Most know that exposure to lead, even at low levels, can cause serious health problems in early childhood and adulthood. However, new research published in Science Advances shows how lead exposure at an early age can have long-term health implications on cognitive function.
The researchers found people who grew up in cities with lead-contaminated drinking water as a child had lower cognitive function later in life as an adult. In addition, they found the association between childhood lead exposure and cognitive function as an adult was equivalent to the effect of eight additional years of aging, the authors wrote.
The association between childhood lead exposure and cognitive function as an adult was equivalent to the effect of eight additional years of aging.
“This is important because, although it is well-known that lead exposure is bad for kids, there is not much research to investigate whether these consequences are long-lasting,” Mark Lee, PhD, contributing author of the study and research scientist at the Minnesota Population Center, told Seasons. “Our study provides key evidence for a long-term effect of lead exposure on cognitive health across the lifespan.”
Lee and his colleagues analyzed more than 1,000 participants and determined which ones lived in cities with lead pipes and acidic or alkaline water (a condition necessary for lead to leach into drinking water).
Participants then took different cognitive tests to measure cognitive function, including a word recall task, a subtraction test and a counting backward task. Scores from these tests were summed to create a composite cognitive measure, Lee said.
They found people who lived in cities with lead-contaminated water as a child had worse cognitive functioning at age 72 compared to other participants who did not. Other factors like income, wealth, stroke, hypertension and heart disease did little to moderate the relationship between childhood lead exposure and cognitive functioning.
“Having lead pipes and acidic or alkaline water is a proxy measure of lead contamination in the drinking water in a city,” Lee said. “So, people who grew up in these cities probably consumed higher levels of lead than people who grew up in cities without these problems.”
Why might lead exposure as a child impact cognitive function in adulthood?
Exposure to lead is dangerous and can have impacts on cognitive function later in life because it mimics calcium, which the body needs for many different functions, Masashi Kitazawa, PhD, associate professor at the University of California, Irvine, told Seasons. This allows lead to accumulate in the bones and slowly leak out to the blood over time as people age and bone loss occurs.
“So, even if individuals were exposed to lead in a short period of time earlier in their life, blood lead levels and its toxic effects could last a very long period of time long after exposure was done.”
He added that if calcium activities are disrupted by lead in the brain, individuals will also experience cognitive decline and lower IQ. And while the blood-brain barrier is able to protect the brain from many potential toxins, lead can cross this barrier.
“This is especially dangerous among children, whose brains are developing, but lead exposure is unsafe for people at any age,” Lee said.
In addition, because lead can enter the brain, it can damage neurons and their functions. Further, it can disrupt cellular signaling, which is critically involved in neurotransmitter release, neuronal communication, strengthening synaptic connectivity and conductivity, and making new synapses, Kitazawa explained.
“Those functions eventually make better neuronal connections between neurons, which contribute to better cognitive functions,” Kitazawa said. “Simply put: More synapses connected together, you have good cognitive functions.”
What other effects could lead exposure have on health, regardless of age?
People can get exposed to lead in different ways, including air pollution (if lead-containing materials are burned), the ground, household lead-containing paints, dust or even water. That exposure can interfere with many biochemical processes in the human body, regardless of age. It can also affect multiple organ systems and result in brain damage, anemia, kidney problems, high blood pressure, stunted growth and other medical problems, said Kelly Johnson-Arbor, MD, a medical toxicologist at the National Capital Poison Center.
“Lead is best known for causing cognitive damage, but it can also cause blood pressure elevation, an increased risk of miscarriage, abdominal pain, and multiple other signs and symptoms in humans,” Johnson-Arbor added.
Lead exposure also has no physiological role in the human body, and there is no known “safe” level of exposure to lead.
What does this mean for you?
If you believe you were exposed to lead as a child and have concerns about cognitive function, experts recommend talking with your doctor about taking a blood lead level test. If your health care provider determines you qualify, they will take a blood sample and determine if you have lead in your blood.
From there, your doctor can determine if you need certain therapies or treatments intended to draw lead out of the body.
Johnson-Arbor also suggests undergoing early screening for cognitive problems and talking with your doctor about any potential signs or symptoms of cognitive decline you may be experiencing.
Beyond these measures, you can identify sources of lead around your environment, including from drinking water, paints and dust by using purifiers or home testing kits.
“The best approach is to remove the source of lead. Maintain the house and renovate and remove all lead-containing goods or stuff,” Kitazawa said. “Lead poisoning can be prevented, but it requires everyone’s effort to do so.”