[ballenf]

Why the focus on bioaccumulation over harmfulness? Is it that bioaccumulation means that there is no safe exposure level to a substance that might have even minimal harmfulness?

Now I'm really going to reveal my ignorance...

I also don't understand how a substance with such a strong bond that we can't break it down, can interact with anything in the body. Is it something like a catalyst?

[hammock]

Bioaccumulation can cause harm in a number of different ways.

One of the biggest risks is cancer. For example, lung cancer is often caused (in part) by accumulation of soot in your lungs, or asbestos particles, that your body cannot remove. And yes, they say there is no safe exposure level to smoking or asbestos.

Other effects include mental illness, diseases of the liver or kidneys, often seen with heavy metals.

When foreign objects get in protected nooks and crannies of your body, like vital organs, and stay there for the rest of your life, bad things happen.

[rwcarlsen]

But just because our bodies bioaccumulate things doesn't mean they cause cancer. You didn't really address any of GP's questions. Do PFOA (and similar) molecules affect cancer rates, and if so - how significantly? Also if PFOA and friends are so unreactive with the body - can't be removed, then what is the mechanism by which they cause problems?

[hammock]

>But just because our bodies bioaccumulate things doesn't mean they cause cancer

And just because we can't pinpoint a mechanism of action doesn't mean it doesn't cause cancer :) There have been a number of MoA's proposed for PFOA specifically. Here are a couple:

https://www.ncbi.nlm.nih.gov/pubmed/22120428

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2516576/

Not everything has been studied. And may things are difficult to study. The "little black dots" or fake dirt on fancy astroturf fields are made from recycled road tires, which are a cocktail of all kinds of bad chemicals. And when they get lodged in goalkeepers' skin over time, they enter the body and cause some pretty rare and bad blood cancers. Do I have a study I can point to that says how? No. But do you want your daughter diving on one of those turf fields? https://www.cnn.com/2017/01/27/health/artificial-turf-cancer...

[reitanqild]

> The "little black dots" or fake dirt on fancy astroturf fields are made from recycled road tires, which are a cocktail of all kinds of bad chemicals. And when they get lodged in goalkeepers' skin over time, they enter the body and cause some pretty rare and bad blood cancers.

If this is true it should soon show up in people who work with tires or live near highways as well?

[hammock]

Yes and it does. https://www.theguardian.com/environment/2016/sep/11/pollutin...

In addition to that story there is another story I cannot find at the moment, that referenced a vegetable farm in Mexico which was linked to some bad human effects. Turns out it was right next to the highway and the pollution from diesel trucks was making it into the food. They moved the farm farther from the roadside and the problem stopped.

[refurb]

That's the real question. From a 2010 paper (admittedly dated):

Data on the human health effects of PFOA are sparse. There is relatively consistent evidence of modest positive associations with cholesterol and uric acid, although the magnitude of the cholesterol effect is inconsistent across different exposure levels. There is some but much less consistent evidence of a modest positive correlation with liver enzymes. Most findings come from cross-sectional studies, limiting conclusions. Two occupational cohort studies do not provide consistent evidence for chronic disease; both are limited by sample size and reliance on mortality data. Reproductive data have increased recently but are inconsistent, and any observed adverse effects are modest.

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2920088/

[mirimir]

> I also don't understand how a substance with such a strong bond that we can't break it down, can interact with anything in the body. Is it something like a catalyst?

No, just an agonist or antagonist for some hormone, neurotransmitter, etc. Just search Google Books for "fluorinated agonist" or "fluorinated antagonist". That is, it's about 3D shape, to fit some receptor protein, and not about chemical reactivity.

[KyleBerezin]

Teflon is mostly inert and does not have much of an effect on the body. There is no reason to believe it is bad for you. It also does not generally bio-accumulate.

PFOA however has a head group that is not inert (the acid part).

More generally though the reason we don't like bio-accumulation is because it can have effects that are hard to detect and could take 20 years to show up (think asbestos). With something that is only in you body for a week, whatever it does to you would be detectable in that time.

[cwkoss]

I'm also interested in the answers to those questions.