My question earlier this week about Beijing's ozone levels has been answered, but it does not satisfy my curiosity. I was wondering how Beijing's ozone compared to the San Joaquin Valley's levels.

According to today's Washington Post, officials monitor ozone but they don't tell the public what the numbers say.

There is no way to compare Beijing to the Valley. But I just realized I have my own unscientific yardstick.

My son, Joseph, spent six months in Beijing in 2007. He is a long-time runner. He said outdoor exercise hurt his lungs.

When he returned to Fresno in September that year, he remarked that the sky looks really blue here compared to Beijing. He said he could breathe much easier here.

China has more than ozone problems, though. Sulphur dioxide and nitrogen dioxide pollution from cars, factories, pulp mills and other industries can get to dangerous levels.

Still, there may be value in publicly confronting the smog problem and telling people about the levels of ozone, which is a corrosive gas that triggers lung disease.