RE: [CPEO-MEF] REPOST:natural attenuation -- the reality

[CPEO Moderator <cpeo@cpeo.org>]

The following message is repost of the previous MEF message.


-Original message from Richard McMurtry <RICHARD_McMURTRY@compuserve.com>

Andy assumes that action levels are protective of public health and the
environment and that the widespread dispersal of low concentration
carcinogens and endocrine disruptors below action levels is of no
consequence. Also, implied in his assertions is an assumption that  using
groundwater resources as a place to store and allow the low level spreading
of carcinogens in areas where no drinking water wells exist or where no
discharge to ecological areas exists is an appropriate use of the resource.
Implied in this is the assumption that the process of developing action
levels is scientifically sound or "is the best we can do with our existing
knowledge".

This is one way of looking at this subject.

Another way of looking begins with acknowledging that MCLs for drinking
water are developed through a process that more resembles witchcraft (in
the negative sense) than science.  That is to say, that public policy
makers take the scientific evidence (e.g. cancer impacts at high dosage)
and then extrapolate it beyond the point where they can verify their
results through the scientific method of experimentation (that is they
extrapolate high dosage cancer results into the realm of low dosage and
probability calculations).  At that point, where they extrapolate it into
unverifiable realms, it departs from science.  No one really knows the
shape or the slope of the curve in these realms.  To call this science is
to mislead the public and to practice self deception within the scientific
community. 

Also, even within the conventional methodology of cancer calculations there
is an acceptance of the fact that there is no safe level.  Some increase in
cancer will result in a susceptible individual at a critical time with even
exposure to one molecule.  The ambiquity is what the dose response curve
looks like with increased dose above zero and what the curve looks like in
response to exposure to mixtures of chemcials that humans are exposed to in
the real world of pesticide-laden foods, benzene-laden air, tri-halomethane
laden water and a host of other exposures.

Another element of this alternative way of looking is to question whether
the conventional way is indeed the "best we can do with our existing
knowledge".  The questioning begins with acknowledgeing that we don't
really understand what are the causes of many of the human and ecological
health problems that plaque our society. Admitting our ignorance allows us
to conclude that the risk-based numbers may be useful as a point of
departure, as a bottom line to our action levels, but that a more
responsible public policy in view of the uncertainties would be to
determine how close to zero we can get with a reasonable incremental cost. 
\
With such an approach, one might conclude that even though there are no
existing drinking water wells or ecological receptors impacted above action
levels, that aggressive source control efforts (including remediation of
contaminated soils) would be employed to reduce the mass of contaminants
that would be allowed to disperse in the aquifer.  Perhaps also some pump
and treat would be employed until the source control and high
concentrations were reduced before natural attenuation would be employed

This requires judgement to weight the benefits against the costs but this
might be the "best we can do with existing knowledge", rather that deceive
ourselves that action levels are protective.

Richard McMurtry Silicon Valley Toxics Coalition



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