Air Quality Indicator:  Daily and Annual PM 2.5 Levels

Measure: Percentage of days with PM 2.5 levels over National Ambient Air Quality Standards (NAAQS); Annual PM 2.5 concentration.   

Particle pollution, or particulate matter, consists of particles that are in the air like dust, dirt, soot and  smoke, and little drops of liquid.  Some particles are large or dark enough and can be seen like soot or smoke.  Other particles are so small you cannot see them. Long-term exposure to PM 2.5 has been associated with problems such as reduced lung function, the development of chronic bronchitis, heart disease and premature death.

Particle pollution comes from motor vehicles, factories and construction sites.  It can also be created when gases react in the atmosphere. Particle pollution can be a problem at different times of year, depending on where you live. Air monitoring stations across the country measure air concentrations of two particles sizes: PM 10 and PM 2.5.  Monitoring stations are placed around the country, but tend to be near larger cities. The target for PM 2.5 is that everyone lives in an area that meets the National Ambient Air Quality Standard (NAAQS) by 2018.

The table, graph and map below show the proportion of days during which the measured PM 2.5 concentration was higher than the National Ambient Air Quality Standards (NAAQS), as well as the average annual PM 2.5 concentration. The proportion of days can be interpreted as the number of days that PM 2.5 levels were unhealthy for sensitive populations. The annual average links population counts to air concentrations estimate the proportion of the population that lives in areas with unhealthy air. 

The data shows strong regional variations in daily and annual exceedances of the NAAQS, with Lane, Klamath and Jackson counties having the highest numbers. These counties are known to have geographical features and weather patterns that trap air pollutants.

Table 1: Percentage of monitored days during which the measured PM 2.5 concentration exceeded the NAAQS of 35 mcg/m3. 

Table 2: Number of person-days (in thousands) during which PM 2.5 concentrations exceeded the NAAQS of 35 mcg/m3.  

Graph 1: Annual average PM 2.5 concentration by year and county. 

Graph 2: Annual percentage of the Oregon population that lived in counties in which the annual average PM2.5 concentration exceeded the NAAQS of 15 mcg/m3. 

Map 1: Annual average PM2.5 concentration by county, averaged from 2000 to 2002. 

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Table 1: Percentage of monitored days during which the measured PM 2.5 concentration exceeded the NAAQS of 35 mcg/m³. No data were available for counties not shown here. Empty table cells also indicate missing data.

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Table 2: Number of person-days (in thousands) during which PM 2.5 concentrations exceeded the NAAQS of 35 mcg/m3. No data were available for counties not shown here. Empty table cells also indicate missing data.

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Graph 1: Annual average PM 2.5 concentration by year and county. The NAAQS for annual mean PM 2.5 of 15 mcg/m³ is indicated as a dashed line. No data were available for counties not shown here. For counties shown in the left panel, no data were available after 2003.

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 Graph 2: Annual percentage of the Oregon population that lived in counties in which the annual average PM2.5 concentration exceeded the NAAQS of 15 mcg/m³.

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Map 1: Annual average PM2.5 concentration by county, averaged from 2000 to 2002. No data were available for counties shown in white.

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