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From the Townsend Letter for Doctors & Patients
July 2003
Environmental Issues
by Rose Marie Williams, MA
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Atrazine's Assault on Health and the Environment
Atrazine, introduced in 1958, is the most widely used pesticide in the United States. Between 70 and 90 million pounds of the active ingredient are used annually to combat weeds in agriculture, commercial, and domestic areas. It is used on lawns, playing fields, roadsides and golf courses. Atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) is a chlorinated triazine herbicide used to control certain weeds in crops, particularly corn – sorghum – sugarcane – pineapple - macadamia nuts and citrus. Atrazine is the active ingredient in many herbicide products including Aatrex, Atrataol, Gesaprim and Zeophos, while it is a component of other herbicides including Alazine, Bicep, Bullet, Extrazine, Prozin, Rastra, Stuazine, and Tomahawk.1,2

The largest producer of atrazine has been the Ciba-Geigy Corporation that became Novartis, and is now Syngenta, the world's largest agribusiness company with 6.3 billion dollars in sales of agrichemicals. Atrazine is also manufactured by E.I. duPont de Nemours & Co., Drexel Co., Oxon Italia, and Prodotti Chimici. Around 1970, only 12 years after being introduced, farmers were beginning to notice weed resistance to atrazine. By 1983 more than two-dozen weed species showed resistance to atrazine, and to other herbicides as well.1-3

In spite of its wide use in this country, atrazine has been banned in most western European countries, with France announcing a ban in 2001 due to atrazine's presence in water and risks to human health.4

Environmental Impact
A major environmental concern is atrazine's mobility in soil and ground water. It has been found in the groundwater of 24 states, some of which do not even use the pesticide. The highest concentrations of atrazine were found in the corn-belt states of Illinois, Indiana, Iowa, Nebraska, and Kansas. It has been detected in 30 out of 33 samples of treated drinking water, indicating that it is not eliminated by ordinary treatment technology. More expensive activated charcoal filtration and ozonation are necessary for removing atrazine and its metabolites from drinking water.1

Another concern of atrazine's presence in water is the possible production of N-nitrosoatrazine (NNAT), a class of potent carcinogens. There is an increased incidence of non-Hodgkin's lymphoma in Nebraska counties with nitrate-contaminated wells, raising the question of a link. A study of rural ponds in Ontario, Canada, found atrazine to be the most common contaminant from drift and run-off. A study of 18 lakes in Switzerland found atrazine present in all 18, besides being detected in rainwater.1

Atrazine molecules attach to dust particles and travel in clouds, fog and snow. Atrazine has been detected in drinking water sources in France, Italy, the Netherlands, Germany, the United Kingdom, Spain and Greece.1,2

Due to additional findings linking atrazine to increased health risks, the US Environmental Protection Agency (EPA) attempted to reduce the amount of atrazine in the water by requiring more detailed label instructions limiting the sale and use of atrazine to certified applicators only, and requiring a 66' buffer zone between area of use and any surface water. The problem is much more extensive and the herbicide more pervasive than previously recognized.5

Atrazine persists in soil from one growing season to the next. It degrades into at least eleven metabolite products, some of which are as toxic as the original, according to manufacturer, Ciba-Geigy.1

Atrazine's presence in water has been studied since 1981. In 1988 the EPA finally called attention to the problem and began to investigate possible adverse health effects of atrazine, and to reduce its presence in water.

Health Risks
The National Institute for Occupational Safety and Health acknowledges atrazine's toxicity as a severe eye, and mild skin irritant. Chronic toxicity includes diminished weight gain, increased irritability, and probable anemia in rats. Studies with dogs demonstrated increased mortality; decreased food consumption; increased liver, ovary, and heart weights (in females). Both sexes showed electrocardiographic changes in the heart accompanied by detectable pathology.1

Atrazine's ability to disrupt endocrine function in lab animals is well-known. Pregnant and nursing rats exposed to atrazine and one of its metabolites resulted in slow maturation of the offspring's sexual organs. Offspring of both sexes showed modified pituitary activity with strong inhibition of certain hormone receptors and a reduction in weight. A survey of 856 Iowa municipal water supplies (1986-1987) found levels of the herbicides - atrazine, metolachlor, and cyanazine were each significant predictors of intrauterine growth retardation.1,3,6

