Earlier quoted context omitted.
Yes and no. Evolution theory would require those who get dementia to go extinct. Usually by the time you develop dementia, you already reproduced, so even if some people become "immune" to pollution, the others won't get removed from the gene pool.
This is an interesting angle. Next generation will pretty much be exposed to pollution by the moment they're born. Technically their kids will inherit a slightly mutated version already even though it might not yet be enough. Does our gene "remember" how much exposure it had accumulated from the previous generation? We often hear from the news how they found some individuals who were immune to certain diseases due to…
Your bodies DNA replication machinery also has an error rate which can be worked out, and you can extrapolate that to get a rate of mutation. Knowing this rate can give you an estimate of how long ago two species diverged based on the number of different bases when you line up their DNA sequences against eachother, for example.