Created by: Chang Zhao

Research Methodologist at NORC at the University of Chicago

Last update: 2021-01-13

This report investigates how air quality during the COVID-19 period changes compared to a baseline for the City of Chicago, based on environmental sensor data collected by the AoT project. It also examines neighborhood variability of air pollutant concentrations and COVID-19 cases, deaths and tests, to achieve a better understanding of the spatial patterns in air quality, COVID-19 statistics, and their spatial congruence and disagreement. Data for this report is updated weekly.

To explore the tool, you could select 1) the daily statistics of interest, 2) the date range of the baseline period for comparison, 3) the date range in which you expect air quality would change in response to the COVID-19 pandemic, and 4) the type of data source. The rest of the report will be updated according to your selections.

There are two types of data source: (1) Raw version: we keep all raw AoT records unless they are beyond sensor's minimum and maximum limits, such as negative values. (2) 'Cleaned' version: some excluded AoT data points reported air pollutant concentrations above the maximum level of instantaneous concentrations found in the literature (Stern, 1968). In particular, data points where O3 > 1 ppm, H2S > 1 ppm, SO2 > 5 ppm, NO2 > 1 ppm are considered extremely rare in reality and are removed from the raw dataset for visualization. There is a critical need to discuss with the AoT team to reach resolution about what should count as valid measurements so as to further clean the dataset.

* Because all of the 2020 PM2.5 and PM10 data come from the Ashburn sensor, city-level aggregated estimates for PM2.5 and PM10 are suppressed.

* Because all of the 2020 PM2.5 and PM10 data come from the Ashburn sensor, city-level aggregated estimates for PM2.5 and PM10 are suppressed.

Figure 1 shows trends in air quality over several weeks with the most recent data representing approximately 1-2 days ago-this is how long it takes AoT to publish real-time air quality data. The blue region on the plots represents baseline period, and the red region represents COVID-19 period, for which 2020-03-10 was specified as the default start date (red vertical line) unless otherwise reset by user. It was empirically chosen based on Google's COVID-19 community mobility report, which shows a significant reduction in human activities in IL, likely in response to policies aimed at combating COVID-19 (https://www.google.com/covid19/mobility/). You are encouraged to try different values of the start and end dates, as well as the type of statistics, Figure 1 (and Table 1) will be updated accordingly.

As another reference point, the orange line on the graph indicates the first complete day when Illinois statewide Stay-At-Home Order was in effect for Illinois residents. This order is expected to begin at 5 p.m. 2020-03-21 and continue through May 30.

We also examine how air quality changes during the COVID-19 period in 2020 compared to the same dates in 2019 (Table 2, Figure 2). Again, you are encouraged to experiment with different values of the input dates and type of statistics, Table 2 and Figure 2 will be updated accordingly.

* Data may be coming from different sensors in the two time periods. PM2.5 and PM10 sensors are only available in Ashburn in 2020, as opposed to multiple communities including Ashburn in 2019. As a result, city-level aggregated estimates for PM2.5 and PM10 are suppressed.

* Data may be coming from different sensors in the two time periods. PM2.5 and PM10 sensors are only available in Ashburn in 2020, as opposed to multiple communities including Ashburn in 2019. As a result, city-level aggregated estimates for PM2.5 and PM10 are suppressed.

Here we look at how air quality varies by Chicago neighborhood and also allow the user to add a layer of data (upper right-hand corner of map) on cases and rates of COVID-19 testing, infections, and deaths by zip code area in order to investigate possible links between the two.

COVID-19 Data Source:

The City of Chicago Data Portal provides COVID-19 cases, tests, and deaths by ZIP Code on a weekly basis. The map is showing data in/through the week ending 2021-01-09 02:00:00. Map is updated weekly to reflect the most recent data changes. Please contact dataportal@cityofchicago.org or @ChicagoCDO with any questions, comments, or concerns related to the COVID-19 dataset. For subject matter questions about this dataset or any other COVID-19 datasets, please contact the Department of Public Health's epidemiology team at epidatarequests@cityofchicago.org. For general information about COVID-19 in Chicago, please visit https://www.chicago.gov/coronavirus or contact coronavirus@chicago.gov.

Here we look at how air quality changes across months in 2020. Monthly averaged air quality monitored data of AoT were interpolated to grid cells that cover the city of Chicago extent using Inverse Distance Weighting techiniques. Values were displayed based on quantile classification to allow for comparison across months.

Stern, A.C., (Ed.). (1968). Air Pollution, 2nd edition. Academic Press, New York.