It's that time again--that balmy stretch of late spring when America's war on the dandelion is in full swing. The weapon of choice is the weed killer 2,4-D, most commonly mixed with fertilizer in "weed and feed" treatments. Each year Americans apply an estimated 27 million pounds of it to parks, cemeteries, home lawns and anywhere else mown grass is found.
It is thought to be the most widely used herbicide in the world. The appeal is that 2,4-D, chemical shorthand for dichlorophenoxyacetic acid, is selective: It kills broad-leaf plants such as dandelions but spares grass. It overwhelms the dandelion's hormone system, causing the weed to essentially grow itself to death. This "uncontrolled growth," says Thomas M. Cahill, an environmental chemist at Trent University in Ontario, Canada, is a kind of "cancer for plants."
The question among environmentalists and medical researchers is: Does cancer for plants also mean cancer for people?
The Environmental Protection Agency, which ruled in 1997 that 2,4-D was not classifiable as a human carcinogen, is now reviewing the chemical's registration. Specialist committees are looking at the issue, says Joanne Miller, product manager for the EPA's pesticide registration section. The EPA decision about registration is due in two years. Until then, "the bottom line is: We can't make a call," she says. "We can't rule out, and we can't say for sure."
That uncertainty is roiling the world of American lawn care, where the EPA estimates as much as 20% of world production of 2,4-D is used.
Although 2,4-D has been used for decades, increasingly worried activists at the local level are demanding warning notices when it is used, blocking its use in city parks, and in some cases even getting it banned.
The manufacturers contend that hundreds of studies have shown no danger to humans.
"As long as label instructions are followed, it certainly poses no unreasonable risk," says Don Page, executive director of the industry's task force on 2,4-D research data. "The only verified examples of 2,4-D poisoning in humans is in suicides. If you drink enough of it, you can kill yourself."
Dandelions were not always reviled. Colonists brought the first seeds to North America almost four centuries ago. Early Americans boiled the leaves, battered and fried the flowers and roasted and ground the roots for "coffee." Today, foodies toss leaves in Italian-style salads and hippies make dandelion wine, but homeowners largely regard the plant as a nuisance.
Wind-borne seeds have propagated the plant everywhere in the United States outside the desert and the Arctic, from sea level to 12,000 feet and, most conspicuously, in 30 million acres of residential lawns.
Virginia Scott Jenkins, author of "The Lawn: An American Obsession," credits the golf industry and the U.S. Department of Agriculture with investing in the technology required to sustain all that grass. Scott Co. of Marysville, Ohio, the leading lawn care firm in the country, agrees.
"People were playing golf and they said, 'Gosh, we'd like to have grass like this at home,'" says Ashton Ritchie, a Scott agronomist. "In 1928, we started selling turf builder--fertilizer for lawns--to go along with the grass seed."
The better homeowners got at growing grass, the more vain they became about it, says Stan Spalding, retired UCLA turf breeder. "People were taught by advertising to be proud when they could show their neighbors and friends a pure grass lawn. So dandelion and clover became weeds," he says.
In 1944, a weed killer developed in Britain for wheat farming was reformulated by the USDA for turf and launched on the lawn care market. In 1946, American Chemical Paint Co. released 2,4-D in a product called Weedone with the slogan, "This year have a lovelier, golf-green lawn."
By 1947, Scott had mixed 2,4-D with fertilizer into the first weed-and-feed combination. The company promised customers that they would "get as much of a kick out of putting pesky dandelions to rout as we have."
Hints of Illness Prompt Research
But by the 1980s, question marks were looming over the safety of 2,4-D. In 1986, a study published in the Journal of the American Medical Assn. suggested that Kansas crop workers who had applied 2,4-D had a heightened rate of non-Hodgkin's lymphoma, a cancer of the immune system. A later study also found higher than normal levels of the disease in lawn service applicators. In 1989, the National Academy of Sciences estimated that homeowners are likely to use 10 times more chemicals per acre on their lawns than farmers use on agricultural land.
Amid the furor sparked by the Kansas study, the EPA began its first review of 2,4-D since the chemical's introduction in the 1940s.