Since I raised the possibility two weeks ago that sewage sludge fertilizer could have contaminated the Obamas' White House vegetable garden with lead, there has been a flurry of press on the subject. Various food and gardening blogs and dueling Huffington Posters weighed in, followed by the AP, Reuters, and the New York Times after a White House spokeswoman publicly addressed the lead issue on Thursday. Much of the coverage has sought to quell misperceptions that produce from the White House garden is unsafe to eat. Indeed, as I pointed out in my original post, the levels of lead in the garden are still well below those that the EPA says can cause health impacts. But in obsessing over whether the Obamas are poisoning themselves and their guests--and there's no proof that they are--most of the media missed the more interesting question: Is it really a good idea to grow vegetables on land that has been fertilized with sewage sludge?
The EPA thinks so, and has promoted the practice for decades as an alternative to landfilling sludge or dumping it in the ocean. In what was probably the single most effective component of a vast marketing campaign for sludge fertilizer, the National Park Service tilled it into the White House's South Lawn through much of the 1990s. Interest in the President's preferred brand of sludge spiked to the point that its makers had a hard time meeting the demand. Today, more than half the poop flushed in America ends up as fertilizer.
The safety of sludge might not be such a concern when it's spread your lawn and covered in a layer of grass, but chew on this: Food companies such as H.J. Heinz and Del Monte won't accept produce grown on sludge-treated land. The Netherlands and Switzerland effectively ban the use of sludge on farmland, and the practice is expressly prohibited by the USDA's organics standards. If sludge has been spread on the South Lawn anytime since about 2006, the Obamas' pesticide-free garden could not be certified as organic.
The human poop in sludge isn't necessarily the problem. Sludge can contain traces of anything that gets poured down the drain, from Prozac flushed down toilets to lead hosed off factory floors. The EPA sets concentration limits for several heavy metals found in sludge, including lead, but the limits are higher than what is deemed safe in some European countries. For example, the EPA permits sludge to contain up to 300 parts per million of lead, but the Netherlands raises concerns about soil with more than 40 ppm of lead.