UC Researchers Expand Tijuana Lead Study

TIJUANA, Mexico —  Two U.S. doctors involved in an effort to track lead in Mexico’s soil have expanded their study to measure the amount of lead lurking in home remedies and traditional pottery.

Suspicious of border factories that emerged after the 1994 North American Free Trade Agreement, two UC-Irvine researchers wanted to record the amount of lead in Tijuana’s soil. That level would serve as a baseline against which to compare future samples.

But, in isolating lead sources from 1,600 families and interviewing family members, the doctors realized they had to examine benign household items that were contaminated with lead--food cooked in lead-glazed pots and a traditional infant analgesic comprised almost entirely of lead.

“These two are substantial sources of lead for those of Mexican descent or heritage,” said Dean Baker, epidemiologist and coauthor of the study and director of the Occupational and Environmental Health Center at UC Irvine.

The same two factors have resulted in elevated lead levels even among Mexico’s educated middle-class, which had lead levels slightly higher than those of Latino populations in the United States, according to results based on about one-quarter of the analyzed data from Tijuana.

The UC researchers’ findings were not surprising. In 1993, scientists at the Centers for Disease Control and Prevention in Atlanta had found that a higher proportion of children with elevated lead levels also had Hispanic surnames. They traced the higher levels to the lead-glazed pots and the infant analgesic.

Mexico has lead guidelines, but Baker and his colleague, John Erickson, found little adherence to them. But health officials in Baja California approved the three-year research project and are assisting the U.S. researchers in collecting data.

Mexican federal officials donated 500 lead-free glazed pots to families interviewed, but they have not been able to offer a suitable substitute for the traditional sleeping powder.

The majority of middle-class Tijuana women who agreed to be interviewed for the study said they cook a daily vat of beans in lead-glazed pottery. They also said they administer traditional home remedies called greta or azaron to soothe babies with colic or constipation.

The powdery home remedy can contain lethal amounts of lead--up to 90%--and can be purchased at any herbal-remedy shop.

“Burn a battery and produce lead white--that would be the basis of the greta,” Erickson said. “Lead is a neurotoxin, which means it puts you in a stupor. The body stores parts of it, and then can partition it in the brain or kidney.”

On a recent weekday morning at the Guaycuna Preschool in a well-paved, middle-class neighborhood, participants said they were grateful for lead testing paid for by the U.S. study.

“I just found out there was lead in some of my painted pots,” said Nancy Esparza, 30, who was waiting for her 4-year-old son, Manuel, to undergo a blood test.

Normal blood contains up to 10 milligrams of lead per deciliter. If Manuel’s blood was found to contain 11 to 19 milligrams per deciliter, data collectors would visit the Esparza home to identify contaminated items, such as candies wrapped in lead-painted wrappers. Scientists also would gather dust and soil samples inside and outside the home.

Higher levels, from 20 to 44 milligrams, would prompt a doctor’s visit.

A child with more than 44 milligrams per deciliter would require hospital treatment. In a process called chelation, medication binds the lead so that it can be excreted.

Baker and Erickson have yet to analyze data collected from Tijuana’s shantytowns--places they suspect will show dramatically high levels of lead because of their proximity to border factories.

“We think people who live near industry or a major roadway, after we adjust for social class and home remedies, will have higher levels of lead in their blood,” Baker said.

Baker and Erickson wanted to begin the study immediately after the implementation of NAFTA in 1994, but funding from the Environmental Protection Agency and the CDC only came through last year.