This indicator shows how many days per year were assessed to have air quality that was worse than “moderate” in Champaign County, according to the U.S. Environmental Protection Agency’s (U.S. EPA) Air Quality Index Reports. The period of analysis is 1980-2024, and the U.S. EPA’s air quality ratings analyzed here are as follows, from best to worst: “good,” “moderate,” “unhealthy for sensitive groups,” “unhealthy,” “very unhealthy,” and "hazardous."[1]

In 2024, the number of days rated to have air quality worse than moderate was 0. This is a significant decrease from the 13 days in 2023 in the same category, the highest in the 21st century. That figure is likely due to the air pollution created by the unprecedented Canadian wildfire smoke in Summer 2023.

While there has been no consistent year-to-year trend in the number of days per year rated to have air quality worse than moderate, the number of days in peak years had decreased from 2000 through 2022. Where peak years before 2000 had between one and two dozen days with air quality worse than moderate (e.g., 1983, 18 days; 1988, 23 days; 1994, 17 days; 1999, 24 days), the year with the greatest number of days with air quality worse than moderate from 2000-2022 was 2002, with 10 days. There were several years between 2006 and 2022 that had no days with air quality worse than moderate.

This data is sourced from the U.S. EPA’s Air Quality Index Reports. The reports are released annually, and our period of analysis is 1980-2024. The Air Quality Index Report websites does caution that "[a]ir pollution levels measured at a particular monitoring site are not necessarily representative of the air quality for an entire county or urban area," and recommends that data users do not compare air quality between different locations[2].

[1] Environmental Protection Agency. (1980-2024). Air Quality Index Reports. (Accessed 13 June 2025).

[2] Ibid.

Source: Environmental Protection Agency. (1980-2024). Air Quality Index Reports. https://www.epa.gov/outdoor-air-quality-data/air-quality-index-report. (Accessed 13 June 2025).

AQS data is a publicly available dataset, which is part of this study. This data can be found on EPA website https://aqs.epa.gov/aqsweb/airdata/download_files.html (accessed on 1 April 2023). PA data is a 3rd party data and restrictions apply to the availability of these data. Data was obtained from Purple Air and are available from PurpleAir API https://community.purpleair.com/t/making-api-calls-with-the-purpleair-api/180 (accessed on 1 April 2023) with the permission of Purple Air. HMS smoke plume data is publicly available and can be downloaded at Office of Satellite and Product Operations website https://www.ospo.noaa.gov (accessed on 1 April 2023). The codes to download and analyze data in this paper is available at this GitHub repo https://github.com/hyang199723/PAFusion (uploaded on 30 June 2023). This dataset is associated with the following publication: Yang, H., S. Ruiz-Suarez, B. Reich, Y. Guan, and A. Rappold. A data fusion approach to assessing the contribution of wildland fire smoke to fine particulate matter in California. Remote Sensing. MDPI, Basel, SWITZERLAND, 15(17): 1, (2023).

OpenAQ has collected 231,965,688 air quality measurements from 8,469 locations in 65 countries. Data are aggregated from 105 government level and research-grade sources. https://medium.com/@openaq/where-does-openaq-data-come-from-a5cf9f3a5c85 Note: this dataset is temporary not updated. We're currently working to update it as soon as possible.Disclaimers:- Some records contain encoding issues on specific characters; those issues are present in the raw API data and were not corrected.- Some dates are set in the future: those issues also come from the original data and were not corrected.

This GIS dataset contains points which depict air quality monitors within EPA's Air Quality System (AQS) monitoring network. This dataset is updated weekly to reflect the most recent changes in the monitoring network. The monitors are generally operated by State, local, and tribal air pollution control agencies using procedures specified by the U.S. EPA. These agencies collect the data, quality assure it, and then submit it to the EPA Air Quality System (AQS). The GIS dataset includes monitor information and links to download historic air quality data at each monitor.

