Frequently Asked Questions (FAQ)

1. Where can I find more information on PM10 monitoring? https://www.epa.gov/naaqs/particulate-matter-pm-air-quality-standards

2. Where is the monitor located for this study?
   The monitoring site is located north of Valley View Park in City of Duarte.

3. Does South Coast AQMD measure other pollutants at this site?
   No. Coarse PM (PM 10 microns and smaller) is the primary emphasis of this monitoring study, but other criteria pollutants are monitored at nearby sites maintained by South Coast AQMD in Azusa, Glendora, and Pasadena. For more information on the South Coast AQMD Air Monitoring Network, please visit: http://www.aqmd.gov/home/library/clean-air-plans/monitoring-network-plan

4. How is PM10 measured at the monitoring site?
   South Coast AQMD uses an U.S. EPA Federal Equivalent Method (FEM) instrument to measure levels of PM10 in real-time to provide hourly average results. 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. The closest continuous PM10 monitor of a similar type operated by the South Coast AQMD is in Glendora: http://www.aqmd.gov/docs/default-source/default-document-library/map-of-monitoring-areas.pdf

   Additionally, PM10 is monitored at Azusa using a different methodology (Federal Reference Method, or FRM) that provides a 24-hour average level and is determined by laboratory analysis. While FRM methods cannot provide real-time/instantaneous data output, the FRM methodology is the standard method by South Coast AQMD for determining whether the federal national ambient air quality standard (NAAQS) is met.

5. Can windblown dust/sand affect the PM10 monitor?
   Yes. During conditions of high sustained winds (typically greater than 10mph), windblown dust significantly elevates PM10 concentrations. Such conditions are unusual but nonetheless diminish air quality conditions. South Coast AQMD Rule 403 applicability for sources of fugitive dust is exempted when gusts exceed 25 mph. High PM10 concentrations can be sustained for hours after the winds subside due to the fallout of airborne particulate matter.
   Wildfires and fireworks are known to increase PM10 and PM2.5 levels across large areas temporarily. The foothills in San Gabriel Valley are prone to such events particularly during dry months of summer and fall, and are exacerbated by Santa Ana wind conditions that drop humidity for several days.

6. What types of sources contribute to PM10 pollution in the atmosphere?
   PM10 is attributed to many natural and human causes, including a portion of vehicle tailpipe and roadway emissions. The I-605/I-210 freeways interchange contribute a significant portion of the mobile source PM in the foothills and Duarte. Nearby cement/aggregate operations are also sources of PM10. Fallout of larger particles is faster than that of smaller particles, meaning that PM10 from a known source typically stays more localized (i.e. <1 mile depending on source).
   - What can I do if I suspect that dust emissions are making my local air quality bad?
   South Coast AQMD Rule 403 pertains to fugitive emissions of windblown dust from industrial operations. Details are provided here:

   http://www.aqmd.gov/docs/default-source/rule-book/rule-iv/rule-403.pdf?sfvrsn=4

   Any activity not explicitly listed in the exempt categories of the rule are responsible for the escape of dust emissions over the fence-line of a property. Community members who are concerned about a suspected violation in this regard are encouraged to report their observations to the AQMD hotline: 1-800-CUT-SMOG (1-800-288-1664)

7. What is the Federal Standard for PM10?
   PM10 is a Federal Criteria Pollutant, which is categorized for its known impacts on human health. The particles in PM10 are small enough to be inhaled into the lungs and cause adverse health effects. In contrast, larger dust particles are usually not inhaled into the lungs, and instead are removed in the upper respiratory system of humans. The EPA uses PM10 mass concentration (micrograms per cubic meter) in the National Ambient Air Quality Standards (NAAQS) as follows:
   Primary standard (for protection of human health): 150 µg/m3 averaged within a single 24-hour period (midnight-midnight). This level is not to be exceeded more than once per year on average over 3 years.

For more information on PM pollution, please visit https://www.epa.gov/pm-pollution for basic information and technical documents on PM regulation and monitoring programs under the EPA.