Normal air pollution is a mixture of local and distant sources. In Beijing, roughly half comes in from outside. The outside component passes through regular quasi-weekly cycles. I call them sawtooths, because they rise gradually over several days, then crash in just a few hours as a cold front passes and bring clean air from Mongolia. Superimposed on this gradual increase are strong daily cycles of local origin.
Pollen counts and particle counts are two very different things. Pollen counts tend to be local, because the grains are relatively large and do not usually stay in the air for more than some hours. Particle counts are dominated by the finest particles, which have long-enough lifetimes to travel hundreds to thousands of miles. Particle counts do not represent total mass well, because the larger particles have 1000 times more mass per particle than the smaller particles.
Regarding where to live, I sympathize with you. It all depends on what you are most sensitive to. We in the U.S. have cleaned up our atmosphere so much that I don't think it is a major factor anymore in choosing where to live. The exceptions could be in places like the Southeast (Atlanta and Houston come to mind), where the burgeoning population and the climate promote the formation of ozone. But if you are not sensitive to ozone, it shouldn't bother you.
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