Citywide raster files of annual average predicted surface for nitrogen dioxide (NO2), fine particulate matter (PM2.5), black carbon (BC), and nitric oxide (NO); summer average for ozone (O3) and winter average for sulfure dioxide (SO2). Description: Annual average predicted surface for nitrogen dioxide (NO2), fine particulate matter (PM2.5), black carbon (BC), and nitric oxide (NO); summer average for ozone (O3) and winter average for sulfure dioxide (SO2). File type is ESRI grid raster files at 300 m resolution, NAD83 New York Long Island State Plane FIPS, feet projection. Prediction surface generated from Land Use Regression modeling of December 2008- December 2019 (years 1-11) New York Community Air Survey monitoring data.As these are estimated annual average levels produced by a statistical model, they are not comparable to short term localized monitoring or monitoring done for regulatory purposes. For description of NYCCAS design and Land Use Regression Modeling process see: nyc-ehs.net/nyccas

The Environmental Protection Agency (EPA) provides air pollution data about ozone and particulate matter (PM2.5) to CDC for the Tracking Network. The EPA maintains a database called the Air Quality System (AQS) which contains data from approximately 4,000 monitoring stations around the country, mainly in urban areas. Data from the AQS is considered the "gold standard" for determining outdoor air pollution. However, AQS data are limited because the monitoring stations are usually in urban areas or cities and because they only take air samples for some air pollutants every three days or during times of the year when air pollution is very high. CDC and EPA have worked together to develop a statistical model (Downscaler) to make modeled predictions available for environmental public health tracking purposes in areas of the country that do not have monitors and to fill in the time gaps when monitors may not be recording data. This data does not include "Percent of population in counties exceeding NAAQS (vs. population in counties that either meet the standard or do not monitor PM2.5)". Please visit the Tracking homepage for this information.View additional information for indicator definitions and documentation by selecting Content Area "Air Quality" and the respective indicator at the following website: http://ephtracking.cdc.gov/showIndicatorsData.action

The National Air Pollution Surveillance (NAPS) program is the main source of ambient air quality data in Canada. The NAPS program, which began in 1969, is now comprised of nearly 260 stations in 150 rural and urban communities reporting to the Canada-Wide Air Quality Database (CWAQD). Managed by Environment and Climate Change Canada (ECCC) in collaboration with provincial, territorial, and regional government networks, the NAPS program forms an integral component of various diverse initiatives; including the Air Quality Health Index (AQHI), Canadian Environmental Sustainability Indicators (CESI), and the US-Canada Air Quality Agreement. Once per year, typically autumn, the Continuous data set for the previous year is reported on ECCC Data Mart. Beginning in March of 2020 the impact of the COVID-19 pandemic on NAPS Operations has resulted in reduced data availability for some sites and parameters. For additional information on NAPS data products contact the NAPS inquiry centre at RNSPA-NAPSINFO@ec.gc.ca Last updated March 2023. Supplemental Information Monitoring Program Overview The NAPS program is comprised of both continuous and (time-) integrated measurements of key air pollutants. Continuous data are collected using gas and particulate monitors, with data reported every hour of the year, and are available as hourly concentrations or annual averages. Integrated samples, collected at select sites, are analyzed at the NAPS laboratory in Ottawa for additional pollutants, and are typically collected for a 24 hour period once every six days, on various sampling media such as filters, canisters, and cartridges. Continuous Monitoring Air pollutants monitored continuously include the following chemical species: • carbon monoxide (CO) • nitrogen dioxide (NO2) • nitric oxide (NO) • nitrogen oxides (NOX) • ozone (O3) • sulphur dioxide (SO2) • particulate matter less than or equal to 2.5 (PM2.5) and 10 micrometres (PM10) Each provincial, territorial, and regional government monitoring network is responsible for collecting continuous data within their jurisdiction and ensuring that the data are quality-assured as specified in the Ambient Air Monitoring and Quality Assurance/Quality Control Guidelines. The hourly air pollutant concentrations are reported as hour-ending averages in local standard time with no adjustment for daylight savings time. These datasets are posted on an annual basis. Integrated Monitoring Categories of chemical species sampled on a time-integrated basis include: • fine (PM2.5) and coarse (PM10-2.5) particulate composition (e.g., metals, ions), and additional detailed chemistry provided through a subset of sites by the NAPS PM2.5 speciation program; • semi-volatile organic compounds (e.g., polycyclic aromatic hydrocarbons such as benzo[a]pyrene); • volatile organic compounds (e. g., benzene) The 24-hour air pollutant samples are collected from midnight to midnight. These datasets are generally posted on a quarterly basis. Data Disclaimer NAPS data products are subject to change on an ongoing basis, and reflect the most up-to-date and accurate information available. New versions of files will replace older ones, while retaining the same location and filename. The ‘Data-Donnees’ directory contains continuous and integrated data sorted by sampling year and then measurement. Pollutants measured, sampling duration and sampling frequency may vary by site location. Additional program details can be found at ‘ProgramInformation-InformationProgramme’ also in the data resources section. Citations National Air Pollution Surveillance Program, (year accessed). Available from the Government of Canada Open Data Portal at open.canada.ca.

