PFAS and cancer: what do we know about forever chemicals? – Cancer Research UK

The International Agency for Research on Cancer (IARC) has finalised its evaluation of possible links between two ‘forever chemicals’ and cancer in humans. 

Forever chemicals, known to scientists as poly and perfluoroalkyl substances (PFAS), are a group of thousands of man-made chemicals used for manufacturing and in various everyday products.  

They’re nicknamed forever chemicals because the special chemical structures that make them so useful are also extremely difficult to break down. As a result, PFAS can stick around long after people have finished with them. They can also enter the surrounding environment, which means we can encounter them without knowing it. 

The two chemicals IARC looked at are no longer produced or used in the UK. IARC has now classified one of them, perfluorooctanoic acid (PFOA), as cancer-causing, or carcinogenic (Group 1), but this decision wasn’t based on strong evidence showing an increase in cancer cases in people exposed to PFOA.

Instead, IARC noted ‘sufficient’ evidence for PFOA-linked cancers in one species of experimental (lab) animal. They also found ‘strong’ evidence that PFOA can cause changes in the human body that may lead to the development of cancer. 

When looking specifically at cancer cases in humans exposed to PFOA, IARC only found ‘limited’ evidence of a direct link to renal cell carcinoma and testicular cancer. For all other cancer types, IARC’s committee considered the evidence for a direct link ‘inadequate’. 

The other chemical IARC reviewed, perfluorooctanesulfonic acid (PFOS), has been classified as ‘possibly carcinogenic to humans’ (Group 2B). This decision was also based on ‘strong’ evidence that PFOS may cause changes within our body that could be linked to cancer.  

But, in this case, IARC noted that there was ‘inadequate’ evidence that PFOS directly causes any type of cancer in people. The evidence in experimental animals was also ‘limited’. Overall, this suggests there is currently no convincing evidence that PFOS causes cancer in humans.  

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