A study of three rural sewer sites in Germany found that human water use contributed more trifluoroacetate than known background sources could explain.
Researchers built a water and chemical balance for three rural sewer sites to trace where trifluoroacetate, a very persistent and highly water-soluble member of the PFAS group, came from. They compared contributions from groundwater, drinking water, rainwater and human water use under dry and rainy conditions.
Human water use made up the largest share of the trifluoroacetate load at every site, and concentrations peaked during the morning rise in wastewater. The researchers attribute much of this surplus to people excreting trifluoroacetate taken in through food and drink, but an approximate dietary intake estimate could not account for all of it. They suggest that products such as cosmetics may also contribute.
Where the chemical came from
At two sanitary sewers, groundwater and drinking water supplied the largest background loads of trifluoroacetate. During a storm, rainwater dominated the load in the combined sewer, even though it diluted the chemical’s concentration.
Across all three sites, the trifluoroacetate load linked to human water use exceeded the combined contribution from groundwater, drinking water and rainwater. Its concentration also peaked during the morning wastewater surge. The researchers say excretion after dietary exposure likely accounts for part of the surplus, but their approximate estimate of dietary intake was too low to explain it on its own. Other sources, such as cosmetics, may contribute.
Evidence and open questions
The study used a mass balance at three rural sewer sites in Freiburg, Germany. The researchers estimated contributions from groundwater and drinking water using end-member mixing analysis, and estimated rainwater’s contribution by comparing flows during dry weather and a storm event.
The dietary comparison was approximate, and the study did not identify or measure a specific additional source. Cosmetics are presented as a possible contributor, not as a demonstrated cause. The authors call for more data on human trifluoroacetate uptake and excretion and on other sources linked to human water use. Because the work covered three rural sites, its findings may not represent all sewer systems or communities.