This dataset contains quality assured and DOEE-certified air quality data collected from the District’s five air monitoring network sites. The dataset covers a three-year period and includes hourly concentration data points from the Environmental Protection Agency (EPA)’s criteria pollutants, air toxics, and speciation. It also includes hourly surface meteorology data points.

The Air Quality Index (AQI) for each monitoring station is provided hourly. The original data version is announced on the Air Quality Monitoring Network website https://airtw.moenv.gov.tw

The Air Quality Health Index (AQHI) is a scale designed to help quantify the quality of the air in a certain region on a scale from 1 to 10. When the amount of air pollution is very high, the number is reported as 10+. It also includes a category that describes the health risk associated with the index reading (e.g. Low, Moderate, High, or Very High Health Risk). The AQHI is calculated based on the relative risks of a combination of common air pollutants that are known to harm human health, including ground-level ozone, particulate matter, and nitrogen dioxide. The AQHI formulation captures only the short term or acute health risk (exposure of hour or days at a maximum). The formulation of the AQHI may change over time to reflect new understanding associated with air pollution health effects. The AQHI is calculated from data observed in real time, without being verified (quality control).

Download service for the data set: Air quality data; Air quality data reported to the Swedish Environmental Protection Agency’s data host is made available via a web service called Sensor Observation Service (SOS). Data is made available via SOS in real time (i.e. concentrations for the last hour) for a sample of air pollutants and measurement stations. Historical data is also made available through the service. Data on levels of different air pollutants, including particulate matter, nitrogen dioxide and ground-level ozone, in Swedish cities and rural areas. All data reported to the Swedish Environmental Protection Agency’s air data host is made available via the service. This includes quality-assured historical data and so-called real-time data reported directly from measuring instruments without quality review. Available data are produced by municipalities, county administrative boards, the Swedish Environmental Protection Agency and other organisations such as air pollution associations, in accordance with the provisions of the Air Quality Ordinance (SFS 2010:477) and the Swedish Environmental Protection Agency’s regulations on air quality control (NFS 2016:9).

This is a bulk data download resource for air pollution measurements hosted by Defra's UK-AIR web pages - see also http://uk-air.defra.gov.uk/.

Monitoring networks and pollutants included are those covered by http://uk-air.defra.gov.uk/networks/ with the exception of diffusive sampler measurements which are not in scope at this stage. Measurements are available for the period 1973 to 2014 inclusive. Measured pollutant concentrations, aggregated statistics and station configuration information (location, analyser type, inlet height etc.) are provided in XML format based the European Air Quality e-Reporting schema (further information at http://www.eionet.europa.eu/aqportal/).

The Air Quality System (AQS) database contains measurements of air pollutant concentrations from throughout the United States and its territories. The measurements include both criteria air pollutants and hazardous air pollutants.

The available data are fetched from http://pollution.gov.np by crawling and extracting web data. The activities of the fetching, cleaning, and publishing are done by the automated software bot and depend completely upon the quality of data published on the government websites, OKN does not guarantee the quality & validity of the data.

