]]]]]]]]]]]]        Danger, Natural Pesticides       [[[[[[[[[[[[[[[[
    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-
   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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