A new study found that exposure to lead in childhood can affect the IQ in adulthood. The study was published Tuesday in the Journal of the American Medical Association (JAMA), and researchers wrote that there is a link between lead exposure as a child and some issues in adulthood related to low cognitive abilities and socioeconomic status.
In the United States, lead can come from several sources such as old paint, contaminated soil or from water that runs through lead pipes. Lead was even found in particles from the fumes that leave car tailpipes, before policies that ensured to get rid of lead in gasoline.
Lead has been studied for decades, and there’s proof that when a human being is in direct contact with it, the brain’s development can be affected.
“It’s toxic to many parts of the body, but in particular it can accumulate in the bloodstream and pass through the blood-brain barrier to reach the brain,” explained Aaron Reuben, study’s lead author and graduate student in clinical psychology at Duke University.
Lead exposure can seriously affect cognitive abilities
Reuben worked among other colleagues to determine the results of lingering lead in the human body. The investigation lasted decades since researchers needed to keep track of participants since their childhood. The study focused on 560 people that have been monitored since they were born in the 1970s in Dunedin, New Zealand all the way to the present.
When they were children, the research participants were tested on their cognitive abilities. The researchers determined the IQ scores based on tests of pattern recognition, working memory, ability to solve problems and verbal comprehension, to name a few. After the kids had turned 11 years old, researchers tested their blood looking for any lead traces. Such test is designed to be a rough indicator of lead exposure in the months before the blood is drawn and tested.
Finally, as participants turned 38 years old, their cognitive abilities and IQ were measured again by researchers. They wrote on the study that after results had come in, they found a worrisome pattern in the results.
The data showed that subjects who had low blood levels in their childhood had an IQ as high as when they were children. However, Reuben explains that children who were more exposed to lead, their intellectual abilities decline from their IQ starting point as time went by.
“People who saw that decline also experienced downward social mobility,” added Reuben.
The study also found that participants that had higher exposure to lead as children – which was defined as more than 10 micrograms per deciliter of blood – were more likely to end up in jobs that required slightly less education and brought in less income compared to their parent’s. In the research, Reuben and his colleagues explain that every five microgram increase in lead concentration in the bloodstream of the subjects when they were 11 years old corresponded to a drop in IQ of 1.6 points at the time they were 38 years old, primarily attributed to a score drop in perceptual reasoning and working memory.
In recent times, the Centers for Disease Control and Prevention (CDC) have standardized lead concentrations, considering five micrograms per deciliter of blood as high exposure. The CDC believes that no amount of lead is safe.
The changes in IQ and socioeconomic status were mild, but despite this Reuben believes that even small changes in IQ still played a part influencing the course that the person’s life took.
David Bellinger, a neurophysicologist and environmental epidemiologist at Boston Children’s Hospital and Harvard Medical School, believes that there is a thin silver lining to the study’s results. For Bellinger, the study lends credence to an estimate that over the last 40 years, policies to reduce lead may have helped to raise the IQ level in adults by as much as 4.5 points.
Children in low-income areas in the U.S. are exposed to lead
Still, the neurophysicologist believes that the problem is far from solving. He says that there’s no reason to think that the study, which had New Zealanders as subjects, wouldn’t prove the same if conducted with American subjects. The results don’t apply only to the generation now entering middle age, Bellinger says that lead exposure could potentially affect more generations.
Several policies have been put to work in the United States to prevent lead exposure by eliminating it from paint, gasoline, and plumbing. However, there is still a lot of lead in the U.S. and kids can ingest it. Bellinger stated that people would continue dealing with the consequences of lead on children and adults unless something is done to eliminate the remaining sources in the environment.
He notes that unlike New Zealand, where lead exposure apparently has affected all socioeconomic groups, U.S. lead exposure is particularly risky for children living in low-income areas of the country.
“In Flint and other places we know now experiencing higher lead exposures than we would like, most of these kids are starting out already disadvantaged in life,” said Reuben, according to NPR.
For Reuben, lead exposure may be one more thing that will hold back these children in decades to come.