First-ever Aussie study of “forever chemicals” in rain finds safe concentrations for drinking water

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First-ever Aussie study of “forever chemicals” in rain finds safe concentrations for drinking water

The first Australian study of PFAS – so called “forever chemicals” – in rainwater has found safe concentrations of the chemicals according to the NHMRC Australian Drinking Water Guidelines.

Researchers from RMIT University and EPA Victoria detected eight PFAS compounds in rainwater samples collected in Melbourne between 2024 and 2025.

PFAS are a large family of human-made chemicals comprising thousands of individual compounds used in products ranging from firefighting foams and food packaging to textiles, cosmetics and non-stick cookware.

While the findings may reassure people who rely on rainwater tanks, the study also offers clues about how these chemicals reach waterways and catchments far from obvious sources of contamination.

PFAS can enter the atmosphere attached to dust particles or tiny water droplets, travelling long distances before returning to the environment through rainfall.

Based on Melbourne rainfall and the concentrations measured in the study, the researchers estimated that rain might deliver about 10.6 kilograms of PFAS directly to Port Phillip Bay each year. That is about 5.5 grams/km² for the entire Port Phillip Bay, which has a surface area of 1,930 km².

The estimate suggests rainfall could be an important pathway for PFAS entering waterways, alongside better-known sources such as wastewater, urban runoff and landfill.

Two researchers wearing lab coats and safety glasses operate analytical laboratory equipment at RMIT University

RMIT University researchers Nav Singh (left) and Professor Oliver Jones prepare samples for PFAS analysis in their laboratory. Credit: Ant Bragaglia, RMIT University

Managing contamination risks

Lead researcher Professor Oliver Jones, from RMIT’s School of Science, said the findings addressed a long-standing question about how PFAS sometimes appear in places where there were no obvious nearby sources.

"Finding PFAS in rain isn't surprising given how widespread these chemicals are in the environment," Jones said.

Jones said detecting a chemical did not automatically mean there was a health risk.

“The more useful question isn't whether a chemical is toxic, but whether it's present at a concentration that could actually cause harm,” he said.

“Dose and exposure matter.”

The researchers hope the work will encourage broader monitoring of PFAS in rainfall across Australia and improve understanding of how these chemicals move through the environment.

"The more important questions are how much is there, where did it come from and what does it tell us about how PFAS moves through the environment?"

"In our samples, concentrations of the two most well-known PFAS – PFOS and PFOA – were below current Australian drinking water guideline values, which should provide some reassurance for people who use rainwater as a source of drinking water."

Two men walking along a road with buildings and trees and other people in the background.

RMIT University researchers Nav Singh (left) and Professor Oliver Jones on campus at RMIT University in Melbourne. Credit: Ant Bragaglia, RMIT University

Tracking PFAS through the atmosphere

The project aimed to test a new analytical method designed to measure very low concentrations of contaminants in small-volume samples such as rainwater.

The researchers analysed rainwater collected on three occasions and tested for 30 PFAS compounds.

“Eight compounds were detected, with concentrations generally measured in nanograms per litre,” Jones said.

“For context, one nanogram per litre is one part per trillion, so we are talking very low concentrations indeed.”

The study took a new turn when EPA Victoria collaborators contributed atmospheric modelling data, enabling the team to investigate the origins of air masses associated with each rainfall event.

Using atmospheric modelling, the researchers found rain linked to air travelling over land contained higher PFAS concentrations compared to over the ocean.

The finding suggests urban and industrial areas may be important sources of airborne PFAS deposited elsewhere through rainfall.

Lead author, PhD student Nav Singh, said the study contributed new and important knowledge on PFAS in the environment.

“This is an important environmental challenge, and I’m proud to be part of research that helps improve our understanding of it.”

EPA Victoria Deputy Chief Environmental Scientist Caroline Martino said the regulator was proud to be part of the study.

“This study provides valuable insights into how PFAS moves through the environment,” Ms Martino said.

“Robust, peer-reviewed evidence is essential for effective regulation, risk assessment and management."

“Science is at the heart of everything EPA does, and we’re always pleased to work with great institutions like RMIT.”

“Forever chemicals” is a misnomer

“PFAS are often called ‘forever chemicals’, but that term can be misleading because it suggests they never break down, which isn't actually the case,” Jones said.

“A more accurate description is that they are highly persistent, or ‘lingering’, chemicals that can remain in the environment for a long time, which is why understanding their behaviour is so important.”

The paper, 'Concentrations of per- and polyfluoroalkyl substances in the rainwater of South-Eastern Australia', is published in the international journal Environmental Chemistry and Toxicology (DOI: 10.1093/etojnl/vgag204).

Story: Will Wright

Society and Environment

10 September 2026

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10 September 2026

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