An unprecedented analysis of rainwater in Australia detected eight PFAS compounds, but at concentrations below the reference values defined in the Australian drinking-water guidelines. The study, conducted by researchers from RMIT University and the EPA Victoria, analyzed samples collected in Melbourne between 2024 and 2025.
PFAS, or “forever chemicals”, are a family of thousands of human-made chemical compounds used in products such as firefighting foams, food packaging, textiles, cosmetics, and non-stick cookware. While the results may be reassuring for those who use rainwater for drinking, the researchers note that the presence of these compounds in precipitation can help explain their arrival in rivers and other ecosystems distant from obvious contamination sources.
PFAS can be transported in the atmosphere attached to dust particles or to small droplets of water, traveling long distances before returning to the environment via rain. Based on the rainfall recorded in Melbourne and the concentrations measured, the team estimated that rain could transport about 10.6 kilograms of PFAS annually directly into Port Phillip Bay. The value corresponds to about 5.5 grams per square kilometer for the entire bay, which covers an area of 1,930 square kilometers.
This atmospheric deposition could constitute a significant pathway for PFAS entry into waterways, alongside better-known sources such as wastewater, urban runoff, and landfills.
The lead investigator, Oliver Jones, from the School of Science at RMIT University, emphasizes that the detection of a particular chemical compound does not, by itself, mean there is a health risk.
“Rather than asking whether a chemical is toxic, the more useful question is whether it is present at a concentration that can actually cause harm,” he says. “Dose and exposure are important.”
In the samples analyzed, the concentrations of the two best-known PFAS, PFOS and PFOA, were below the values currently defined in the Australian drinking-water guidelines. The researchers consider that the result may be particularly relevant for people who use rainwater as a source for drinking.
PFAS present at very low concentrations
The study also sought to test a new analytical method capable of measuring very low concentrations of contaminants in small quantities of water, such as those available in rain samples.
Thirty PFAS compounds were analyzed, of which eight were detected. The concentrations found generally lay in the range of nanograms per liter. One nanogram per liter equals one part per billion, meaning the compounds were found at very low concentrations.
Collaboration with EPA Victoria also allowed the results to be cross-checked with atmospheric modeling data, in order to investigate the origin of the air masses associated with the rainfall episodes analyzed.
The team found that rainfall associated with air masses that had traversed land areas showed PFAS concentrations higher than those recorded when the air had passed over the ocean. The result points to the possibility that urban and industrial areas contribute to the presence of PFAS in the atmosphere and their subsequent deposition via rain.
The researchers now advocate further monitoring of the presence of these compounds in precipitation across different regions of Australia, in order to better understand how they circulate between the atmosphere, soils, and aquatic systems.
Although often referred to as “forever chemicals”, PFAS do not necessarily remain in the environment indefinitely. According to Oliver Jones, the expression can be misleading, as these compounds can degrade, although they are highly persistent and can remain in the environment for long periods.
The study, titled “Concentrations of per- and polyfluoroalkyl substances in the rainwater of South-Eastern Australia”, was published in the scientific journal Environmental Chemistry and Toxicology.
