Technical Assistance Document for the Reporting of Daily Air Quality – the Air Quality Index (AQI) EPA 454/B-18-007 September 2018 Technical Assistance Document for the Reporting of Daily Air Quality – the Air Quality Index (AQI) U.S. Environmental Protection Agency Office of Air Quality Planning and Standards Air Quality Assessment Division Research Triangle Park, NC CONTENTS I. REPORTING THE AQI II. CALCULATING THE AQI III. FREQUENTLY ASKED QUESTIONS IV. RESOURCES LIST OF TABLES Table 1. Names and colors for the six AQI categories Table 2. AQI color formulas Table 3. Pollutant-Specific Sensitive Groups Table 4. Cautionary Statements Table 5. Breakpoints for the AQI LIST OF FIGURES Figure 1. The AQI is reported in many formats Figure 2. Display of AQI forecast Figure 3. The NowCast Figure 4. Airnow.gov page showing the AQI at U.S. Embassies and Consulates Figure 5. The AQI on AirNow’s Fires: Current Conditions page Figure 6. The AirNow widget This guidance is designed to aid local agencies in reporting air quality using the Air Quality Index (AQI) as required in 40 CFR Part 58.50 and according to 40 CFR Appendix G to Part 58. I. REPORTING THE AQI Do I have to report the AQI? Metropolitan Statistical Areas (MSAs) with a population of more than 350,000 are required to report the AQI daily to the general public. The population of an MSA for purposes of index reporting is based on the latest available U.S. census population. How often do I report the AQI? MSAs must report the AQI daily, which is defined as at least five days each week. This definition allows for days when personnel are not available to provide the AQI report or for equipment failures. What goes in my AQI report? Required reporting: It takes a full 24 hours to obtain an AQI value (that’s 24 hourly values for PM or the max 1-hour or 8- hour value in a 24-hour period for other pollutants), so you are in effect required to report yesterday’s AQI, including: • the reporting area • the reporting period • the critical pollutant (the pollutant with the highest AQI value) • the AQI value • the category descriptor and color (if your report uses color) shown in Table 1 • the sensitive groups for all pollutants with an AQI over 100, as shown in Table 3 Voluntary reporting: To make AQI reporting more useful to the public, most agencies also choose to report some or all of the following: • Forecast and current AQI values • Health effects and cautionary statements • Causes for unusual AQI values • The AQI for sub-areas of the reporting area • Pollutant concentrations • The name and AQI for other pollutants, particularly those with an AQI greater than 100 • Statements that “blend” health effects and cautionary information for more than one pollutant, if there is more than one pollutant with an AQI greater than 100 1 Table 1. Names and colors for the six AQI categories For this AQI… use this descriptor… and this color 0 to 50 Good Green 51 to 100 Moderate Yellow 101 to 150 Unhealthy for Sensitive Groups Orange 151 to 200 Unhealthy Red 201 to 300 Very Unhealthy Purple 301 to 500 Hazardous Maroon Note: Values above 500 are considered “Beyond the AQI.” Follow recommendations for the Hazardous category. How are the AQI colors defined? The colors are defined by the formulas RGB (red, green, blue) and CMYK (cyan, magenta, yellow, black) as shown in Table 2. Table 2. AQI color formulas Color R G B C M Y K Green 0 228 0 40 0 100 0 Yellow 255 255 0 0 0 100 0 Orange 255 126 0 0 52 100 0 Red 255 0 0 0 100 100 0 Purple 143 63 151 51 89 0 0 Maroon 126 0 35 30 100 100 30 Notes: RGB is traditionally used for screen colors, while CMYK is traditionally used for printing. The color models are based on a 0 - 255 scale (e.g. 50% is 126). 2 Table 3. Pollutant-Specific Sensitive Groups When this pollutant Report these Sensitive Groups has an AQI above 100… Ozone People with lung disease, children, older adults, people who are active outdoors (including outdoor workers), people with certain genetic variants, and people with diets limited in certain nutrients are the groups most at risk PM2.5 People with heart or lung disease, older adults, children, and people of lower socioeconomic status are the groups most at risk PM10 People with heart or lung disease, older adults, children, and people of lower socioeconomic status are the groups most at risk CO People with heart disease is the group most at risk NO2 People with asthma, children, and older adults are the groups most at risk SO2 People with asthma, children, and older adults are the groups most at risk Notes: Statements may be combined so that each group is mentioned only once. What cautionary statements should I use in my AQI report? Table 4 lists cautionary statements for each pollutant. 