Standing at the rim of the Grand Canyon 35 years ago was one of the most dramatic experiences of my life. Revisiting this summer, I was stunned and confused with the view, until I read a sign posted right at the rim about air pollution. Air pollution at this natural wonder far from cities and industry! In summer, the pollutants blow in from far away places like California, southern Arizona, and northern New Mexico. On a clear day, you can see the San Francisco Peaks boldy against the sky. This day was not such a day.