3M knew firefighting foam contained toxic 'forever chemicals', files reveal

3M told customers that its firefighting foams were harmless and biodegradable when it knew they contained toxic "forever chemicals" banned in many countries including the UK, newly uncovered documents show.

- Rachel Salvidge, Leana Hosea

From the 1960s until 2003, the US multinational made foams containing PFOS and PFOA, synthetic chemicals that can take tens of thousands of years to degrade. They have been linked to cancers and a range of other health problems such as thyroid disease, high cholesterol, hormonal problems and fertility issues.

Pollution from these substances in soils and water is now widespread across the globe and has been detected in animals, human organs and blood. They are part of a wider family of more than 15,000 chemicals known as per- and polyfluoroalkyl substances, or PFAS, but are commonly known as "forever chemicals".

Experts describe PFAS pollution as "one of the greatest threats facing mankind"; last year 59 scientists signed an open letter to the government calling for stricter regulation.

Documents uncovered by journalists at Watershed Investigations and the Guardian reveal that evidence showing PFOS did not biodegrade began to appear as early as 1949. However, until the 1990s 3M continued to produce information stating that natural processes would break the foams down.

Brochures from 1979 describe them as being "environmentally neutral" as well as "biodegradable, low in toxicity, and can be treated in biological treatment systems".

In a 1986 document, 3M states that "if 3M Light Water Brand aqueous film-forming foams (AFFF) products were pure chemicals instead of mixtures, OECD guidelines would classify them as 'readily biodegradable'.

Data sheets from 1993 still recommended that the foams be discharged to sewers because they were "treatable in a biological wastewater treatment system" although they noted that some elements might remain in treated wastewater.