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Weed War  What price freedom from dandelions? The EPA is
rethinking a long-used herbicide's cancer risk to humans.   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