The majority of the valley's population—and the emission sources—are concentrated in Ada and Canyon Counties. Although air pollution is generated in Elmore County as well, the county's location and distance from other populated areas in the valley prevent significant exchange of air pollutants. Remaining counties in the valley are sparsely populated with few emission sources. Emission sources in eastern Oregon also are believed to contribute to air pollution in the Treasure Valley.

Due to topography and weather patterns, the Treasure Valley is subject to some of the most severe wintertime inversions in the intermountain West. During an inversion, colder, heavier air settles into the valley while warm air sits above the inversion. This causes air stagnation as the cold air and accumulating air pollution is trapped. The pollution builds up under the inversion until a strong weather system moves through and mixes the air. During these events, air pollution monitors in the valley have recorded levels above the national health-based standard for both fine particulate matter (PM2.5) and coarse particulate matter (PM10).

The valley experiences air pollution problems in the summer months as well, as stagnant air conditions, heat, and intense sunlight combine to produce unhealthful accumulations of ozone pollution. Monitoring has shown increased levels of ozone in the valley, sometimes to unhealthful levels, during the past several summers.

In the past, air pollution management strategies have been applied based on specific political jurisdictions within the Treasure Valley. Air pollution does not stop at city, county, or state lines, however. Air pollution that is emitted in one area may travel for miles, affecting the air quality across an entire region and across multiple political boundaries.

Meteorological analyses and modeling results show that the Treasure Valley is a single airshed, with shared pollution problems that impact both Ada and Canyon Counties.

An airshed is an area covered by a volume of air with similar characteristics and separated from other volumes of air by weather patterns, topography, or distance.

To facilitate the development and application of solutions and controls throughout the airshed, DEQ has developed an airshed management program aimed at preventing deterioration of air quality through proactive planning. The foundation of airshed management is community involvement and community-directed initiatives to protect air quality. Goals of the program are:

1. Air is clean and healthy.
2. Air pollution does not detract from quality of life and aesthetics.
3. The community is aware of, and educated about, air quality issues.
4. Government agencies and the community cooperate and coordinate to address air quality issues.
5. Airshed management is applied consistently across the entire Treasure Valley airshed.
6. Objective and accurate science is used in the airshed management decision-making process.
7. Measures taken to meet airshed management goals strive to balance benefits and costs.
8. Long-term community planning is highlighted as an important factor in reducing air pollution problems.

View DEQ's Strategy for the Development of an Airshed Management Program for the Treasure Valley for detailed information on the program.

The Treasure Valley has had a history of problems with coarse particulate matter, known as PM10, and carbon monoxide (CO), primarily due to smoke from wood stoves, emissions from older vehicles and road dust. These problems have been largely resolved, however, as a result of new federal regulations, technological changes, and the development and implementation of comprehensive air quality management plans. DEQ continues to monitor PM10 and CO levels in Ada and Canyon Counties.

 Particulate Matter (PM10)

Particulate matter, or PM, is the term for small particles found in the air, including dust, dirt, soot, smoke, and liquid droplets. Depending on size, particulate matter is classified as either coarse (PM10) or fine (PM2.5). Some fine particles are directly emitted into the air while others are formed in the air through chemical reactions. Click here to learn about the health impacts of PM.

Violations of the health-based PM10 standard were first documented in the Treasure Valley in the winter of 1985-86, the year PM10 monitoring began. Northern Ada County was designated a PM10 nonattainment area by the U.S. Environmental Protection Agency (EPA) in 1987.

A geographic area that meets or has pollutant levels below the national ambient air quality standard is called an attainment area. An area with persistent violations of federal health-based standards for outdoor air pollution is designated a nonattainment area. Classification as a nonattainment area can have serious public health and economic repercussions and lead to loss of federal highway funding. more

In 1991, DEQ developed and submitted an air quality improvement plan to EPA, outlining strategies to reduce PM10 levels and minimize the likelihood of future PM10 violations. Wood burning restrictions, road sanding improvements, and new industrial permits were implemented to reduce PM10 levels. As a result of these control measures, only one exceedance for PM10 (in 2002) has been recorded. In September 2002, DEQ submitted the Northern Ada County PM10 Maintenance Plan to EPA. This plan demonstrates how compliance with the PM10 standard will be achieved through the year 2020. EPA approved the plan in September 2003, restoring northern Ada County to attainment status for PM10.

View Northern Ada County PM10 Maintenance Plan. (DEQ Publication, September 2002: pdf 1.3 mb, 72 pages)

Carbon monoxide is a colorless, odorless and poisonous gas that forms when the carbon in fuels does not completely burn. Sources of CO include vehicle exhaust, fuel combustion in industrial processes, and natural sources such as wildfires.

Monitoring for CO in the Treasure Valley began in 1977. Violations of the health-based standard for CO occurred every winter from 1977 through 1985-86. As a result of these high levels of CO, northern Ada County was designated a CO nonattainment area by EPA. To address northern Ada County's nonattainment classification, DEQ developed a CO air quality improvement plan for northern Ada County. The plan includes a commitment to continue monitoring CO levels and assurances that existing measures to control CO emissions, such as the vehicle emissions testing program in Ada County, will remain in effect. The plan also includes contingency measures that will be activated if CO levels reach specified conditions. The plan was approved by EPA in December 2002, putting the area into attainment. No exceedances of CO have occurred since 1991.

