Air pollutants affect the central nervous system and can cause neuroinflammation when the body tries to attack it. If pollution from the air continues to make its way into the body, this can lead to chronic neuroinflammation. As polluted air particles enter the body, it goes through the lungs and can enter the bloodstream, allowing them to travel to the brain. In many cases, they are able to work their way past the blood brain barrier. Combine this with the chronic neuroinflammation and you end up with issues that are fundamentally changing brain structure, brain chemicals, and behavior. One of the biggest issues is the breakdown of the myelin sheath, which is needed to protect the axons. The scientists here studied adults in both the U.S. and in Denmark and chose people from places with varying degrees of air pollution. The results indicated that people who live in areas with more pollution had a much greater percentage of the population with illnesses like bipolar disorder, major depression, and personality disorders . The study of the people in Denmark went a little longer to see the more long-term effects for older adults, which saw an increase in diseases like Parkinsins and Alzheimer's. The study also accounted for differences in gender and race. 

The purpose of this study was to determine if people who were pre-disposed to depression genetically, would be more impacted by air pollution. The study did tests and chose individuals that had the genetic risk mechanisms associated with depression. They then got each individuals addresses so they could find the nearest air monitoring stations near where they lived. This way they could measure the differing levels of air pollution based on where these people lived. The test subjects were then instructed to perform WM maintenance/stress tests. While they were taking their tests, they would get scans of their brain using an fMRI to measure the cortical and subcortical brain networks associated with depression. The results of the study showed that areas with more air pollution/lower air quality, greatly influenced/activated depression-related connectivity networks. It shows that people who are pre-disposed to depression are more likely to develop symptoms in places with higher levels of air pollution. 

The purpose of this study is to see if ambient air pollution (PM 2.5) has adverse effects on brain matter/structures in older women. They surveyed women who were part of the Women's Health Initiative Memory Study. They took structural brain magnetic resonance imaging scans in order to obtain the volumes of grey and white matter within the various structures of the brain. They then figured out the pollution levels of where these women lived using existing air monitoring data of their areas. The results found that women exposed to more air pollution had significantly smaller white matter volumes, but the volume of grey matter didn't. These adverse effects on white matter volumes was found in the frontal lobe, the temporal lobe, and the corpus callosum. However, hippocampal volumes didn't differ. They also noted that further data would be needed to see if there was any myelination disturbance, disruption of axonal integrity, or damages to oligodendrocytes. 

Chen, T., Lo, Y., Li, S., Lin, Y., Chang, C., Liang, Y., Laiman, V., Hsiao, T., Chuang, H., Chen, Y. "Assessing traffic-related air pollution-induced fiber-specific white matter degradation associated with motor performance declines in aged rats." Ecotoxicology and Environmental Safety, vol. 263, 2023, pp. 1-13.  

Nathan, C., Calingasan, N., Nezezon, J., Ding, A., Lucia, M.S., La Perle, K., Fuortes, M., Lin, M., Ehrt, S., Kwon, N.S., Chen, J., Vodovotz, Y., Kipiani, K., Beal, M.F. "Protection from Alzheimer’s-like disease in the mouse by genetic ablation of inducible nitric oxide synthase." The Journal of Experimental Medicine, vol. 202, 2005, pp. 1163-1169. 

The purpose of this study was to test the impact of early and/or late exposure to concentrated ambient ultrafine particles (CAPS) on behavior, neurobiological, and cognitive functions in mice. The research examined behaviors like impulsivity, learning/memory, and locomotor activity. They also assessed brain neurotransmitters, amino acids, and glial markers in brain regions associated with these functions. They did this testing four groups based on postnatal/adult exposure. The groups would be both postnatal and adult groups being exposed to air, postnatal exposed to air and adult exposed to CAPS, postnatal exposed to CAPS and adult exposed to air, and both exposed to CAPS.  The results indicated that both males and females experienced short-term memory impairment and had a preference for immediate reward associated with impulsivity. Locomotor activity also saw impairment as well. Changes also occurred in the dopamine and glutamate systems. The study revealed alterations in amino acids in hippocampal regions, which could lead to excitotoxicity. Persistent glial activation was observed in the frontal cortex and corpus callosum in both sexes, indicating enduring and sex-dependent neurotoxicity. Overall, the study suggests that exposure to air pollution during critical development stages and at stages later in life can lead to detrimental changes in behavior, can harm the central nervous system, and lead to various diseases/disorders. However, more research is needed to fully understand the exact mechanisms behind the effects.