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Dirt Alert: Test for Lead, Vegetable Gardeners

March 17, 2009 - PORTLAND -- It won't be long now before we're turning soil, planting seeds and watching the lettuce and peas sprout.

And this spring, financial worries and doubts about food safety will likely turn even more backyards into vegetable gardens.

It's hard to see a downside to that trend, unless you've taken a close look at the dirt in places such as downtown Portland. For Samantha Langley-Turnbaugh, a soil scientist and professor at the University of Southern Maine, there's a real public-health risk to the spring ritual: lead poisoning.

Soil can be so contaminated with lead that digging or playing in it, or eating vegetables grown in it, can be dangerous. Contaminated soil is a known problem throughout downtown Portland because of a long and dirty industrial history, but it can also be a risk in places where industrial contamination is the last thing a gardener expects to uncover, Langley-Turnbaugh said.

"As we kind of deal with the problem of lead in houses, that's becoming less of a concern," she said. "Now we're realizing here's this other (source) we really haven't thought about yet."

Would-be gardeners can easily test their soil to make sure it's safe, she said. The standard $15 soil test through any Cooperative Extension office (www.umext.maine.edu) includes lead screening.

And there are ways, such as raised beds, to safely grow vegetables in a backyard even if it has some lead in the soil. Langley-Turnbaugh has even found a way to use gardens to remove contamination. It turns out that spinach plants can take up so much lead that, as long as no one eats them, they gradually clean the soil and reduce the risk.

The trouble is that many gardeners don't know there could be a problem, or underestimate the risk, she said.

"I think I'm going to go back and do a round of more concentrated (soil) tests," Lisa Fernandes of Cape Elizabeth said after hearing Langley-Turnbaugh talk about the danger this week.

Langley-Turnbaugh spoke to members of Portland Maine Permaculture, a group that focuses on sustainable living. Even experienced gardeners in the group were surprised about how much lead is out there and how hard it is to predict where, Fernandes said.

"We really think people should be able to grow food in their yards." But, Fernandes said, more people need to know that testing the soil first is essential.

The risk is clearly highest in urban areas such as downtown Portland.

Langley-Turnbaugh and Travis Wagner, a fellow professor at USM, have studied soils on the peninsula and found that the lead problem is both widespread and deep.

The toxin was left behind by a paint maker and other long-gone manufacturers, lead paint coming off old houses, lead gasoline and car exhaust, and piles of industrial waste that were sometimes used as fill in neighborhoods such as Bayside. Because the lead spread through the air and because so much of Portland's dirt has been mixed up and moved around, it pretty much could be anywhere. "You don't see any nice patterns," Wagner said.

In less urban settings, lead can be found along roads, around the foundations of older homes or even in former apple orchards, which once used insecticides that contained lead. And, while the old sources of lead have been eliminated, it is still moving around in wind-blown dust, Langley-Turnbaugh said.

So order the seeds, plan out the garden and imagine plump red tomatoes.

But also consider the advice of a scientist who has seen the dark side of our dirt.

Keep the garden at least a few feet away from the old house. And, she said, "Definitely, have your soil tested."

JOHN RICHARDSON, Portland Press Herald, March 14, 2009


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