Air Quality Monitoring Data
Bethel Particulate Matter 2.5 (PM2.5)
The interactive charts below show historical data from PM2.5 monitoring at the Bethel air quality monitoring site. Sampling began on May 31st, 2018 and ended in June 2020. The Alaska Air Monitoring Plan contains more information about this site.
Note: The vertical axis of these charts extend from -10 µg/m3 to 100 µg/m3. Negative PM2.5 concentrations are included based on EPA reporting guidelines and are within the noise levels of the instrument when the ambient PM2.5 concentration is near zero. The PM2.5 concentrations represent the concentration at local conditions and have not been corrected for local temperature and pressure.
The following graphs show the 24-hour averaged PM2.5 concentrations measured at the Bethel Air Quality Monitoring Site from 2019 through 2018.
2019
The 2019 PM2.5 24-hour concentrations were below the 24-hour NAAQS of 35 µg/m3 except for two days due to summertime wildfire smoke pollution. To date, DEC has not filed an Exceptional Events Waiver Request to EPA because the summertime wildfire concentrations are not yet regulatory significant. The 98th percentile concentration was 8.5 µg/m3. The site shutdown in June 2020.
2018
The 2018 PM2.5 24-hour concentrations were all below the 24-hour NAAQS of 35 µg/m3. No data were flagged as exceptional events this year. The 98th percentile concentration was 9.9 µg/m3.
Glossary
- NAAQS
- National Ambient Air Quality Standard - A health-based air quality standard set by EPA based on a review of available scientific information. NAAQS exist for criteria pollutants including Particulate Matter (PM2.5 and PM10), Carbon Monoxide (CO), Sulfur Dioxide (SO2), Nitrogen Dioxide (NO2), Ozone(O3), and Lead(Pb).
- EPA's NAAQS Webpage
- Concentration, µg/m3
- The amount of PM2.5 suspended in the air with units of micrograms(one-millionth of a gram) per cubic meter
- Exceedance
- A day when the 24-hour measured concentration of PM2.5 exceeds the NAAQS.
- 98th Percentile
- The daily value out of a year of PM2.5 monitoring data below which 98 percent of all daily values fall. 40 CFR 50 Appendix N - see section 4.5(a)
- 24-hour Design Value (DV)
- A three-year average of the 98th percentile value. An area is in violation of the NAAQS when the Design Values is greater than the 24-hour NAAQS for PM2.5, which is currently set at 35 µg/m340 CFR 50 Appendix N - see section 4.5(b)
- Clean Data Year
- A year when the 98th percentile value is less than the NAAQS.
- Exceptional Events
- Unusual or naturally occurring events that can affect air quality but are not reasonably controllable.
- EPA's Exceptional Events Webpage
- DEC's Exceptional Events Webpage
- Compliance with PM2.5 NAAQS
- 24-Hour: 98th percentile, averaged over 3 years, must be below the standardAnnual: Annual arithmetic mean, averaged over 3 years, must be below the standard. 40 CFR 50 Appendix N - see sections 4.1 and 4.2
| Standard | 1997 - 2006 | 2006 - 2012 | 2012 - 2024 | 2024 - current |
|---|---|---|---|---|
| 24-hour | 65 µg/m3 | 35 µg/m3 | 35 µg/m3 | 35 µg/m3 |
| Annual | 15 µg/m3 | 15 µg/m3 | 12 µg/m3 | 9 µg/m3 |