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 different herbicides.
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 of June.
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. …