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Comment by diacritical | Hacker News Reader

> There is no 'safe' level for endocrine disruptors that mimic our natural hormones

Can someone knowledgeable comment on this? It seems extreme to say there's no safe level.

There's a safe amount of cyanide (apple seeds), radiation (everywhere), safe speed of a bullet flying at you (if I just throw it gently at you) and so on. Even if the cyanide is technically poisoning you, the radiation from bananas is damaging you and the bullet I threw lightly grazed your skin, it's still safe in practical terms.

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It's hard to define what 'safe' is.

The research is kind of hazy. Bisphenol-A has been shown to be a very very weak estrogen when measuring receptor binding affinity (about 37,000 times lower than human estrogen https://pmc.ncbi.nlm.nih.gov/articles/PMC2774166/#sec2), but has also been shown to be a potent stimulator in vitro for specific cell types (https://pubmed.ncbi.nlm.nih.gov/22227557/).

The lowest concentration of BPA that's been shown to be estrogenic according the second article is 0.1pMol/L which is around 230 picograms per litre of blood, or 1.1ng total for an average adult.

BPA's biological half life in humans is up to two to five hours depending on a range of factors (https://pmc.ncbi.nlm.nih.gov/articles/PMC2685842/), so taking the worst case you'd need to be continually exposed to around 2.5ng of BPA over a day.

So 'safe' as defined right now would be keeping the absorption below that 2.5ng per day threshold.

I don't know how how much BPA in plastics can transfer out per day, the research I've seen seems to indicate that unless it's a food container it's pretty minimal but I don't know enough to evaluate the quality of that research.

Your skin is also a pretty good barrier so only around 2.2% of any BPA on your skin can pass through in an ideal situation, so absorption from non-food sources is much lower (https://pmc.ncbi.nlm.nih.gov/articles/PMC9210257/)

The other problem is what do they replace BPA with? To be safer it would need at least as well studied as BPA, but often it seems like the 'safer' options are just not very well studied yet and could actually be worse.

> research I've seen seems to indicate that unless it's a food container it's pretty minimal

I use glass jars for storing food. One of the reasons is stuff like BPA leaching from the plastic to the food. Another is that it's much easier to have hundreds of identical jars to have a pretty and consistently filled kitchen cabinets. A third is that transparent plastic becomes less transparent after multiple washes with a sponge.

But what I hit "reply" for was to say that heating plays a role. So putting hot food inside a container is likely worse than putting something at room temperature in a container and then putting it in the fridge.

> 1.1 ng total for an average adult

Wow, that's so little. I wonder if malicious BPA poisoning cases have been reported. It's probably undetectable unless you search for it specifically.

> The other problem is what do they replace BPA with?

I remember reading that BPA could be replaced with BPB. Obviously it may be OK, but to a layman it's like saying "we no longer add rat shit to our food, now it's bat shit".

1.1ng is a very small amount, but the effect is really not that well understood. It’s definitely something we should minimise.

However it’s not a dangerous dose, it’s just the dose that produces detectable changes and we can detect really really small changes. The toxic dose is around 4g/kg body weight. So an average adult would need to consume over 300 grams of pure BPA to be poisoned by it.

Of course the answer is to use non-plastic containers, though the most common plastic used for food (PET - milk bottles, most soft drinks etc) don’t contain any BPA. It’s the reusable ones that do.

I have glass containers for food, though I do still use plastic ones for short term storage for things I won’t heat. Honestly this seems like the best answer, metal, wood and glass if you can.

> Can someone knowledgeable comment on this? It seems extreme to say there's no safe level.

Not a direct answer, but the article reports the maximum exceeding amount:

> Maximum concentrations reached 351 mg/kg, dramatically exceeding the 10 mg/kg limit originally proposed by the European Chemicals Agency (ECHA).

For things you put on your skin that could be absorbed, shouldn't the limit take into account the area touching your skin? If I lay on a bed containing 10 mg/kg BPA, I would absorb a lot more than if I touch a headphone. So maybe it should be mg/kg*m^2 or something?

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