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Comment by jihadjihad | Hacker News Reader

Doesn't toxicity depend on dose? Have studies been done on maximum allowable dose of these chemicals?

Organic/medicinal chemist here. Some toxin, endocrine disruptors and many other things have widely variable toxicity curves. Something we often see is U curves. With high toxicity in both small and high doses. The small doses can induce cascade effects (like hormones).

I’m having trouble imagining how a smaller dose could cause a larger effect, can you elaborate some more on the biochemical mechanism for that?

This effect has always puzzled me, so much that initially thought it was pseudoscience (like homeopathy). I mean, in a real U curve, the highest effect is at a zero dose and it makes no sense.

But it looks serious, peer reviewed papers and all that. The main reason seems to be that at a low dose, the chemical doesn't trigger "defense" reactions and can do its thing unimpeded (high effect), on a medium dose, our body starts to notice and dampen the effect (low effect). High doses are simply overwhelming and the effect becomes high again.

I still think there is a lot of pseudoscience around that effect that helps selling a lot of "natural", "detox", etc..., but I don't think all of it is bullshit anymore.

As other posters note some feed-forward defense mechanism requires a larger dose to elicit a response. Sometimes small doses have a cascade effect meaning A->2xB->6xC etc whereas a larger dose would activate a feed-backward mechanism between B and C.

A classic example is endocrine disruptors (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4036398/), a small dose induces a hormonal response, a medium dose the body fights due to detecting it as foreign and a high dose is just regular toxic. Please note this is somewhat simplified but used as an example.

> Doesn't toxicity depend on dose? Have studies been done on maximum allowable dose of these chemicals?

Ubiquity increases the changes of high dose. There are now plastics in human blood for example:

* https://www.smithsonianmag.com/smart-news/microplastics-dete...

Dose where? In potato or surrounding soil or nearby fields or rivers which have runoffs from the farms? In farm animals that will eat it for 10 months and then be butchered? In fish living in those rivers or migrating to oceans to be eaten by other animals up in the food chain?

Farmers, just like any other industry, is very good at reading rules and finding very creative ways in between them how to maximize profits regardless of human costs. I don't blame them per se, but let's not be naive about farmers being some sort of saints doing whatever possible to feed the needy with as-healthy-as-possible healthy food.

Banning makes things much easier to actually govern and enforce, and doesn't leave endless amounts of backdoors for serious catastrophes 20-50 years down the road. We already had plenty of them to take lesson or two, most started with good intentions but lack of deep scientific understanding which we still don't have in such scale to clear any of these substances to be actually safe.

Also, some of us have kids and actually want to leave an OK world for them, if not better, not a scorched wasteland just to have marginally better retirement financial situation.

Sure, but you can’t control the dose on an entire population. Let’s say only 1% of people get brain cancer because of their habits/lifestyle. That’s still unacceptable, despite 99% not getting a dose that’s lethal.

An example of this type of selective poisoning is cashiers handling receipts laced with BPA all day.

But if it accumulates in the environment ?

Oxygen meets this definition, and is toxic to humans in high enough concentrations.

It's a different argument though, it's an organic material to start with which existent long before the industrial revolution. It's also 100% required for our survival.

Fire retardants which are known to cause cancer or birth defects, I'm not so sure. Then there's the fact that Oxyten is literally everwhere, do you want those retardants to be everywhere too, in your lungs?

> Fire retardants which are known to cause cancer or birth defects, I'm not so sure.

On the other hand, they’re very good at stopping you from burning to death. Even the ones we have banned (or will ban) and replaced with others are very good at preventing a really really bad way to die.

Also, quite a lot of toxic things are also organic, regardless of if you’re using that word in the chemical sense or the “it’s natural” sense.

They’re not good though. Hold an open flame or shorting electrical wire to a coated surface and it will burn just the same.

Flame retardants only really give you a slight edge vs a burning cigarette on a couch.

We coated our couches, clothes, carpets etc in cancerous chemicals to save a few smokers that passed out drunk

Burn isn’t binary, rate matters to give humans time to flee…

Flame retardants have no measurable impact on burn rate once the burn has started.

We literally coated everything in carcinogenic chemicals for the dumbest of reasons.

In addition to what @mensetmanusman says:

They also save the families of those smokers, and people like my sister who knocked over a candle and had enough time to put it out despite not having a fire extinguisher, and people like me who forgot food on the stove one time, or people like my dad who missed when pouring burning brandy onto a Christmas puddings.

If you still find this unconvincing, ask yourself why life expectancy has gone up rather than down since the invention and mandated use of fire retardants.

My argument is the net harm of coating everything in carcinogens and endocrine disruptors outweighs the fringe benefit. Flame retardants don’t eliminate fire, they give you an extremely small chance of preventing one in very specific scenarios.

And where on the planet do you find oxygen in such concentrations? It doesn't build up in the environment to a lethal degree, unlike most local pollutants.

CO would be a better comparison, and we have actual detectors for it in houses.

> And where on the planet do you find oxygen in such concentrations?

That shouldn’t matter. My point is the standard being called for is ridiculous because it would also ban oxygen for being (1) toxic and (2) accumulating in the environment.

> for being (1) toxic and (2) accumulating in the environment to a harmful degree

I'm sure the actual standard surely takes accumulation levels into account otherwise it wouldn't make any sense at all, as you say. Unlike in the US, EU laws aren't usually written by idiots.

It's partial pressure not concentration. Air is toxic if you have 60 m of water above your head, but nowhere on earth do you have oxygen at 1.4 atm of partial pressure.

(Oxygen toxicity is really the one thing in recreational scuba diving training where they tell you "do this and you will positively die").

Oxygen does not accumulate in the environment in sufficient doses to be toxic. It is plausible that the other chemicals under discussion do, or at least it makes it much more difficult to have dosing discussions when its unclear at what level it accumulates in environment.

It caused one of the major mass extinction events on earth, some life still finds it toxic, and the point I was trying and failing to make is that the definition given was insufficient because dose is important.

Nobody disagrees that dose is important. Your point is failing to land because you are attacking a straw man and not the point the original person was making.

Noted. I sincerely got the impression the person I was responding to was disagreeing that dose is important, given what they were responding to.

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