Evaluating the Pattern of Kava (Piper methysticum) Consumption in Australia by Wastewater-Based Epidemiology

Kava (Piper methysticum) is a plant native to the Pacific Islands, used in the preparation of a beverage consumed during ceremonies. The plant has gained popularity in other countries as a supplement for the treatment of anxiety and insomnia. Nevertheless, products containing P. methysticum were associated with liver damage, which led to the kava ban in several jurisdictions across the world, including Australia. However, in 2019, the Australian government started relaxing import restrictions as part of the kava pilot. It is therefore of interest to establish a baseline of kava consumption on a national population scale, serving as a reference point for understanding the long-term effect of this policy change.

Wastewater analysis of kavalactones and metabolites was employed to establish a baseline measurement of use in Australia. Influent samples were collected from 54 wastewater treatment plants from December 2023 to December 2024. Liquid-liquid extraction was used for sample preparation, followed by liquid chromatography-tandem mass spectrometry analysis.

Eight chemical markers were detected in wastewater collected from all participating treatment plants. The highest excreted loads were measured in regional Western Australia and the capital cities of New South Wales and the Northern Territory.

The use of kava and P. methysticum containing products was on average higher in regional areas compared to capital cities, and elevated at the weekend, suggesting recreational use. Wastewater analysis can provide specific insights into the use of kava and P. methysticum containing products and is implemented as part of routine drug epidemiology programs.