- Q.I'm doing a whole-house
remodel on an old home. It's the height of the
gardening season, and the owners - knowing that many
layers of lead-based paint had been scraped off the
house over the years - asked me what I thought about
planting tomatoes in the soil next to the south wall.
Is there a danger that soil lead could be taken up into
vegetables in dangerous quantities?
A.Carl Rosen, a soil
scientist at the University of Minnesota,
responds: In general, plants do not take up
large quantities of lead even when grown in soil
with elevated lead levels; however, lead levels in
plants will increase as the soil lead level
increases. The amount of lead taken up depends on
the type of plant being grown. Lead accumulates
more in leafy vegetables like lettuce and in root
crops like carrots than in the fruiting part of
plants like tomatoes, squash, and strawberries.
The only way to know if soil is safe for
gardening is to have it tested; the homeowners can
contact their local extension service for the name
of a reputable lab. Some states use 500 ppm (parts
per million) as the cutoff for vegetable gardens;
in Minnesota we use 300 ppm.
If the soil does contain high lead levels, there
are ways to reduce the risk so that the space can
be used for gardening. For example, the homeowners
can amend the soil with lime and organic matter to
immobilize the lead, or simply make raised beds
with clean soil. If they decide not to garden
there, covering the soil with sod will protect
children who might be playing in the area. There's
a much higher risk of lead exposure through direct
ingestion of contaminated soil than there is
through eating plants grown in the soil.