The air in SF is very clean. The prevailing winds come from the very-wide pacific ocean and blow all the pollution across the Bay into Oakland and Berkeley.

It does however have a fog problem, because those nice clean prevailing winds are quite cold and moisture condenses rise when encountering the hills along the coast. This is in fact the major source of water for the coastal giant sequoias.

"Coast redwoods (Sequoia sempervirens) are distributed along a narrow band of California's northern coast. During the summer these red giants take advantage of the fog to capture water out of the air—and summer is the critical growing season for the trees, despite being California's dry season."

http://www.scientificamerican.com/article/fog-that-nourishes...

No, not really - the prevalent winds are from the west, and to the west is half a world of ocean. Pretty much any pollutants from SF itself are going to get blown east in short order.

Of course, they have a fog problem, but that's a different matter!

Perhaps you are thinking of Los Angeles?

In my experience, urine is a bigger problem with the smell of SF's air. Surely that's localized, though.

Right state, wrong city.

Los Angeles is the California city that is known for its smog problem. The US is big, so its easy to get the various cities confused.

It doesn't help that California is huge. San Francisco to Los Angeles is a 381 Mile (613.16 km) journey... which is 20% longer than the distance between Paris, France and Amsterdam, Netherlands.

I've lived here 10 years and there has been smog for 2 weeks of that time (during the mega drought this winter, when there was no wind or precipitation for months straight).