Urban parks built on former waste incineration sites could be major hotspots, the study finds

For most of the last century, many cities across the United States and Canada have burned trash and waste in municipal incinerators. Most of these facilities were closed in the early 1970s due to concerns about the pollution they added to the air, but a new study from Duke University finds that their pollution legacy can live on in urban soil.

“We found that city parks and playgrounds built on the site of a former waste incinerator still had very high levels of lead in their topsoil several decades after the incinerator closed,” said Daniel De Richter, a soil professor at Nicholas Duke University. School of Environment, which co-led the research.

Exposure to lead in soil has been linked to potential long-term health problems, especially in children. These include potential damage to the brain and nervous system, slowed growth and development, and learning and behavior problems.

To conduct their study, Richter and his students collected and analyzed topsoil samples from three parks in Durham, North Carolina, which are located on the sites of former incinerators that closed in the early 1940s.

Samples collected from a two-acre section of an east Durham park contained lead levels of more than 2,000 parts per million, more than five times the current U.S. Environmental Protection Agency (EPA) standard for safe soil in children’s play areas.

Samples collected from Wooltown Park mostly contained low levels of lead, Richter noted, “but about 10% of them were of concern, and a few were very high.”

The samples collected from East End Park all had soil lead levels below the EPA’s current threshold for child safety “and represent no cause for concern,” he said.

He stressed that the sharp differences in lead levels between the three parks underscore the need for increased monitoring.

“Determining where pollution risks persist, and why pollution is decreasing at different rates in different locations, is essential for identifying hotspots and mitigating risks,” Richter said. “Many cities must mobilize resources to do extensive sampling and monitoring, create soil maps and, more specifically, soil lead maps.”

“This is where we really need to go,” Richter said. “Not just in Durham but in hundreds of other towns where parks, as well as churches, schools and homes, may have been built on former waste incinerators and ash disposal sites.”

By analyzing historical surveys of municipal waste management, the Duke team found that about half of all cities studied in the United States and Canada burned solid waste between the 1930s and 1950s.

“These incinerators burned all types of trash and garbage, including paint, pipes, food cans and other products that contained lead at the time,” Richter said. The remaining ash, which concentrated lead and other contaminants, was sometimes covered with a very thin layer of topsoil or even spread around parks, new construction sites or other urban spaces as a soil amendment.

“Historical surveys show a lack of appreciation for the health and environmental risks from ash from urban waste incinerators,” he said. “At the time, they didn’t know what we do now.”

He added that new technology could help make sampling and monitoring more feasible at thousands of sites across the country that may be contaminated. Using a portable X-ray fluorescence instrument, his lab is now able to perform a preliminary analysis of a soil sample for multiple metals, including lead, in just 20 seconds.

Leveraging historical records about waste incineration and ash disposal can also speed up efforts to identify hotspots. In their paper, Richter and his students present a history culled from archived public works records, old street maps, and newspaper clippings that show where ash was burned and disposed of in six sample cities: Los Angeles; New York City; Baltimore; Spokane, Washington; Jacksonville, Florida; and Charleston, SC

“This is something you can do for many cities to direct monitoring efforts,” Richter said.

“There has been a lot of interest in mitigating lead exposure in cities, but most of it so far has focused on reducing risks inside the home. Our study reminds us that risks exist in the outdoor environment as well,” he said.

Richter and his students published their findings on September 11 Environmental science and technology letters.

Co-authors of the new paper were Eniko Bihari, a 2023 Master of Environmental Management graduate from Nicholas College who conducted much of the research as part of her master’s project, and Garrett Grewal, a senior at Duke University specializing in earth and climate sciences. .