Artificial sweeteners in surface waters from Asian, African and Middle Eastern countries: Utility as molecular markers and water pollution status in 2010–2019

To explore the utility of artificial sweeteners (Acesulfame: ACE; sucralose: SUC; saccharin: SAC; cyclamate: CYC) as molecular markers and to establish a historical benchmark of the water pollution status in the 2010 decade, 272 surface water samples, including river water, sewage, and livestock wastewater, were collected from African (Ghana Kenya, Mozambique, South Africa), Asian (Vietnam, Indonesia, Thailand, Philippines, Cambodia, Malaysia, India, and Japan) and Middle Eastern (Iran and Lebanon) countries during 2010–2019 and were analyzed for the artificial sweeteners by high performance liquid chromatograph with tandem mass spectrometer coupled with online solid-phase extractor. ACE was most frequently detected (87% of the samples) due to its widespread use and lower detection limit (2 ng/L). SUC was less frequently detected (51%) because of its lower sensitivity and detection limit of 100 ng/L, and less widespread use in some low-income countries, probably due to its higher price. SAC and/or CYC were abundant in surface waters of most countries, despite their biodegradable nature. This was ascribed to intensive usage of SAC and CYC and extensive inputs of untreated sewage to rivers due to limited installation of sewage treatment systems. Concentrations of the sweeteners were higher in urbanized rivers (~1 μg/L to ~100 μg/L) than those in corresponding suburban and rural sites, reflecting spatial patterns of sewage inputs. Furthermore, concentrations of the sweeteners were positively correlated with those of linear alkylbenzenes (LABs) for all countries except Malaysia. These results confirm the utility of artificial sweeteners as indicators of sewage inputs. SAC and CYC could be indicators of untreated sewage inputs. ACE has proved to be the most sensitive and reliable marker to assess inputs of sewage, i.e., both treated and untreated, to surface waters. However, ACE concentrations in secondary effluents and receiving waters in Tokyo decreased two orders of magnitude from 2011 to 2019, while sucralose did not show such a marked decrease. This is probably due to the upgrading of activated sludge treatment, i.e., introducing anaerobic-anoxic-oxic (A2O) treatment and resultant higher removal of ACE. Therefore, the measurement of multiple markers, including SUC, is recommended for long-term monitoring.

Key words: molecular markers; artificial sweeteners; river water; Africa; Asia; Middle East; linear alkylbenzenes; monitoring; A2O; sewage treatment, antibiotics