View Northern Ada County Carbon Monoxide Limited Maintenance Plan.

Although the Treasure Valley has been successful at solving its CO and PM10 problems, rapid growth in the area and recent modifications to EPA air quality standards pose new air quality challenges. Monitoring shows two new pollutants of concern—fine particulate matter (PM2.5) and ozone (O3). During the summer of 2002, exceedances of the ozone standard were measured on monitors in both Ada and Canyon Counties. (An exceedance is a violation of the pollutant levels permitted by environmental protection standards.) Additionally, both counties experienced exceedances of the PM2.5 standard in December 2002. These exceedances raise the possibility of ozone and/or PM2.5 nonattainment designation for the Treasure Valley. Moreover, continued degradation of air quality will jeopardize public health and could severely impact the economy and development of the region.

PM2.5 is comprised of particles less than 2.5 microns in diameter. It is both a primary and a secondary pollutant, meaning it can be directly emitted into the air or formed as other pollutants and chemicals combine in the air. In the Treasure Valley, nitrogen oxides (NOx), sulfur dioxide, and ammonia particles are the common chemicals that form to make PM2.5. The main sources of NOx in the valley are vehicles, including cars, SUVs, trucks, commercial vehicles, and construction and farm equipment. Almost two-thirds of ammonia emissions in the valley are from livestock waste, including dairies.

Measurements of PM2.5 are recorded daily at all air quality monitoring locations in the Treasure Valley.

Ozone is a gas and it can be "good" or "bad" for your health and the environment, depending on its location in the atmosphere. Ozone is an essential and natural part of the upper atmosphere that protects us from the sun's ultraviolet rays, but ground-level ozone is an air pollutant that is harmful to breathe and it damages crops, trees and other vegetation. It is a main ingredient of urban smog and is caused by chemicals from many sources, such as smoke, gasoline and diesel exhaust, and industrial emissions.

Ozone is never emitted from a source. It is created by chemical reactions of NOx and volatile organic compounds (VOC) in the presence of sunlight. Motor vehicle exhaust and industrial emissions, gasoline vapors, and chemical solvents are some of the major sources of NOx and VOC, which react to form ground-level ozone.

Ozone levels are measured during the summer (May - September) at three locations in the Treasure Valley. DEQ began monitoring ozone at two sites in Ada County in 2001. Two exceedances of the eight-hour ozone standard were measured in the first year of monitoring. An additional monitoring site was added in Canyon County in 2002. Five exceedances of the eight-hour standard were measured during the 2002 summer ozone season. Exceedances occurred in both Ada and Canyon Counties. One exceedance was measured in the 2003 summer season.

Although monitoring data collected in the Treasure Valley since 1996 show levels of NOx are below health-based standards, it is of concern because it contributes to the formation of ozone and PM2.5. The largest source of NOx in the area is motor vehicle emissions. Other sources include open burning and non-road vehicle emissions such as those from aircraft and from lawn, construction, and agricultural equipment.

Volatile organic compounds (VOCs) are common in household and industrial products, such as paints and varnishes, cleaners, disinfectants, and degreasers. All of these products can release organic compounds. Fuels, too, are made up of organic chemicals, and the handling and distribution of fuel is a significant contributor to the VOCs in the air throughout the valley.

VOCs are of particular concern in the Treasure Valley because they are a precursor to ozone. They also can form secondary organic particulate, an important component of PM2.5.

Ammonia is a pollutant of concern due to its role in the formation of PM2.5. Analysis of DEQ monitoring data indicates that during recent wintertime stagnation events, the atmosphere was ammonia-rich, creating prime conditions to chemically form PM2.5. Livestock wastes from dairies and agricultural operations are the largest source of ammonia emissions in the valley.

Ammonia, VOCs, and dust from livestock operations have the potential to impact air pollution levels and public health. In light of growing concern over air pollution from fine particulate matter and ozone, DEQ conducted research in early-2003 to determine the impact of these pollutants from livestock operations on air quality in the Treasure Valley. Results of this research showed that:

• The largest source of ammonia in the Treasure Valley, accounting for 64% of all emissions, was livestock urine and solid waste. As urban and industrial development increases, adding to the availability of other precursors, ammonia could become a more significant factor in the formation of secondary particulate matter.

• Large livestock operations (those with more than 5,814 head of cattle) would generate PM10 equivalent to a "major" source of air pollution. (Industrial sources emitting more than 100 tons per year of PM10 are considered "major" sources of air pollution and must undergo a rigorous permitting procedure.)

• VOC emissions from large dairies are very difficult to accurately quantify. Properly designed, sized, and maintained lagoons and land application sites can minimize VOC emissions.

As a result of this research, DEQ recommended that local planners consider air quality impacts when siting new livestock facilities in the Treasure Valley and is working with local governments and the dairy and beef industries to reach agreement on new siting and monitoring procedures.

