Multi Year Summary Data

This page provides a summary by year of the air quality data since continuous air monitoring operations began in 2020, which is considered the base year for year to year comparison purposes. This table is updated once a year each spring after all the previous year’s data have been analyzed.


Gregory-Portland Air Quality Through the Years
Parameter Calendar Year → Base Year – 2020 2021 2022 2023
NAAQS or TCEQ AMCV Design Value to Compare with NAAQS or TCEQ AMCV
Nitrogen Dioxide (NO2) GF Only Annual average less than 53 ppb 6.3 ppb 5.6 ppb 6.2 ppb 7.3 ppb
Sulfur Dioxide (SO2) GF Only 99th p-tile less than 75 ppb 2.5 ppb 2.0 ppb 2.6 ppb 1.9 ppb
Fine Particulate Matter (PM 2.5) GF, PBG & PBway Annual average less than 9 1 µg/m3
(Averaged over 3 Years)
8.9 µg/m3 7.6 µg/m3 8.1 µg/m3 8.4 µg/m3
Benzene GF, PBG & PBway Annual average less than 8.4 ppbC 0.67 ppbC 0.65 ppbC 0.58 ppbC 0.58 ppbC
Total Nonmethane Hydrocarbons N/A; annual averages shown 63.3 ppbC 52.0 ppbC 51.0 ppbC 51.8 ppbC
    Highest Maximum Hourly or 24-Hourly Values Measured at Any Station
Benzene GF, PBG & PBway 1-hr less than 1080 ppbC 22.2 ppbC 22.9 ppbC 40.2 ppbC 49.3 ppbC
1,3-butadiene GF, PBG & PBway 1-hr less than 6,800 ppbC 14.2 ppbC 16.4 ppbC 200 ppbC 38.6 ppbC
Ethylene Oxide PBG & PBway 24-hr less than 4.8 ppbC 0.36 ppbC 0.80 ppbC 0.38 ppbC 0.60 ppbC
Total Nonmethane Hydrocarbons GF, PBG & PBway NA highest 1 hr value shown 2,317 ppbC 1,321 ppbC 2,786 ppbC 5,135 ppbC
[1] New NAAQS value announced Feb. 2024
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