PFAS and PFOS: What is the difference?

Perfluoroalkyl and polyfluoroalkyl substances - or as they are more commonly known, PFAS - are a group of manmade chemicals that resist breaking down in the environment.

They were first developed for industrial use in the 1940s, but during the 1960s and 70s became commonly used in everything from carpets to cleaning agents, sprays and paints to textiles and hydraulic fluid.

One of the most well-known PFAS chemicals is perfluorooctane sulphonate, or PFOS, which has been at the centre of a long-running legal dispute between the States of Guernsey and the British manufacturing giant, 3M.

The States of Guernsey argued this week that the use of 3M's firefighting foam, which contained the chemical, contaminated soil and water around the island's airport.

Legal fees for the failed bid have racked up to £8 million for the States, with millions more being spent on tackling the pollution risk caused by the chemical.

What is PFOS?

Perfluorooctane sulfonate was widely used in products to provide protective coatings to man-made materials because it doesn't break down at high temperatures.

The production of PFOS largely came to an end in 2002, when it was banned by the EU because of health concerns.

Why was PFOS phased out?

A report from the UK government's Public Health England states there are potential risks of PFOS to the environment and human health.

Studies with animals fed PFOS for a long period showed effects on their stomach, liver and thyroid hormones.

Animal studies also showed compounds may cause cancer at relatively high levels.

The general public is exposed to trace levels of PFOS as contaminants in food and water, and such small concentrations are not thought to pose any cancer risk.

What is 3M?

The American conglomerate has around $30 billion in annual sales and is perhaps best known for making Post-It notes and Scotch tape.

From 1976 to 1999, 3M United Kingdom PLC sold its film-forming foam to Guernsey, primarily for use at the Guernsey and Alderney airports.

In May 2000, the company announced it would phase out the production of products containing PFOS.