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By Thomas Kingsley, Publishing Associate: Researcher and Writer at Save the Water™ | June 26, 2026
Edited by Ernest Chea, Publishing Associate: Director at Save the Water™
Per- and polyfluoroalkyl substances (PFAS) are often referred to as “forever chemicals.” This is because of their persistence in the environment and their tendency to build up in the bodies of living organisms that are exposed to them. Before we learned about the effects of PFAS contamination, these chemicals were commonly used in products that benefitted from their resistances to heat and water.
Aqueous film-forming foams (AFFF) are firefighting foams that contain PFAS. They were widely used until the 2000s when they began to be phased out due to concerns about their toxicity. While highly effective at putting out fires, they were hard to contain, meaning they could leach into and contaminate groundwater.
Researchers at Western Sydney University examined two transport accidents in the Australian state of New South Wales that required AFFF. The study aimed to understand how long PFAS contamination can linger after the initial exposure. The first accident happened in 1992 near the small township of Medlow Bath. This resulted in PFAS contamination of a creek that forms part of the drinking water catchment supplying the Medlow Dam reservoir. The second incident was in 2000 near the highway exit for the township of Ourimbah. This affected Ourimbah Creek, which is a short distance from the Ourimbah bore field, where groundwater is extracted. The two incidents posed a potential risk to the drinking water supplies of the surrounding communities.
Water testing at several locations near and downstream of the accident sites revealed concentrations of multiple PFAS compounds. These contaminants exceeded the acceptable environmental guidelines for safe drinking water. The most commonly detected compounds were Perfluorohexane (PFHxS) and Perfluorooctane sulphonate (PFOS). They were present at five of the seven sampling sites.
In the Medlow Bath area, PFAS concentrations were highest closer to the initial accident site. The average PFOS result near the accident site was 270 times higher than the acceptable levels, with PFHxS being 30 times higher. However, the concentrations decreased at the sites further downstream. The amount of PFOS stayed higher than acceptable levels but gradually reduced. PFHxS concentrations dipped into safe levels at the furthest testing site.
Similarly, in Ourimbah Creek, testing at the two wetland areas near the accident also showed unsafe PFOS and PFHxS levels.
The researchers also conducted sediment testing of the soil in areas closest to the accident sites. These tests revealed PFOS concentrations that exceeded the acceptable environmental levels.
The highest concentrations were again observed at the site near the Medlow Bath accident. These areas are swampy and therefore have a higher organic matter content in the soil. This organic matter content can bind with PFAS molecules, thus increasing their long-term retention in the environment. This creates a problem for residents near the creek, as food grown in those areas can introduce PFAS into their diets.
This study highlights the long-term presence of higher PFAS concentrations in the environment, even after small-scale spill events. While the initial concentrations in the water supply at the time of contamination are not fully known, higher levels of PFAS remain present in the environment over 20 years later
In 2024, the Australian government identified the contamination and stopped using those areas to supply drinking water to the Greater Sydney area. Overall, these findings further demonstrate why PFAS are referred to as “forever chemicals” and highlight the need to find solutions for removing them from water.
Save the Water™ is a 501 (c)(3) non-profit organization with a mission to conduct research to identify and remove harmful contaminants in water and to raise public awareness about water contamination and its health impacts.
