Some scientists say the nation needs to pay more attention to lead in soil, because it increases the exposure for children and adds to lead buildup in their bodies.

"One of the things that bothered me for a long time is what I think might be construed as an overemphasis on lead in houses," said Dave Johnson, a chemistry professor at the State University of New York in Syracuse who has studied lead contamination in soil.

"There is no question that lead paint is a hazard. But I think we might do some of our children a disservice if we don't look any further."

Nobody knows how many children are poisoned from playing in tainted soil -- putting dirty fingers and toys in their mouths, or eating lunch without washing their hands. Some research says children can tolerate just 6 micrograms of lead per day, an amount smaller than a grain of salt. But there is no clear science yet about how much dirt a child would have to ingest at various levels of contamination before being poisoned. The reason most contaminated sites are ignored is that the U.S. Environmental Protection Agency tends to pursue cleanups only when a clear polluter can be identified and held accountable. At times, local development efforts also prompt cleanups because lenders, fearing liability, require it.

EPA officials say the reason for a limited number of cleanups is simple: money.

"If we got into cleaning all those urban lead areas, it would be phenomenal, the cost associated with it," said Mike Sanderson, Superfund division director for the EPA region overseeing Kansas, Nebraska, Iowa and Missouri.

Mielke and a research team collected 406 samples throughout Wayne, Oakland and Macomb counties. The team found that 41 samples had lead levels above 400 parts per million, the EPA's level of concern for children's play areas. An additional 132 showed more than 140 ppm, the guideline Canada sets for residential areas.

In general, most of the areas with high lead levels were in Detroit, with the amount of lead in the soil decreasing farther from the city.

For example, they found a lead level of 9 ppm on a piece of property along a residential street near 22 Mile and Hayesin Macomb Township. A piece of property along a street in northwest Detroit, near Wildemere and Midland,showed a level of 189 ppm. And a spot north of downtown Detroit, at Beaubien and Erskine, had 752 ppm -- nearly double the EPA guideline for children's play areas. This area is surrounded by elegant brick homes, vacant lots and the Brewster Homes, a public housing complex.

Lead occurs naturally in the soil, usually at levels below 50 ppm. In Michigan, a 1995 report to Gov. John Engler from the lead panel of the Michigan Environmental Science Board cited a state survey that found levels generally between 2.5 and 55 ppm.

But in the Free Press survey, many sites had much higher levels.

One sample from a Rochester Hills neighborhood of spacious brick colonials near Tienken and Brewster roads tested at 810 ppm.

Far more typical of outer suburbs, however, was a sample taken in Ken and Lori Ann Karam's subdivision near Brewster and Walton in Rochester Hills. Tests showed 4 ppm in the neighborhood of tudors and brick colonials, built in the 1980s. The results were among the lowest found.

The Karams have two children -- Christopher, 4, and Patrick, 2 months -- and were relieved by the news.

"When you have small children, you are concerned about these things," said Lori Ann Karam, 32. "One of the reasons we were not interested in an old house was because of the lead in the paint."

The news was not as good elsewhere. On a residential street south of 9 Mile off Warner in Warren, a lead soil reading came backat 398 ppm -- two points shy of the level the federal government says can be harmful for children.

Renee Kazmirowski, 35, lives in the neighborhood of tidy red brick ranches. She said she and her husband, Tom, never gave lead poisoning a thought.

"I'm a little surprised, a little worried," said Kazmirowski, who has an 11-year-old daughter, Erin, and 2-year-old son, Tommy. Kazmirowski said Tommy has never been tested for lead poisoning. But now it is something she plans to bring up with her son's pediatrician. Several samples taken in Pontiac showed some of the highest readings in Oakland County. One sample near Jefferson and Euclid revealed 495 ppm. Another sample, taken from along Saginaw Street near Lewis, had a reading of 390 ppm.

Lynette Zanoni, 33, who lives near where the sample was taken, said she wasn't surprised to hear of the high level. A foundry used to operate about a quarter-mile from her house. A dark, smelly soot used to spew out of the stacks, covering the surrounding ground, she said.

She said she suspects the foundry, which closed about a dozen years ago, polluted the neighborhood.

Many researchers, including Mielke, attribute much of the high lead levels in soil to decades of leaded gasoline use. Lead was in automobile gasoline until 1986.

In the late 1970s, the National Health and Nutrition Examination Survey found 88.2 percent of all American children between ages 1 and 5 had a blood-lead level greater than 10 micrograms per deciliter, the level considered by the government to be a safety concern. When a new version of the study was done in the early 1990s, the percentage of children in that danger range had dropped to 4.4 percent. Much of the decline was attributed to the elimination of leaded gas.

When lead was in gasoline, it literally spewed from cars in a fine particle mist. When the mist hit a building, the particles slid to the ground and collected at the foundation, Mielke said. This explains why the soil at the foundation of many brick buildings has high lead levels, he said, even if the buildings had no lead paint.

