http://www.nytimes.com/2009/08/13/garden/13lead.html?_r=1&nl=pol&emc=pola1WHEN the Obamas decided to turn some of the South Lawn at the White House into a kitchen garden, they did what many smart urban gardeners do: they had the soil tested for its nutrients and potential contaminants, like lead. The results prompted a number of headlines suggesting that the level of lead in the garden, 93 parts per million, was dangerous.
It wasn’t. The level is well below the 400 p.p.m. considered hazardous by the Environmental Protection Agency, though not below the more stringent goals recommended by some countries like the Netherlands, at 40 p.p.m.
Work done to improve the fertility of the soil before planting helped reduce the lead level, and test results just released by the White House indicate that the levels are now so low (14 parts per million) that they are similar to those found in places where there are no automobiles.
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While acknowledging that 93 p.p.m. was not a hazard, Mother Jones magazine’s Web site attributed the long-term use of sludge as a fertilizer on the White House lawn for the presence, not just of lead, but of many other undesirable substances like antibiotics and sleeping pills. Sludge comprises the solids in sewage that separate out during treatment. According to the magazine, sludge was used for at least a decade on the White House lawn, possibly until the late 1990s.
But Irvin Williams, who retired as head groundskeeper at the White House last year, after 59 years on the job, said sludge was used only once there, in 1985.
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Sam Kass, White House food initiative coordinator and an assistant chef, who now combines his duties of cooking for the first family with garden expertise, explained what the White House had done before planting to make sure the soil was safe for vegetables.
First it was tested and then amendments were added accordingly: lime, green sand and crab meal as well as organic matter in the form of compost made by the National Park Service. The pH was adjusted to between 6.5 and 7. When the pH is in that range, lead is unavailable to the plants.
Gardening experts say that good sources of organic matter also include composted leaves, nonacid peat, and well-rotted manure. If soils have high levels of lead, one-third by volume of organic matter should be added to reduce lead availability .
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l testing is available from the nearest Cooperative Extension office. The Environmental Protection Agency’s lead hot line, (800) 424-5323, can refer callers to health departments, which will either do soil testing or provide names of local certified labs.
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