Airborne lead from recycled car batteries at the Exide plant in Vernon, California, was found in the baby teeth of children living nearby, according to the University of Southern California (USC).
“We found the higher the level of lead in the soil, the higher the amount of lead in baby teeth,” said Jill Johnston, PhD, assistant professor of preventive medicine at the Keck School of Medicine of USC and first author of the study.
“There’s no safe level of lead. It’s a potent neurotoxin. Our study provides insight into the legacy of the impact of industrial contamination on children,” said Johnston.
The Exide plant, located just southeast of downtown Los Angeles, recycled 11 million auto batteries per year and released 3,500 tons of lead until it closed in March 2015 as part of a legal settlement for hazardous waste violations.
As many as 250,000 residents, mostly working class Latinos, face a chronic health hazard from exposure to airborne lead and arsenic that subsequently settles into the soil, according to a 2013 health risk assessment by the South Coast Air Quality Management District.
The researchers collected 50 baby teeth from 43 children in Boyle Heights, Maywood, East Los Angeles, Commerce, and Huntington Park. They recruited families through churches, schools, and door-to-door visits. A local organization, East Yard Communities for Environmental Justice, dubbed the report the “Truth Fairy” study.
Using laser ablation and an analytical technique for molecular-level information, the researchers examined the teeth layer by layer and assigned time points for lead contamination, such as the second trimester of pregnancy, when teeth are starting to form in the mother’s womb.
The researchers also measured lead and arsenic in the dentin that begins to form in the third trimester, when the baby is growing rapidly and incorporates nutrients and toxins from its mother.
Finally, the researchers could see contamination acquired after birth, during the baby’s first year. Infants are at higher risk of exposure because they crawl and put their hands in their mouths.
The teeth findings were matched with soil contamination data from the California Department of Toxic Substances Control, which collected 117,356 samples from the upper layers of soil on nearly 8,000 properties.
The researchers found that the median concentration of lead in soil was 190 parts per million, which is well above the state of California’s threshold of 80 parts per million. Also, 14% of soil samples exceeded 400 parts per million.
Communities with the highest soil lead levels also had the highest lead levels in children’s teeth. Boyle Heights and East Los Angeles had the highest levels, followed by Maywood, Huntington Park, and Commerce. The higher levels in Boyle Heights and East Los Angeles could be a function of prevailing winds, the researchers said.
In some cases, higher exposure occurred while the baby was still in the womb, meaning the mother’s exposure to lead such as from dust tracked inside on the feet of people and pets was transmitted to the unborn child.
Few studies have looked at lead in teeth, the researchers said, so there is no established baseline for comparison. However, the communities around the Exide smelter had twice as much lead as that found in a similar urban community in Boston that did a tooth-based study.
Measuring lead in shed baby teeth is a promising technique to assess prenatal and early life exposure, the researchers said. Though lead exposure is typically measured via blood tests, they only reflect recent exposure. Lead from past exposures measured via teeth may be an important indicator of harm, the researchers said.
“Higher lead in teeth means higher lead in the brain, kidney, and bones,” Johnston said. “Testing women for lead during pregnancy, or even earlier, as they enter child-bearing age may be needed to decrease lead exposure to their future offspring.”
The study, “Lead and Arsenic in Shed Deciduous Teeth of Children Living Near a Lead-Acid Battery Smelter,” was published by Environmental Science and Technology.