Perfluoroalkyl and polyfluoroalkyl substances (PFAS) including PFOA, PFOS, GenX, Teflon

see also:

• toxinology
• phthalates
• bisphenols (Bisphenol A (BPA), etc)
• US EPA basic information on PFAS
• NSW Health advisory
• https://www.pfas.gov.au/about-pfas/affects
• July 2020: A Probabilistic Approach to Evaluate the Risk of Decreased Total Triiodothyronine Hormone Levels following Chronic Exposure to PFOS and PFHxS via Contaminated Drinking Water
• Youtube - a doco on the history of Teflon and PFOA

• perfluoroalkyl and polyfluoroalkyl substances (PFAS) or perflouroalkyl acids (PFAAs) are synthetic potentially dangerous toxins which including perfluorooctanoic acid or PFOA (which includes polytetrafluoroethylene /PTFE or “Teflon”), perfluorooctane sulfonate (PFOS), GenX and other substances made from the 1940's, primarily by the US chemical company Dupont, up until they were formally recognized as being potentially dangerous in around 2013.
• these substances are virtually indestructible and animal and human bodies tend to accumulate them over time as there is no efficient mechanism to excrete them once they are absorbed
• these substances unfortunately have become so common in the environment that it is thought over 99% of humans have been contaminated globally
• levels in 2 yr old children are particularly high - mainly from ingestion via contaminated fingers or foods ¹⁾
• high levels of PFOS contamination can cause characteristic white foam in rivers which have some turbulence such as waterfalls, rapids when the weather is cold as it tends to foam in colder temperatures, and seems to accumulate heavy metals

• they are generally well absorbed by inhalation, or, in the GIT via a range of transport systems including organic anion transporters, and urate transporters
• they are highly protein bound (>99% bound to albumin in blood as well as LDL-binding and globulin binding) and in rats are distributed mainly in descending order to liver, heart, kidney, blood, lung, testicle, brain/spleen and they are excreted in breast milk
• they are known to activate peroxisome proliferator activated receptor (PPAR) pathways by increasing transcription of mitochondrial and peroxisomal lipid metabolism enzymes , sterol and bile acid biosynthesis, and retinol metabolism genes.
• some are excreted by the kidneys with half life in the body of hours or days (eg. many of the shorter chain molecules) but for most, it is years which allows small exposures to build up
• none were manufactured in Australia but have been widely used in Australia
• these PFAS accumulations have been shown to cause a variety of conditions (although it seems risk is low for significant negative health outcomes but research is still in its infancy)⁵⁾ including:
  • characteristic birth defects - facial deformity (PFOA)
  • low infant birth weight
  • developmental neurotoxicity (in rats)
  • ulcerative colitis (PFOA)
  • various neoplasia / cancer / tumours (PFOA in animals at least; insufficient data for PFOS other than adenomas in rats)
  • hyperlipidaemia (PFOS)
  • hyperuricaemia (PFOS)
  • dental discolouration (PFOA)
  • possible mild thyroid dysfunction (PFOS)
  • possible immune effects
  • increased liver weight in most animals (PFOS)
  • long term behavioural effects in male mice (PFHxA) ⁶⁾

• perfluorooctanoic acid (PFOA) aka C8 was made by 3M and used by DuPont to manufacture the relatively non-toxic PTFE which was marketed as Teflon
• PFOA soil and waterway contamination in the US caused animal tumours and deaths - this story has been promoted in the docu-movie Dark Waters
• it has not been manufactured in Australia
• it has since been replaced by a 6 carbon version called GenX which may have similar issues

• PTFE was discovered by DuPont in 1938, used on army tanks in WWII and then marketed as Teflon in 1945 with products sold with this non-stick, heat resistant material from 1946⁷⁾
• heating a PTFE coated pan to above 260degC repeatedly tends to break it down and risks creation of degraded PTFE fumes which are toxic at least to birds
  • workers in Teflon factories did become unwell for a few days if inhaled these fumes “poly fume fever” and generally causes fever, chills, body aches, headache, and fatigue which lasts a few days after exposure to Teflon when heated above 300degC
• Teflon-coated non-stick cookware especially likely in non-stick cookware manufactured prior to 2013
  • by law as of 2015, all cookware sold in the US is PFOA-free but this does not mean it is PTFE-free.
  • there are only 2 groups of non-stick cookware⁸⁾:
    • PTFE based - and this includes those made more durable by the addition of titanium, granite, “earth-stone” or diamond and also most of those marketed as PFOA-free, APEO-free (alkylphenols) or BPA-free
    • ceramic (which should be PFAS-free and is made from clay and sand although some may contain lead or cadmium used in their manufacture)
      • unfortunately, the ceramic surface does not last as long as PTFE surfaces
      • you may wish to use properly seasoned cast iron cookware which is almost as non-stick and will last for decades longer

• PFOS is a flourosurfactant
• due to is poor biodegradability, 3M discontinued its manufacture in 2002
• it is soluble in fresh water to 519mg/L but solubility declines substantially as salt level increases, to 12mg/L in “salt water”
• the potassium salt of PFOS has a low vapor pressure
• human half-life is 5.4yrs apparently due to high levels of biliary and renal reabsorption ⁹⁾
• can cross to the fetus and is apparently present at higher levels in the fetal serum and blood than in the maternal circulation

• fire-fighting foam
  • training centres (including airports and military bases) and major fires may have high levels of soil contamination
• food and food packaging which has been contaminated by PFAS in the water or soil including via accumulation in living organisms
• contaminated drinking water due to land fill, run off of firefighting foam, etc
• many commercial household products such as stain and water repellents, polishes, waxes, paints, cleaning products, dental floss
• may still be present in manufactured paper, packaging, carpet, rubber, plastics from non-US companies
• water-repellent clothing, textiles, furniture
• high local levels may cause an issue with inhalational route via dust, etc

• PFOS fire fighting related contamination:
  • CFA training centre at Fishville near Ballarat
  • 200 tonnes of PFOS-containing foam was used to contain the 1991 Coote Island petrochemical fire in Melbourne and this soil contamination which was exposed during the Westgate Tunnel project in 2019
    • bore holes reveal levels of PFAS 1000-2000 x the EPA threshold level
    • this creates risks of contaminating the nearby Yarra River and thus Port Phillip Bay as well as leaching into the water table and inhalational dust risks
    • https://toxic-tunnel.com/
    • https://www.theage.com.au/national/victoria/worst-of-pfas-contamination-revealed-on-west-gate-tunnel-20200306-p547l0.html
    • https://www.theage.com.au/national/victoria/pfas-soil-stockpiles-sitting-in-melbourne-s-inner-west-20200309-p5488p.html

• bile acid sequestrants such as cholestyramine appear to substantially enhance the faecal clearance of certain PFAS from the body, particularly, PFOS, but urinary clearance was unchanged by probenecid¹¹⁾