Ozone is a colorless gas composed of three atoms of oxygen. Ozone occurs both in the Earth's upper atmosphere (good ozone) and at ground level (bad ozone). Ozone can be good or bad for human health and the environment, depending on where it is found:
Ozone occurs naturally in the Earth's upper atmosphere where it forms a protective layer that shields us from the sun's harmful ultraviolet rays. Manmade chemicals are known to destroy this beneficial ozone and can create ozone “holes.”
On the ground level, ozone is not emitted directly into the air, but is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC). This happens when pollutants emitted by cars, power plants, industrial boilers, refineries, chemical plants, and other sources react chemically in the presence of sunlight. Ozone is most likely to reach unhealthy levels on hot sunny days in urban environments, which is why Phoenix is so susceptible to ozone concerns. Ozone at ground level is a harmful air pollutant. Learn more about Ozone and related health concerns from EPA
What is being done in Phoenix?
In 2019, The City of Phoenix alone reduced commuting miles by 25 million by participating in the Travel Reduction Program, preventing 143 tons of pollution. For Maricopa County results, click here (PDF).
The Environmental Protection Agency (EPA) selected the City of Phoenix as a recipient of the Diesel Emission Reduction Act (DERA) grant. The proposed project for vehicle replacement and technology installations will achieve significant reductions in diesel emissions in terms of tons of pollution produced and directly improve air quality. These grants will reduce NOx, PM2.5, HC, and CO emissions from diesel fleets over the remaining lifetime of the affected engines, thereby reducing local and regional air pollution and fleets impact on resident's health.
In October 2017, Phoenix recieved a DERA grant to replace 17 model year 1997-2003 heavy-duty diesel municipal vehicles with vehicles powered by model year 2017, or newer engines. The project will also involve the installation diesel oxidation catalyst (DOC) exhaust retrofit devices on 10 heavy-duty diesel fire pumpers. Learn more (PDF)
In October 2019, Phoenix recieved a DERA grant that will help replace 10 Class 8 diesel refuse trucks with year 2019 or newer Class 8 trucks powered by compressed natural gas. Learn more (PDF)
What you can do to reduce ozone:
- Consider alternative modes of transportation like walking, riding a bike, car or van pool, or using public transportation.
- Avoid waiting in long drive-thru lines, for example, at coffee shops, fast-food restaurants or banks. Park your car and go inside.
- Re-fuel your vehicle after dark (or during cooler, evening hours).
For current Air Quality conditions click the photo below.