Earlier studies had hinted at a link between fine soot particles and lung cancer.

Some light bounces off soot particles in the air and goes back into outer space.

In other words, how fast are the soot particles moving toward the ceiling?

And today's diesel engines produce far fewer tiny soot particles than just seven years ago.

Those are two factors that her engineers suspect would make the vehicle produce more soot particles.

Some light bounces off soot particles in the air.

But violations of the Federal health standard for soot particles are likely at other locations that have similar traffic and buildings, she said.

Children, the elderly and people with respiratory disease are more vulnerable to the soot particles than the rest of the population.

This is due to incandescence of very fine soot particles that are produced in the flame.

Only about 20-30% of air-borne soot particles come from inner-city traffic.