Farming's Toxic Legacy

This story is accompanied by two sidebars: Backyard poisons and How to play safely in the soil.

YAKIMA, WASHINGTON

Nothing about the quiet summer morning suggests a reason to worry. Two-year-old Kian plays happily in the dirt of the empty lot where his family's new house will eventually stand. Nearby, his mother, Tara Compton, points out interesting "buggies," and when he toddles down the steep hillside, she holds his hand. Dust rises from the soil as though from a phantom stampede, and dirt covers the little boy's hands and face.

"This is where I plan to grow our garden," says Compton, pointing to a wide plot of earth near a peach tree that yields delicious fruit. She's pregnant, but with her tall, strong build, it hardly shows. "It's important to me to grow a lot of our own vegetables because it's so hard to know what's in the food you buy at the store."

Compton, a 38-year-old intensive care nurse, is a conscientious mother. She buys organic produce, filters her water, and uses lotions and sunscreens that are paraben-free. Compton and her husband, Ron, who's studying to become a teacher, chose Yakima out of a host of Western cities largely because of the nearby hiking and camping opportunities. Yet despite the natural beauty and the good, clean living, their new home hides a potential threat to her children -- one that Compton is hard-pressed to control.

Some 30 years ago, this upper-middle-class neighborhood, with its two-story brick houses and generous views of Mount Adams, was all orchards and farmland. In this way, Yakima resembles many communities. Over the past 28 years, more than 5.5 million acres of former farmland in the West have been plowed under and transformed into subdivisions, schools and parks. But even though the apple trees and cotton fields are long gone, they can leave a hidden toxic legacy.

Throughout much of the 20th century, farmers in Yakima and across the country blanketed crops with now-banned pesticides, including lead arsenate and a suite of long-lasting, synthetic organic compounds laced with chlorine, such as DDT, dieldrin, toxaphene and chlordane. Today, decades after they were sprayed, these compounds and their breakdown products often persist in the soil.

That doesn't necessarily mean they're harming people; in many places, the levels are likely negligible. There are no immediate health effects associated with exposure to these chemicals in the soil. And existing research indicates that the known health risks of living on former agricultural lands are relatively low -- especially where the soil has been capped with a grassy lawn. Still, children who are exposed regularly over a long time period to contaminated dirt through direct contact -- perhaps by playing in it or gardening or eating vegetables grown in it -- may develop cancer or other health problems decades later, according to the Environmental Protection Agency.

Washington state has decided that low risk is not the same as no risk. Since 2006, it has spent close to $7 million removing soil from 20 elementary schoolyards in the central part of the state, wherever lead and arsenic, the primary components of lead arsenate, exceeded levels set by the state to protect human health. The project -- which includes some Yakima schools -- is unique in the West.

Washington state's Department of Ecology is cleaning up schoolyards in the central part of the state where it found unsafe levels of lead and arsenic. These hazardous elements are likely remnants from pesticides sprayed when the area was farmland. This map shows schools that have had their contaminated soil removed and replaced (green markers), and those that have not yet been cleaned up (brown markers.) Zoom out to see data for Wenatchee and other areas of Central Washington.

Because the dangers posed by legacy pesticides are insidious and poorly understood, agencies and advocacy groups have focused on more obvious threats. Neither the federal government nor any Western state requires testing the soil prior to development of privately owned farmland, leaving the burden on landowners like the Comptons. Meanwhile, real estate agents say it's the buyers' responsibility, not theirs, to find out about possible pesticide contamination. A survey of over 20 national environmental groups, including ones that focus on pesticides, reveals that none are working to change this dynamic.

"As a nation, we're flying blind on this issue," says John Wargo, Yale University professor of environmental risk analysis and policy. "The Environmental Protection Agency is so overwhelmed by new chemicals and managing the changing science on existing chemicals that are licensed that they're interpreting the ban (on legacy pesticides) as having solved the problem. That's shortsighted. We're not even asking questions, we're not doing the testing, and the result is people are being exposed without their knowledge and certainly without their consent."

A hundred years ago, land speculators lured people to plant orchards in the Yakima area with promises that "here fortunes grow on trees." Hand-colored postcards from that era depict row after row of verdant orchards, neat fields and two-story white-painted homes. Ads in East Coast newspapers touted Yakima as the "orchard city," where "ten acres in fruit makes a man independent for life."

But that abundance did not come naturally. It relied on pesticides like lead arsenate, which helped control insects like the codling moth, an apple-loving scourge that thrives in the West's arid climate. "Without lead arsenate, there would be no industry," says Frank Peryea, professor emeritus of soil science at Washington State University and one of the nation's foremost experts on arsenical pesticides. At the university's tree fruit research center in Wenatchee, a few hours north of Yakima, Peryea snaps a small unripe apple from a tree and slices it open with a pocketknife. These trees have not been treated with modern pesticides or pheromones, which disrupt the moths' mating cycle. Where the white flesh of the apple should be is a crater filled with the moth larvae's black excrement. "You want to eat that?" Peryea asks dryly.

Nope. Neither did consumers in the early 1900s. When researchers first introduced lead arsenate, farmers quickly became hooked on it, using handgun sprayers to coat apples, potatoes, cotton, cherries and other crops. Not only did the U.S. Department of Agriculture recommend spraying crops, but if growers didn't do so, state pest control boards in Oregon, Washington and California would spray for them -- and charge the farmers for the effort, put a lien against their land, or even remove their trees. As early as 1915, the bugs had developed some resistance; farmers responded by spraying more. In 1941, U.S. farmers sprayed more than 60 million pounds of lead arsenate.

Then, in the late 1940s, American farmers abandoned their old standby in favor of DDT, then hailed as the savior of mankind. By the early '70s, an estimated 1.35 billion pounds of DDT had been sprayed in the U.S. -- enough to fill more than 238 Olympic-size swimming pools. But public outcry against the pesticide began building after the 1962 publication of Rachel Carson's Silent Spring, which reported that DDT accumulates in living tissue in greater and greater concentrations as it moves up the food chain. Soon, other scientists linked the chemical with the near extinction of many birds. Several notable studies, presented to the nascent EPA, showed that DDT could cause cancer in humans. The EPA banned the chemical in the U.S. in 1972, and by 1990 had followed suit with lead arsenate and most other organochlorine pesticides.

Unfortunately, the very thing that made organochlorine pesticides like DDT effective for a long period of time also makes them hard to get rid of. Because chlorine binds strongly to other elements, the compounds are stable and do not break down easily. Organochlorines also bind to organic matter in soil, and to the fat cells of the organisms that consume it. When they eventually do degrade, they can break down into other toxic compounds. Lead arsenate, meanwhile, is composed of lead and arsenic, the party lingerers of the elements. Neither breaks down over time. They also bind to organic matter in the soil and don't dissolve readily in water, so rain can't easily wash them away. All of these chemicals can remain in the top 12 to 18 inches of the ground for decades -- perhaps even hundreds of years.

• Growth & Sustainability