Mapping lead levels in Chicago soil is the first step in understanding contamination risks in foods grown in urban areas. Photo by Andrew Margenot, assistant professor in the Department of Crop Sciences at University of Illinois.

Unleaded: Developing better ways to predict and detect household lead

The water crisis in Flint, Michigan, brought lead contamination to the forefront of the public eye, although it wasn’t an isolated incident. Lead contamination lurks in environments across the country — both water and soil — regardless of whether residents are aware of it. 

A couple of Midwestern research projects are advancing awareness of lead and its prevalence in the environment. Both projects aim to develop innovations that provide residents with greater insight by predicting or detecting lead exposures.

Household testing

Across the country, state and local agencies determine which households have lead hazards by examining lead levels in children’s blood tests. But that method is not ideal considering people already must have experienced lead exposure for it to be found. Indiana University researchers are working with a team in North Carolina on a better way to predict household lead exposure risk.

“Our vision is to create a 21st-century approach that prevents lead exposure before it ever happens by predicting houses where lead is most likely to be a problem,” Jacqueline MacDonald Gibson, IU environmental and occupational health professor, said in a news release.

The study employs machine learning techniques and publicly available data about residential lead exposure risks to create a mapping tool and website that predicts Indiana and North Carolina households’ lead exposure. 

The team is soliciting residents’ participation. Residents will use test kits to gather and ship water, soil, and dust samples to the researchers for lead analysis. Individual results remain confidential, and each participant will receive recommendations for decreasing lead exposure, if needed.

Public mapping project

Chicago is another area where lead is known to be present in the environment. The city has been criticized for its slow removal of lead water pipes — including by President Joe Biden, who recently called for Chicago to remove its 400,000 lead service lines in the next 10 years. 

Public knowledge of the problem varies widely. Now, for the first time, communities will have access to a citywide digital map showing how much lead is in their soil, thanks to University of Illinois researchers.

Chicago area communities have access to a city-wide map showing how much lead is in the soil where they live. Credit: University of Illinois
Chicago area communities have access to a city-wide map showing how much lead is in the soil where they live. Credit: University of Illinois

They partnered with some researchers from Chicago-based Advocates for Urban Agriculture. In 2018, they started gathering soil samples as part of the Chicago Safe Soils Initiative. They offered free soil tests to Chicago residents and were able to gather data from thousands of samples across the city.

Results indicate widespread lead contamination in Chicago’s soil:

  • The median lead amount was 220 parts per million, which is 11 times higher than the natural level of 20 ppm. 
  • Scientists determined that about 6% of soil in Chicago contains lead levels higher than 400 ppm.
  • The Illinois Environmental Protection Agency follows guidance from the U.S. Environmental Protection Agency suggesting lead levels of 400 ppm are hazardous, especially to children. The California EPA’s threshold is far more conservative, at 80 ppm.

“This work identifies that soil contamination by lead is widespread across Chicago, and most of the city exceeds limits of the more conservative environmental health guidelines,” Andrew Margenot, University of Illinois assistant professor, told Centered. “This raises the need for additional risk identification and mitigation efforts at finer scale to ensure safety and support decision making by Chicagoans who use soils for recreation, gardening, and other activities.”

Pertinence to planting

Problems can arise from direct contact with lead-contaminated soil, such as when gardening. Scientists also have expressed concern about whether it’s safe to consume produce grown in contaminated soil, especially as urban agriculture is increasing. 

The Illinois scientists wanted to determine how much lead fruits and vegetables absorb from soil. They worked with local growers to conduct experiments including growing tomatoes in the soil both with and without added phosphate nutrients. Phosphate is recommended by the EPA for reducing lead in soil, but it hasn’t explicitly been addressed for reducing lead in plants.

The plants grown in different soils with and without phosphate didn’t show differences in lead levels. Tomatoes’ lead levels were more impacted by where and during what season they were grown, Margenot said. However, another paper by these researchers shows that adding phosphate affects the amount of lead kale takes from soil.

Margenot says the researchers do not plan to replicate the study in other locations due to funding constraints. But they hope the methodology and insights provide guidance for other cities looking for environmental lead mitigation solutions.