Accessible Navigation.

The Air We Breathe

UM researcher finds young brains
harmed by urban air pollution

Air pollution may be affecting young brains in Mexico City. (Photo by Kim Seng)

By all appearances, Maria Fernanda is a normal 13-year-old girl. She comes from a good family, lives in a neighborhood with trees and dogs and attends a good school. She has a high IQ and is clinically healthy. There’s just one problem: The air she breathes is sabotaging the development of her brain.

Fernanda is a middle school student in Mexico City, the largest metropolis in the western hemisphere, home to 20 million people, roughly 4 million cars and some of the most polluted air on Earth. She should represent the best and brightest of her country’s future. Instead, her body bears the marks of air pollution’s most insidious side effects.

Because of the particulate matter entering her body with every breath, Fernanda’s lungs resemble those of a smoker. Her brain is spotted with lesions in her white matter — a condition seen in patients with Alzheimer’s disease and vascular dementia. Her heart is strained, her IQ has dropped six points in the past five years, and she’s having trouble focusing in school. Worse, in a city with 8 million children, Fernanda is far from alone.

"Everybody’s affected," says Dr. Lilian Calderón-Garcidueñas, an associate professor at UM’s College of Health Professions and Biomedical Sciences who studies air pollution and brain development in Mexico City.

Calderón-Garcidueñas first became aware of the health effects of Mexico City’s air pollution when she was chief of research at the Naval Medical Center there. Visiting staff members complained of nosebleeds and headaches whenever they came to the city. Calderón-Garcidueñas started researching the effects of pollution on the hearts and lungs of dogs. Then her daughter, who was in medical school at the time, suggested she look at the dogs’ brains. What Calderón-Garcidueñas saw was disturbing. Dogs as young as 11 months had brain lesions that were reminiscent of Alzheimer’s disease.

The implications were troubling. An 11-month-old dog is equivalent in age to a 7-year-old child. Could children be suffering from the same lesions? Calderón-Garcidueñas shifted her research from dogs to humans, leading her to children such as Fernanda.

Calderón-Garcidueñas has studied Fernanda closely since she was 5 years old. In that time, the lesions in her prefrontal cortex have expanded, impairing her problem-solving skills, attention span and goal-directed behavior. As a result, Fernanda’s cognitive performance for select tasks is several years below her age.

The delay in her brain’s development doesn’t bode well for Fernanda’s teenage years, when her stunted decision-making skills may make her vulnerable to peer pressure. Fernanda’s stable family will help her navigate those difficult times, but not all children are as lucky. And not all victims of Mexico City’s air pollution are children.

Mexico City sits in a valley at almost 8,000 feet — about the same elevation as Aspen, Colo. — and is surrounded by mountains on three sides. Millions of vehicles and tens of thousands of factories emit contaminants into the air, which are trapped by frequent inversions.

"The air doesn’t go anywhere," Calderón-Garcidueñas says. "We call it the biggest exposure chamber ever. Heart conditions are common in people younger than 30. Adults, in general, present an increase in the number of massive heart attacks, development of tumors in nasal passages and, in some cases, the clogging of their liver."

The effects of pollution can be detected empirically. First, many people have lost their sense of smell. Calderón-Garcidueñas says that in the dogs and humans olfaction is one of the first parts of the brain damaged by air pollution. Second, people’s memories are poor.

"You ask them what they had for dinner, and they look at you blankly," Calderón-Garcidueñas says. Road rage on the traffic-choked streets also is common. Air pollution causes neural inflammation, which alters the brain’s behavioral control centers and leads to increased aggression, Calderón-Garcidueñas says.

The effects of air pollution have implications at home, at work and in between. But the citywide scale of the symptoms also helps obscure them.

Lilian Calderón-Garcidueñas says pollution in many cities threatens brain development in children."Many people are not aware of their deficiencies," Calderón-Garcidueñas says. "Everybody has the same problems, so it becomes normal. And people adjust."

Mexico City certainly isn’t the only city where pollution causes major health risks. Tokyo, New Delhi, Shanghai and other global metropolises all have alarming levels of air pollution. "I don’t know of any major city that’s clean," Calderón-Garcidueñas says.

But Mexico City’s pollution is compounded by its unique geography and sheer size. The city’s factories constitute a major part of the national economy. Their emissions are the collateral damage of a booming industrial sector.

Meanwhile, these emissions are inhaled by children such as Fernanda. Particulate matter in the air is passing through her blood brain barrier and causing lesions in her white matter — the tissue that connects the regions of the brain. Calderón-Garcidueñas estimates that in 50 years, children like Fernanda will develop full-blown Alzheimer’s or Parkinson’s disease.

"There is a 50-year window of opportunity to avoid a 10-year-old kid becoming a 60-year-old who says, ‘I don’t know where I put my car,’" Calderón-Garcidueñas says. "By the time you get to that stage, there’s nothing I can do, as a physician, to help you."

In the meantime, however, some activities can help mitigate the damages to children’s brain development. Chief among them is building up a child’s cognitive reserve through mental calisthenics such as learning a second language. Exercise helps, too, although it must be done indoors to be beneficial.

A good diet also is important. Calderón-Garcidueñas recently found that doses of dark chocolate reduced neuro-inflammation in mice. Broccoli has been shown to do the same. You can’t take all the children out of Mexico City, Calderón-Garcidueñas says, so you have to find ways to help them where they are.

Now Calderón-Garcidueñas is turning her attention to the factors that make children more susceptible to the pollution. Is it genetics? Stress? Nutrition? "Who is most affected?" she wonders. "And more importantly, how can we help them?"

The fate of Mexico City’s children — and children in cities around the world —hangs in the balance.

"Millions of exposed children need to be protected from the harmful effects of air pollution," Calderón-Garcidueñas says. "Preventative medicine is our goal."

The issue is an urgent one. Learning how pollution damages the brain, and what can be done to prevent it, will help children like Maria Fernanda grow into the healthy, smart young woman that she should.

— By Jacob Baynham 

Next >