11% of Tijuana Children Have High Levels of Lead in Blood

About 11% of Tijuana’s children show unhealthful amounts of lead in their blood--mostly because of lead-glazed cookware and contaminated soil--but at levels far lower than feared, UC Irvine researchers concluded after a three-year study in the United States and Mexico.

Similar testing in Mexico City previously found that 27% of children there had unhealthful levels of lead in their bloodstreams. Lead poisoning can affect brain activity and motor skills; in young children, it can cause permanent damage to the central nervous system.

The $600,000 study was funded by the U.S. Environmental Protection Agency and the Centers for Disease Control and Prevention, with contributions from the city of Tijuana and the state of Baja California. It tested 1,719 children ranging in age from 18 months to 7 years in and around Tijuana.

The study concluded that about 37,000 children, out of a population of 344,000, probably have unhealthful levels of lead in their blood, but only 0.1% reach a higher, critical level requiring medical intervention and treatment. The rest could be helped simply by removing the lead sources from their environment.

As part of their work, researchers started a lead laboratory and clinic at Tijuana General Hospital. They trained Mexican health workers to conduct follow-up visits to the homes of children with high lead levels and counsel parents about reducing lead contamination in the household. In many cases that meant replacing ceramic cookware that turned out to be a major lead source.

That simple step reversed the lead buildup in most of the affected children, according to the study, which included follow-up testing. Only a fraction of 1% of the children had so-called Stage 3 lead amounts, which require medical treatment.

The EPA sponsored the research in Tijuana because many children living in Tijuana--nearly 30%, according to some estimates--eventually relocate to the United States. One goal was to reduce the number of U.S. immigrants with lead poisoning.

The mean lead level in the blood of Tijuana’s children is about twice that of children in the United States, but lower than in other parts of Mexico, said Jonathon Ericson, an environmental scientist at UC Irvine, who helped lead the project.

“The good news is that 89% of the population [in Tijuana] is below the threshold level for lead poisoning,” Ericson said.

At a news conference at Tijuana City Hall attended by U.S. and Mexican researchers, Ericson said the study found 186 children with unhealthful levels of lead in their bloodstreams.

Although researchers found that most cases of lead poisoning originated from cookware whose lead glaze was not thoroughly fired in kilns, there were examples of children who contracted lead poisoning in bizarre ways.

“We had a case we called the ‘Chiclets boy.’ He would chew his gum and then put it on the wall of his house to chew later,” Ericson said. “Well, the paint on the wall had lead. He was poisoning himself this way.”

Badly fired cookware allows lead to leach into food during cooking. Increased risk is also associated with pets going in and out of houses and tracking lead-contaminated soil into living areas.

Poorer children were more likely to have higher lead levels than children of higher socioeconomic status, researchers said.

Researchers and Mexican officials praised the collaborative program, which left in place an ongoing testing, surveillance and outreach program.

Maria Luisa Volker, lab director at Tijuana General Hospital, said the new equipment and expertise of the technicians who run it is already making a difference.

“We’re now making a positive diagnosis of lead poisoning. Before, it wasn’t always easy to tell a parent why their child was sick or lethargic,” Volker said.