Using technical atrazine (only the active ingredient, not formulated products) research with lab subjects found dose-related breast tumors in females, testicular tumors in males, increased incidence of cancers of the lymph system (leukemia, lymphoma), increase in benign mammary tumors in males, and an increase in cancer of the uterus of females.1

Women exposed to atrazine develop ovarian tumors 2.7 times more than non-exposed women. Residents of eastern Nebraska exposed to atrazine showed an elevated risk of non-Hodgkin's lymphoma. For over a decade the EPA has classified atrazine as a possible human carcinogen (Class C) based on information of increased incidence of mammary tumors in female rats.1

Prostate Cancer
Environmental illness expert, author, and respected champion of disease prevention, Dr. Sherry Rogers warns that, "Atrazine, a common weed killer… has caused enlargement of the prostate (hypertrophy)…, (and) has lowered testosterone levels and caused depression by interfering with serotonin synthesis." She admonishes that the epidemic use of pesticides has contributed to the increase in prostate cancer over the last 20 years.7

The finger of suspicion now points to an atrazine manufacturing plant in Louisiana where workers are suing their employer because the incidence of prostate cancer appears to be nine times that of the general public. The Natural Resource Defense Council (NRDC) is claiming Syngenta illegally suppressed its own study on atrazine and prostate cancer among workers by withholding information from the EPA. Documents obtained through the Freedom of Information Act indicate that Syngenta was aware of prostate cancer among workers in the mid-1990s, but failed to disclose this information to the EPA until 2001.8

In the late 1980s concerns arose about atrazine's potential to cause cancer in humans. In spite of a decade's worth of documentation of cancer cases at Syngenta's primary manufacturing plant, the EPA reversed its previous stand which designated atrazine as a (Class C) probable human carcinogen, and reclassified the chemical in June 2002 as "not a likely human carcinogen."8

Transsexual Frogs
Tyrone Hayes, a biology professor at the University of California at Berkeley, has been collecting frogs since his youth in South Carolina. His current research on frogs and atrazine has created quite a stir between environmental advocates and industry. Frogs' permeable skin makes them unusually vulnerable to environmental toxins. Scientists find it convenient to study the impact of hormone mimicking chemicals on frog development because their transformation from egg to tadpole is rapid and visible to the naked eye.2

Controversy over atrazine escalated in 1998 when Syngenta asked Hayes to study the herbicide's safety. Hayes was using concentrations at one-thirtieth the safe level set by the EPA for drinking water and it appeared that this trace amount was creating hermaphrodites. He tested frogs and water samples from Indiana, Wyoming, and Utah. His findings were first published in the Proceedings of the National Academy of Sciences (Apr 2002) and in Nature (Oct 2002).2

Hayes theorizes the effect atrazine plays in frog abnormalities begins with testosterone acting as a precursor to estrogen. In male frogs testosterone causes their voice boxes to grow and their vocal sacs to develop. Atrazine exposure in frogs switches on a gene that makes the enzyme aromatase, which turns testosterone (male hormone) into estrogen (female hormone) causing frogs to be demasculinized and feminized. Estrogen stimulates growth of ovaries, eggs, and yolk. Under normal conditions male frogs do not make aromatase and would not be turning testosterone into estrogen.2

Many experts are quick to point out that humans are not frogs, and that we should not leap to conclusions regarding atrazine's negative effect on sexual development. Other scientists, like Theo Colburn of the World Wildlife Fund, and author of Our Stolen Future, point out that all species have similar signaling systems and similar chemical reaction. For this reason testing medical drugs on animals has become a standard procedure.2

Frogs spend more time in pesticide-laden waters than do humans, however, the human fetus spends nine months in a watery habitat. Several studies of farm families show that babies conceived in spring when pesticide runoff is highest have much higher rates of birth defects than babies conceived at other times.2

When presented with Hayes' findings in August 2001, Syngenta was not too pleased, and refused to acknowledge his work. No longer under contract with Syngenta, Hayes continued research on his own. Syngenta then turned to Texas Tech to repeat the frog experiments, in which almost no hermaphrodites appeared. Lab conditions were not identical at Texas Tech. According to Hayes, the water temperature was too cool, frog density too high, atrazine levels not properly controlled, and diet was insufficient, thereby inhibiting gonadal development making it difficult to recognize deformities.2

A point of major interest is that the Texas lab used glass tanks while Hayes used plastic tanks.2 Chemicals in plastics are increasingly recognized as estrogen mimics and endocrine disruptors in wildlife and in humans.

