Smog can negatively affect brain development in children
Air pollution has a negative impact not only on the respiratory and circulatory systems, but also on the nervous system, and children are particularly vulnerable. Pollution causes inflammation of the nerve tissue and may increase the risk of developing Alzheimer’s disease later in life.
Air quality is usually determined by the concentration of six pollutants: particulate matter (PM), ozone (O3), carbon monoxide (CO), sulfur dioxide (SO2), nitrogen oxide (NO) and lead (Pb). The most harmful to the nervous system are PM2.5 particulates (particles with a diameter less than 2.5 μm) and ultrafine particles UFP (particles with a diameter less than 0.1 μm).
Although air pollution is harmful to everyone, children are especially sensitive to it. This is due to their faster breathing and less developed natural barriers in the lungs. The development of natural barriers such as the blood-brain barrier, the lining of the nose, gut and lungs are very important for the healthy development of a child. Research indicates that these barriers are broken in children exposed to air pollution, reducing the brain’s ability to protect itself from toxins and dust.
Air pollutants entering the body trigger a response from the innate immune system. Cytokines such as interleukin-1β, interleukin-6 and tumor necrosis factor (TNF-α) increase in blood and cerebrospinal fluid. These cytokines are responsible for the development of the inflammatory response, which leads to inflammation of the nerve tissue in the brain and its damage and a decrease in density. Structures undergoing damage include the frontal and prefrontal cortex, the olfactory bulb, and the hippocampus, which are essential for cognitive functioning.
The brains of children exposed to high air pollution also develop disorders of myelination – clusters of white matter or areas on neurons without the myelin sheath, which impede communication between neurons.
It has also found that children developing in polluted air contain proteins that are characteristic of Alzheimer’s disease. These are the hyperphosphorylated tau protein and amyloid-beta (Aβ) protein clusters. It has also been noticed that children who carry the ApoE allele 4 (a well-known risk factor for Alzheimer’s disease) have higher levels of these proteins than carriers of the more common allele 3 of this gene. This is a good example of what a gene-environment interaction is all about. Children who carry the 4 allele and who live in polluted air are especially prone to developing Alzheimer’s disease later in life. Moreover, Alzheimer’s disease patients who have high levels of tau and Aβ have a faster cognitive decline than patients who have lower levels of these proteins.
Research has shown that children living in the Mexican metropolitan area perform lower on cognitive tests than children developing in places with better air quality. In turn, studies conducted among children living, among others, in New York, Boston and Barcelona showed that pollution from heavy car traffic can negatively affect children’s behavior, reducing their attention span.
Brockmeyer S., D’Angiulli A. (2016). How air pollution alters brain development: the role of neuroinflammation. Translational Neuroscience, 7(1), 24-30. (text at degruyter.com)
Author: Maja Kochanowska