Andrea's monster lives up here.

It breathes lead dust that coats her windows and her baby toys. It sweats rivers of arsenic and cadmium and antimony that seep into her water and the soil where her children play. It squats on a hilltop above her home, horrible and poisonous.

"There it is," says Andrea Pedro Aguilar, breathing heavily from the hike up the hill.

She is standing in front of her monster, the derelict remains of a lead smelter that everyone here calls Metales. For more than a decade, an American-owned company, Metales y Derivados, took in thousands of U.S. car and boat batteries, cracked them open to extract their lead, melted it into bricks and shipped the bricks back to the United States.

Mexico shut the plant in 1994 and the next year its owner, a U.S. citizen named Jose Kahn, crossed the border back into San Diego. Mexican arrest warrants were outstanding, charging him with gross environmental pollution. He still lives in a comfortable neighborhood of San Diego.

According to the Mexican government, he left behind up to 8,500 tons of toxins from battery guts that lie strewn over three acres, in open piles, rusted barrels and in rotted bales. Every time the wind blows or the rain falls, more of the toxins end up in Colonia Chilpancingo, a worker's village of 10,000 people directly below the plant.

According to Mexican environmental officials and the U.S. Environmental Protection Agency, the toxic dump here exemplifies how much of the border area is a no man's land, a place where international companies have polluted the environment.

When the Metales furnaces were still burning in 1990, a Mexican university study found levels of lead more than 3,000 times higher than U.S. standards and levels of cadmium more than 1,000 times higher in a stream that runs through the community and eventually flows north over the border into the United States. A 1999 study by the enforcement division of Mexico's environment ministry found lead concentrations in the soil near the plant 50 times higher than the limit set by Mexican law. That report called the Metales site a "major health risk."

A cleanup of the site could cost $6 million or more. Two months ago, the state of Baja California and Kahn filed a joint loan request for $800,000 from the North American Development Bank, which was created as part of the 1994 North American Free Trade Agreement (NAFTA). A bank official said the unusual request -- coming amid rising demands from residents for a cleanup -- is being reviewed. He said one concern is that the loan might not cover the cost of the cleanup.

In the meantime, the toxins bake in the sun and blow in the wind. The pollution keeps flowing into Chilpancingo, from Metales and from some of the other 130 factories, known as maquiladoras, in the huge industrial park where it sits.

"Danger, hazardous waste" is stenciled on the concrete wall that partially surrounds Metales. But the place is still a favorite for dare-taking kids who scoot through holes in a fence into the forbidden site.

Reached by telephone, Kahn, who is in his late eighties, said, "We are negotiating a loan to clean up the place. I really can't tell you anything more than that." He declined further comment on Friday. In an interview published in December in the San Diego Union-Tribune, Kahn said the loan request shows that he is serious about cleaning up Metales: "We all want a solution. No one wants to walk about without a cleanup."

It hasn't rained in Chilpancingo for nearly two months, but dirty water still runs down the middle of Andrea's street. It starts in a gaping drainage pipe emerging just beneath the industrial park that emits a milky white substance made of God-knows-what that flows downhill to Andrea's neighborhood. Factories there are required by law to treat their own hazardous waste, but state environmental officials say many still dump illegally.

"I don't know what they were thinking," says Andrea, who had two feet of acrid, filthy water in her living room when heavy rains caused flooding last year. "People live down there."

People like her kids. Lupita is 4 and Ivan is 6. They ride scooters in their living room and watch Monsters Inc. and Rugrats for hours on end. Andrea thinks it's safer for them to be inside even though her little lead-testing kits have turned up elevated levels of the toxin on her dishes and on the sill of her kitchen window. Outside, the fruit trees and grass that her mother planted 20 years ago have all died.

Just before Christmas, 20 Chilpancingo children under the age of 6 were tested for lead. Officials from the Environmental Health Coalition, a San Diego-based organization, said that all the results showed significant and potentially dangerous levels of lead in their bloodstreams. Lupita's blood had the highest level, 9 micrograms of lead per deciliter, just under the level of 10 micrograms per deciliter, classified as elevated for children by the U.S. Centers for Disease Control and Prevention. Lead, especially in children, can damage organs and severely retard mental development, and studies suggest it may cause cancer and birth defects.

Officials at the CDC said arsenic, cadmium, antimony and other byproducts of the smelting process are carcinogens. CDC officials also said that exposure to those metals can cause skin rashes, nosebleeds and hair loss.

Lupita's hair slips out by the brush-full every day, and she has suffered spontaneous bleeding in her nose and throat for the past couple of years. It got so bad in November that Andrea and her husband slept with Lupita, out of fear that she might drown in her own blood. Andrea says they did not know what was causing her problems. Then her lead test came back positive.

Now Andrea stands before the monster, a mile south of the U.S. border, shaking her head in disgust.

