4 ms·

Since PFAS never really breaks down and we're still creating it, is a 200 ppt inevitable at some point?

by jcrben 4y ago

superchroma 4y ago
The scary thing for me is that it's in the rain, so it'll be in crops, water reservoirs, trickling into the water table and into drinking supply. We have to stop this right now.
- bob1029 4y ago
  > You can't use techniques like distillation to remove PFAS Can we get a citation on this? I’m not a chemical engineer, but distillation seems like a pretty good way to get rid of virtually everything.
  - superchroma 4y ago
    I'm sorry, I had it wrong. I've checked my facts. It works. This is actually a relief for me.
  - loosescrews 4y ago
    Rain is a form of distillation.
    - superchroma 4y ago
      This is a good point. I don't know what to think now. I presume 3M isn't spraying this stuff into the air as an aerosol.
      - tadfisher 4y ago
        PFAS components do end up in the atmosphere from the manufacturing process, which is how it precipitates (droplets nucleate around the airborne particles). Same story with any particulate emissions, like soot, dust, tires, etc.
    - serf 4y ago
      a form of distillation with virtually no isolation, compartmentalization, and unlimited precursor conditions, which pours into a huge mass of possibly dirty air and debris.
  - colechristensen 4y ago
    Some things absolutely distill over, it’s not magic, but depends on (to simplify) the boiling point of the substance compared to the boiling point of water. For example it is not possible to completely separate ethanol and water with distillation. A quick internet search seems to indicate PF* can be separated with distillation.
mlyle 4y ago
Most of the PFAS do break down -- a half life of a few years. It's mostly PFOA that's of grave concern.
- jcrben 4y ago
  Citation? I tried googling and couldn't find anything to confirm that. When I searched on half-life, the results that came up mostly seemed to discuss the half-life in the body, not the half-life in an environmental sink such as the ocean.
  - mlyle 4y ago
    > the results that came up mostly seemed to discuss the half-life in the body Yah, there's a lot of data on "serum" or "elimination" half lives. What you care about is "atmospheric", "aqueous abiotic", and "aqueous biotic" half lives. So, e.g. for PFOA, atmospheric half lives are about 130 days... https://pubs.acs.org/doi/pdf/10.1021/jp036343b https://pubs.acs.org/doi/pdf/10.1021/jp036343b I can't come up with a link to share for PFOA in aqueous solutions, but it looks like 90-150 years.
    - jcrben 4y ago
      It's an interesting article from 2004; might not be reading it right but seems like this one from 2020 is less optimistic about hydroxyl radicals (OH) breaking down PFOA in the atmosphere. https://pubmed.ncbi.nlm.nih.gov/31978654/ https://pubmed.ncbi.nlm.nih.gov/31978654/ Your same link notes that the majority of PFOA is not broken down in the atmosphere and points to "wet and dry deposition" mostly, which sounds like it's being dropped down to Earth remaining as PFOA.
      - mlyle 4y ago
        > It's an interesting article from 2004; might not be reading it right but seems like this one from 2020 is less optimistic about hydroxyl radicals (OH) breaking down PFOA in the atmosphere. https://pubmed.ncbi.nlm.nih.gov/31978654/ https://pubmed.ncbi.nlm.nih.gov/31978654/ That's an interesting paper. If so, multiply the atmospheric time by 2-4. > Your same link notes that the majority of PFOA is not broken down in the atmosphere and points to "wet and dry deposition" mostly, which sounds like it's being dropped down to Earth remaining as PFOA. Yes. That doesn't affect the "half life" here. In the end, not much PFOA ends up in the atmosphere in the first place, and most precipitates out to less convenient places where it lives longer. Of the stuff resident in the atmosphere, it does break down on human timescales, at least...
deleted 4y ago
[deleted]

Since PFAS never really breaks down and we're still creating it, is a 200 ppt inevitable at some point?

by jcrben 4y ago

Since PFAS never really breaks down and we're still creating it, is a 200 ppt inevitable at some point?

The scary thing for me is that it's in the rain, so it'll be in crops, water reservoirs, trickling into the water table and into drinking supply. We have to stop this right now.

bob1029 4y ago
> You can't use techniques like distillation to remove PFAS Can we get a citation on this? I’m not a chemical engineer, but distillation seems like a pretty good way to get rid of virtually everything.
- superchroma 4y ago
  I'm sorry, I had it wrong. I've checked my facts. It works. This is actually a relief for me.
- loosescrews 4y ago
  Rain is a form of distillation.
  - superchroma 4y ago
    This is a good point. I don't know what to think now. I presume 3M isn't spraying this stuff into the air as an aerosol.
    - tadfisher 4y ago
      PFAS components do end up in the atmosphere from the manufacturing process, which is how it precipitates (droplets nucleate around the airborne particles). Same story with any particulate emissions, like soot, dust, tires, etc.
  - serf 4y ago
    a form of distillation with virtually no isolation, compartmentalization, and unlimited precursor conditions, which pours into a huge mass of possibly dirty air and debris.
- colechristensen 4y ago
  Some things absolutely distill over, it’s not magic, but depends on (to simplify) the boiling point of the substance compared to the boiling point of water. For example it is not possible to completely separate ethanol and water with distillation. A quick internet search seems to indicate PF* can be separated with distillation.

mlyle 4y ago

Most of the PFAS do break down -- a half life of a few years. It's mostly PFOA that's of grave concern.

jcrben 4y ago
Citation? I tried googling and couldn't find anything to confirm that. When I searched on half-life, the results that came up mostly seemed to discuss the half-life in the body, not the half-life in an environmental sink such as the ocean.
- mlyle 4y ago
  > the results that came up mostly seemed to discuss the half-life in the body Yah, there's a lot of data on "serum" or "elimination" half lives. What you care about is "atmospheric", "aqueous abiotic", and "aqueous biotic" half lives. So, e.g. for PFOA, atmospheric half lives are about 130 days... https://pubs.acs.org/doi/pdf/10.1021/jp036343b https://pubs.acs.org/doi/pdf/10.1021/jp036343b I can't come up with a link to share for PFOA in aqueous solutions, but it looks like 90-150 years.
  - jcrben 4y ago
    It's an interesting article from 2004; might not be reading it right but seems like this one from 2020 is less optimistic about hydroxyl radicals (OH) breaking down PFOA in the atmosphere. https://pubmed.ncbi.nlm.nih.gov/31978654/ https://pubmed.ncbi.nlm.nih.gov/31978654/ Your same link notes that the majority of PFOA is not broken down in the atmosphere and points to "wet and dry deposition" mostly, which sounds like it's being dropped down to Earth remaining as PFOA.
    - mlyle 4y ago
      > It's an interesting article from 2004; might not be reading it right but seems like this one from 2020 is less optimistic about hydroxyl radicals (OH) breaking down PFOA in the atmosphere. https://pubmed.ncbi.nlm.nih.gov/31978654/ https://pubmed.ncbi.nlm.nih.gov/31978654/ That's an interesting paper. If so, multiply the atmospheric time by 2-4. > Your same link notes that the majority of PFOA is not broken down in the atmosphere and points to "wet and dry deposition" mostly, which sounds like it's being dropped down to Earth remaining as PFOA. Yes. That doesn't affect the "half life" here. In the end, not much PFOA ends up in the atmosphere in the first place, and most precipitates out to less convenient places where it lives longer. Of the stuff resident in the atmosphere, it does break down on human timescales, at least...

deleted 4y ago

[deleted]