What kinds of particles are there in soot pollution?
There are currently two kinds of particles regulated by the federal and state governments. “Fine” particles (PM 2.5) are 2.5 micrometers in diameter or smaller. Larger or “coarse” particles (PM 10) are between 2.5 and 10 micrometers in diameter. Both are smaller than the width of a human hair. Leading-edge research suggests the existence of even smaller, more-damaging “ultrafine” particles. Because science is still emerging, these particles are not regulated by federal or state air agencies.
