Climate change and the COVID-19 pandemic have shown us that we live in a deeply uncertain world with various risks, in the meantime, science and technology have a relatively high epistemic position to inform decision-makers with scientific evidence about how to understand, assess, and solve these issues. However, the technocratic paradigm of environmental and risk governance has been criticized and reflected for a long time. Studies have shown from STS field that these scientific judgments are still social practices which involve human emotion, material resources and interests. Besides, the traditional risk assessment paradigm is in the pro-industry tone which helps produce systematic ignorance of potential risks which will harm the public good. Forever chemicals, or say, perfluoroalkyl and polyfluoroalkyl substances (PFAS), have been a re-emerging concern around the world. It is exceptionally stable and persistent because of its special chemical structures. These substances are widely used in products which are used in people’s daily life. There has been evidence that shows its toxicity on human health, and lots of countries have launched relevant regulatory policies on PFAS. However, challenges remain due to its ubiquity and its huge number of varieties; contestations exist on how we make judgments on assessing it, for instance, how to understand its harmfulness to humans and nature, and whether it needs to be regulated as a whole class or not. These controversies have been classic about industrial chemical issues and science has been a key player. Thus, this project aims to understand how PFAS which has thousands of substances is seen as a problem (or not a problem) in Australia. Further, this project hopes to understand the epistemic cultures which shape how experts make judgements on this chemical compound in a specific socio-political context, and thus provide some implications for a broader scope of environmental governance.