Weed Killers By The Glass
September 1, 1995

Weed Killers By The Glass: Des Moines, Iowa

Citizen Monitoring Results

Des Moines drinking water is contaminated with cancer causing weed killers that have exceeded federal standards on at least one occasion. Tests of city tap water found four different pesticides in a single sample. The most common pesticide contaminant is atrazine, which was found in 81 percent of tap water samples collected between May 15 and July 1, 1995. Cyanazine was found in 38 percent of these samples. During this test period approximately 1,250 infants in Des Moines consumed infant formula reconstituted with water contaminated with four toxic weed killers. (Note 1: Ershow, Abby G., and Cantor, Kenneth P. 1989. Total Water and Tapwater Intake in the United States: Population-Based Estimates of Quantities and Sources. Life Sciences Research Office; Federation of American Societies for Experimental Biology. Bethesda, MD)

Most of these weed killers are used in corn production. Since 1985, taxpayers have subsidized Iowa corn growers at a rate of $809 million per year, for a ten year total of $8.09 billion. Farmers in turn pay nothing to clean up the water. The pesticide industry claims that farmers' weed control cost would double if these polluting herbicides were banned. Assuming the industry claim is true, the added costs to farmers would amount to just 11 percent of the value of the subsidy taxpayers pay to these corn farmers each year.



Causes mammary gland cancer in female rats in repeated studies.(Note 2: Copley, Marion. 1989. Follow-up to the Third Peer Review of Atrazine. EPA. Washington, D.C.; International Agency for Research on Cancer. 1991. World Health Organization. IARC Monographs on the Evolution of Cancer Risk to Humans. Vol. 53.) Classified by the EPA as a possible human carcinogen. Federal health standard in drinking water -- 3 parts per billion (ppb), European Drinking Water Standard -- 0.1 ppb.


  • Found in 81 percent of 16 tap water samples
  • Highest level found -- 1.80 ppb
  • Average concentration -- 0.53 ppb.



Causes mammary gland cancer in rats and birth defects in rats and rabbits in repeated studies. Causes genetic mutations. According to the EPA this makes cyanazine a potent carcinogen.(Note 3: Dykstra, William. 1991. Peer Review of Cyanazine (Bladex). EPA. Washington, D.C.) Classified by the EPA as a possible human carcinogen, required birth defects warning on the product label. Federal health guideline in drinking water -- 1 ppb. European Drinking Water Standard -- 0.1 ppb.


  • Found in 38 percent of tap water samples.
  • Highest level found -- 1.30 ppb, above the federal health advisory.
  • Average concentration --0.18 ppb.


Tests for Multiple Weed Killers


  • Four pesticides -- atrazine, cyanazine, metolachlor, and acetochlor -- were found in a single sample of Des Moines tap water collected on June 3, 1995.
  • These four pesticides include one pesticide classified by EPA as a probable human carcinogen, three pesticides classified by EPA as possible human carcinogens, one pesticide that causes birth defects in animal studies, and two pesticides that disrupt the normal functioning of the hormone system.
  • Federal drinking water standards do not account for this simultaneous exposure to multiple pesticides (or other contaminants) in drinking water, and allow cancer risks from these weed killers up to 29 times higher than the federal government allows from the same chemicals in food.


Use of 6 Major Herbicides on Iowa Corn Reached 32.1 Million Pounds in 1994, up 4.85 Million Pounds Since 1990


Herbicide Acres Treated, 1994 Use, 1994 (lbs.)
Acetochlor 1,170,000 2,164,000
Alachlor 1,690,000 4,115,000
Atrazine 8,580,000 7,471,000
Cyanazine 3,380,000 7,768,000
Metolachlor 4,940,000 10,664,000
Simazine 0 0


(Note 4: USDA 1995. Agricultural Chemical Usage: 1994 Field Crops Summary.)