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models for risk assessment because the effects only occur at high doses or
under very artificial exposure conditions.
The problem goes beyond the act of taking in vitro data to predict an in vivo
response that is, a response in a living organism. Often in intact animal or
32 CHAPTER 2
human trials, the ridiculously high doses of chemicals used induce specific
defense mechanisms that may do more harm than good against these unnat-
ural high-dose exposures. For example, chronic irritation of continuous high-
dose chemical treatment is often responsible for the cancer. If you were
exposed to such irritating doses, you would leave the area. Our laboratory
animals do not have that option. The stress of extensive handling has even
been implicated as a contributing factor to the disease seen. Some studies are
conducted in highly inbred strains of mice that are unusually sensitive or
more susceptible to specific classes of chemicals because their receptors are
more accessible or are present in increased numbers. Even control animals in
these studies have much higher incidences of tumors than other strains of
mice. There is no argument that these studies are important because they do
shed light on the mechanism of action of these chemicals. Their use in risk
assessment is the focus of the debate.
There is one facet of low-dose exposure that violates the dose-response
paradigm allergic reactions or hypersensitivity to minute quantities of
chemicals. Most known allergens are natural in origin, and many of us have
had experience with them. There are a number of well-documented drug
allergies with penicillin being the most common. It has been estimated that
25% of the population has some type of allergy. Only a low percentage of indi-
viduals are allergic to a specific drug or to other natural compounds. The reg-
ulatory philosophy has always been not to withhold drugs because of this
effect. There is nothing fundamentally different with pesticides. Our scientists
will never develop drugs and chemicals that are absolutely safe in all 280 mil-
lion inhabitants of the United States. There will always be a fraction of indi-
viduals who are allergic to something in the environment. Although this is
unfortunate, much like other diseases, it is not completely avoidable. This
phenomenon of extreme chemical sensitivity will be addressed when the so-
called multiple chemical sensitivity (MCS) syndrome is discussed later in the
book. There comes a point when the huge investment required to remove the
offending molecule is too great and may inadvertently cause other deaths in
the population, for example, by reducing availability of fresh fruits and veg-
etables. The better approach would be to further understand the mechanism
of this effect in the affected individuals and design strategies to block their
sensitivities much as allergists have been doing for decades to protect their
patients from natural allergens.
Part of this concern over synthetic chemicals has arisen because of the dra-
matic increase in our ability to actually detect chemicals in our body and envi-
ronment through advances in analytical chemistry, immunology and biotech-
nology. However, the mere presence of a chemical does not mean that an
effect will occur or has already occurred. And are we ever getting good at
detecting chemicals!
DOSE MAKES THE DIFFERENCE 33
There have been numerous advances made in traditional analytical chem-
istry which have pushed the level of detection to parts per billion and even
parts per trillion. The sensitivity is phenomenal, but what does it mean?
Similarly, tremendous advances in immunology have harnessed the power of
antibodies to detect molecules of drugs in biological or environmental sam-
ples. Biotechnology has cloned specific receptors to develop supersensitive
chemical detectors. Some amazing advances have even coupled biological
receptors with computer chips for chemical detection. Thus chemicals can be
detected at levels millions of time lower than ever could produce a biological
effect. We already know from laboratory animal studies and our discussion of
statistics that much higher amounts of chemicals produce no effects. Since we
could never prove a total absence of activity, and since the one in a million
responder would be lost in the background noise of spontaneous disease, how
should we react when chemists continue to find ever-decreasing amounts of
chemicals in our food? A trivial and almost absurd analogy would be this: You
know that if a one-ton brick fell on you, you would die. If you could detect a
brick one millionth in size, or 0.032 ounces (just under 1 gram), would you be
concerned?
This area of residue safety is a field in which I have had experiences since
our laboratory has served as a national information resource for drug and
chemical residues in food-producing animals. This service, the Food Animal
Residue Avoidance Databank (FARAD), has published four technical com-
pendia and maintains a national hotline for residue avoidance questions.
For the last decade we have been compiling drug, chemical, and pesticide con-
centration data in meat and tissues to assure veterinarians and farmers that
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