Researchers at Harvard School of Medicine have discovered that a type of small particle pollution that can be given off by car exhausts can lead to brain damage as serious as aging your brain 1 year. They looked at scans of over 900 seniors, age 60 and comparing the seniors who lived in highly polluted air of a city to those who lived in places with less air pollution they saw that the seniors who lived in the more polluted areas had a ".32 percent reduction in brain volume" and a "46 percent higher risk of mini-strokes" than those who lived in less polluted air. The researchers now believe this is the most solid evidence that their is association between high levels of pollution and brain damage.
So this is the most a huge problem for people who live in cities. One of the biggest concerns is the mini-strokes. These are a big concern because they do not do as much damage as a large stroke so most people do not realize that they are having them. They get symptoms that they may associate with aging like dizziness or blurred vision. They will not realize what is happening and if they continue they can do real damage if they happen in certain parts of the brain. All of these things are major concerns for people who live in cities.