Dan Richter, a professor of soils at Duke University’s Nicholas School of the Environment, samples the edges of a creek bed on the site of a former municipal waste incinerator in Durham, NC. Credit: Dan Richter, Duke University
The more research is done, the more lead exposure is linked to damage to the brain and nervous system, especially in children. But thus far, this research has mostly focused on risks in homes, especially lead-based paint.
Now, a new study by researchers at Duke University reminds us that risks exist in outdoor places as well—especially city parks and playgrounds built on the site of former waste incinerators.
For many years, cities across the United States and Canada burned their trash and waste in municipal incinerators. However, after concerns about air pollution and toxins, most of the facilities closed by the early-1970s. That’s not to say their impact doesn’t live on. In this project, Daniel Richter, professor of soils at Duke University, discovered that parks and playgrounds built on the sites of former waste incinerators can still have greatly elevated levels of lead in their surface soils—even more than 80 years after the incinerators stopped operating.
For the study, published in Environmental Science & Technology Letters, Richter and his students collected and analyzed surface soil samples from three city parks in Durham, N.C. that are located on former incinerator sites closed in the early 1940s.
Samples collected from East Durham Park contained lead levels over 2000 parts per million, more than 5x higher than the current U.S. Environmental Protection Agency (EPA) standard for safe soils in children’s play areas. Meanwhile, samples collected from Walltown Park mostly contained low lead levels, “but about 10% were concerning and a few were very high,” said Richter. Lastly, samples collected from East End Park contained levels of soil lead below the current EPA threshold for children’s safety and presented no cause for concern.
“These incinerators burned all kinds of garbage and trash, including paint, piping, food cans and other products that contained lead back then,” Richter said.
Then, the leftover ash—in which lead and other contaminants were concentrated—was either covered with a too-thin layer of topsoil or spread around parks, new construction sites or other urban spaces as a soil “add-on.”
That’s why Richter and team turned to historic surveys and records to get a full picture of the landscape 50+ years ago. By analyzing historic surveys of municipal waste management, the team found that about half of all cities surveyed in the U.S. and Canada incinerated solid waste between the 1930s and 1950s. Additionally, in their paper, the team provides histories gleaned from archived public works records, old street maps and newspaper clippings showing where ash was burned and disposed of in six sample cities: Los Angeles; New York City; Baltimore; Spokane, Wash.; Jacksonville, Fla.; and Charleston, S.C.
“Historical surveys indicate a lack of appreciation for the health and environmental hazards of city-waste incinerator ash. Back then, they didn’t know what we do now,” Richter said.
Between ash being moved post-incineration and the sharp differences in lead levels between the three parks in the study, Richter says sampling and increased monitoring are necessary. The soils professor also said the historical records could speed efforts to identify hotspots, as well as the use of advanced technology like portable X-ray fluorescence (XRF).
In their study, Richter’s lab used portable XRF to complete preliminary analysis on a single soil sample for multiple metals, including lead, in just 20 seconds.
“Determining where contamination risks persist, and why contamination is decreasing at different rates in different locations, is essential for identifying hotspots and mitigating risks,” Richter said. “Many cities should mobilize resources to do widespread sampling and monitoring, and create soil maps and, more specifically, soil lead maps.”