"In urban areas -- Indianapolis, Detroit, St. Louis -- soil lead, even away from the home or the road, is 8 to 10 times higher than natural soil [not exposed to the burden of lead]," noted Gabriel Filippelli, professor of earth sciences and department chair at Indiana University-Purdue University Indianapolis.
He conducted a review of the data on urban soils as a persistent source of lead poisoning, published in a recent issue of the journal Applied Geochemistry. The work was done with lead author, Mark A.S. Laidlaw, formerly a student at the university.
The two also investigated the current "lead burden" in soils from Indianapolis and other cities. Older American cities have a very high lead burden, and it's enough to adversely affect children's health, Filippelli contended.
It's especially bad when the wind kicks up in dry temperatures and spreads the lead-laden soil around. "That is when kids' blood levels go up," the expert said.
While blood levels during these windy times have not been shown to typically rise past what's considered a healthy limit by federal guidelines, Filippelli said, many studies have shown that ill health effects can kick in below that established level.
According to Filippelli and other experts, a child's developing digestive system is especially susceptible to lead poisoning. At the atomic level, lead looks similar to calcium, he said, since the two substances are similar in size and ionic charge. That means the body's nervous system can readily take up lead instead of calcium, potentially leading to neural deficits.
Solutions? Municipalities have to try aggressively to control the lead-laden soil, Filippelli said. Spraying the dirt with water using high-powered shower systems is one way to decrease the lead content and minimize lead poisoning. But this must be done regionally, since doing one house but not the one next door won't solve the problem, he added.
Another remedy, much more costly and probably less feasible, is to put a layer of clean soil on top of the contaminated soil and then grass seed, Filippelli said.
And what can the average consumer do? "Water your yard regularly," the expert said, unless you live in an area with water rationing or restrictions. Meanwhile, Filippelli is continuing research to convince municipalities that efforts spent on getting rid of lead in soil is money well spent.
Getting the Lead Out
The finding that lead is prevalent in soils, especially in urban areas, is no news to Ruth Ann Norton, executive director of the Coalition to End Childhood Lead Poisoning, based in Baltimore.
"Urban soil is an important source of lead," she said. But she added that housing still tops the list for lead exposure due to old lead-based paints. Numerous products that used lead as a stabilizer, such as furniture, old mini-blinds, old paint and old costume jewelry, may still be in people's homes, she added.
Some tips on avoiding or removing lead:
- Repair chipping paint, especially old paint. "If you live in an older home (pre-1978), and you have chipping peeling or flaking, you want to repair that safely," she said. That means not dry scraping but wet scraping -- and probably getting professional advice if you decide to do it yourself.
- Know that a little lead can go a long way. "A lead chip the size of a nickel, if broken down, could contaminate a 3,000-square-foot house," Norton said.
- Minimize exposure, especially if you live in an older neighborhood that's likely to have lead in the soil. "Leave your shoes at the door," she said. "Have a welcome mat you can wash off."
Find out more about lead poisoning at the U.S. Environmental Protection Agency.