pfas_pfoa

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

Introduction

  • 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
  • In Australia, the main concerns and risks centre around PFOS-contaminated soils following use of fire fighting foams and the associated risk of contamination of waterways
    • PFOA itself was not manufactured in Australia
    • the risks of PTFE / Teflon itself appear to be minimal as long as it is not overheated

Biological considerations

  • 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.
  • none were manufactured in Australia but have been widely used in Australia
  • these PFAS accumulations have been shown to cause a variety of conditions including:
    • characteristic birth defects - facial deformity (PFOA)
    • low infant birth weight
    • developmental neurotoxicity (in rats)
    • various neoplasia / cancer / tumours (PFOA in animals at least; insufficient data for PFOS other than adenomas in rats)
    • dental discolouration (PFOA)
    • possible mild thyroid dysfunction (PFOS)
    • possible immune effects
    • increased liver weight in most animals (PFOS)
  • The value of blood testing is limited to assessing exposure at a population level, such as monitoring over time, which may help determine the success of exposure reduction measures.
  • Given the long biological half-life of PFASs, frequent blood monitoring is of no value.

PFOA

  • PFOA was 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

PTFE / Teflon

  • 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 19461)
  • heating a PTFE coated pan to above 400degF repeatedly tends to break it down and risks creation of degraded PTFE fumes which are toxic at least to birds
  • 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 cookware2):
      • 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

  • 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 3)
  • can cross to the fetus and is apparently present at higher levels in the fetal serum and blood than in the maternal circulation
Australian Food Standards recommendations4) PFOS/PFHxS PFOA
Tolerable Daily Intake (μg/kg/d)​​ 0.02 0.16
Drinking Water Quality Guideline (μg/L) 0.07 0.56
Recreational Water Quality Guideline (μg/L) 0.7 5.6

Environmental sources

  • 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
  • may still be present in manufactured paper, packaging, carpet, rubber, plastics from non-US companies
  • water-repellent clothing and textiles
  • high local levels may cause an issue with inhalational route via dust, etc

Contamination in Victoria, Australia

pfas_pfoa.txt · Last modified: 2020/06/28 18:02 by gary1