National Ambient Air Quality Standards (NAAQS) Update
by Nate Stroup, Quality Assurance and Monitoring Coordinator

The Clean Air Act, which was last amended in 1990, requires EPA to set National Ambient Air Quality Standards (NAAQS) for wide-spread pollutants from numerous and diverse sources considered harmful to public health and the environment. The Clean Air Act requires periodic review of the science upon which the standards are based and the standards themselves. There are several NAAQS that are being revised in the upcoming year by the Environmental Protection Agency. Here is the status of those NAAQS:

Ozone (O3)
The previously proposed 2008 8-hr primary O3 standard of 75 parts per billion (ppb) is being reconsidered. The level of the standard being evaluated is between 60 and 75 ppb. A final rule is expected in July of 2011. Possible changes may include a revised O3 season for some parts of the country by 2012 or 2013.

Oxides of Nitrogen (NOx)/Oxides of Sulfur (SOx)
A proposed secondary standard for NOx/SOx is anticipated to be complete by July of 2011. The final rule is expected in March of 2012. The rule will focus to protect against aquatic acidification. A potential element of the rule includes dividing the nation into 84 ecologically relevant regions for monitoring, as opposed to viewing regulated areas strictly along state lines.

Carbon Monoxide (CO)
A notice of proposed rulemaking was issued for CO in February 2011. The proposal includes retaining the current CO standard. CO monitoring near roadways will, however, be required in areas that meet a certain population threshold. Public comment closes on this rule on April 12, 2011. The final rule is expected in August of 2012.

Sulfur Dioxide (SO2)
A proposed hybrid monitoring/modeling approach is being considered to assess compliance with the one-hour standard. A refined source-oriented dispersion model would be used to identify violations and determine compliance.

Particulate Matter (PM) below 2.5 Microns in Diameter (PM2.5)
A proposal to revise the current PM2.5 standards is expected to be released sometime during 2011. Both standards are expected to be lowered from the current levels: 35 micrograms per cubic meter (µg/m³) for 24 hour average and 15 µg/m³ for the annual average.

Near-Roadway Monitoring for Nitrogen Dioxide (NO2)
A final draft of the technical assistance document (TAD) for establishing near-roadway monitors for the measurement of NO2 will be issued in fall of 2011.