(Left) Juan Jose Costilla Villa is the mayor of Doctor Gonzalez, a Mexican community that depends heavily on a factory that recycles the lead found in old car batteries. (Right) Roman Eden Peña Esparza plays with his cat outside his home in Doctor Gonzalez. He says that the Eléctrica Automotriz Omega plant, as one of Doctor Gonzalez's most prominent companies, holds a lot of influence. (Dominic Bracco II/Prime for the Washington Post)

It’s a problem that shouldn’t exist, at least not in the industrial West. Scientific studies a half-century ago documented the insidious health effects of lead exposure, prompting a U.S. ban on lead additives in paint and gasoline as well as increasingly tougher safeguards for people working around the metal.

The discovery of lead in the water supply in Flint sparked a scandal in part because such problems are so rare now in the United States.

Automobile batteries are among a handful of common consumer products that still contain large amounts of lead. And in the United States, nearly all spent batteries end up being recycled, which involves removing the plastic, acid and other chemicals and then melting down the lead to use in new batteries.

U.S. battery recycling takes places mainly in a small number of high-capacity, high-tech smelters. Workers wear protective clothing to ensure no traces of lead leave the plant with them. Special exhaust scrubbers trap tiny lead particles so that they do not escape into nearby neighborhoods. Electronic monitors sniff the air to guard against accidental exposures.

“We have an infrastructure here that was built to handle these materials,” said Robert Finn, chief executive of RSR Corp., a Texas smelting company. Finn’s firm recently purchased expensive pollution-control systems that far exceed the requirements set by the Environmental Protection Agency — an investment Finn says was morally necessary to protect workers and surrounding communities.

But RSR and other U.S. smelters have seen much of their business leave the country since exposure limits for American workers were tightened. Some U.S. companies have purchased or built smelters just over the border, and batteries unclaimed by the American firms are distributed to Mexican companies, ranging from the medium-size Omega facility to tiny shops that operate out of private homes and garages. “The U.S. government can’t tell you where these batteries are going,” Finn said.

While Mexico also has updated its laws in the past three years, the regulatory climate there remains far more permissive, said Whitehouse, who is now president of Cyan Environmental Group, a consulting firm.

“Mexico has neither the regulations nor the capacity to make sure that lead is recycled in a way that protects human health,” he said.

[Budget woes threaten Mexico’s reputation as a conservation leader]

The result: Americans, while seeking to eliminate an environmental problem at home, are exporting contamination abroad, to a region less capable of defending itself, charge Whitehouse and other legal and environmental experts.

“I’ve been in facilities that look as modern as those in the United States from the outside,” Whitehouse said, “but they just don’t follow the same rules.”

The Eléctrica Automotriz Omega plant, a low-slung factory with twin smokestacks, employs several dozen workers who say they earn about $13 for a 12-hour shift. Located in the Monterrey suburb of Doctor Gonzales, the plant melts down battery lead into ingots that help make new batteries at a facility in the nearby town of Pesqueria, according to several employees.

On occasion, workers say, the company has bought used U.S. batteries directly from dealers in Laredo, Tex., where they are stacked by the thousands on pallets for shipping.

Municipal officials in Doctor Gonzalez concede that the oversight of the Omega plant is less than rigorous. As one of their most prominent companies, Omega has a lot of influence, said Roman Eden Peña Esparza, an environmental inspector for the municipality.

“We do an inspection, but it’s not very strict,” he said. “The municipality is in agreement with the company.”