contained within an area no more than 300 or so feet downwind.

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-- Paul A. Eisenstein, The Detroit Bureau