First exceedence of ozone standard since 2003
August 2007 –
The hot, stagnant days of August produced two code orange air quality days for the Roanoke Valley. On August 5, the particulate matter 2.5 (PM 2.5) monitor in Roanoke reported an air quality index (AQI) of 109. On August 15, the Roanoke Valley experienced its first violation of the ozone health standard since 2003, when the ozone monitor in Vinton reported an AQI of 104.
A code orange day is when the AQI falls within the range of 101 – 150. Code orange means that the air quality is unhealthy for sensitive groups. People with respiratory or heart disease, the elderly, and children should limit prolonged exertion.
The last code orange day was in 2005. On September 10, 2005, PM 2.5 reached an AQI of 104. The Roanoke Valley had 2 additional code orange days in August 2005, both for PM 2.5.
At ground level, ozone is formed by a series of reactions, under the influence of sunlight, involving volatile organic compounds (VOCs) combining with a group of air pollutants known as nitrogen oxides (NOx). VOCs and NOx are called ozone precursors. Volatile organic compounds are emitted by automobiles and various commercial and industrial sources. Nitrogen oxides are by-products of burning fuel in automobiles and heavy industries. Ozone, a colorless gas, is the main ingredient of smog.
Particulate matter, or PM, is the term for particles found in the air, including dust, dirt, soot, smoke, and liquid droplets. Particles can be suspended in the air for long periods of time. PM 2.5 refers to fine particles that are 2.5 micrometers in diameter and smaller. PM 2.5 is primarily the result of industrial burning, tailpipe emissions, smoke from wood stoves, and open and prescribed burning.
Despite the August 15 exceedence of the ozone health standard, the Roanoke Valley has experienced a reduction in ozone produced code orange days.
Ozone Exceedences Per Year (1990 – 2007)
(Number of Code Orange Ozone Days)
– source VA DEQ
To determine if an area is in compliance (attainment) with the ozone 8-hour health standard, EPA takes the fourth highest reading for three consecutive years then averages them. In April 2004, EPA designated the Roanoke area as nonattainment for the 8-hour ozone standard based on the 3-year average from 2001 – 2003.
However, Roanoke entered into an Ozone Early Action Plan (EAP), which deferred nonattainment designation. Roanoke Valley government leaders agreed to the EAP in December 2002. Shortly after, the Roanoke Valley-Alleghany Regional Commission formed an ozone task force to formulate the plan. The Greater Roanoke Valley Asthma and Air Quality Coalition was an active participant on this task force.
As part of the plan, EPA will use Roanoke’s 3-year average from 2005 – 2007 to determine if Roanoke is now in compliance. It is almost assured that the Roanoke Valley will be in attainment, thus meeting the EPA health standard, based on the 3-year average.
Although the Roanoke Valley often experiences some of the highest concentrations of PM 2.5 in the state, Roanoke is in attainment for the PM 2.5 health standard. In 2004, based on the 3-year averages from 2001 – 2003, EPA determined that Roanoke is in attainment. PM 2.5 does remain a concern for the Roanoke area. The Roanoke Valley-Alleghany Regional Commission is forming a stakeholders group to discuss voluntary measures to reduce particulate matter.
Recent Roanoke Valley Code Orange Air Quality Days*
|Date||Pollutant||Air Quality Index
|August 15, 2007||Ozone||104||86 ppb|
|August 5, 2007||PM 2.5||109||44.6 ug/m3|
|September 10, 2005||PM 2.5||104||41.9 ug/m3|
|August 13, 2005||PM 2.5||102||41.0 ug/m3|
|August 5, 2005||PM 2.5||103||41.3 ug/m3|
|June 25, 2003||Ozone||116||91 ppb|
– table compiled from VA DEQ website data
Ozone is measured in parts per billion (ppb). The AQI is determined by an 8-hour average (The highest average during an 8-hour period in a day). Particulate Matter 2.5 is measured in micrograms per cubic meter (ug/m3). The AQI is determined by a 24-hour average.
*AQI based on Virginia Dept. of Environmental Quality website data. Data is not “officially validated” until quality assured by VA DEQ/ US EPA.