Nitrogen dioxide (NO2) is one of a group of highly reactive gasses known as "oxides of nitrogen," or "nitrogen oxides (NOx)." NO2 can be formed
naturally by lightening strikes, from plants and soil, however it is also formed through the internal combustion process that uses air as the oxidant.
On September 22, 2012, the EPA adopted a new 1-hour NO2 standard at the level of 100 parts per billion and retained the existing annual NO2 standard
of 53 ppb.
A key part of the new 1-hour standard is the new ambient air monitoring network and reporting requirement:
- In urban areas, monitors are required near major roads and areas where major concentrations are expected
- Additional monitors are required in large urban areas to measure areas with the highest NO2 concentrations
- The new monitoring system must be in place and fully compliant by 2013
- The first non-attainment designations for the 1-hour standard (with a compliant monitoring system) will be in the 2016 to 2017 timeframe.
EPA Nitrogen Dioxide (NO2) Home Page:
Ozone is found in two regions of the Earth's atmosphere, in the upper regions where it prevents damaging ultraviolet light
from reaching the Earth's surface, and ground level . Both ground level and upper region ozone has the same chemical
composition of (O3).
- Ozone is caused by the interaction of sunlight and nitrogen oxides
- When nitrogen oxide is present in the air, and sunlight hits the nitrogen oxide, this results in the creation of ozone
The 8-hour ozone standard was last revised in 2008 from .084 to.075 parts per million. EPA undertook the process of
revising the standard over the 2010 to 2011 timeframe however, on September 2nd, 2011, the EPA was instructed to
withdraw the revision. The EPA will now review the standard under the following schedule:
- First draft due April 2012
- First proposal due October 2013
- Final rule by July 2014
EPA Ozone (O3) Home Page:
Particulate matter is a term used to describe a mixture of a complex group of fine airborne solid particles and liquid droplets (aerosols) which includes components of nitrates, sulfates, elemental carbon, organic carbon compounds, acid aerosols, trace metals, and geological material.
EPA has developed two PM standard categories:
- PM10 which are particles with a diameter smaller that 10 micrometers and larger than 2.5 micrometers and are known as "Inhalable coarse particles," such as those found near roadways and dusty industries
- PM2.5 which are particles with a diameter smaller than 2.5 micrometers and are known as "Fine particles“
On December 14th, 2012 the EPA concluded a revision of the PM2.5 fine particle standard. The results of the revision include:
- Retained the 24-hour standard at 35 ug/m3. This was last revised in 2006.
- Strengthen the annual fine particle standard from 15 down to 12 ug/m3
- EPA modeling projects/estimates this revision will result in 66 non-attainment counties, however they will utilize a two-year review process and will finalize non-attainment designations by December, 2014.
- Adds a “heavily traveled road in large urban areas” monitor requirement which will require the re-location of 52 of the existing 900 monitors.
- The 12 ug/m3 standard is to be met by 2020, however states can request and an additional 5-year extension.
- State implementation plans (SIPs) are due 2018 that outline the steps that each state (in nonattainment) will take to meet the standard.
EPA Particulate Matter Home Page: