This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Researchers from RMIT University and 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 nonstick 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, traveling 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 (23.4 pounds) of PFAS directly to Port Phillip Bay each year.
That is about 5.5 grams/km² across 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 landfills. The paper is published in the journal Environmental Toxicology and Chemistry.
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 move 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." 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 analyzed rainwater collected on three occasions and tested for 30 PFAS compounds. "Eight compounds were detected, with concentrations generally measured in nanograms per liter," Jones said.
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