San Diego is choking in smog. I just returned from a vacation there over the holidays and decided to look up the air quality at the weather website. I was getting headaches every day and found that the air was "unhealthy for sensitive groups." I don't know if the required gasoline blend to alleviate smog is keeping the situation from getting worse. San Diego is not known for its bad air (like LA) and who knows if that will have an impact on the important tourism industry there. There are trade offs to consider.