Mielke has studied traffic patterns in New Orleans and Thibodaux, a small older city near it, and discovered that intersections with 100,000 cars passing through them daily had about 10 times as much lead in the soil as intersections with about 10,000 cars passing through. Traffic volumes, he said, help explain why smaller, old cities have less lead in the soil than old, larger ones.

In Michigan, cars and trucks emitted about 182,000 metric tons of lead between 1950 and 1984, Mielke said. Lead is heavy and doesn't evaporate. So it remains long after it was deposited.

Lead also came from industrial sources. In 2000, for instance, Michigan companies released 24,345 pounds of lead and lead compounds in the air, according to the EPA's Toxic Release Inventory. That was the most recent year numbers were available.

Between 1996 and 2000, the New Haven Foundry in northern Macomb County ranked first or second on the list. The foundry in downtown New Haven released 52,872 pounds of lead in that time, the EPA reports show. It closed and filed for bankruptcy in 2001.

Bernardo Sia, senior environmental engineer with the DEQ's air quality division, said the foundry broke no laws. As an older facility, it had no lead-release limits, he said.

A report commissioned by the EPA, called "A Three-City Lead Study," found that reducing lead in soil shrank blood-lead levels in some children, but not always in a statistically significant amount.

In 1992, the federal Agency for Toxic Substances and Disease Registry, after reviewing a variety of studies, issued a report showing some scientists found anything above 100 ppm of lead in soil could be unsafe. Others found anything above 1,000 ppm might be of concern.

"There's no one number all the studies pointed to," said Lynn Goldman, a professor in environmental health sciences at Johns Hopkins Bloomberg School of Public Health in Baltimore. "If anybody tells you differently, they're saying that because that is their political point of view."

Goldman worked at the EPA during the Clinton administration and led the division that set the 400 ppm soil guideline for children. The guideline said anything above 1,200 ppm overall in a yard is of concern, but the levels should be no higher than 400 ppm in areas where children play. The guideline became effective after being published in the Federal Register two years ago, nine years after Congress passed a law asking the agency to create a guideline.

One reason for the delay was the absence of clear scientific data, said Dave Topping, an environmental scientist for the EPA's National Program Chemicals Division.

Besides the variety of recommendations by researchers, it is also difficult to calculate how much lead children are exposed to when they play, Topping said. Some children may literally eat dirt; others may not want to get dirty. Also complicating the equation is how soil lead levels fit with other lead exposures for children, he said.

For instance, a child in a city where the water system has lead pipes or lead solder may drink lead. A child in a home with lead paint or lead dust may eat lead. Lead can be in the air some children breathe, in canned food imported from other countries or in ceramics or leaded crystal.

Topping said those multiple factors have contributed to scientists being unable to agree on a single safe number for lead contamination in soil. Another issue is how lead reacts in soil. If a child eats a lead paint chip, the child ingests a highly concentrated dose of lead. Lead in soil binds itself to dirt particles, making it less dangerous when it is ingested, some scientists say.

"Lead in soil has not led to as much exposure of people as was initially suspected," said Valerie Thomas, a research scientist at Princeton University's Environmental Institute. "It gets more and more bound to soil particles, which means even if you eat it, you don't absorb it as much. Because we have so much lead in our houses, it makes sense to work on getting lead out of the houses, or tearing down the houses."

But Johnson, the professor at State University of New York, said that doesn't mean lead in the soil should be discounted. Johnson recently concluded research that found a strong connection between high lead levels in children's blood and their exposure to high lead levels in soil. His work, and that of others, also traces a rise in children's blood-lead levels during the summer and a decrease in the winter.

Some researchers tie this to the role sunlight plays on a child's metabolism. The theory is sunlight draws lead out of a child's bones, where it is stored, and puts it back into the bloodstream.

But other researchers believe the connection is from children playing outside in the summer in lead-contaminated dirt. The extra lead exposure then increases their blood lead levels.

"Pretty quickly, you can convince yourself the amount of lead in the soil from using gasoline for 50 years is maybe just as important an exposure source as the lead in an old house," Johnson said of this research.

Mielke conducted a 1996 studyof the amount of lead on children's hands at day-care centers in New Orleans. By wiping the children's hands before sending them off to play, then wiping them after they returned, he found that children generally had 4 microgramson each hand after playing inside, but had 28 microgramson each hand after playing outside.

When children get lead on their hands, it gets on their toys and into their mouths, Mielke said. He found a direct relationship between the amount of lead in soil and the amount on children's hands.

The federal government's method for determining which sites should be cleaned depends largely on the land's use.

In Detroit, the Free Press found some of its highest lead readings in a neighborhood on Klein Street near Conant. Tests showed 751 ppm.