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Soil Safety: Detecting Lead Contamination

Supplies:

Results of a lead test on several places in your garden soil

This chart:

Lead Levels (estimated parts of lead per million in the soil)

                                                            LOW                 Less than 500

                                                            MEDIUM           500 to 999

                                                            HIGH                1,000 to 3,000

                                                            VERY HIGH      greater than 3,000

           

            If your garden's neighborhood has houses and fences built before the mid-1970s, you might have too much lead in your soil from old paint on the wood that has rubbed off.

            Lead, a heavy metal, occurs naturally in soils. But if even a little extra lead gets in the soil from old paint that is chipped off a house in the repainting process, or left literally in the dust when the house was remodeled or removed, it can definitely get into the plants that grow in that soil. And if you grow vegetables in that soil, and then eat the vegetables, the lead will get into YOU!

            Lead is a neurotoxin - poison to the brain. Children with elevated lead levels, as shown by a blood test, may be fine, or they may have irritability, stomachaches, poor appetite, diarrhea, colic and distractibility. It is believed that lead is one of the causes of learning disabilities. It can decrease your intelligence. So naturally, you will want to make sure there isn't too much lead in the soil your garden is going to be.

            Besides old paint, lead can be a problem if you live near a busy roadway, an old gas station, or if someone in the past used lead-containing insecticides.

You can ask the Environmental Protection Agency to test your soil for lead levels, or call your county Extension office. Another idea is to work with a certified private soil testing laboratory. But be advised: all of these resources get extremely busy in the spring, when everybody wants to dig their gardens. So do your best to get this step accomplished in the summer or fall, ahead of time.

            When you're planning where to locate your garden, it would be smart to pick a spot that is far away from where old painted structures might be, or might have been. Avoid roads and driveways, too, since lead used to be in gasoline. Don't locate a garden near an old garbage dump site or landfill, which may have lots of lead in old paint cans and so forth.

            If you find out you have a medium lead level, but still tolerable amounts in which to grow food crops, avoid lettuce, spinach and other leafy greens, because they are hard to wash properly. Tiny bits of dirt can easily stay on them and those tiny bits might contain lead. For the same reason, don't plant carrots, potatoes, radishes and other plants with edible parts that grow underground. They could absorb lead from the soil.

You can plant thicker veggies (tomatoes, peppers, cucumbers, etc.) and plants that bear fruit in the air, like corn and sunflowers, with little or no worries, if you have low or medium lead levels.

Always, always, discard the outer leaves of vegetables and peel root crops before eating. Do NOT compost these, but throw them away.

If you're concerned about lead, wash vegetables with vinegar and water in solution, or mild soap and water, making sure to rinse thoroughly.

A fence or hedge between your garden and the street or older buildings can protect against airborne lead. And mulch is a great top-coat to protect your soil against all sorts of contaminants.

However, if your lead test comes back and you have a high lead level, from 1,000 to 3,000 parts per million, you had better grow all crops in raised beds or containers, with fresh soil that you bring in from the outside.

And if your lead levels are higher than 1,000 parts per million, do not garden in this soil, contact your local health department, and don't let children dig in the dirt around that area.

As always, you improve your soil if you add peat moss, compost and manure to your garden. And it's a good idea to add lime to your soil for a pH level of 6.5 or greater to reduce lead contamination.

What is meant by "pH"? See the next article on www.KidsGardenClub.org!

By Susan Darst Williams • www.KidsGardenClub.org • Practices 02 © 2010

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