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Particulate Matter Trends in Pima County

(click on graphs below to view the pdf version of the graph)

Short-term Trends:

In Pima County, the natural desert background comprises about one third of the typical particulate matter concentrations. Particulate concentrations tend to be higher in winter and increase during dry periods.

The graph below shows the monthly average trend of PM10 and PM2.5 concentrations at the Orange Grove monitoring site for 2012.

Long Term Trends:

PM10 levels have shown large annual fluctuations due to changing meteorological conditions and localized emissions around the monitoring sites. PM10 monitoring began in Pima County in 1988. Tucson violated the 24-hour PM10 standard after four exceedances were recorded in 1999. The exceedances were found to be due to high wind natural events, along with an extended period of low rainfall. The Pima Cuonty Department of Environmental Quality (PDEQ) has measures in place to protect public health and welfare from airborne dust.

PM2.5 levels over the 15-year monitoring period have been well below the federal health standards.

Effective programs in the Tucson area that help reduce particulate matter levels by promoting the use of alternate modes are:

Alternate modes such as carpooling, taking the bus, walking, and bicycling, and the use of telecommuting all serve to reduce the number of motor vehicles on the road.

For dust control, Title 17 of the Pima County Code outlines activity permits and performance standards required for construction activities.

For tips on how to keep our air healthy, visit or the Clean Air Starts With Me Facebook page.      


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