3 Table 4. Pollutant-Specific Sub-indices and Cautionary Statements for Guidance on the Air Quality Index (AQI) AQI Ozone (ppm) Particulate Matter (μg/m3) Carbon Monoxide Sulfur Dioxide Nitrogen Dioxide Categories (ppm) (ppb) (ppb) [8-hour] [1-hour] PM [24-hour] [24-hour] (Index 2.5 PM10 [8-hour] [1-hour] [1-hour] Values) Good 0 - 0.054 0 – 12.0 0 - 54 0 – 4.4 0 - 35 0 - 53 (Up to 50) None None None None None None Moderate 0.055 - 0.070 12.1 – 35.4 55 – 154 4.5 – 9.4 36 - 75 54 - 100 (51 - 100) None None Unusually sensitive Unusually sensitive Unusually sensitive people should consider individuals should people should reducing prolonged or heavy exertion. consider limiting consider reducing prolonged exertion prolonged or heavy especially near busy outdoor exertion. roads. Unhealthy for 0.071 - 0.085 0.125 - 0.164 35.5 – 55.4 155 – 254 9.5 – 12.4 76 - 185 101 - 360 Sensitive Groups People with heart People with asthma People with asthma, (101 - 150) People with lung disease (such as asthma), People with heart or lung disease, older adults, disease, such as should consider limiting children and older children, older adults, people who are active children, and people of lower socioeconomic status angina, should limit outdoor exertion. adults should limit outdoors (including outdoor workers), people should reduce prolonged or heavy exertion. heavy exertion and prolonged exertion with certain genetic variants, and people with avoid sources of CO, especially near busy diets limited in certain nutrients should reduce such as heavy traffic. roads. prolonged or heavy outdoor exertion. 4 Unhealthy 0.086 - 0.105 0.165 - 0.204 55.5 – 150.4 255 – 354 12.5 – 15.4 186 – 304 361 - 649 (151 - 200) People with lung disease (such as asthma), People with heart or lung disease, older adults, People with heart Children, people with People with asthma, children, older adults, people who are active children, and people of lower socioeconomic status disease, such as asthma, or other lung children and older outdoors (including outdoor workers), people should avoid prolonged or heavy exertion; everyone angina, should limit diseases, should limit adults should avoid with certain genetic variants, and people with else should reduce prolonged or heavy exertion. moderate exertion and outdoor exertion. prolonged exertion near diets limited in certain nutrients should avoid avoid sources of CO, roadways; everyone prolonged or heavy outdoor exertion; such as heavy traffic. else should limit everyone else should reduce prolonged or prolonged exertion heavy outdoor exertion. especially near busy roads. Very Unhealthy 0.106 - 0.200 0.205 - 0.404 150.5 – 250.4 355 – 424 15.5 – 30.4 305 – 604 [24-hour] 650 - 1249 (201 - 300) People with heart Children, people with People with asthma, disease, such as asthma, or other lung children and older People with lung disease (such as asthma), People with heart or lung disease, older adults, angina, should avoid diseases should avoid adults should avoid all children, older adults, people who are active children, and people of lower socioeconomic status exertion and sources of outdoor exertion; outdoor exertion; outdoors (including outdoor workers), people should avoid all physical activity outdoors. Everyone CO, such as heavy everyone else should everyone else should with certain genetic variants, and people with else should avoid prolonged or heavy exertion. traffic. reduce outdoor exertion. avoid prolonged diets limited in certain nutrients should avoid exertion especially near all outdoor exertion; everyone else should busy roads. reduce outdoor exertion. Hazardous - 0.405 - 0.604 250.5 – 500.4 425 – 604 30.5 – 50.4 605 – 1004 [24-hour] 1250 - 2049 (301 - 500) People with heart Children, people with People with asthma, disease, such as asthma, or other lung children and older Everyone should avoid all outdoor exertion. Everyone should avoid all physical activity outdoors; angina, should avoid diseases, should remain adults should remain people with heart or lung disease, older adults, exertion and sources of indoors; everyone else indoors; everyone else children, and people of lower socioeconomic status CO, such as heavy should avoid outdoor should avoid all outdoor should remain indoors and keep activity levels low. traffic; everyone else exertion. exertion. should limit heavy exertion. 5 What health effects and cautionary statements should I use if the AQI goes above 500? If the AQI is higher than 500, it is called “Beyond the AQI.” Use the same information that is for the Hazardous category. Do I have to report the AQI if my values are low? If the AQI values for all of the pollutants remain below 50 for a year, then you may report the AQI at your discretion.