April | What I'm Curious About
There are concerns in New Zealand about chemicals used in fire-fighting foam, specifically PFOA and PFOS. What are these chemicals and what are they used for?
Fire-fighting foams manufactured with the chemicals PFOS and PFOA were the standard from the 1970s until the early 2000s. Since 2011, no import, manufacture or use of the compounds is permitted in New Zealand.
PFOS and PFOA are part of a family of chemicals known as per- and poly-fluoroalkyl substances (PFAS). PFAS are used mainly as surfactants, that is, as detergents, foaming agents, and emulsifiers. They have many industrial and household applications, including fire-fighting foams (also called ‘aqueous film-forming foams’), non-stick cookware (e.g. Teflon), waterproof clothing (e.g. Goretex) and stain repellents (e.g. Scotchgard). The two most commonly used and studied PFAS are perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA).
All members of the PFAS family, including PFOS and PFOA contain fluorine atoms. The carbon-fluorine bond is exceptionally strong, and this property is what makes them useful for industrial applications. It also means PFAS don’t break down easily in the environment, can travel long distances (e.g. through contaminated groundwater), and bioaccumulate in the food chain. In humans, it takes 4-5 years for the amount of PFAS in your blood to reduce by half. There is concern about environmental contamination with PFOS and PFOA because they are persistent, capable of long-range transport, and bioaccumulate.
There is a deep divide in the scientific community regarding the human health effects following PFAS exposure. A study of 70,000 residents exposed to PFAS-contaminated drinking water was undertaken in West Virginia, USA. The study found a probable link between PFAS exposure and high cholesterol, ulcerative colitis, thyroid disease, testicular cancer, kidney cancer and pregnancy-induced hypertension. Additionally, in 2016 the United Nations found that PFOA was likely to ‘lead to significant adverse human health and environmental effects such that global action is warranted’. A study commissioned by the Department of Health & Human Services [Victoria, Australia] summarises the most recent evidence of possible adverse health effects. The main concern is regarding association with thyroid disease, reproductive and fertility changes, neurodevelopmental effects, effects on blood lipids, and immunomodulation. Note, these are associations, and do not provide evidence that PFAS cause any of these conditions. However, Commonwealth Government [i.e. Australian Federal Government] enHealth Guidance Statements (last updated September 2017) advise that ‘research has not conclusively demonstrated that PFAS are related to specific illnesses, even under conditions of occupational exposure’.
This month's answer comes from Dr Amy Heffernan, NHMRC-ARC Dementia Development Research Fellow, The Florey Institute of Neuroscience & Mental Health, Australia, for the Science Media Centre.
18 April 2018