This guidance is designed to aid local agencies in reporting air quality using the 42530, August 4 1999: 3.epa/ttn/oarpg/t1/fr_notices/airqual.pdf.
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EPA 454/B -18-007 September 2018 Technical Assistance Document for the Reporting of Daily Air Quality Πthe Air Quality Index (AQI) U.S. Environmental Protection Agency Office of Air Quality Planning and Standards Air Quality Assessment Division Research Triangle Park, NC
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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 . Airn ow.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
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1 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 Sta tistical Areas (MSAs) with a population of more than 350,000 are required to report the AQI daily to the general public. The population of a n MSA for purposes of index reporting is based on the latest available U.S. census population. How often do I repo rt 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 report ing area the reporting period the critical pollutant (the pollutant with the highest AQI value) the AQI value the category descriptor and color (if you r 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 report ing more useful to the public, m ost agencies also choose to report some or all of the following: Forecast and current AQI values Healt h 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 fiblendfl health effects and cautionary information for more than one pollutant, if there is more than one pollutant with an AQI greater than 100
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2 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 fiBeyond the AQI. fl 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).
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4 Table 4. Pollutant -Specific Sub -indices and Cautionary Statements for Guidance on the Air Quality Index (AQI) AQI Categories (Index Values) Ozone (ppm) 3) Carbon Monoxide (ppm) [8-hour] Sulfur Dioxide (ppb) [1-hour] Nitrogen Dioxide (ppb) [1-hour] [8-hour] [1-hour] PM2.5 [24 -hour] PM10 [24 -hour] Good (Up to 50) 0 Р0.054 None 0 Π12.0 None 0 Р54 None 0 Π4.4 None 0 Р35 None 0 Р53 None Moderate (51 Р100) 0.055 Р0.070 12.1 Π35.4 55 Π154 4.5 Π9.4 None 36 Р75 None 54 Р100 Unusually sensitive individuals should consider limiting prolonged exertion especially near busy roads. Unusually sensitive people should consider reducing prolonged or heavy outdoor exertion. Unusually sensitive people should consider reducing prolonged or heavy exertion. Unhealthy for Sensitive Groups (101 Р150) 0.071 Р0.085 0.125 Р0.164 35.5 Π55.4 155 Π254 9.5 Π12.4 People with heart disease, such as angina, should limit heavy exertion and avoid sources of CO, such as heavy traffic. 76 Р185 People with asthma should consider limiting outdoor exertion. 101 Р360 People with asthma, children and older adults should limit prolonged exertion especially near busy roads. People with lung disease (such as asthma), children, older adults, people who are active outdoors (including outdoor workers), people with certain genetic variants, and people with diets limited in certain nutrients should reduce prolonged or heavy outdoor exertion. People with heart or lung disease, older adults, children, and people of lower socioeconomic status should reduce prolonged or heavy exertion.
