The number of dirty-air days for smog has fallen almost by half in 2009. But it’s not all good news.
Here are some statistics of note:
Number of times the federal standard for ozone (75 parts per billion) has been breached in 2009, through August: 2,631.
Compared to the number during the same period of 2008: 5,022
States with smog problems in 2009: 37 plus DC
Most polluted county: San Bernadino, CA=86 days. (78 at one monitoring station)
Here are a few likely factors in the change from 2008:
Much of the drop from 2008 appears to be due to cooler, wetter weather which has inhibited smog formation or washed it away.
Here is an example of the weather phenomenon as described last month by a meteorologist with a Washington, D.C, tv station:
Much of the summer thus far has been noted by slightly cooler than average temperatures coupled with an active weather pattern that has yielded nearly daily chances of showers and storms. Compared to 2008 when we transitioned into a more “typical” D.C. summer pattern nearly on cue. Last years “typical” pattern consisted of hot and humid strings of days with a much lower daily opportunity for cleansing rains.
At the same time, the federal Energy Information Administration reports that electricity sales (particularly from coal-burning electric power plants) are down. http://www.eia.doe.gov/cneaf/electricity/epm/flash/august2009.pdf
And the Federal Reserve has noted that industrial production has generally been down though there was a slight uptick in July.
Although cars sales are down,the continuing turnover of the old fleet is leading to cleaner air because new cars meet tougher clean-air standards.
Some scientists are warning that global warming could make it more difficult to achieve clean-air standards in the future: http://www.nwf.org/extremeweather/