Air Quality within the Portneuf River Ecosystem


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Air Quality in the Pocatello Area

Introduction

The federal government set standards for six air pollutants called criteria pollutants (see box below). The six air pollutants that are covered by these standards are sulfur dioxide, carbon monoxide, nitrogen oxide, ozone, lead, and particulates. The standards are based on protection of human health. Air is monitored for these pollutants, and when the health-based standards are exceeded, special notice is taken.

PM-10
The standard for particulates addresses particles that are less than 10 microns in diameter (PM-10). These particles are of particular concern because they can cause health problems. Long-term exposure to high levels of PM-10 can increase the likelihood of developing chronic respiratory conditions such as bronchitis. The Pocatello-Chubbuck area has been a non-attainment area because of some particularly high PM-10 levels that were recorded in the early 1990’s. The EPA determines if an area is in attainment based on the last three years of measurements. Since early 1993 PM-10 levels have been largely within the EPA guidelines.

PM 2.5
In July 1997 the EPA established a new standard for air quality that is based on particulate matter that is less than 2.5 micrometers in diameter (PM 2.5). This new standard was created in response to health studies indicating that these smaller particles are the most likely size to cause serious health problems.

The DEQ began monitoring PM 2.5 in the Pocatello area in November 1998. These measurements are being taken at two sites within Pocatello, near Chubbuck Elementary School and at the intersection of Garrett and Gould.

Criteria Pollutant	Health Concerns
Sulfur Dioxide	Respiratory tract problems; permanent harm to lung tissue
Carbon Monoxide	Ability of blood to carry oxygen impaired; cardiovascular, nervous, and pulmonary systems affected.
Nitrogen Oxide	Respiratory illness and lung damage
Ozone	Respiratory tract problems (difficult breathing, reduced lung function); asthma; eye irritation; nasal congestion; reduced resistance to infection; possible premature aging of lung tissue
Lead	Retardation and brain damage, especially in children
Particulates	Eye & throat irritation; bronchitis; lung damage; and impaired visibility

Information on the Web

The EPA maintains a web page with information about air quality:
http://www.epa.gov/air/urbanair/pm/index.html

You can also find the 1997 Summary Report on PM-10 at:
http://www.epa.gov/oar/aqtrnd97/brochure/pm10.html

Pocatello-Chubbuck SIP
     When an area has air quality that does not meet standards, the federal government requires that the state develop a `State Implementation Plan' (SIP), to show how air quality will be improved.
     The steering committee that developed Pocatello’s SIP identified smoke from wood stoves and fireplaces as one of the causes of high PM-10 in the Pocatello-Chubbuck area. In an attempt to reduce PM-10 associated with wood smoke, the Pocatello and Chubbuck city councils passed local air quality ordinances that restrict the materials that can be burned, limit the use of wood stoves and fireplaces, and require that new buildings have a heating source other than a wood stove or fireplace. These regulations prohibit burning when PM-10 exceeds 120 micrograms per cubic meter, and call for a voluntary ban when PM-10 exceeds 80 micrograms per cubic meter.
      To meet the primary standard for air quality the annual arithmetic mean must be less than 50 micrograms of particulate material that will pass through a 10 micrometer filter (PM-10) per cubic meter of air. In addition, the daily value of PM-10 cannot exceed 150 micrograms per cubic meter of air. This standard was tightened in 1988; prior to 1988 the primary standard was 75 micrograms as an annual mean.

PM 10 Measurements - Changes in Air Quality
The Idaho Department of Environmental Quality (DEQ) maintains air quality monitors at various locations around the city of Pocatello, including the Wastewater Treatment Plant (Batiste & Chubbuck Roads), 5045 Hawthorne Road, Chubbuck, and at Garrett & Gould Roads. Data from the Garrett and Gould site are shown in the figure below. Average values for readings taken in each month are plotted in blue and the maximum value recorded in each month is plotted in red. Average monthly values dropped slightly form 1992 through 1998 and have remained relatively constant since then.

The next figure shows average PM-10 values by month for the period from 1992 through June 2004. Average PM-10 concentrations were highest in August, probably because of dust associated with harvesting agricultural fields. December and February also had higher than average PM-10 concentrations, probably because of inversions that trap particulates near ground level.

PM 2.5 Measurements
In response to the PM 2.5 standard developed by the US EPA in 1997, the Idaho Department of Environmental Quality has been measuring PM 2.5 since late 1998. Measurements have been taken at two sites, one in Chubbuck and one at the intersection of Garrett and Gould Roads. Data from the Garrett and Gould site are plotted in the figure below. Average values for readings taken in each month are plotted in blue and the maximum value recorded in each month is plotted in red. PM 2.5 concentrations are highest during the winter months. This is the time of year when inversions develop, trapping warm particulate-laden air near the ground surface. These are also the months when more people use wood-burning stoves, contributing smoke and particulates to the air, and when automobile and truck engines operate less efficiently.

The next figure shows average PM-2.5 values by month for the period from November 1998 through March 2004. In contrast to average PM-10 concentrations, PM-2.5 concentrations were highest in December, January, and February, and not in August. This suggests that airborne particulate matter that is responsible for the elevated levels of PM-10 in July, August, and September is from a different source than the PM-2.5 material that contributes to poorer air quality during the winter.

[All of the data presented on this page were provided by the Idaho Department of Environmental Quality.]