December 2, 2003
Edible Urban Plants Found to Contain Lead
EVANSTON, Ill. --- Chicago has one of the highest rates of lead
poisoning in the United States, an extremely persistent health
problem that particularly plagues urban areas. Now a new study
by Northwestern University researchers shows that edible plants
grown in urban gardens could contain potentially hazardous amounts
of lead.
Kimberly A. Gray, associate professor of civil and environmental
engineering at Northwestern University, and her team tested a variety
of plants cultivated in Chicago residential gardens rich with lead-contaminated
soil. They found that leafy vegetables and herbs were highly likely
to also be contaminated with lead.
The findings were published online by The Science of the Total
Environment and will appear in an upcoming print issue of the journal.
The researchers harvested fruiting plants, leafy greens, herbs
and root vegetables from 17 gardens, washed and dried the plants,
and then separated root, shoot and fruit before analyzing them
for lead content.
While the
majority of the lead was concentrated in the roots, some lead
was detected in shoots, which is often the portion of
the plant that people eat. Gray’s team calculated what amount
of lead would be ingested by consuming some of the herbs such as
cilantro. They found that those levels exceeded what would be excreted
in children or women, which means lead would be stored in the body.
These findings are very important for children and women of childbearing
age.
“We are concerned about the edible portions of leafy vegetables
and herbs that were found to contain lead,” said Gray. “It
is important that urban gardeners locate fruit and vegetable gardens
away from buildings, test the lead levels in their soils and develop
strategies to ensure safety for them and their children.”
The lead concentration in the fruit of other plants, such as
strawberries and tomatoes, was not found to be hazardous. Root
vegetables, such as carrots and onions, are likely to have high
levels of lead, but the very small sample size did not allow the
researchers to draw a conclusion about this group.
Much of the
soil’s lead contamination comes from deteriorated
paint, past use of lead-containing gasoline and industrial air
pollution. Lead in soil does not biodegrade or decay.
The study
grew out of an earlier federally funded, two-year phytoremediation
project in Chicago’s West Town community in which Gray and
colleagues wanted to see if green plants could remove lead from
contaminated soil or, at a minimum, stabilize the lead in the soil
to reduce exposure of humans and animals to the toxin.
Other authors
on the paper are Mary E. Finster, a Northwestern University graduate
student working with Gray, and Helen Binns,
M.D., an associate professor of pediatrics at Northwestern’s
Feinberg School of Medicine.
The research was supported by a grant from the U.S. Department
of Housing and Urban Development. |