Air Quality Awareness Days

The EPA has designated June 29 - July 1, "Air Quality Awareness Days". This designation is well-timed--the past two weeks have seen an unusual number of very hot days with light winds across large areas of the U.S. This, combined with June's high levels of UV light (which is needed to drive the chemical reactions that make smog), have conspired to produce some of the highest levels of air pollution across the U.S. in many years. Ground level ozone, the primary pollutant of concern in the summer, has been a particular problem. The EPA standard for ozone pollution is 80 ppb for an 8-hour period. If three or more violations of this standard occur in a year, the offending city must take action to reduce emissions or pay fines. There are a lot of cities that will be paying big bucks to reduce emissions, thanks to this June's hot weather. A sampling of who's been violating can be seen in the animation below. Everywhere the image is orange (AQI greater than 100), is an ozone air quality violation.



Chicago has had multiple sampling sites violate the ozone standard on 7 consecutive days.

Houston or Dallas (or both) have exceeded the ozone standard nearly every day the past week, with Houston posting a very unhealthy 103 ppb over an 8-hour period on June 28.

Denver recorded ozone violations at 2 locations on June 18.

California continues to lead the U.S. in air quality violations. If we take a look at the list of the 10 U.S. cities with the most ozone air pollution violations for 2004, five of the top seven cities are in California:

Number of 2004
City ozone violations
---------------------------------
Bakersfield,CA 103
Riverside, CA 88
Los Angeles, CA 65
Houston, TX 37
Sacramento, CA 25
Fresno, CA 23
Dallas, TX 20
Ventura, CA 17
Ft. Worth, TX 15
Orange County, CA 12

As part of Air Quality Awareness Days, the EPA urges everyone to be more aware of the types of air pollution their area encounters. They also have suggestions on what to do to protect your health during a high pollution event, and how you can cut down our contribution to air pollution levels. I highly recommend the EPA Airnow web site for those interested to learn more.

The good news is that overall, we have been making progress on reducing ozone pollution in the U.S. Nationally, 2003 levels were 9% lower than 1990 levels and 21% lower than 1980 levels. However, these statistics were unadjusted to reflect variations in meteorology, and the real ozone improvements are less than this. Certainly, this summer's hot weather will skew the statistics, perhaps so far as to make it so no net progress in ozone levels may be seen when compared to 10 years ago.

Dr. Jeff Masters