Mapping Vulnerability to Lead Water Exposure

My project visualizes census tracts with the highest risk of lead exposure from lead service lines in Chicago. Although the federal government prohibited lead-based paint in 1973, lead service lines in new housing construction were not banned in Chicago until 1986. Historically, prior Chicago mayors have not addressed this problem and today there are an estimated 400,000 service lines, the most of any U.S. city.

While the Lightfoot administration made promises to tackle the issue, to date, the city has replaced well under 1,000 service lines or less than 1%. The urgent need to replace all lead service lines cannot be overstated enough as this is a public health issue. It has been well documented that lead exposure is harmful to human health and particularly children. Lead exposure among children can lead to Lower IQ, academic disabilities, and decreased cognitive functioning (e.g. attention, memory, language). The hope of this project is to provide a path forward on where the city can invest immediate replacement based on the limited funds available, so that the census tracts most vulnerable to lead exposure can have access to healthy drinking water.

With this in mind, I created a vulnerability index to measure risk of lead exposure in households’ water supply based on sociodemographic and housing data. Below, you can read about the six factors examined and why they were chosen.

Median Household Income: More discretionary income indicates a greater ability for a household to replace their own lead service lines (as they are considered private property, and thus, not the city's responsibility).

Residences Built Pre-1980: Residences built prior to the federal ban on lead service lines.

Single Family or Two Flat Residences: Most lead service lines are connected to single family homes or two flats.

Population without Health Insurance: Individuals without access to healthcare may not identify or treat the effects of lead exposure.

People of Color (Black and/or Latinx): Studies show that people of color are more prone to have lead exposure. Please read more about this in the limitations section below.

Presence of Children: Children are more at risk to serious, long-term effects of lead exposure and for this study, children was identified as below 9 years old.

To display the process of creating the index, I included additional maps to visualize each factor used in the index (featured below). The findings of this project can encourage accountability in remediation efforts and inform investments in lead service line replacement.

To better understand this problem, let's begin with a timeline explaining how both corporate and government partnerships created the lead water crisis Chicago faces today.

Please click on images to see them enlarged

To construct the map for this project, I sourced sociodemographic and housing data at the census tract level from the U.S. Census Bureau's American Community Survey, using 2021 5-year estimates. I chose the six factors (Race/Ethnicity, Presence of Children, Median Income, Rate of Uninsurance, Age of Housing, and Type of Housing) based on the literature review of similar analysis in Chicago and other vulnerability indices.

Unfortunately, for median income, there were 10 census tracts with missing data and as a result, I conducted a few interpolation methods to generate estimates. Once this was completed, I ran a hot spot analysis on the six factors mentioned above using the Getis-Ord Gi* tool. This tool provided a z-score for every census tract, which revealed spatial clusters of either high or low value. The red (hot spot) represents clustering of high values whereas the blue (cold spot) represents clustering of low values. For the purpose of my research, I was especially curious to learn which census tracts had clustering of high values, as a method to determine areas of highest vulnerability.

Once the six hot spot maps were created, I received a z score for each census tract, however, I then needed to normalize these z scores so that I could combine the results of all six layers accurately. The normalization range was from 0-1, meaning that the lowest z score would receive a 0 and the highest z score received a 1. Finally, I combined the normalized z scores from the six vulnerability factors to determine which census tracts had the highest vulnerability score. As there were six factors, the highest score possible for a census tract was 6 and the lowest score was 0. The image gallery walks you through my methodology and the following section is an interactive map of the final results.

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Interpolation

Hot Spot Analysis

The Lead Risk Exposure Index (LREI) is a composite of the listed factors associated with lead exposure risk, and it included 862 census tracts in Chicago. The LREI score is out of 6 (6 representing most vulnerable) and the average LREI score was 3.65. Out of the total census tracts in Chicago, 512 or 59% had a LREI score above 3.65.

Please explore the map below by using the address search tool in the top left corner.

The LREI revealed that not a single census tract is completely free of lead exposure through a service line. That said, the areas that tested above average are located throughout most of the city, but do not include areas like the Loop or neighborhoods on the North side like Lincoln Park, Near North Side, Uptown, and Lakeview. The research completed for this project confirms existing literature whereby historically disinvested and marginalized communities are more at risk for lead exposure. Furthermore, the neighborhoods with the highest LREI score in Chicago were Brighton Park, Gage Park, Chicago Lawn, New City, Englewood and West Englewood.

The findings from this analysis align with previous research on lead testing in Chicago homes, which has demonstrated an inequitable distribution of lead exposure risk. Furthermore, the results of LREI also indicate where investments in lead remediation are most critical in Chicago. As the City seeks to expand water testing and lead service line replacements, interventions should be targeted in the communities (listed above) with the highest risk for lead risk exposure.

My analysis was limited by data availability and time. As there is no public lead service line data for Chicago, I had to create the index as a proxy for where lead service lines are likely located, and where their impacts pose the greatest threat.

Due to time restraints I was not able to consider other important factors such as existing health conditions (e.g. blood lead levels in children) and levels of pollution which would highlight other compounding factors that increase the threat of lead exposure on human health, primarily children. Additionally, as both Black (29%) and Latinx (30%) residents are the two largest POC communities in Chicago, representing nearly 60% of the entire city's population, this study focused on their experience which means that other communities of color (e.g. Asian, Indigenous, Native Hawaiian, and Pacific Islander) would need to be examined further. In Chicago, the communities mentioned above in parenthesis make up 8% of the city's population.

Lastly, there were some census tracts that are missing median income data and for these, I had to run interpolation methods which provided an estimate, but not the exact number.

It cannot be overstated enough how important it is that the City of Chicago prioritizes the replacement of all lead service lines. My research shows that lead exposure affects a substantial amount of the city, and the most impacted areas are in Brighton Park, Gage Park, Chicago Lawn, New City, Englewood and West Englewood. In moving forward, the findings of this project can inform where to direct the most immediate investment of lead service line replacement.

Given the findings of my project, it is highly encouraged that you test your water at home, check out the following resources to learn more about lead service lines in Chicago, and advocate for the city to prioritize this issue.

Reach out to your local alderperson to stress this as an important issue to Chicago residents and learn how city officials are working to protect our community from lead exposure.

This project would not have been possible without a lot of support! I would like to thank Anton Rozhkov, Andrea Craft, Christopher Silber, Bailey Foster, and Grace Li.