• Frequently Asked Questions (FAQ)

  • Where can I find more information on PM2.5 monitoring?

    • http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_index.html

  • Where is the monitor located for this study?

    • The monitoring site is located almost three miles east of the CPV Sentinel power generation facility in the city of Desert Hot Springs, CA.

  • Does SCAQMD measure other pollutants at this site?

    • No.  Fine particulate is the primary emphasis of this monitoring study, but other criteria pollutants are monitored at nearby sites maintained by SCAQMD in Palm Springs and Indio.   For more information on the SCAQMD Air Monitoring Network, please visit: http://www.aqmd.gov/home/library/clean-air-plans/monitoring-network-plan

  • How is PM2.5 measured at the monitoring site?

    • SCAQMD uses U.S. EPA Federal Equivalent Method (FEM) instruments to analyze concentrations of PM2.5 in real-time.  Hourly concentrations are calculated by the instrument and communicate with a database through cellular modem.  The monitoring site is configured to meet the EPA siting criteria for PM monitoring, which limits obstructions and proximity to sources that could bias the measurement.  Based on the location of the monitoring site, the measurement is representative of a city scale up to regional scale.  The closest continuous PM2.5 monitor of a similar type operated by the SCAQMD is in Banning (Area 29): http://www.aqmd.gov/docs/default-source/default-document-library/map-of-monitoring-areas.pdf
      
      Additionally, PM2.5 is monitored at Palm Springs and Indio using a different methodology (Federal Reference Method, or FRM) that gives 24-hour concentrations and is determined by laboratory analysis.  While FRM methods cannot provide real-time/instantaneous data output, the FRM methodology is the standard method for determining whether the federal national ambient air quality standard (NAAQS) is met.
      
      NOTE: data published to the website is preliminary and therefore subject to change upon final review.  Data QC and review for the continuous hourly measurement are performed later to confirm the validity of the measurements, and this process follows the EPA guidelines for data handling.
      
      For finalized/official data, please contact SCAQMD Public Affairs and submit a Public Records Request: http://www.aqmd.gov/contact/public-records

  • Can windblown dust/sand affect the PM2.5 monitor?

    • Generally no, but during extreme conditions PM2.5 can elevate during sandstorms.  Airborne particulate is a mixture of particle sizes ranging from 1 nanometer (ultrafine particles) up through 50 micrograms and larger (coarse PM).  This mixture is comprised mainly of particles somewhere in the middle of that range; usually between 2.5-20 microns.  When particles become airborne, PM10 and larger particles settle out more quickly, while PM2.5 and finer particles become suspended indefinitely.  During a high wind episode, PM10 increases at ground level as the top layer of dust and sand become airborne, while PM2.5 concentrations can vary.
      
      Wildfires and fireworks are known to increase PM2.5 levels across large areas temporarily.   Cooler months are known to have higher PM2.5 due to increased fireplace use and calmer atmospheric conditions that rid the basin of pollutants more slowly.

  • What types of sources contribute to PM2.5 pollution in the atmosphere?

    • While PM2.5 can be caused by dozens of types of natural and man-made sources, a significant portion of PM2.5 comes from combustion processes of automobiles and stationary sources.  Although a specific source cannot be determined from other contributors with this monitor alone, other data sources such as meteorology and activity data can be included to assess contributions from various sources, including the CPV Sentinel Power Plant.

  • What is the Federal Standard for PM2.5?

    • PM2.5 is a Federal Criteria Pollutant, which is categorized for known impacts on human health.  Although PM2.5 pollution is small, it can end up deeper in the lungs and have more severe effects than larger dust that is usually removed in the upper respiratory system of humans.  The EPA uses PM2.5 mass concentration (micrograms per cubic meter) in the National Ambient Air Quality Standards (NAAQS) as follows:

      • Primary standard (for protection of human health): 12 µg/m3 Annual Arithmetic Mean, averaged over 3 years

      • Secondary Standard (for protection of environmental quality and visibility): 15 µg/m3 Annual Arithmetic Mean, averaged over 3 years

      • Primary and Secondary: 35 µg/m3 (24-hour average), 98^th Percentile Value averaged over 3 years

For more information on PM pollution, please visit http://www.epa.gov/air/particlepollution/index.html for basic information and technical documents on PM regulation and monitoring programs under the EPA.