Mat-Su PM2.5 Design Value Comparison


The EPA established a health based standard (National Ambient Air Quality Standard, (NAAQS)) for fine particulate matter (PM2.5), which is a byproduct of combustion. The 24 hour PM2.5 standard is based on the 98th percentile averaged over 3 years. The interactive chart below shows the 98th percentiles and design values as measured since 2000 at the Butte and Palmer air monitoring stations.  An area is in violation of the NAAQS when the Design Value is greater than the 24 hour NAAQS for PM2.5, which is currently set at 35 µg/m3.

 

Note: The vertical axis of this chart extends to 100 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 Dioxode (SO2), Nitrogen Dioxide (NO2), Ozone(O3), and Lead(Pb).
https://www3.epa.gov/ttn/naaqs/

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)

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/m3
40 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 standard
Annual:   Annual arithmetic mean, averaged over 3 years, must be below the standard.
40 CFR 50 Appendix N - see sections 4.1 and 4.2

PM2.5 NAAQS Values

Standard

1997 - 2006

2006 - 2012

2012 - current

24-hour

65 µg/m3

35 µg/m3

35 µg/m3

Annual

15 µg/m3

15 µg/m3

12 µg/m3

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