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[ron thigpen <ron AT fuzzsonic.com>]

Jeremy Portzer wrote:

> Just because construction vehicles are putting out visible crud (i.e.,
> carbon in the smoke) doesn't mean they are polluting all that badly. 

particulates in diesel exhaust do have negative effects, just different 
ones from some of the more commonly regulated internal combustion 
by-products.  small particulates are increasingly seen to cause lung 
cancers.

> What really matters is things like sulfur (causes acid rain), nitrous
> oxides (causes smog), etc -- these are invisible.  

well, they all matter to some extent, but you are right in that it's not 
always the stuff you can see that is the most toxic.

> The EPA's "Tier 2" program for deisel emissions is making a big dent
> in these problems.

or rather, it will, when the provisions actually start to kick in. 
those big engines last a long time, and replacement under these regs is 
likely to take 20+ years.  on the positive side, the Clinton era 
low-sulfur diesel rules were allowed to take effect and the US will soon 
be refining much cleaner diesel road fuels.  locomotives and heavy 
equipment will not be required to burn it, but it may not be cost 
effective for the refineries to keep producing the high sulfur stuff.

> However, I have heard that much of the pollution, even among
> automobiles, is caused by a very small number of vehicles.  This is
> partially driven by the desire to "grandfather" all old cars from new
> pollution requirements.  

very true.  closed-loop fuel injection systems and other engineering 
advances have done wonders for emissions and performance.  there have 
acutally been economists who advocated the buying up of cheap, high 
polluting older vehicles and "retiring" them as a very cost effective 
means of reducing output of certain pollutants.  one rusty, old buick 
can be cheaper than one hundred new catalytic converters.  the 
politically more palatable solution seems to be to let nature -- and 
either oxidation or the collector's marketplace -- simply run their 
course.

and i seriously doubt you're going to convince scott that sending all 
pre-1974 vehicles to the crusher is a good idea.  and let thee who comes 
for my old ducati proceed with extreme caution.

if you want to see where the various pollutants in your area are coming 
from, try scorecard.org.  here's the summary for my zip (watch wrap):
<http://www.scorecard.org/community/index.tcl?zip_code=27608&set_community_zipcode_cookie_p=t&x=0&y=0>

--rt