Re: Tap Water Blues, Opinion, and Facts
I have read David Baker's comments on the EWG report in
several publications. The PR people did their job. David Baker
has done excellent work over many years in monitoring water
quality. He is not a toxicologist nor a politician, and hence his
opinions on the size and severity of cancer risk from herbicides,
and their acceptability to society are just that, his opinions,
just as mine are or anyone else's.
The issues Hoog and others have raised in criticizing "Tap
Water Blues" are important and deserve more discussion. As I said
in my earlier post, the major contribution the report makes is a
much more sophisticated and data-rich analysis of actual herbicide
residue exposure levels in finished drinking water through the
midwest. They had to develop a new methodology to sort through
and synthesize the EPA's huge STORET database (which includes much
of Baker's Heidelberg College data), producing community/city
specific estimates of herbicide levels in water during specific
periods of the year. They then used a method pioneered by Goolsby
of the USGS to calculate seasonally adjusted annual exposure
estimates, capturing peaks in the spring and early summer months,
but not over-estimating exposure in the fall and winter, when
levels in surface water tend to be much lower. I have yet to see
any criticism of their methodology, or estimates; some have
questioned why they singled out certain towns/cities. Apparently
they reported only on those communities/cities they had enough
data for to produce statistically reliable estimates.
Critics argue that the risk estimates are wrong, and that EWG
chose the wrong risk standard to use as a benchmark. The report's
risk estimates use EPA methods and data, nothing more and nothing
less. For each of the 5 herbicides, the applicable Q star (the
so- called cancer potency factor) was multiplied by estimated
exposure levels, by various populations cohorts. Those who
criticize this part of the report are really criticizing cancer
risk assessment methods in general, since EPA's methods are pretty
much in the conservative mainstream of the toxicological community
and other regulatory agencies. I agree with Hoog and Baker and
industry that risk assessment remains an imperfect science, and
that more research is warranted. I differ with them, I suspect on
how much weight should be placed on findings that risk exceeds a
certain level, and on the importance of re-assessing exposure and
risk levels faced by infants and children. Industry believes in
and vigorously defends risk assessment when it appears to
exonerate a chemical, but not when the same methods and new data
implicate a profitable product that poses risks over generally
accepted standards of "acceptable" risks.
Last, the EWG's use of one-in-one million risk as the
"standard" against which risk was measured. Here the EWG made a
value judgement, just as Hoog, Baker, and others in industry do in
arguing this is too stringent a standard. The one-in-one million
standard for cancer risk is embodied in dozens of regulations and
laws, at both the state and federal level. It is the level of
risk deemed acceptable under exemptions to the Delaney Clause. It
is the level of risk embodied in most proposed food safety reform
bills. It is the level EPA considers acceptable in food. In
assessing a pesticide's dietary cancer risk, EPA considers and
treats drinking water as a food, and counts any exposure from
residues in water as part of total dietary exposure and risk. For
these reasons EWG chose one-in-one million as the standard.
Others believe a less rigorous standard is justified; debate goes
on regarding acceptable risks, and will undoubtedly re-surface in
the 104th Congress.
I am trying to get a copy of Baker's critique of the report
so I can understand more fully where he is coming from. Many of
the quotes attributed to him about the number of cancer cases, and
percent of cases caused by herbicides are nonsense, and reflect
inappropriate and unscientific uses/interpretations of risk
assessment -- mistakes, by the way that the EWG was careful not to
make or assert. People in the ag community do not want to hear or
believe this, I know, and think that anything an environmental
group does must be wrong. Sometimes environmentalists/industry
types/aggies are right and basically stick to the facts, sometimes
they are not, and do not. People can and will argue with risk
assessment as a statistical tool, and over what the level of
acceptable risk is or ought to be, but let's not use these debates
to undermine or confuse otherwise solid contributions.
I will also try to find out if EWG has responded to Baker's
critique, and will try to keep people informed of the debate,
which may yet generate some light on an important subject/set of
policy issues that will not go away until farmers switch to less
chemical intensive weed control methods, new water filtration
techniques are developed, or it stops raining in the midwest.