Findings by University of Montana Professor Dr. Lilian Calderón-Garcidueñas, MA, MD, Ph.D., and her team of researchers reveal that children living in large cities are at increased risk for brain inflammation and other neurodegenerative changes, including Alzheimer’s and Parkinson’s disease.
Calderón-Garcidueñas’ findings are detailed in a paper in the Journal of Alzheimer’s Disease.
The study found when air particulate matter and their components such as metals are inhaled or swallowed, they pass through damaged barriers — including respiratory, gastrointestinal and the blood-brain barriers — and can lead to long-lasting harmful effects.
Air pollution is known to affect small and large blood vessels throughout the body, leading to an increased risk of cardiovascular conditions like stroke and heart attack. By permanently affecting vascular structures in the brain, air pollution can also have serious effects on neural functioning and neural matter.
In past studies assessing exposure to pollutants in animals, Calderón-Garcidueñas and colleagues have found that air pollution causes damage to the central nervous system by altering the blood–brain barrier, causing neurons in the cerebral cortex to degenerate, destroying glial cells found in white matter, and by causing neurofibrillary tangles. These changes can permanently alter brain structure and chemistry, resulting in various impairments and disorders.
Sometimes, the effects of neural remodeling do not manifest themselves for a prolonged period of time, while others can be seen as early as childhood.
Air pollution causes healthy children to make ‘autoantibodies against their own brain components’
In the new study, Calderón-Garcidueñas and her team compared 58 serum and cerebrospinal fluid samples from a control group living in a low-pollution city and matched them by age, gender, socioeconomic status, education and education levels achieved by their parents to 81 children living in Mexico City.
The results found that the children living in Mexico City had significantly higher serum and cerebrospinal fluid levels of autoantibodies against key tight-junction and neural proteins, as well as combustion-related metals.
“We asked why a clinically healthy kid is making autoantibodies against their own brain components,” Calderón-Garcidueñas said. “That is indicative of damage to barriers that keep antigens and neurotoxins away from the brain. Brain autoantibodies are one of the features in the brains of people who have neuroinflammatory diseases like multiple sclerosis (MS).”
The issue is important and relevant for one reason, she explained. The breakdown of the blood-brain barrier and the presence of autoantibodies to important brain proteins will contribute to the neuroinflammation observed in urban children and raises the question of what role air pollution plays in a 400 percent increase of MS cases in Mexico City, making it one of the main diagnoses for neurology referrals.
Calderón-Garcidueñas points out that there is a need for a longitudinal follow-up study to determine if there is a relationship between the cognitive deficits and brain MRI alterations previously reported in Mexico City children, and their autoimmune responses. But what is clear is that the kids are suffering from immune dysregulation.
Childhood exposure to pollutants ‘is of pressing important for public health’
Once there is a breakdown in the blood-brain barrier, not only will particulate matter enter the body but it also opens the door to harmful neurotoxins, bacteria and viruses. “The barriers are there for a reason,” she explains. “They are there to protect you, but once they are broken the expected results are not good.”
The results of constant exposure to air pollution and the constant damage to all barriers eventually result in significant consequences later in life. She explains that the autoimmune responses are potentially contributing to the neuroinflammatory and Alzheimer’s and Parkinson’s pathology they are observing in young urban children.
While the study focused on children living in Mexico City, others living in cities where there are alarming levels of air pollution such as Los Angeles, Philadelphia-Wilmington, New York City, Salt Lake City, Chicago, Tokyo, Mumbai, New Delhi or Shanghai, among others, also face major health risks. In the U.S. alone, 200 million people live in areas where pollutants such as ozone and fine particulate matter exceed the standards.
“Investing in defining the central nervous system pathology associated with exposure to air pollutants in children is of pressing importance for public health,” Calderón-Garcidueñas said.
Indeed, several recent studies suggest that the brain may be particularly susceptible to the toxic effects of air pollution. While we’ve long known that air pollution has presented various health risks such as cardiovascular disease and ischemic heart disease, research also links exposure to pollutants with pathological changes in the brain leading to conditions like autism and schizophrenia, as well as declines in cognitive abilities and poorer mental functioning.
In 2011, researchers used air samples from the congested Interstate 110 freeway near the University of Southern California campus, to recreate the polluted freeway atmosphere in a laboratory. After exposing mice to the air for a total of 150 hours over 10 weeks, the team found that the contaminated air kept neurons from developing, resulting in permanent brain damage. The researchers theorized that the air would have the same effect on humans.
“Our data would suggest that freeway pollution could have a profound effect on the development of neurons and brain health in children and young kids,” said Todd Morgan, lead author of the 2011 study, as quoted in the Los Angeles Times, “especially those who attend schools built alongside freeways.”