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]]]]]]]]]]]] Danger, Natural Pesticides [[[[[[[[[[[[[[[[
(5/24/1989)
by Bruce N. Ames, Chairman of the Dpt. of Biochemistry,
Univ. of Calif. at Berkeley.
(Bergen County, NJ) Record 5-21-89.
[Kindly uploaded by Freeman 97656GAED]
The bad news is that our plant foods contain carcinogens. Carrots,
celery, parsley, parsnips, mushrooms, cabbage, Brussels sprouts,
mustard, basil, fennel, orange and grapefruit juices, pepper, cauli-
flower, broccoli, raspberry, and pineapple contain natural pesticides
that cause cancer in rats or mice and that are present at levels
ranging from 70ppb (parts per billion) to 4 million ppb--levels that
are enormously higher than the amounts of man-made pesticide residues
in plant foods.
All plants produce their own natural pesticides to protect them-
selves against fungi, insects, and predators such as man. Tens of
thousands of these natural pesticides have been discovered,and every
species of plant contains its own set of toxins, usually a few dozen.
When plants are stressed or damaged, such as during a pest attack,
they increase their natural pesticide levels manyfold, occasionally
to levels that are acutely toxic to humans.
Only a tiny percentage of these natural pesticides has been tested
in animal cancer tests, but of those that have been tested, the per-
centage that turns out to be carcinogenic is about as high as for
man-made pesticides (about 30 percent). The same appears to be true
for natural teratogens (agents that cause birth defects). It is high-
ly probable that almost every plant product in the supermarket con-
tains natural carcinogens and teratogens.
The pesticides that we are eating are 99.99 percent all natural
(we eat 10.000 times more natural than man-made pesticides),are rela-
tively new to the modern diet, because most of our plant foods were
brought to Europe within the last 500 years from the Americas,
Africa, and Asia (and vice versa).
In response to the environmentalist campaign about tiny traces of
man-made pesticides, plant breeders are active in developing
varieties that are naturally pest resistant. However, the primary way
plant breeders are able to increase natural resistance to pests is to
breed plants with increased levels of natural pesticides.
It should be no surprise, then, that a newly introduced variety of
insect-resistant potato had to be withdrawn from the market, due to
acute toxicity to humans caused be much higher levels of the terato-
gens solanine and chaconine than are normally present in potatoes.
Similarly, a new variety of insect-resistant celery recently
introduced in the United States had to be withdrawn after it caused
widespread outbreaks of dermatitis due to a concentration of carcino-
gens at 9,000 ppb rather than the usual 900 ppb.
Many more such cases are likely to crop up--they are undetected as
yet due to lack of immediate observable effects--because there is a
fundamental trade-off between nature's pesticides and man-made pesti-
cides.
The good news is that it now appears that the risk of cancer is
negligible from carcinogens at levels far below the maximum tolerated
dose given to rats and mice in cancer trials. I am not even very
concerned about the cancer risk from allyl isothiocyanate, a natural
carcinogen present in cabbage at 40,000 ppb and in brown mustard at
900,000 ppb, because I, along with most other leading scientists, am
very skeptical about all of these worst-case, low-dose extrapolations
from high-dose animal tests.
What must be emphasized is that "the dose makes the poison." For
example, consuming five alcoholic drinks per day is clearly a risk
factor in humans for cancer, and in pregnant women for giving birth
to mentally retarded babies. However, there is no convincing evidence
as yet that consuming one alcoholic drink per day is dangerous.
As another example, sunlight can cause cancer, but the evidence
suggests that the carcinogenic danger is from repeated sunburns. In
fact, ultraviolet light at low doses induces a tan, which protects
against the burning of skin by ultraviolet light.
My own estimate for the number of cases of cancer or birth defects
caused by man-made pesticide residues in food or water pollution--
usually at levels hundreds of thousands or millions of times below
that given to rats or mice--is close to zero.
The Food and Drug Administration and the Environmental Protection
Agency are doing an adequate job of protecting our food supply from
carcinogenic contaminants and are much more credible then the
activists lawyers with the Natural Resources Defense Council who
spend their time wooing the media with scientifically unfounded
claims about the dangers of pesticides, but who have never assembled
a knowledgeable board of scientific advis-ers.
The cost to the American public from such misplaced efforts is
enormous, both in terms of a very large hidden tax on our economy and
in terms of lives lost by diverting resources from basic scientific
reserch. We are spending $70 billion per year on pollution because
of wildly exaggerated fears and only $9 billion per year on all of
our basic scientific research.
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