DENVER--More than 2 decades ago, the United States began phasing out lead additives in gasoline and paint. But new research suggests that many children living in large cities are still at risk from lead lingering in soil. A study finds that contaminated soil in Indianapolis correlates with high blood levels of lead in kids, and other cities are likely to have similar problems.
In the 1970s lead poisoning was identified as a serious threat to children, causing behavioral disorders, permanent drops in IQ, paralysis, and even death. Children are the most vulnerable because before the age of six, they will absorb about 80% of any lead they ingest, whereas adults only absorb around 15%. These revelations spurred legislation to reduce lead exposure, but an important source of lead may have been overlooked, says geochemist Gabriel Filippelli of Indiana University-Purdue University in Indianapolis (IUPUI).
Filippelli and graduate student Mark Laidlaw tested some 100 surface soil samples from around Indianapolis and found that high levels of lead were pervasive. The lead in the soil is left over from automobile emissions before gasoline was unleaded, says Filippelli. Not surprisingly, levels are highest near heavily traveled roadways, but water and wind have slowly spread it further. He then compared the soil levels with public health records of blood lead levels in kids. "There's a halo of high lead levels around the city, and it's linked particularly well to children's blood lead levels," he says. Filippelli reported the results of his study here this week at the meeting of the Geological Society of America.
The risks of lead in soil have been overlooked, says Filippelli. Kids come into contact with lead in playgrounds and even their own backyards, and then track it into their homes, he says. This could explain why high blood lead levels have been found in children who live in brick houses, which tend to have little paint, and don't play near roads.
"We thought we had solved the problem when we took lead out of gasoline," says environmental toxicologist Howard Mielke of Xavier University in New Orleans, who has found similar lead levels in other cities. "The good news is the problem is very solvable," he says. The new study found that 95% of the lead was in the top 13 centimeters of soil, so removing the top soil layer in areas where children play would go a long way toward reducing exposure.
--BETSY MASON
Related sites
IUPUI Biogeochemistry lab
Info on lead poisoning, from the National Library of Medicine
