On the trail of pollution in Lausanne

In 2021, dioxins and furans were discovered in the soil of Lausanne’s Vallon neighborhood, leading a group of five researchers – Aurélie Berthet (Unisanté), Florian Breider (EPFL ENAC), Alexandre Elsig (EPFL CDH), Céline Mavrot (UNIL), and Fabien Moll-François (EPFL CDH, Unisanté) – to join forces to better understand how the incinerator operated, the composition of the pollution, and why the pollution had gone undetected until 2020. Their project was part of the Collaborative Research on Science and Society (CROSS) program, funded jointly by EPFL’s College of Humanities (CDH) and the University of Lausanne (UNIL).

Reconstructing the history of an incinerator

"It's very difficult to know what happened in this incinerator, how emissions are evolving and, potentially, how the population is being exposed,” explains Florian Breider, an environmental chemist who directs the Central Environmental Laboratory at EPFL’s School of Architecture, Civil and Environmental Engineering (ENAC).

To better understand what happened, the team worked together to ‘time travel’ to the past by accessing municipal, cantonal, and federal archives, political debates, and technical documents.

Through these methods, the researchers learned why the Vallon neighborhood was chosen as the site of the incinerator. Initially the La Sallaz neighborhood was considered, but after resistance from those residents, the site in Vallon was chosen, as it was a working-class neighborhood that was already considered “degraded” by some. And as it was in a valley, the visible chimney wouldn’t stand out as much. History would later show that the Vallon's topographical situation posed problems for optimal smoke dispersion.

The researchers were able to trace not only how the incinerator's technology worked, but also how the typology of the waste burned evolved over time, contributing to a better understanding of the pollution profile of dioxins and furans in soil.

"There is no single dioxin or furan compound, but a set of 210 congeners with varying structural characteristics and levels of toxicity. Prior to this research, knowledge of this historical pollution profile was lacking," explains Aurélie Berthet, toxicologist at Unisanté.

"We were able to find information in the archives on the nature and quantity of waste burned, as well as technical specifications on combustion temperature and the flue gas filtration systems that were successively installed," explains Fabien Moll-François, historian and sociologist of science at EPFL CDH and Unisanté. By learning from historical archives how much paper and green waste, for example, was incinerated, and in what quantities, the researchers were able to assess the chemical composition of the waste and its environmental impact.

Two ENAC master’s students in environmental engineering, Alexis de Aragao and Xiaocheng Zhang, also assisted in the research as part of their design projects. Using the data and records collected by the CROSS team, they found that in the early 1970s the incinerator had been used beyond its capacity, meaning that sometimes more than 50% of the total waste burned stayed behind as residue, important information from an environmental and socio-historical point of view.

The study also highlighted governance problems, such as the abandonment of another incinerator project, which would have reduced overcapacity at the Vallon incinerator. In the 1980s, management of the incinerator became more complex due to relations between the city, Canton, and Confederation. Despite several warnings about heavy metals as early as the 1970s and dioxins in the 1990s, the incinerator was not brought up to standard within the normal regulatory timeframe.

"The canton has significant competencies in terms of waste planning, management and monitoring, which tends to put it in the position of judge and jury," points out UNIL political scientist Céline Mavrot.

An interdisciplinary approach

Using their different profiles, the team was able to combine each of their expertise to carry out an interdisciplinary work that used tools and methods specific to their individual research areas of environmental chemistry, history of science and the environment, public health, and political science.

"It's quite rare for disciplines to work hand in hand like this and collaborate from the outset,” says Alexandre Elsig, a historian at CDH. “Usually, the research is done consecutively, whereas here we were doing the whole process as a team, allowing the historical archive data to be injected into the environmental chemistry work, and knowledge of environmental chemistry to guide the archive work as well.”

By bringing together their different disciplines and working collaboratively, the team was able to answer many important questions and developed an approach that can be applied in other cases.

Addressing local issues

"As CROSS projects are co-funded by EPFL and UNIL, it means we can tackle local issues,” says Breider. “We thought about applying for SNSF funding, but this type of funding is usually not geared toward local topics. So CROSS was an ideal funding tool for this type of research, and I don't know how we could have done this project without it."

After initial discussions with local residents to define the problem, the team returned to present the results on March 27 to around 100 people living in the neighborhoods most affected by pollution. The audience was very engaged, sharing their experiences and asking questions, for example about the possibility of pollutants other than dioxins being present in the soil, and the amount of time needed for pollutants to disappear from the soil. There were also questions about how pollution monitoring was organized and why the dioxin contamination was discovered so late. The team was able to provide answers to these questions while gathering valuable information on the frustrations that local residents have experienced.

Going forward, the team and the two ENAC students will submit a scientific paper on the mathematical model they have developed to assess past emissions of dioxins and furans from waste incineration plants. Breider will also present the work at an international conference in Taiwan on micropollutants and ecological risks. The researchers would also like to continue their investigations to include the timeframe of 2006-2020, which they were not able to do due to a six-month delay in accessing certain archives.