21 September 2023

Waste incineration leaves a heavy legacy in soils


Where waste was once burned, higher concentrations of lead are detected in the soil, says research from Duke University. With obvious health consequences

by Matteo Cavallito


City soils that have hosted waste incineration plants in the past may still be contaminated, even decades after operations have closed. This is suggested by research from Duke University in Durham, North Carolina. Used for many decades of the last century in many cities in the United States and Canada, municipal incinerators were largely shut down in the 1970s in the face of growing concerns about air pollution.

The consequences of their presence, however, would still be visible today. “We found that city parks and playgrounds built on the site of a former waste incinerator can still have greatly elevated levels of lead in their surface soils many decades after the incinerator was closed,” said Daniel Richter, a Duke professor who collaborated on the research, in a note released by the university.

The study

In the study, whose results were published in the journal Environmental Science & Technology Letters, researchers collected and analyzed surface soil samples from three urban parks – East Durham, Walltown and East End – located on former incinerator sites closed in the early 1940s. “In 2021–2022, seven decades after parks were created, two parks had soil-Pb > 400 mgPb/kg, the U.S. Environmental Protection Agency (EPA)’s threshold for safe soil in play areas,” the study states.

“At Walltown Park, six of 97 surface samples ranged from 416 to 1338 mg Pb/kg within meters of a basketball court and a park path. East Durham Park had a hectare-sized area where 12 samples averaged 1294 mgPb/kg (median 1335 mg/kg).”

In the samples collected from East Durham Park, in other words, lead levels were more than five times higher than the safety threshold set by the EPA for children’s play areas. Those from Walltown Park showed lead levels of concern in about 10 percent of cases. In contrast, the levels detected on the East End grounds were within the normal range. According to the authors, these significant differences in lead levels highlight the need for more extensive monitoring.

The legacy of waste is a widespread problem

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

And the problem, the researchers explain, is that the occurrences of waste contamination could be quite extensive, at least in North America.

“Engineering surveys of United States and Canadian cities in 1941 and 1958 suggest that half incinerated solid wastes,” the study says. “Many records describe how incinerator ash was dumped with little regard for health or environmental hazards.” These, in particular, were sometimes covered with a thin layer of topsoil. Or even scattered in parks, new construction sites or other urban spaces as soil conditioner.

New studies are needed

According to scientists, it now becomes necessary to further study the problem. Crucial, on the one hand, is to continue on the path of soil analysis, relying on new technologies that can detect the presence of metals, such as lead, almost instantaneously.

Second, it is necessary to collect historical data on waste incineration and ash disposal to identify potentially contaminated areas. “There’s been a lot of interest in mitigating lead exposure in cities, but most until now has been focused on reducing risks within the home,” Richter concludes. “Our study reminds us that risks exist in the outdoor environment, too.”