Last summer the Mississippi River Basin Alliance, with
headquarters in St. Louis, and the Environmental Working Group, in
Washington, D.C., sponsored a study of pesticides in drinking
water. The St. Louis Audubon Society participated in the study.
From the middle of May through the end of August, samples of
drinking water taken at a downtown office location were mailed to
the University of Iowa for analysis. Each sample was tested for two
commoniy used herbicides or weed killers, atrazine and cyanazine. A
few samples were subjected to tests capable of detecting up to 11
Atrazine, marketed by the Swiss firm Ciba Geigy under the trade
name AAtrex, is also widely used in combination with other weed
killers. It is most often used on corn and is the most widely used
herbicide in the United States. Cyanazine belongs to the same
family of herbicides, the triazines. It is manufactured by DuPont
and sold under the trade name Bladex. It is also used in corn
fields and is the fourth most commonly used herbicide.
Our survey found that concentrations of atrazine and cyanazine
both peaked on June 11 when drinking water samples contained 2.6
and 2.4 parts per billion, respectively, of the two herbicides.
Farmers apply these herbicides in the spring and early summer, when
they reach their highest concentrations in our rivers. Average
concentrations for atrazine and cyanazine during the testing period
were 1.56 and 0.66 ppb, respectively. Six different pesticides in
varying concentrations were detected in one sample taken at the end
Atrazine has been demonstrated to be a carcinogen in animals,
but studies with humans are less conclusive. Hence, atrazine is
classified by the EPA as a "possible human carcinogen." EPA's
Office of Ground Water and Drinking Water ignores possible
carcinogenic effects in setting federal standards for drinking
water. Using toxicological effects unrelated to possible
carcinogenic activity, the agency has set a maximum contaminant
level of 3 ppb for atrazine. Federal standards require only that
the average concentration over a period of a year be below the
maximum contaminant level.
One reason the levels of atrazine in our city water samples
were below the federal standards for drinking water is that, during
the season of pesticide use, the city analyzes the water daily and,
when necessary, adds powdered activated carbon, which absorbs much
of the contaminant and is subsequently filtered out. Many other
cities may not do that.
The Office of Pesticide Programs, which regulates pesticide
concentrations in foods, has set a permissible level for atrazine
in food about 19 times lower than the standard for drinking water.
Under this standard, the acceptable level for drinking water would
be approximately 0.16 parts per billion.
In many European countries the equivalent standard is 0.1 parts
per billion. Atrazine is banned in Italy, Germany, Sweden, the
Netherlands, Austria and Hungary.
Cyanazine has been shown to be a carcinogen in animals, where
it also causes birth defects and skeletal abnormalities. …