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New research has found increasing levels of artificial sweeteners in wastewater treatment plants, with downstream impacts on the environment.

Artificial sweeteners, widely used in soft drinks, processed foods and sugar-free products such as toothpaste, are increasingly turning up far from supermarket shelves—in our rivers, waterways and natural ecosystems.

Some sugar substitutes have faced controversy for potential negative health effects, including links to type-2 diabetes, heart disease and cancer. Some also pose toxicity risks to aquatic animals. In zebrafish, sucralose causes birth defects and high levels of saccharin are neurotoxic.

In a systematic review, researchers from the University of Technology Sydney (UTS) examined the type and prevalence of artificial sweeteners in wastewater treatment plants across 24 countries, changes in concentration, and how effectively they are removed.

The study was led by Dr. Xuan Li, from the UTS Center for Technology in Water and Wastewater, and UTS Professor of Environmental Engineering Qilin Wang. It was recently in the Journal of Hazardous Materials.

The researchers found that globally, sucralose, acesulfame, saccharin, and cyclamate are the most prevalent artificial sweeteners. The highest concentrations of these chemicals were found in the U.S., Spain, India and Germany.

Concentrations were 10%–30% higher in summer for most countries, however, in China they were highest in winter. Other artificial sweeteners found in wastewater include neotame, stevia, acesulfame-K and neo hesperidin dihydrochalcone (NHDC).

Unlike natural sugars, artificial sweeteners are designed to resist digestion, meaning they often pass through the human body largely unchanged. As a result, they enter wastewater systems where standard treatment processes aren't always equipped to deal with them.

The researchers found that while saccharin and cyclamate were easily removed from wastewater, other artificial sweeteners such as sucrose and acesulfame were harder to remove, and were released into the wider environment.

There is a lot of attention on per- and polyfluoroalkyl substances (PFAS) at the moment because these "forever chemicals" can accumulate in the environment and in drinking water, affecting living organisms. It is a similar pathway for artificial sweeteners, which also accumulate in the environment.

"Sweeteners such as sucralose are incredibly persistent. Its chemical stability means it can survive both conventional and advanced treatment processes, so it eventually makes its way into rivers, lakes and coastal waters where it can affect aquatic ecosystems," Professor Wang said.

The findings are likely to be of interest to environmental protection agencies, water authorities and public health experts due to the potential ecological impacts of these chemicals, and as a marker of human-derived pollution.

"We are also looking at using wastewater analysis to measure the consumption of artificial sweeteners at a population level. People are often not aware that the product they are consuming, such as a protein shake, contains artificial sweeteners," said Dr. Li.

The study calls for ongoing monitoring, tighter regulations, and improved treatment technologies to reduce the environmental risks posed by artificial sweeteners.