As sewage markers in untreated rivers worldwide
Artificial sweeteners—or low-calorie sweeteners—have recently again been the subject of controversy due to the ongoing debate surrounding their possible role in life-threatening diseases, such as cancer.
Two results can occur when ingested, depending on the sweetener’s chemical nature.
The body absorbs one type and not the other.
The latter type is the focus of collaborative research, led by the Tokyo University of Agriculture and Technology, investigating regional surface waters from Africa to Japan.
The team evaluated four types of low-calorie sweeteners—acesulfame (ACE), sucralose (SUC), saccharin (SAC), and cyclamate (CYC)—and found that the human body does not absorb and metabolise ACE and SUC. So, they persist in the sewage via the toilet.
The other two are generally biodegradable and theoretically unsuitable as sewage markers.
However, neither ACE nor SUC is perfectly persistent in the environment. With advancements in biological sewage treatments in limited regions, differences exist in surface-water ACE and SUC use. While the US, for example, prefers SUC for its chemical profile and ease of use, this sweetener may not appear in other countries opting for more affordable sweeteners.
For the study, the international team coordinated to collect and analyse 272 buckets of water samples from 14 countries spanning Africa, the Middle East, Southeast Asia, India, and Japan.
Results showed an 88% detection rate for ACE, highlighting its wide popularity as an artificial sweetener across different continents. SUC showed up at 51% despite being chemically more resistant than ACE in the environment.
Although SUC was less detected, its significant persistence suggests its overall low sensitivity and sewage concentration.
Counterintuitively, surface waters across many regions contained significant amounts of the biodegradable sweeteners SAC and CYC. Their widespread use and inadequate sewage treatment systems may explain the increasing inflow, posing challenges to some countries.
For example, India’s exceptionally high SAC-to-ACE ratios in river-water samples reflect the country’s SAC use and outdated treatment facilities.
Positive correlations were also found between the distribution patterns of artificial sweeteners and traditional molecular markers, supporting the use of sweeteners to monitor hydrophobic substances, such as antibiotics, in river sewage inputs.
Springing from the benchmark set by the 2010 water pollution status in Asia, Africa, and the Middle East, the study’s results herald the team’s call to action: Sewage treatment systems worldwide require upgrades to ensure consistent water quality and public health.