BROKEN HILL, Australia (AP) _ A century of mining for zinc, silver and lead has piled up a huge slag heap that looms over town like the great, stepped pyramids the Mayans built for their gods.

Broken Hill's man-made mountain is a monument to the riches of its minerals, but it also is a source of ill for the city of 25,000 people. For decades winds have swept its slopes, whipping up lead dust that drifts across town, settling into attics, backyards and parks _ slowly poisoning the children.

Seventy percent of Broken Hill's children have elevated levels of lead in their blood, which can lower learning ability, cause hyperactivity and damage the body's organs.

Of the children under age 5, whose nervous systems are especially vulnerable, 40 percent have more than 10 micrograms of lead per deciliter of blood, a danger level cited by world health experts.

With one mine still in operation, Broken Hill is the worst spot in Australia for lead in the blood. Port Pirie, where the lead smelters are, and the mining city of Newcastle also have problems.

U.S. experts say a few, small mining towns in the American West have similar, but less serious, problems. Lead-based paint on walls in inner cities is the main source of lead poisoning in the United States and other Western nations, say the experts, who are studying the lead-control program in Broken Hill.

The state-financed Broken Hill Environmental Lead Center began a $2.5 million program two years ago to educate families, monitor children's blood levels, remove lead dust from houses and pave over some areas to cover lead-contaminated dirt.

Bill Balding, director of the center, says the agency is concentrating on that rather than trying to link any child's specific ailments to lead poisoning. It is hard to pinpoint among the variety of ailments that can cause the health problems known to be linked to high lead levels.

Troy Read, a father of two, stands in front of his house, which is next to an old slag heap. Twisted, rusting wreckage from a mine abandoned decades ago juts out of the pile; the sunlight glints off bits of metal ore mixed in among the dusty dirt.

``I used to play cowboys in that field,'' he says. ``My dad's brother died at age 11 of lead poisoning; he used to eat dirt. I just wonder how smart the last generation would have been if it hadn't been for the lead.''

His 22-month-old son, Oliver, scurries through the house and yard on stubby legs, endlessly touching things that intrigue him _ and sometimes putting his fingers into his mouth if no one is nearby to stop him. That is one of the ways youngsters in Broken Hill ingest lead.

Lead-rich dust accumulating in houses over the years is another source of contamination, and Read's house was a mother lode.

A contractor hired by the Lead Center to decontaminate the house removed 8,000 pounds of dust just from among the attic floorboards.

``The four- by two-inch rafters were buried in dust. The whole space was buried,'' Read says.

When the living room carpet was taken out for cleaning, he says, ``There were two 2-gallon buckets-worth of dirt under it.''

Tests found the dirt was 1 percent to 2 percent lead.

Oliver is one of the 1,135 children whose blood is monitored periodically by the Lead Center. In all, 87 percent of the city's young people participate in the voluntary lead-monitoring system.

The city's people are relying on government to deal with the problem because they have little legal recourse in such a complicated situation.

Like many nations, Australia bars lawyers from representing clients without charge in return for a promise for a share of any monetary damages won in court _ the system that allows average people to pursue cases against big companies in the United States.

That means a family with a child possibly suffering a lead-related health problem would have to come up with the money to file what likely would be a hard-to-win suit. Most of the mines ceased operations years ago. And in a further complication, the surface soil of the area is high in lead, which could make the source of a child's contamination hard to prove.

So the problem has fallen to New South Wales state.

In addition to monitoring blood levels and decontaminating houses, the state-financed Lead Center educates children and parents about the importance of washing hands and playing in grassy areas rather than on dirt.

The center also is planting more ``green belts'' and parks to cover bare dirt and paves some problem areas.

So far, the anti-lead program has reduced the percentage of young children with lead levels above the danger level from 60 percent two years ago to 40 percent, the center says.

No child has had to be sent for special medical treatment for ultrahigh lead levels in the past two years. Before that, six or more were referred for treatment annually.

But Broken Hill is doomed by its geology and history to lead problems.

``It's all over town,'' says Richard Murphy, a miner for 30 years who now is a guide in an underground tourist mine.

``Years ago we used to have big dust storms, and when I say dust storms, I mean you wouldn't be able to see _ absolutely black. I remember being at school, and I'd be in the school yard, and I'd be standing here and my mate there, 10 feet away, and I couldn't see him.

``You could see it coming, thick, rolling black clouds of dust, and that's what used to pick all this up and spread it everywhere.''