In a large part of Portland, it is unsafe to grow vegetables in the soil. The same is true in other Maine communities where buildings are old and close together.

Soil in those communities contains enough lead to poison people, with children under age 7 and pregnant women facing the highest risk. Lead can cause miscarriages, lower intelligence, behavior problems, reproductive issues and more.

The Cumberland County Soil & Water Conservation District is in the second year of a two-year program financed by the U.S. Environmental Protection Agency that deals with lead in Portland soils. A survey the district took of the Portland peninsula last year found that Bayside, West Bayside, Parkside and the West End have the highest concentrations of lead in the soil, said Damon Yakovleff, a district environmental planner. The district’s website gives more details, noting that any soil with more that 400 parts per million (ppm) of lead is considered high risk; those neighborhoods averaged 1,086 ppm. Keep in mind, though, that the data does not mean every property was that bad. The lead is unevenly distributed: Some properties that were tested had as few as 10 ppm, while others tested at 25,000 ppm.

The EPA program offers free soil tests to anyone who lives in those neighborhoods and wants to determine the lead content of their soil. If you live elsewhere, you can buy a soil test from the University of Maine testing laboratory for $18, which will tell you how much lead is in your soil, as well as give you information on its fertility. You can order a test kit online (go to umaine.edu and search for “soil test kit“) or by calling a county extension office. The soil you collect is sent to Orono for testing.

The lead that is contaminating soils mostly comes from old homes. Before 1978, much of the paint used to paint homes contained lead. But the Portland peninsula has more lead than many other places because when most of the town was destroyed by fire in 1866, the fire ash, which included lead, was not removed. Other sources of lead include factory pollution, lead pipes and leaded gasoline; the last was phased out after 1975 and banned for cars in 1996.

Although the EPA lead program is directed at Portland, lead is a problem in other Maine communities, as well, largely because the state has the oldest housing stock in the nation. “Absolutely any older urban center, like Gorham Village for example, could have lead levels in the top danger zones,” Yakovleff said.

Even if your soil has a high level of lead, you can still garden. Obviously, you can grow anything you do not plan to eat – flowers and other ornamentals. But you should still take precautions: Take your shoes off before going indoors and wash your hands and clothing regularly and thoroughly.

If there are moderate amounts of lead, 100 to 400 parts per million, it’s possible to grow some food plants directly in the soil. Start by tilling in a lot of clean compost, which serves to dilute the lead. Then, before you eat them, wash all vegetables grown in such soil thoroughly, perhaps even removing the outer leaves on leafy plants. Avoid root vegetables, such as beets, carrots, potatoes and onions, the district website advises, as well as leafy vegetables like kale, lettuce, spinach and cabbage. Fruiting vegetables like tomatoes, peppers, eggplant, squash, cucumbers berries and apples are the safest.

If the lead is above 400 ppm, planting fruits and vegetables safely requires a raised bed – at least 12 inches and maybe as much as 24 inches deep, filled with soil and compost you’ll bring in from outside your own garden. In addition, before adding the soil to the raised beds, put in a barrier of landscape fabric, wire mesh or cardboard, to keep the existing soil out.The district’s website has instructions for building raised beds.

Yakovleff stressed that lead is a bigger problem for children than adults. Children should be prevented from digging and playing in highly contaminated soil – although covering the soil with mulch is helpful.

Over the years, I have regularly suggested that gardeners get soil tests. Lead contamination is yet another reason to do so.

Tom Atwell is a freelance writer gardening in Cape Elizabeth. He can be contacted at: [email protected]


Only subscribers are eligible to post comments. Please subscribe or to participate in the conversation. Here’s why.

Use the form below to reset your password. When you've submitted your account email, we will send an email with a reset code.