University of Pittsburgh

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Brain Drain

The dangers of heavy metal are real and lasting

Written by David Templeton

Morrow

Morrow

It’s a brisk fall day as a student scurries across the campus of an all-women’s college in Missouri. She’s on her way to make a presentation in psychology class, clasping her visual aid—a heavy glass jar—in both hands. Along the way, students stop her to gawk at the jar and ask about the oatmeal-colored mass sloshing around inside. The fledgling scientist, a former theater major, pauses a moment to heighten the impact of her response: “This,” she says, “is a brain.”

That was more than 30 years ago. Today, Pitt researcher and neuropsychologist Lisa Morrow is still intrigued by the mysteries of the brain—and what makes it falter. Her journey has brought her to the University of Pittsburgh, where, over the years, many clients have shown up in her office to describe their symptoms.

Less than a decade ago, two separate visitors especially piqued her interest. They had very different backgrounds but similar symptoms. One of them complained of feeling queasy and said she couldn’t “think straight.” She had recently been stripping paint from a staircase in an old home. The other talked about feeling ill and said his mind was “messed up.” He was an ironworker who had been removing paint from a West Virginia bridge.

Morrow suspected there was a common connection between the two cases. Earlier tests showed that both individuals had high levels of lead in their blood, and Morrow confirmed that both had measurable cognitive decline.

The neuropsychologist, having observed the metal’s harmful short-term effects, wondered about lead’s longer- term influence, especially on the brain. After all, the substance is still widely used in batteries, solder, pewter, and other products; and the world is full of lead paint from past eras. She wanted to know more about the nature and effects of lead exposure in humans.

In her pursuit, she relied upon research she had helped compile in 1982 that focused on workers in three lead-battery plants near Reading, Pa. The study compared levels of lead in the body and cognitive abilities of the lead workers to those of a group of plant workers from a separate manufacturing plant who had never been exposed to lead. At the time, the tests showed higher levels of lead in the blood of the exposed workers but no significant short-term effects from the lead exposure.

Morrow decided to find as many of the original Reading lead workers as possible and retest them—nearly 22 years later. She wanted to look more closely at the effects of lead over time. Now, based on the research of Morrow and her colleagues in Pitt’s School of Medicine and Graduate School of Public Health, it appears that the heavy metal is even more harmful than past studies suggest. The biological effects of lead can be long lasting, with negative consequences as people age, even long after the exposure occurs.

To begin their study, the Pitt researchers located Terry,  a union worker at a Reading battery plant who had been affiliated with the 1982 study. He found a union list that allowed Morrow’s team to track down the workers who were tested back then. With workers’ names in hand, Terry recruited as many as possible, including some still employed at one of the plants.

Ultimately, the research team located 83 of the original 288 lead-exposed male workers, who agreed to be retested. Ranging in age from 40 to 60, the men traveled to Pittsburgh for bone scans and cognitive tests. The Pitt research team also recruited a control group of 51 workers without lead exposure who also had been tested in 1982.

Based on the retesting of the Reading plant workers, the researchers discovered that lead from the initial exposure years ago was recirculating in the blood of exposed workers as they aged. The study results suggest that lead circulates in the blood after the initial exposure, then finds its way into soft tissues and organs, and eventually settles into bones. Some of the lead is purged from the body over time, but much of it remains in the bones. Eventually, bone deterioration from age-related osteoporosis and other health problems causes the embedded lead to be released back into the bloodstream later in life.

Fluorescent x-ray scans of the exposed workers’ tibia bones revealed that the bones still stored high levels of lead, and notable levels of it circulated in their blood. There was another significant finding, too: The higher the lead levels in the tibia bone, the greater the decline in cognitive ability 22 years later. Lead-exposed men older than age 55 showed five times the decline in cognitive function than did younger lead-exposed workers.

In essence, the results show that lead exposure has lasting effects on human biology, producing cognitive decline as a person ages. Morrow says that persistent lead in the blood penetrates the brain’s blood barrier and collects around brain neurons, where it damages cognitive ability. The Pitt study, “Association of Cumulative Lead and Neurocognitive Function in an Occupational Cohort,” was published earlier this year in the journal Neuropsychology. Coauthors include other Pitt researchers: Naila Khalil, lead-research pioneer Herbert   Needleman, Evelyn O. Talbott, John W. Wilson, and Jane A. Cauley.

The outcomes offer an intriguing example of how the brain can falter, even though the effects might not be noticeable for years. The study also illustrates how the work of scientists can guide prevention of harmful conditions and, potentially, improve treatments.

No wonder that, years ago, the college co-ed was fascinated by the contents of the jar she carried to psychology class. For Lisa Morrow, the brain remains a complex enigma, but answers are possible for those who continue to ask.

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