Energy & Industry Would you like some DDT with that organic cucumber?

Consumers might assume that buying organic means the produce they purchase lacks chemical residues and the farmers and farm workers growing organic crops aren't exposed to toxic chemicals. This may not always be the case. Organic farmers across the nation must contend with the possibility that the land they farm has some of the very chemicals their farming methods are designed to avoid.

As Rebecca Clarren's recent cover story, Farming's Toxic Legacy, revealed, many former agricultural lands remain polluted with remnants of now-banned pesticides. Some, like the chlorinated hydrocarbons dieldrin, aldrin, and DDT, have dangerous breakdown products that remain in the soil for a hundred years or more. Others, such as the insect-killer lead arsenate, break down into the elements lead and arsenic, which never go away unless soil is removed.

In Oregon, the only state where extensive testing on organic farmland was ever conducted the certification body Organic Tilth found remnants of those chlorine-based pesticides on much of the farmland that organic producers now use. These tests took place in the early years of the organic movement during the 1970s and 1980s when earnest farmers were trying to figure out what sort of land they were growing on; ever since the United States Department of Agriculture codified organic certification in 2002, soil tests for chemical residues have been voluntary.

"If they [chlorinated hydrocarbon pesticides] were ever put on, for any reason, they're probably still there," says Harry MacCormack, a farmer who headed up much of the group's soil testing on farms around the Willamette Valley. In an ironic twist, high quality soils, known as "Class 1," are more likely to have pesticide remnants, because they were probably used early on for ag production.

Vegetables in the squash family, like cucumbers, zucchini, winter squash (frequently used to make organic baby food) and melons all bioaccumulate chlorinated hydrocarbons in their tissue; if it's in the soil, it's likely it's in the cucumbers grown in that soil. Root crops like potatoes and carrots also tend to soak up these pesticide remnants, says MacCormack.

Vegetables in the cucumber (cucurbit) family, like squash and melons, all tend to uptake remnants of certain pesticides. Photo courtesy Flickr user Larry Hoffman.

The laws governing the transition to certified organic under the USDA require producers to wait three years before growing certified crops on land that was once conventionally farmed. While it is true that organophosphates, another class of popular pesticide that includes malathion and parathion, usually break down in three to five years, other chemicals are far more persistent. The only way to really tell if chemicals have left the soil, and if the soil has built up sufficient quantities of nutrients, microbes, and organic matter, is to conduct soil tests.

When growers do find their soil has contaminants, there's no real way to clean it. Growers can remove contaminated soil and bring in new soil, a pricey undertaking. In Oregon, growers did an experiment trying to use squash crops to capture the DDT and other chlorinated hydrocarbons left in the soil. They purposely grew squash in contaminated soil, harvested and disposed of the vegetables that had bioaccumulated toxins, and then tested the soil to see if there was less contamination. This strategy ultimately did not work, says MacCormack.

If land does play host to long-lasting chemicals, consumers may not even know. Organic crops are rarely tested for residues [PDF, p.7], a failing the program has been criticized for, although USDA deputy secretary Kathleen Merrigan says program officials are trying to implement more frequent testing.

Organic baby food companies like Gerber have responded to consumer concerns by requiring their organic growers go beyond USDA requirements and conduct soil tests for toxic pesticide leftovers, so that they are not selling organic baby food laced with DDT.

Like many political processes, the creation of organic standards was a messy mix of science and compromise. Farmers today still complain that three years is too long a time to be in transition, as they suffer yield losses from not using synthetic chemicals without the price premiums from being certified organic. But without soil testing these farmers, the crops they grow, and the consumers they serve all may be exposed to the remainders of agriculture's toxic legacy.

Stephanie Paige Ogburn is HCN's online editor.

Note: Harry MacCormack, a pioneering organic farmer who was one of the founders of Oregon Tilth, has compiled his research and knowledge on transitioning to organic farming in a book titled The Transition Document.