Today the Arizona Department of Environmental Quality issued the following warning:

FORECAST: Ozone levels will be in the MODERATE to Unhealthy for Sensitive Groups range this week. PM-10 (coarse Particulate Matter) and PM-2.5 will be in the MODERATE range.

An OZONE HEATH WATCH has been issued
for Monday, July 26, 2010

An Ozone “Health Watch” is in effect today for Sensitive Groups. Ozone levels for the rest of the week will be difficult to forecast and may fluctuate due to considerable cloud cover and the possibility of an active monsoon period.

(*Unhealthy for Sensitive Groups: People with heart or lung disease, older adults, and children should reduce prolonged or heavy exertion.)

Valley residents are encouraged to:
- Reduce their driving
- Carpool, ride transit, telework
- Refuel after dark 
- Refrain from using gasoline powered garden equipment or charcoal BBQs.

Todays air quality warning references the current EPA standard of an 8-hour Average Ozone level of 0.075 ppm

On January 6, 2010, the EPA proposed to strengthen the national ambient air quality standards (NAAQS) for ground-level ozone, based on scientific evidence about ozone and its effects on people and the environment. The proposal to strengthen the primary standard places more weight on key scientific and technical information, including epidemiological studies, human clinical studies showing effects in healthy adults at 0.060 ppm.   When this new standard takes effect it is likely that the Arizona Department of Environmental Quality will issue more frequent Ozone “Health Watch”  alerts.

Ground-level ozone is generated when sunlight hits emissions from car exhaust, chemical plants, refineries, and other sources.  It occurs naturally in the Earth’s upper atmosphere and protects us from damaging effects of the sun, but when it’s released at ground level, it becomes a health risk. The more sunlight the more ozone is generated  so it is no mystery why Phoenix has a problem with unhealthy ozone levels not only during the summer but year round.

In 2008, metro Phoenix exceeded the federal health standard for ozone on 28 days, compared with none in 2007 and nine in 2006.