Wenceslao Martinez, a physician, runs a health clinic a few blocks from Andrea's house. He says he constantly sees patients with suspicious diseases, from chronic rashes to cancers to fatal birth defects.

"For a colonia of only 10,000 people, what we see here is very strange," he said. "There is definitely a link to the maquiladoras. But it's hard to prove. So who gets the blame? Nobody."

He treated Margarita Jaimes's 3-year-old son, Serafin Vidrio, who turned up one day last July with swelling in his neck and eyes. He was diagnosed with acute leukemia on Aug. 6. He died on Aug. 24.

Margarita, like the others, is frustrated no one has spent the money to study whether the illnesses around these factories are linked to the toxins they have dumped. As she talks, her daughter, Eva Paulette, 6, sits on her lap. She has been having nosebleeds. Her hair is falling out in clumps. The doctors cannot explain it.

Carmen Garcia used to walk to work every day past Andrea's house, past the open piles of sludge at Metales to a factory where she assembled stereo speakers. When she became pregnant two years ago, she knew her factory was not the best environment, because in the previous two years three of her co-workers had delivered stillborn babies.

Then on Nov. 3, 2000, Carmen delivered Miguel Angel, who suffered from anencephaly, a fatal defect in which babies are born with little or no brain or skull. Miguel Angel's empty skull was open wide like a tulip. He survived for two months.

"It's like a trap here," Carmen said. She's pregnant again. "I'm so scared."

A CDC spokesperson estimated that anencephaly occurs in two to four of every 10,000 births in the United States; hydrocephaly, a related disorder, occurs in about six of 10,000 births.

The state of Baja California, which includes Tijuana, is now conducting its first major study of those two birth defects. Moises Rodriguez Lomeli, the state's chief epidemiologist, said the study was launched 18 months ago after state officials realized the rate of those birth defects in the state was abnormally high. In one two-block area of Chilpancingo, residents count eight babies born with those two defects in recent years.

Andrea and other community leaders, working with the Environmental Health Coalition, filed a complaint about Metales with the Commission for Environmental Cooperation, NAFTA's environmental watchdog agency. The commission issued a report last year noting that "exposure to these heavy metals can severely harm human health" and called the site's cleanup "urgent."

In the commission's 154-page report, the enforcement division of Mexico's environment ministry said that "with alarming regularity" foreign-owned factories are being abandoned, with their hazardous waste left behind. It also said the EPA viewed the Metales situation as "exemplifying a critical public policy issue in the border region: the use of the border as a shield against enforcement." The Mexican government has been reluctant to clean up foreign-made messes, and when the foreigners return home they are beyond the reach of Mexico's laws.

Andrea and other women in the community, with help from the Environmental Health Coalition, are now trying to educate residents about the hazards around them. They pass out lead-testing kits and arrange blood tests for children. They write to government officials and hold all-night vigils outside their offices. They marched on Kahn's office in San Diego, holding up signs with such messages as: "Jose Kahn: you forgot something in Tijuana."

Black smoke is rising from a burning car behind Andrea's house. The local kids again, torching a stolen and stripped Oldsmobile Cutlass for kicks. As if the place didn't have enough problems, Andrea says, punching buttons on her phone to rouse the fire department.

She's standing in her fenced-in yard, where she rents out a couple of small shacks to make a little money. The woman who lives in one of them gave birth a few months ago to a baby missing most of its lower body. The previous tenant in the same house woke up with her neck swollen like a bullfrog's. "Two months later, she was dead," Andrea says. "Nobody ever knew why."

A couple of unhurried firemen arrive to begin hosing down the burning car. Andrea, who is pregnant again, says she dreams of the day when all the toxic pollution is gone, when Chilpancingo is clean and healthy, filled with flowers and trees, the way she remembered it as a girl.

Then she closes her eyes against the thick, black smoke.

A resident of Colonia Chilpancingo crosses a bridge over the polluted Alomar River that cuts through the shantytown where assembly plant workers live mostly in shacks. Rotting bales and corroded barrels filled with lead and other heavy metals litter the abandoned U.S.-owned lead smelter just across the Mexican border. Toxic dust and sludge seep into nearby Colonia Chilpancingo.Resident Andrea Pedro Aguilar, left, and Magdalena Cerda, with the San Diego-based Environmental Health Coalition, survey the contaminated site of an abandoned lead smelter blamed by residents for causing severe birth defects and other health problems. Neighbors have urged its U.S. owner to clean up the site.Andrea Pedro Aguilar walks down the path from an abandoned U.S.-owned leader smelter to Colonia Chilpancingo, in Tijuana. Each day, hundreds of workers walk past the contaminated site to get to their jobs in nearby assembly plants.Serafin Vidrio, 3, was taken to a local clinic last July with swelling in his neck and eyes. He was diagnosed with acute leukemia on Aug. 6. He died on Aug. 24. His mother blames contamination from an abandoned U.S.-owned smelter.