Scientists build a convincing case for the harm done by lead
Kim Dietrich, PhD, is no stranger to being a lone voice in large, crowded rooms.
Kim Cecil, PhD, is an imaging scientist in the Department of Radiology at Cincinnati Children's.
Kim Dietrich, PhD, is an environmental health scientist at the University of Cincinnati.
About the Cincinnati lead study
Begun in 1979, the Cincinnati lead study is the longest-running study on lead exposure and brain development in the United States. It focuses on African Americans who as children lived in Cincinnati neighborhoods with dilapidated housing built largely before World War II and housing projects constructed in the 1950s-60s. Buildings from those years had high lead levels, especially in the older mixtures of lead-based paint that peeled and flaked with age. For more information about the Cincinnati Lead Study, call 513-558-5816.
New model for studying environmental brain damage
Advanced imaging techniques used in the Cincinnati lead study to confirm brain damage from lead exposure bring a bold new approach to investigating how toxic environmental exposures can cause neurological harm.
“I want to use this approach as a model for the next generation of neuro-toxicants,” says Kim Cecil, PhD, a Cincinnati Children’s imaging scientist and co-investigator on the lead study.
“We can use imaging to analyze changes to the brain so we don’t have to do decades of observational and behavioral studies in humans as was done with lead, “ she says. “Instead, we can have for instance five years of imaging studies and be able to say, ‘Whoa, this chemical is bad for the brain.’ We’re setting up the foundation for a whole new way of conducting environmental research.”
A wide range of chemicals in use today may potentially pose environmental threats, Cecil notes. Under the 1976 Toxic Substances Control Act, the Environmental Protection Agency (EPA) can request testing if evidence exists that a chemical may be dangerous.
As leader of the groundbreaking Cincinnati Lead Cohort Study, he has dedicated three decades to convincing the world that exposure to lead damages children’s developing brains – contributing to a plethora of behavioral problems, even criminal behavior, later in life.
Over the years, Dietrich has presented at conferences the findings made by his multidisciplinary research team. His talks review extensive lead exposure and behavioral data for people his research has followed from birth into adulthood. This is typically when the University of Cincinnati environmental health scientist encounters the wave of skepticism.
“I’m always challenged, often by lead industry representatives, who say, ‘You have no direct evidence that lead is having any impact on the brain at all. You just have these behavioral measures and they are soft, and no one knows what they mean,’” he says.
Now Dietrich is launching into yet another follow up study of the same research participants – roughly 250 people approaching 30 years of age. And the evidentiary tide is turning. It started when Dietrich began collaborating several years ago with Kim Cecil, PhD, an imaging scientist in Cincinnati Children’s Department of Radiology.
The two published their first collaborative study in 2006 of the group who as children lived in poor, inner-city neighborhoods of Cincinnati where lead content in the buildings was high. Using a battery of innovative magnetic resonance imaging (MRI) techniques, Cecil generated a body of startling research. It details with high precision the negative effects long-term lead exposure in children has on brain anatomy and biochemistry.
Lead and the brain
The research shows that when exposed to lead, certain regions of the brain do not fully develop. Most affected is the frontal lobe responsible for critical decision making, reason and what Cecil describes as “the part of the brain that makes us most human.” It is also the last region of the brain to fully develop.
Her examinations also show “lead-exposed” brains come up short in their supply of chemicals vital to normal brain function, especially N-acetylaspartate (NAA). One of the most abundant chemicals in the brain, NAA is considered an important indicator of neuron integrity and viability.
“Children who had high levels of lead in their blood at ages 4, 5 and 6 show the greatest impact in the frontal lobe,” Cecil says. “We think lead interferes with normal development. When you are born, the frontal lobe is not fully myelinated, which means the brain’s electrical circuits do not have the insulation and protection of the myelin sheath. It takes healthy living into your 20s to get that protection.”
When lead enters the developing brain it mimics calcium, tracing the same developmental pathways that calcium follows. This, in essence, shorts out the development process and blocks the proper maintenance of neuronal connections. The researchers found that the individuals who had these lead exposures struggle through life, have difficulty holding a job or fall into criminal behavior.
They also found that lead-blood levels do not have to be high to cause problems. Long-term exposures at low or moderate levels also can be devastating. And they affect male subjects more than female.
“We have found that even a 5-microgram-per-deciliter increase in blood level concentrations increased the rate of arrest for violent offenses among the study group by 30 percent, which is a pretty large effect,” explains Dietrich.
The MRI technology and brain modeling Cecil brings to the Cincinnati lead study open “a whole new world” for environmental scientists trying to demonstrate lead exposure’s impact, says Dietrich, whose training is in neuropsychology.
“These data are absolutely unique – no one has ever done this before,” he says. “Now, I can go to meetings and show the evidence. It was my lucky day when I connected with Dr. Cecil.”
Lead exposure continues
Considered a problem of the past because lead has long been banned from gasoline and paint, lead exposure it still very much a concern today, Dietrich explains. People continue to live in the same dilapidated, older houses, and their children are exposed to lead paint residues and lead-laden dust on the ground.
“There are still children today who live in a world of lead exposure. They get it on their hands and put their fingers and their toys in their mouths. It is normal 2-year-old childhood behavior,” he says.
He adds that some toys and jewelry manufactured overseas and sold in this country and elsewhere still contain high levels of lead.
Institutions in other parts of the country have studied the impact of lead and found similar results. What makes the Cincinnati study unique – especially as it enters the latest follow-up phase – is its comprehensive nature. It will give researchers a 30-year view of lead’s impact on brain development and behavioral outcomes.
Specific study points include: extensive lead exposure data, thorough assessments of MRI results, behavioral measures and even the influence of genetics on how lead exposure harms brain development.
The Cincinnati researchers are also revisiting what by far is the most closely, frequently followed (20 follow-up points for each research subject over the last 30 years) and well-characterized population for lead exposure.
Perhaps the biggest challenge for Dietrich and Cecil is locating research subjects who have grown up.
“Recruiting is harder with every wave of the study,” explains Dietrich. “They are adults now and have their own lives, and they tend to move around, so we are using billboards, flyers at grocery stores and social agencies.
“I’ve even tried to do home visits and walk down the streets of these old neighborhoods and knock on doors at the last known addresses.”
Elusive end game
Among the tragic truths of lead exposure is that no medical treatments exist to stop or reverse the damage it causes to the body’s most complex organ. This makes prevention key. For those already affected, the best available interventions involve counseling and vocational treatment.
“These are people who live in impoverished environments and have many hits against them,” says Cecil. “Unfortunately, from a medical perspective, we can’t really repair their brain.”
Barring a scientific breakthrough, Cecil and Dietrich say the best approaches to battling lead exposure involve public policy, cleaning up inner-city housing and making people aware of the danger. It is a big job, especially because of the nature of the culprit.
“Lead never decays into something else. It just stays lead,” says Dietrich.