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!