View a report on Treasure Valley Air Quality Issues: Ammonia, Particulate, and VOC Emissions (DEQ Publication, February 2003: pdf 57 kb, 10 pages)

Hazardous air pollutants (HAPs) are pollutants that cause or may cause cancer or other serious health problems, such as reproductive problems or birth defects, or adverse environmental and ecological effects. No health-based standards have been established limiting the amount of HAPs allowed in the air, but EPA has identified 188 HAPs for which industrial sources are required to meet certain technology requirements to control HAP emissions. more

A recent nationwide Cumulative Exposure Project conducted by EPA and a 1986 site source inventory for Boise show a higher than average health risk from HAPs in the Treasure Valley. In the absence of standards limiting the amounts of HAPs that can be in the air, regulation of HAPs has focused on limiting emissions from large industrial sources. DEQ began monitoring ambient levels of HAPs in the Treasure Valley in January 2003. After sufficient data have been collected, DEQ will evaluate public exposure and health risks from these pollutants to help determine if further actions are necessary.

Efforts are underway to develop proactive measures to address PM2.5 and ozone problems in the Treasure Valley. In fall 2003, DEQ partnered with the Idaho Council on Industry and the Environment to organize the Governor's Conference on Air Quality in the Treasure Valley: Practical Paths to Clean Air, resulting a host of recommended actions to help prevent air pollution in the valley. more

DEQ is working to coordinate efforts among citizens, businesses, and government agencies to bring pollutant levels down and improve public awareness of air quality conditions and associated health risks. As part of this effort, DEQ developed wintertime and summertime pollution response plans that provide a mechanism for informing the public of air quality conditions and corresponding actions to relieve and reduce the pollution load on the airshed and protect public health.

Based on DEQ's analysis of pollutant indicators and meteorological conditions, a color-coded system notifies the public of the forecasted air quality condition for the following day. When air quality is expected to be good, a green alert is issued; when air quality is deteriorating, a yellow alert is issued; when air quality is poor and expected to deteriorate even further, a red alert is issued. Precautionary measures are prescribed for each type of alert. more

Link to Wintertime Air Pollution Response Plan (DEQ Publication, Updated December 2006: pdf 57 kb, 5 pages)

Link to Summertime Air Pollution Response Plan (DEQ Publication, Updated May 2006: pdf 215 kb, 5 pages)

In fall 2003, more than 200 local leaders from government, business, and citizen groups participated in the Governor's Conference on Air Quality in the Treasure Valley: Practical Paths to Clean Air. The conference focused on how to protect air quality in the valley and avoid nonattainment, and explored proactive, prevention-based solutions to reduce air pollution such as alternative fuels, commuting practices, alternative transportation, industrial best management practices, agricultural best management practices, corporate leadership, and energy conservation.

Speakers at the conference included John Iani, EPA Region 10 Administrator; Idaho Governor Dirk Kempthorne; George Beatty of the Houston Chamber of Commerce; the mayors of Nampa and Caldwell; and other local government and business leaders. Speakers from outside Idaho were invited to share their experiences with nonattainment and examples of proactive solutions that could be adopted in Idaho. more

Among the recommendations developed by conference participants to protect air quality in the Treasure Valley were:

• Investigate the feasibility of emissions trading programs between mobile and industrial sources.
• Consider using company investments in mass transit as an offset for industrial emissions.
• Use computer modeling to demonstrate reduced emissions from industrial controls.

• Develop a clearinghouse for aneffective and uniform information exchange.

• Build coalitions that can create open, creative, and innovative solutions to air quality problems.

• Support research and development for anaerobic and aerobic digestion processes.
• Study the processes to improve dust control.

• Identify funding to support community activities, such as local-option taxing.
• Develop a regional entity with authority to set agendas and make decisions for an entire regional area.

• Build coalitions to create a market for maximum participation in the use of alternative fuels.
• Conduct an education campaign to enable citizens and decision-makers to better understand the benefits of alternative fuels.

• Achieve a political consensus among leaders in the region to prompt and attain regional benefits to air quality.
• Identify scientific experts in the region and develop supportive and trusting partnerships between decision-makers and scientific experts.
• Conduct active educational outreach efforts to attain public "buy-in" and participation.

Read a summary report on the Governor's Conference on Air Quality in the Treasure Valley (DEQ Report, December 2003: pdf 192 kb, 10 pages).

Air Quality Alerts

Find out what the red, yellow, and green air quality alerts mean and what you can do to help improve air quality and protect your health when air quality is good, moderate, or deteriorating.

Air Quality Monitoring

Read about how DEQ monitors and analyzes air samples. Learn about National Ambient Air Quality Standards and nonattainment areas in Idaho and find out what's being done to gain redesignation of these areas.

Health and Air Pollution

Breathing elevated levels of air pollutants can adversely affect human health, especially among children, the elderly, and those with heart or lung diseases. Potential health problems include lung damage, birth defects, nerve damage, reduced immunity, and an increased risk of developing cancer. Learn about various air pollutants and their potential health impacts.

Air Publications: Brochures, Fact Sheets, and More for Citizens and Communities

Link to a wide range of publications on how you can help prevent air pollution.