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What is the ozone doing right now in Grass Valley? Click here to find out. You can also download a comma delimited file to your own computer and manipulate the data anyway you like. If you have any feedback, please feel free to contact Joe and give him a piece of your mind. If you want to know what the data means, well, that's going to require you to educate yourself about a host of ozone related facts. Sorry, but some information in life is complicated and requires a bit of foundational knowledge to place that information in the proper context.  Facts rarely exist in a vacuum. Only "believing what you want to believe" can safely be done in complete ignorance.



What Is Ozone, And Why Is It Here?

Most of Nevada County’s ozone is transported by wind from the Sacramento and Bay Areas.  Ozone is formed by volatile compounds (VOC or ROG) and oxides of nitrogen (NOx) reacting in sunlight, especially on hot days.  Ozone is an unstable 3-oxygen molecule that oxidizes substances it contacts.  High ozone levels reduce the elasticity of our lungs and cause breathing problems, burning eyes, sore throats and headaches.  It has been connected with the development of asthma and decreased lung function.  Children, the elderly, individuals with heart and lung ailments, and people exercising outdoors are especially affected.  Ozone also damages rubber, paint, plastics and plants, reducing vegetable yields and timber productivity.  Nearly half of California’s ozone is from car and truck exhaust.  The rest is from power production, off-road equipment, industry, consumer products, vegetation and other sources.

 What Is Non-attainment?

Federal law establishes health-based ozone standards.  Failing to meet those standards results in an area being designated as “non-attainment.”  In 2004, Western Nevada County (west of a line near Soda Springs) was designated non-attainment for the federal 8-hour Ozone Standard of 0.08 ppm.

 What Does The Non-Attainment Designation Mean?

The Federal Clean Air Act sets requirements for non-attainment areas.  Western Nevada County must prepare an Attainment Plan that meets these requirements and shows how ozone levels will be lowered to meet the standards as expeditiously as practicable.  Over the past year, the District adopted all applicable “reasonably available control technologies.”  Major air pollution sources are subject to an emission offset program, and federally funded projects such as highway improvements must be shown to not make the problem worse.  Another requirement is that Western Nevada County must reduce its emissions of ozone precursors by at least 3% per year.  Most necessary reductions are expected from Statewide measures and from cars becoming cleaner.  Additional requirements vary depending on an area’s classification, which is tied to a demonstration that the standard can be met by a specific year. 

 What’s New?

Western Nevada County was originally classified by EPA as a Basic non-attainment area.  A recent court ruling discarded this classification, so EPA must reclassify such areas. Western Nevada County’s new classification will depend on EPA’s process and on how fast the Sacramento Area can reduce emissions.  Also, EPA has proposed a more stringent standard, based on health data, to be finalized in 2008.

 What Happens If The Federal Requirements Are Not Fulfilled?

Several things could happen, depending on which requirements are not met.  EPA might not allow any major sources to be constructed; pollution offsets could jump to a ratio of at least 2:1; federal highway money could be withheld; additional pollution control measures could be mandated; and/or EPA could specify additional requirements.  The County could also become vulnerable to lawsuits.

 What Are The Upwind Districts Doing?

The Bay Area is not allowed to relax pollution control strategies, and the Sacramento area has to reduce emissions by 3% per year.


Additional Resources: 


EPA has proposed revisions to the federal ozone standards.  The Federal Register notice may be found at http://www.epa.gov/ttn/naaqs/standards/ozone/data/frnotice_07-11-07.pdf. 


The following site contains background information for EPA’s proposed ozone standard revisions as well as an excellent 3-part report published in 2006 documenting current scientific understanding and significant research regarding ozone.  That report is available via the three links near the bottom of the following EPA web site: 



A link to ozone data from monitoring sites around the State, including western Nevada County:  http://www.arb.ca.gov/aqmis2/aqmis2.php


50 Things You Can Do To Reduce Ozone



The California Air Resources Board’s page on Air Quality Data, Emissions Inventory and Modeling provides comprehensive information on various types of air pollution:



Finally, information on the State’s ozone attainment plan can be found at: