Airborne -- a word from the field -Reply (fwd)

[Doyle Srader <DSRADER@UGA.CC.UGA.EDU>]

Happy birthday, Doyle.  What is the significance of the distinction you
draw?  Arguably, the difference between primary and secondary
pollutants is artificial at best.  Here's why:

1.  ALL pollutants are toxic only in relationship to the natural environment.
 This is because (a) exposure -- not merely release to the environment --
is necessary before the pollutant is harmful to human health or the
environment; and (b) as all toxicologists say, "the dose determines the
poison."  SO, easily interactive agents (like surface ozone) may present
more persistent environmental problems that relatively dilute or rare air
toxics, like mercury.

2.  The real fight (as I have said before) is over the variety of effects any
pollutant can have.  Here, one distinction is between direct and indirect
effects.  Direct effects come from exposure to the pollutant in the form in
which it appears in the environment, unchanged by interaction with other
species.  Eg, sulfur dioxide is emitted to air, breathed in, and lung cancer
results.  Indirect exposure deals with bioaccumulation or biomagnification
through the food chain (generally).  Eg, mercury accumulates in fish,
finally exceeding a threshold level for toxicity.

Again, post if you want.  Ciao, Scott
--------------------------------------------------------------------------
Points well taken. The excerpt I posted had a couple of themes in it, only
one of which I was interested in promulgating, and I think that theme
reappeared in your second point: the medium boundaries are possibly more
problematic than helpful. Are pesticides an airborne pollutant? Farm
workers are exposed to a hefty dose of those toxins while spraying them
on fields if they don't undertake sufficient safety precautions, and
sometimes even if they do. But one of the <I would speculate> more large-
scale sources of pesticide poisoning is the "circle of poison" problem,
the pesticide residues in food. Regulating the first would be topical,
regulating the second wouldn't. I'm just concerned about the potential for
absurd restrictions under a topic that was confined to one medium -- the
possibility that you could regulate a paper mill because it had dioxin
fumes floating around in the air and the workers were getting sick, but
that you couldn't prohibit that same paper mill from dumping dioxin in
the water and making an entire city sick.

Doyle Srader
University of Georgia
<706> 548-9938

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