Air Quality Five Greenest Cities, 9:44 am, 06/06/2009

1) Portland, OR, 20, 12. Very Clean!

2) San Francisco, CA, N/A, Good. 

3) Boston, MA, 27, 32, forecast Good. 

4) Oakland, CA, N/A, Good. 

5) Eugene, OR, 16, 4. Very Clean!

http://www.popsci.com/environment/article/2008-02/americas-50-greenest-cities?page=1