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5 Unhealthy (151 Р200) 0.086 Р0.105 0.165 Р0.204 55.5 Π150.4 255 Π354 12.5 Π15.4 186 Π304 361 Р649 People with lung disease (such as asthma ), children, older adults, people who are active outdoors (including outdoor workers ), people with certain genetic variants, and people with diets limited in certain nutrients should avoid prolonged or heavy outdoor exertion; everyone else should red uce prolonged or heavy outdoor exertion. People with heart or lung disease, older adults, children, and people of lower socioeconomic status should avoid prolonged or heavy exertion; everyone else should reduce prolonged or heavy exertion. People with hear t disease, such as angina, should limit moderate exertion and avoid sources of CO, such as heavy traffic. Children, people with asthma, or other lung diseases, should limit outdoor exertion. People with asthma, children and older adults should avoid prolon ged exertion near roadways; everyone else should limit prolonged exertion especially near busy roads. Very Unhealthy (201 Р300) 0.106 Р0.200 0.205 Р0.404 150.5 Π250.4 355 Π424 15.5 Π30.4 People with heart disease, such as angina, should avoid exertion and sources of CO, such as heavy traffic. 305 Π604 [24 -hour] Children, people with asthma, or other lung diseases should avoid outdoor exertion; everyone else should reduce outdoor exertion. 650 Р1249 People with asthma, children and older adult s should avoid all outdoor exertion; everyone else should avoid prolonged exertion especially near busy roads. People with lung disease (such as asthma ), children, older adults, people who are active outdoors (including outdoor workers ), people with certain genetic variants, and people with diets limited in certain nutrients should avoid all outdoor exertion; everyone else should reduce outdoor exertion. People with heart or lung disease, older adults, children, and people of lower socioeconomic statu s should avoid all physical activity outdoors. Everyone else should avoid prolonged or heavy exertion. Hazardous (301 Р500) Р0.405 Р0.604 250.5 Π500.4 425 Π604 30.5 Π50.4 People with heart disease, such as angina, should avoid exertion and sources of CO, such as heavy traffic; everyone else should limit heavy exertion. 605 Π1004 [24 -hour] Children, people with asthma, or other lung diseases, should remain indoors; everyone else should avoid outdoor exertion. 1250 Р2049 People with asthma, children and older adults should remain indoors; everyone else should avoid all outdoor exertion. Everyone should avoid all outdoor exertion. Everyone should avoid all physical activity outdoors; people with heart or lung disease, older adults, children, and people of lower socioeconomic status should remain indoors and keep activity levels low.
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6 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 fiBeyond the AQI.fl 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. In subsequent years, if any pollutant level rises to where the AQI would be above 50, then you must report the AQI. If a specific pollutant remains below 50 for an extended period of time (a season or a year), you may exclude that pollutant from your AQI calculation. How is the AQI reported? AQI reports take many forms Πfrom traditional media like television, newspaper, radio, and phone, to more digital forms such as widgets, apps, web pages , and social media . The purpose of the AQI is to inform people about their air quality so they can take steps to protect their health. This is especially important whenever the AQI exceeds 100. To reach the most people, try to deliver the AQI in as many ways as possible. Figure 1. The AQI is reported in many formats. Tomorrow will be a code red air quality day for Center City. The cold winter air, morning traffic, and wood smoke are expected to cause particle pollution to rise to unhealthy levels. People with heart or lung disease, older adults, and children should avoid strenuous activities.
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7 Do I have to forecast the AQI? Forecasting is encouraged, but it is not required. A prediction for the next day or several days allows people to plan their activities so that they can reduce or avoid exposure to air pollution. Good forecasts require data, computational resources, and expertise. EPA provides guidance if you are interested in starting a forecasting program. For more information, see Guidelines for Developing an Air Quality Forecasting Program in the Resources section . Figure 2. Display of AQI forecast Do I need to have air quality action days as part of my program ? No. The use of air quality action days or community action programs, which are usually based on AQI forecasts, is voluntary. However, action days and similar programs can provide significant benefits, especially when they directly a nd effectively communicate to at -risk groups about air quality and associated health effects. Air quality action days may be called by state or local air agencies when the AQI will get into the unhealthy ranges. Different agencies call them at different le vels, such as Orange or Red or sometimes Yellow. How is the AQI reported in real time? EPA uses the NowCast to approximate the complete daily AQI during any given hour. Even on days when the AQI forecast predicts unhealthy conditions, pollution levels may be lower and better for outdoor activities during some parts of the day. Providing current conditions gives people the power to take action to reduce outdoor activities and exposure when necessary and protect their health. The NowCast calculation uses longer averages during periods of stable air quality and shorter averages when air quality is changing rapidly, such as during a fire . The NowCast allows current conditions maps to align more closely with what people are actually seeing or experiencing. Figure 3. The NowCast NowCast less variable air quality more variable air quality Longer term average Ozone: ~8 hours PM2.5: ~12 hours PM10: ~12 hours Real -time Ozone: ~1 hour PM2.5: ~3 hours PM10: ~3 hours
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