Melbourne Rain Found Carrying Eight 'Forever Chemical' Compounds

Researchers from RMIT University and EPA Victoria have detected eight PFAS compounds in rainwater samples collected in Melbourne between 2024 and 2025, offering new clues about how the chemicals travel through the atmosphere. PFAS are a large family of human-made chemicals used in products ranging from firefighting foams and food packaging to textiles, cosmetics and nonstick cookware, and can attach to dust particles or tiny water droplets and travel long distances before returning to the ground in rain.

The findings, published in the journal Environmental Toxicology and Chemistry, come from an analysis of 30 PFAS compounds; eight were detected, generally at concentrations measured in nanograms per liter, equivalent to one part per trillion. Based on Melbourne's rainfall and the concentrations measured, the researchers estimated that rain delivers about 10.6 kilograms (23.4 pounds) of PFAS directly to Port Phillip Bay each year, or about 5.5 grams per square kilometer across the bay's 1,930-square-kilometer surface.

"Finding PFAS in rain isn't surprising given how widespread these chemicals are in the environment," said lead researcher Professor Oliver Jones of RMIT's School of Science. He said detecting a chemical does not automatically mean there is 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. Dose and exposure matter." Concentrations of the two best-known PFAS, PFOS and PFOA, were below current Australian drinking water guideline values, which Jones said should reassure people who use rainwater tanks as a source of drinking water.

Using atmospheric modeling data from EPA Victoria, the team traced the air masses linked to each rainfall event. Rain associated with air that traveled over land carried higher PFAS concentrations than rain linked to air that traveled over the ocean, suggesting urban and industrial areas may be an important source of airborne PFAS, alongside better-known sources such as wastewater, urban runoff and landfills.

Jones said the term "forever chemicals" is somewhat misleading, since it suggests PFAS never break down. "A more accurate description is that they are highly persistent, or 'lingering,' chemicals that can remain in the environment for a long time," he said. Lead author and doctoral student Nav Singh said the study, which tested a new method for measuring very low contaminant concentrations in small samples, adds new knowledge on how PFAS move through the environment.