On the site of a former hat factory in Danbury, Conn., a stand of genetically altered cottonwood trees suck mercury from the contaminated soil.
Across the continent in California, researchers use transgenic Indian mustard plants to soak up dangerously high selenium deposits caused by irrigation of the nation's bread basket.
Still others are engineering trees to retain more carbon and thus combat global warming.
The gene jockeys conducting these exotic experiments envision a future in which plants can be used as an inexpensive, safer, and more effective way of disposing of pollution.
''Trees are really made for this . . . we just have to trick them to do what we want them to do," said Richard Meagher, whose University of Georgia students went to Danbury in 2003 as part of the most advanced, open-air experiment in the United States involving trees genetically engineered to eat pollution.
Biologists for decades have been trying to exploit the genetic mechanisms that let microscopic bugs survive in polluted places where most living things die.
Indeed, a landmark 1980 US Supreme Court case that allowed the so-called patenting of life that launched the biotechnology industry centered on bacteria genetically engineered to clean oil spills.
But simply dumping engineered bugs on polluted sites has its dangers and drawbacks. Elements like mercury can't be broken down into harmless bits, so researchers have turned to engineering plants to draw pollutants out of the ground.
Meagher uses genes from E. coli that enable the common bacterium to live amid mercury. He's spliced them into a variety of plants in the laboratory, where he says his results are dramatically positive.
But proving genetic engineered plants work outside the lab is the real challenge -- and Danbury, which at the turn of the last century reigned as the hat-making capital of the world, was a natural destination for his team.
Animal pelts in the town's many factories were softened in mercury baths, and the resulting waste was dumped outside. Only later did residents understand how mercury attacks the central nervous system. By then, many longtime factory workers had suffered from the ''Danbury shakes."
Meagher's team planted about 45 engineered cottonwood trees in a polluted lot. The trees are expected to treat the mercury as a nutrient and draw the toxic element from the soil with their roots.
Some of the mercury is expected to vaporize into the air while most is stored in the tree.
After several years of growth, the trees will be cut down and incinerated.
Meagher expects to see results from the Danbury experiment this year. He figures hundreds of trees per acre would need to be planted to be effective. But if his removal method works, the cost of cleaning an acre of mercury-laced soil will plummet from about $2 million to $200,000, Meagher estimates.
Meagher agrees with critics who argue that his solution isn't ideal -- but he says the trees beat the current clean-up method of digging out contaminated sites and dumping the tainted soil in toxic dumps.
Meagher said he's also hoping to someday deploy engineered trees in northern India and Bangladesh, where arsenic poisoning is rampant. Drinking water throughout the region has been contaminated by soils polluted naturally and by spills and drainage from factories.
Still, some potential allies are wary.
The Sierra Club and others fret that grime-busting plants and their unnatural, industrial-strength cleaning genes will contaminate naturally growing relatives.
Promises that researchers are engineering sterility into trees don't calm their concerns.
''I'm a pediatrician, and I can tell you birth control doesn't work 100 percent of the time," said Dr. Jim Diamond, the Sierra Club's biotechnology expert. ''I don't see it working in trees either."
The criticism sows seeds of public uncertainty and makes it difficult for researchers to fund and apply their work. Meagher is operating on about $1 million in grants, mostly from the Department of Energy, which is saddled with polluted weapons sites.
Meagher also says he's hindered by political and commercial apathy. A company he helped launch to bring his technology to market is struggling for financing.
''It's not as sexy as trying to cure cancer or give you an erection," Meagher said.
Nonetheless, scientists are increasingly joining this once obscure branch of biotechnology.
Researchers at Purdue University, for instance, are engineering trees so that they will retain more carbon, in an effort to help combat global warming.
And Applied PhytoGenetics Inc., the biotechnology company that Meagher helped to launch, has planted its modified trees at a polluted site in Alabama.