Ask A Scientist© Environmental Science Archive

Author:     joan of arc
Text:       I have a six year old who would like to ask this question. Is the 
black smoke that you see coming out of big trucks on the road pollution? If so 
why are they able to pollute. Don't trucks have to be tested just like cars 
do?

Response #: 1 of 1
Author:     Mark Fernau
Text:       Yes, black smoke from buses and trucks is pollution. It is 
unburned carbon particles that absorb light and so appear black. I am not sure 
but they may cause lung problems in asthmatics, etc. and could be carcinogens. 
In the past, trucks were less heavily regulated than automobiles but the Clean 
Air Act Amendments enacted in 1990 will tighten down on them over the next 
several years. A tune-up can alleviate part of the problem in existing 
vehicles, so maintenance is advised.