Prolonged contact with polluted air can lead to structural changes in the brain’s nerve cells and, consequently, to problems with remembering and learning, and even to depression, indicate research on mice, published in Molecular Psychiatry.
According to lead author Laura Fonken of Ohio State University, these results provide further evidence of the harmful effects of air and environmental pollution on health.
As the researcher reminds, earlier studies have shown that air pollution harms the circulatory system and the lungs. Scientists from her university have shown, for example, in mice that the pollutants referred to as fine dust – PM2,5 cause a general inflammatory process in the body and may contribute to the development of hypertension, obesity and diabetes.
PM2,5 are airborne solid particles (e.g. soot) and liquid particles up to 2,5 microns in diameter (one-thirtieth the thickness of a human hair). They come from, among others from burning coal in old furnaces, illegal waste incineration, from factories and incomplete combustion of diesel fuel. These particles reach the upper respiratory tract, lungs and can penetrate the blood.
Recent studies show that the consequences of the inflammation caused in the body by PM2,5 also apply to the central nervous system.
The mice tested by the Fonken team were kept in an atmosphere contaminated with PM2,5 for 6 hours a day, five days a week for 10 months (almost half of their lives). A control group of rodents was kept in clean filtered air at this time.
After 10 months, the animals underwent a series of tests assessing memory and learning abilities as well as behavior consistent with depression and anxiety disorders in humans.
They found that rodents exposed to PM2,5 took longer to learn to find their way out of a brightly lit space to a safe burrow than mice in the control group. They were also less likely to remember the exit location for longer. Moreover, they exhibited more behaviors consistent with depression and anxiety in humans.
Further research showed that mice inhaling the polluted air were more likely to have symptoms of inflammation in the hippocampus, the brain structure that regulates learning, memory, and mood. At the same time, researchers found changes in the structure of nerve cells in the hippocampus, especially in the structure of the projections of neurons known as dendrites. They were not only shorter, but also had fewer dendritic spines, i.e. structures involved in the formation of nerve synapses and the transmission of information between nerve cells.
Earlier work has shown that this type of brain change is associated with deterioration in learning and memory, recalls study co-author Dr Randy Nelson.
Evidence that exposure to environmental pollution may worsen the mental abilities of children was previously found, among others, by Polish scientists led by prof. Wiesław Jędrychowski from the Collegium Medicum of the Jagiellonian University. In their work, published in 2010 in the journal Environmental Health Perspectives, they showed that children whose mothers were pregnant were exposed to higher concentrations of polycyclic aromatic hydrocarbons (PAHs), present not only in cigarette smoke and diesel exhaust fumes, but also fried or grilled foods, at the age of 5, achieved worse results in tests assessing mental abilities. (PAP)