Unverified raw hourly air pollutant monitoring and meteorological data collected by the Ministry of Environment and Climate Change Strategy. These data sets contain air quality data from 2024 to the most recent hourly readings and meteorological data from 2023 to the most recent hourly readings from air quality monitoring stations across B.C, up to the latest hour in Pacific Standard Time (PST). This does not include data originating from Metro Vancouver and Fraser Valley Regional Districts. For current conditions for Metro Vancouver and Fraser Valley Regional Districts please visit https://gis.metrovancouver.org/maps/air/ This data is not quality-assured. Historical quality-assured air data is available here: https://catalogue.data.gov.bc.ca/dataset/77eeadf4-0c19-48bf-a47a-fa9eef01f409 Please subscribe using the following link if you want to receive the updates on the datasets: https://www2.gov.bc.ca/gov/content/environment/air-land-water/air/air-quality/current-air-quality-data Please click on VIEW resource to access For data files directing to a FTP site, please copy the FTP link to File Explorer (anonymous login), Finder or equivalent, or use a FTP client such as FileZilla to access the FTP link. If using File Explorer, Finder, or equivalent, copy the files requested from the FTP folder to a local location to download. ##### Data files are available for: ##### #### Current Air Quality Data: * Air Quality Health Index (Learn more about this index: http://www.env.gov.bc.ca/epd/bcairquality/readings/aqhi-table.xml) * Carbon monoxide (CO) in parts per million (ppm) * Hydrogen sulfide (H2S) and Total reduced sulfur (TRS) in ppb * Nitric oxide (NO) in parts per billion (ppb) * Nitrogen dioxide (NO2) in ppb * Sulfur dioxide (SO2) in ppb * Ground-level ozone (O3) in ppb * PM2.5 (particulate matter with diameter of 2.5 micrometres or less) in micrograms per cubic metre (ug/m3) * PM10 (particulate matter with diameter of 10 micrometres or less) in ug/m3 * THC (total hydrocarbons) in ppm #### Current Meteorological Data: * Air Temperature (TEMP) in degrees Celsius (°C) * Relative Humidity (HUMIDITY) in percent (%) * Wind Speed (WSPD) in meters per second (m/s) * Wind Direction (WDIR) in degrees from true north/azimuth (°) * Precipitation (PRECIP) in millimeters (mm) * Snow depth (SNOW) in centimeters (cm) * Barometric Pressue (PRESSURE) in kilopascals (kPA) or millibars (mb) * Water Vapor Pressure (VAPOUR) in kilopascals (kPA) or millibars (mb) #### Monitoring Locations * Locations of all current and historical air and meteorological stations including Latitude and Longitude

This dataset provides daily air quality analyses and forecasts for Europe. CAMS produces specific daily air quality analyses and forecasts for the European domain at significantly higher spatial resolution (0.1 degrees, approx. 10km) than is available from the global analyses and forecasts. The production is based on an ensemble of eleven air quality forecasting systems across Europe. A median ensemble is calculated from individual outputs, since ensemble products yield on average better performance than the individual model products. The spread between the eleven models are used to provide an estimate of the forecast uncertainty. The analysis combines model data with observations provided by the European Environment Agency (EEA) into a complete and consistent dataset using various data assimilation techniques depending upon the air-quality forecasting system used. In parallel, air quality forecasts are produced once a day for the next four days. Both the analysis and the forecast are available at hourly time steps and multiple height levels. Note that only nitrogen monoxide, nitrogen dioxide, sulphur dioxide, ozone, PM2.5, PM10 and dust are regularly validated against in situ observations, and therefore forecasts of all other variables are unvalidated and should be considered experimental.

Data sets describing which areas are in nonattainment with NAAQS and characteristics of monitoring locations. These files originated from the EPA Green Book and Air Quality System at https://www.epa.gov/green-book/green-book-data-download and http://aqsdr1.epa.gov/aqsweb/aqstmp/airdata/download_files.html

Air pollution is one of the most important environmental threats to urban populations and while all people are exposed, pollutant emissions, levels of exposure, and population vulnerability vary across neighborhoods. Exposure to common air pollutants has been linked to respiratory and cardiovascular diseases, cancers, and premature deaths. These indicators provide a perspective across time and NYC geographies to better characterize air quality and health in NYC. https://www.googleapis.com/download/storage/v1/b/kaggle-user-content/o/inbox%2F8355503%2F14ef8b505e945d4f7c5aa3ec0385c4c7%2FAir%20qlty.PNG?generation=1697342952820846&alt=media" alt="">

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[Text Source: AirData Program, https://www.epa.gov/airdata/ ]

The AirData website gives you access to air quality data collected at outdoor monitors across the United States, Puerto Rico, and the U. S. Virgin Islands. The data comes primarily from the AQS (Air Quality System) database. You can choose from several ways of looking at the data:

• download data into a file (or view it on the screen)
• output the data into one of AirData’s standard reports
• create graphical displays using one of the visualization tools
• investigate monitor locations using an interactive map

AirData assists a wide range of people, from the concerned citizen who wants to know how many unhealthy air quality days there were in his county last year to air quality analysts in the regulatory, academic, and health research communities who need raw data.