Whatever synergistic impact plastic chemicals might have on the negative effect atrazine confers to frog development should not go unheeded. Human exposure to plastic is ubiquitous, and for individuals in high risk areas of exposure to atrazine the synergy may act as a double whammy, similar to tobacco and asbestos exposure.

Plastic Chemicals are Endocrine Disruptors
The plastic versus glass containers jumps out as a possible major confounding issue that should be addressed in future studies. Plastics are increasingly recognized as endocrine disruptors. Some are estrogen mimics, while others interfere with androgen (male sex hormones). Phthalates have been found to cause birth defects and altered sexual development in lab animals by interfering with normal hormone function. Tests on humans find phthalates present at levels far higher than expected by the Centers for Disease Control and Prevention (CDC).9

It is virtually impossible to avoid plastics in the modern world. Plastics are everywhere – in disposable diapers and chewy toys, in Styrofoam cups and food packaging, in water/soda/juice/baby bottles, even medical equipment, and more.10,11

US Environmental Protection Agency
The EPA has finally acknowledged atrazine's increasing environmental contamination and has announced what it considers "aggressive" measures to protect drinking water. Environmental advocates criticize EPA's action as too little too late. EPA's program will focus on 37 community water systems with high levels of atrazine. Atrazine use will continue as usual, while Syngenta, the manufacturer, collects "frequent monitoring data." If contamination levels for atrazine or its metabolites exceed 37.5 parts per billion (p/p/b) in eight of these water systems, further use of atrazine in those watersheds will be prohibited.12 Once again, we have the fox guarding the henhouse, the same fox accused of withholding prostate cancer information from the EPA and from its own employees.

Furthermore, the EPA and Syngenta are working on an ecological monitoring agreement. By October 2003 EPA plans to address the impacts of atrazine on amphibian development. Professor Hayes' meticulous research has shown as little as 1 ppb of atrazine interferes with frog sexual development.12 Will Hayes' work be disregarded by more favorable, though questionable, outcomes from Texas Tech?

Caroline Cox, editor of the Journal of Pesticide Reform, Eugene, Oregon, believes the EPA could better protect environmental and public health by aggressively cleaning up current contamination of rivers and streams by "showing farmers successful techniques for growing corn without using atrazine."12

Updated information about atrazine is available from:
Jennifer Sass, PhD
Senior scientist with the Natural Resource Defense Council (NRDC)
1200 New York Ave., NW, Suite 400
Washington, DC 20005 USA
Fax: 202-289-1060

Citizens concerned about atrazine can submit comments to the EPA addressed to:
Public Information & Records Integrity Branch
Information Resources & Services Division (7502C)
Office of Pesticide Programs
Environmental Protection Agency
1200 Pennsylvania Ave., NW
Washington, DC 20460-0011 USA
or email to
Attention should be made to: Docket # OPP-2003-0072, Atrazine IRED, 68 Fed. Reg. 9652 (Feb. 28, 2003).

Rose Marie Williams, MA
156 Sparkling Ridge Road
New Paltz, NY 12561
Fax 845-255-5101

1. Uhler, B., "Atrazine," Jrnl. Pesticide Reform, Vol.11, No.4, Winter 1991.
2. Royte, E., "Transsexual Frogs," Discover, Feb 2003.
3. Snedecker, S, "The Ribbon," Vol.7, No.2, Cornell U., Spring 2002.
4. "France Bans Triazine Herbicides,"
5. After Silent Spring, NRDC, (212-727-2700), NY
6. Munger, R., et al, "Intrauterine Growth Retardation in Iowa Communities with Herbicide-contaminated Drinking Water," Dept. of Preventative Medicine & Env. Health, Univ. of Iowa, 12/02/97.
7. Rogers, S., MD, Total Health In Today's World, (800-846-6687) Oct 1998.
8. NRDC, (5/2004: link expired.) (
9. Montague, P., "Here We Go Again," Rachel's Env. & Health BiWkly, #708, (410-263-1584), Sept 14, 2000.
10. Williams, R.M., "Plastics: The 6th Major Food Group – Part 1, TLfDP, #210, Jan 2001.
11. Williams, R.M., "Plastics: The 6th Major Food Group – Part 2, TLfDP, #211/212, Feb/Mar 2001.
12. Cox, C., "EPA Announces 'Aggressive' Atrazine Program," Jrnl. of Pesticide Reform, Vol. 23, No. 1, Spring 2003.

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