Air Quality Memo June 2024

The Clean Air Act requires the EPA to set National Ambient Air Quality Standards (NAAQS) for particulate matter (PM) and five other pollutants considered harmful to public health. The standard specifies the maximum concentrations and duration of PM present in outdoor air before potential health risks arise. The microscopic particle size gives the ability of the pollutant to enter the body’s respiratory system. The larger particle sized PM 10 may be filtered out in the nose and throat, while the smaller PM 2.5 is able to bypass and penetrate deeper into the lungs, resulting in more serious health effects. Sources of PM include dust from construction sites, landfills and agriculture, wildfires and brush/waste burning, industrial sources, wind-blown dust from open lands, pollen and fragments of bacteria.

In response to the Public’s concern regarding dust pollution originating from the drawdown at Copco Reservoir, Siskiyou County (County) worked with the Siskiyou County Air Pollution Control District (District) to install PurpleAir sensors that measure airborne PM. These low-cost sensors were installed at three locations spaced out along the Copco community. The PurpleAir air quality sensors collect continuous data which is published online using the AQI color coding. In addition, the County has an embedded map published on the County’s Klamath Dam Decommissioning Project here.

While the PurpleAir sensors provide a continuous look at air quality, the strength and accuracy of these monitors is less stringent than other available monitors. Therefore, on loan from the California Air Resources Board (CARB) the District installed an EBAM-Plus air quality monitor at the Copco Community Center. This monitor provides the County with a stringent U.S. Environmental Protection Agency standard for monitoring outdoor air quality, specialty focused on larger PM 10 from windblown dust. PM concentration is measured in micrograms per cubic meter, or µg/m3. CARB set air-quality standards for PM 10 of 50 µg/m3 over a 24-hour period and an average of 20 µg/m3 annually. More restrictive than the EPA standard of 150µg/m3 over a 24-hour period and an average of 50 µg/m3 annually.As with the PurpleAir sensors, the EBAM-Plus monitors have been collecting continuous air quality data since mid-May 2024. This memo outlines the sampling results, conclusions and next steps associated with the County’s air monitoring efforts.

Please view the full Memorandum below for more information.