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Oct 172011
 

By Barbara Kessler
Green Right Now

Urban gardening is taking root across the country as cities, suburbs, schools and churches turn to the land to produce food.

But as the trend sweeps across vacant lots and abandoned brownfields, it has raised questions about the safety of using dirt that may have been contaminated by industrial pollution, specifically lead.

Lead is not often a problem, but worth testing for in community gardens.

Lead, which can be found in soil, drinking water and old paint chips, poses a threat to those who have contact with it, especially children who can suffer irreversible speech problems, cognitive delays, hyperactivity and nerve damage from significant lead exposure.

The threat to gardeners is quite small, according to a leading expert, because tests show that the majority of urban dirt does not contain threatening levels of lead, and even when it does the resulting exposure will not result in human harm.

The vast majority of urban and community gardens are quite safe and their keepers needn’t worry that their plots harbor lead residues,  says Dr.  Shawn P. McElmurry of the Civil and Environmental Engineering Department at Wayne State University.

McElmurry’s ongoing research into lead pollution shows that lead may be less of a threat in soil than previously thought, in part because it is not fully “bioavailable” to humans. People excrete much of the lead they ingest, perhaps even most of the lead they ingest, he said.

And yet, there are a few cases in which the ground does contain concerning levels of unwelcome lead contamination, McElmurry said.

Gardeners should take heed.

“My take-home message to everybody is just get your soil tested.”

That’s an easy process, he said. You simply have to find a soil testing service near you. Check the local extension service or university, many offer testing for only a nominal feed. Gardeners should take six samples from separate areas of their plot, mix the dirt together and then submit it for testing.

If you cannot find a local lab, you can mail your soil to the University of Massachusetts Amherst soil lab for testing. The basic test for common nutrients and metals is just $10.

McElmurry offers these tips to minimize the risk of ending up with a garden that contains lead.

  •  Set up your garden away from any house or building that dates to the 1970s, when lead was a component in nearly all paints. (The federal government banned lead-based paint in 1978.)
  •  Be sure your garden is not sited where people once worked on cars, whose oil and gasoline could have contaminated the surrounding soil.
  •  Amend the garden soil with fertilizer that contains phosphorus, which has been shown to render lead less bioavailable to humans.
  •  Wash hands after working in the garden
  •  Remove shoes/boots before coming into your home
  •  Keep a separate set of clothes for gardening

McElmurry acknowledges that some researchers have warned people not to eat root vegetables grown in untested soils because they’re more likely to take up any lead in the ground. But he says he is not persuaded that there’s that much lead to fear.

He notes that creating raised beds doesn’t necessarily reduce the lead contamination in any given garden, because the lead could continue to accrue in the area. But he also notes that people should shun potatoes and carrots over these concerns. The solution is to get the soil tested, and then keep eating healthful produce.

“Fresh produce is very good for you. Even if you had some small amount of contamination…,” he said. “It’s not an all or nothing proposition”

For more information see these resources:

Lead Safe Gardening – The National Institutes for Environmental Health
Lead in Your Home — A Parent’s Reference Guide by the EPA

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