Re: Deaths from fossil fuel burning air pollution

["Otto G. Raabe" <ograabe@ucdavis.edu>]

At 11:00 AM 11/20/00 -0600, Prof. Coehn wrote:
>	Incidently, there is no "linear-no threshold" assumption stated,
>or even implied. There are lots of data on exposure vs health effects, and
>these are analyzed with regression analysis involving other potential
>confounding factors, i.e. multiple regression. Regression analysis by
>definition gives a linear fit to the data, but it is not "linear-no
>threshold"; the (0,0) point is not included in the regression analysis.
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November 20, 2000
Davis, CA

Although it is undoubtedly true that air pollution is injurious and can
lead to premature deaths, the result of these particulate matter
epidemiological studies has been the use by EPA and many of the various
investigators of a Linear No-Threshold (LNT) model of airborne fine
particle induced acute mortality. This is expressed by published statements
such as: "A 2% increase in mortality occurs for every 50 micrograms per
cubic meter increase in particulate air pollution." This is based on
comparison of higher PM levels with lower levels with respect to observed
mortality. In this model, any increase in concentration, NO MATTER HOW
SMALL can be related to an increase in mortality. A 1 microgram per cubic
meter increase in particulate matter concentration then yields a calculated
0.04% increase in deaths. That works out to be 4 additional deaths for
every 1000 deaths that may occur without this increase in particulate
matter; large cities can be said to have many deaths associated with even
this small increase in airborne particulates matter. 

This type of calculation does not depend on the absolute value of the
baseline value. The "zero" level is taken as no increase in concentration
which is associated with no increase in deaths. Any non-zero increase is
taken to yield a linear increase in risk. There is no (0,0) absolute value
because there is always some particulate matter in ambient air and there is
no zero death rate at any level. However, it is implied by this calculation
that every microgram per cubic meter of particulate matter causes a linear
increase in death rates with no threshold. I call that a Linear
Non-Threshold (LNT) risk model.

Otto 

 
**********************************************
Prof. Otto G. Raabe, Ph.D., CHP
Institute of Toxicology & Environmental Health
(Street Address: Bldg. 3792, Old Davis Road) 
University of California, Davis, CA 95616
E-Mail: ograabe@ucdavis.edu
Phone: (530) 752-7754   FAX: (530) 758-6140
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