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Comment by anon321321323 | Hacker News Reader

ok. lets run this:

assume its the year 2000 with a 20 year old having some level of PFOS in blood & cells etc and the half-life of that PFOS is 5 years*

2000 100% of accumulated measured concentration in blood & cells by some measure

2005 50%

2010 25%

2015 13%

2020 6%

2025 3%

2030 2%

2035 1%

2040 <1%

So our fictional 20 year old is 60-70* by the time the stuff has "fully" degraded. This doesn't mean they are now healthy. It just means the toxic stuff is now no longer at the original level. Impact on organs? Not a great picture.

A "Forever chemical" indeed.

* Assumptions just to make things easier to see. PFOS half-life is actually 5.4 years. So the table above is too short. Assume nothing gets stuck where it can't decay. What is toxic for this? What is typical buildup for a 20 year old for various locations/contexts?

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They are called "forever chemicals" because they don't naturally degrade in the environment. That term does not refer to how long they stay in your body. Because they are don't degrade in the environment, the amount found in the environment is continuing to increase: http://marinespecies.org/introduced/wiki/Polyfluorinated_com...

Indeed such compounds do not have a half life. They can only continue to increase in concentration in everyone’s body over time, assuming environmental exposure remains constant. Of course it is theoretically possible to live in an hermetically sealed environment without such compounds, where are all incoming substances are controlled, that would allow the body to naturally excrete such compounds over time. But we don’t know the rate at which this happens.

"Indeed such compounds do not have a half life. They can only continue to increase in concentration in everyone’s body over time"

Wrong.

https://www.foodandwaterwatch.org/insight/these-chemicals-ar...

"PFASs can concentrate in the bodies of humans and animals over time through a process known as bioaccumulation. For example, as a result of PFOA’s tendency to bioaccumulate and its long half-life in humans, PFOA’s presence in the body can persist even after exposure stops. PFOA’s half-life (the length of time it takes for a substance to decrease to half of its original value) in humans is anywhere from over two to nearly four years, while other PFASs have been shown to have a half-life of over eight years. There is also evidence that some PFASs can biomagnify, or increase in concentration, up the food chain."

"That term does not refer to how long they stay in your body."

I didn't assert that. I did state that after 70 years of only getting to some vague level of trace amounts its still likely there and that something of that nature is a "forever chemical" indeed. You haven't cancelled that.

You do realise that PFOS actually does have a half-life when in the body and that the body does break them down? Slowly. My point is that even at 5.3 years or anything around that half-life the stuff is in your body. Basically forever... until you're likely very old or dead.

You want to quibble about "forever" in a human being only 70 years. Ok. That's excessively pedantic however I'm not going to exhaustively iterate over every detail to do so.

Your link is year-on-year PFOS concentrations. Seems that the exposure from the environment is increasing. Sure.

How does that cancel out what I wrote? I fail to see where you've cancelled out my simulation at all.

https://www.foodandwaterwatch.org/insight/these-chemicals-ar...

> So our fictional 20 year old is 60-70* by the time the stuff has "fully" degraded. This doesn't mean they are now healthy.

Without knowing the initial concentration, it doesn't really mean they are still unhealthy either

This also assumes no biological ability to remove the chemical, relying only on the half life. If our systems are not able to do so, I missed that point in the article.

Edit: thank you, I see that now here too - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1964923/

The biological half-life actually does refer to the ability of the body to metabolize the chemical

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