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Comment by jlmorton | Hacker News Reader

Yes you can, because they're all small effects, and we are unsure what other confounding, or correlated factors may occur with the studied chemicals.

It is _not_ the tobacco story all over again, because the health effect of long-term tobacco use "as directed," and as occurs normally in real-life, results in an extremely massive increase in the risk of death from lung cancer, with a staggering 1 out of 4 long-term smokers (using more than 5 cigarettes a day) dying of lung cancer - something like a 5000% increase.

The health linkage between regular tobbaco use and negative health outcomes is overwhelming.

It is not the same thing here. These are small effects and difficult to notice, and there could be other confounding factors. (Maybe people in environments with lots of PFAS chemicals are exposed to other chemicals common in polluted water sources).

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> Yes you can, because they're all small effects,

"A doubling of perfluorooctane sulfonate (PFOS) in maternal serum was associated with a 39% (p < 0.001) reduction in diphtheria antibody concentration in children (age 5 yr), with increased odds of falling below clinically protective values against diphtheria and tetanus at age 7 yr."

> A study of heavily exposed workers (n = 462, geometric mean serum PFOA of 4048 ng/mL) detected significantly increased incident mortality for cirrhosis (relative risk = 3.87, 95% CI 1.18–12.7) and liver cancer (relative risk = 6.69, 95% CI 1.71–26.2)

These are NOT small effects. These are strong p-values with large hazard ratios over and over again throughout the entire review.

> A study of heavily exposed workers

Those are a very small part of the affected ones, probably firefighters or 3M production workers. Remember that the dosage makes the poison.

They're not small values, but where are the real-life effects? Last I checked diphtheria levels in Western world remain at single digits per year levels, and the rare exceptions are almost invariably antivaxxers, not because the DPT vaccine has stopped working.

…Exactly because we put a stop to it, before higher levels became more prevalent.

Or are you going to argue about how antibodies work?

We've been using PFAS for 80 years now. Are the children of heavily exposed people actually contracting diphtheria or tetanus at measurably higher rates?

Again, the headline figure you're quoting sounds alarming, but if it's accurate and applicable to the broader population, then we should be seeing that effect outside the lab as well.

> We've been using PFAS for 80 years now. Are the children of heavily exposed people actually contracting diphtheria or tetanus at measurably higher rates?

Should we wait for that to happen if the risk is obvious?

Don't the kids of mothers heavily exposed wind up deformed?

Entirely possible, but that's quite different from them being more vulnerable to diphtheria, which was the specific claim made earlier in this thread.

Youre really going to bat for this? Incredible.

(relative risk = 3.87, 95% CI 1.18–12.7) and liver cancer (relative risk = 6.69, 95% CI 1.71–26.2)

I have no domain knowledge here but those CIs are quite large and both get close to 1 at the lower edge.

Without having read the study, but going on experience reading other studies of this general type, that’s a common pattern with CIs derived from predictors in logistic regression-like models (which are often used for this kind of analysis)- the CI calculations often end up having a log in there somewhere which results in higher tails. And a RR of 1.7 is still nothing to sneeze at depending on the base rate of whatever is being discussed…

But again, I haven’t read the paper! Just chiming in with some half-forgotten epidemiology. :-)

What is this biased way of reading CIs? Are you paid by 3M?

Yes, it shows that with 5% probability the risk is only 1.18 - why choose to focus on those 5%? According to the study there is an equal chance that the relative risk is 12.7 times normal, why should we ignore that?

You really think pointing out how large a CI is, is "biased"?

Your reading of the CIs is off. It isn't telling you that there's a 5% chance that the real risk is 1.18. It's saying there's a 5% chance the real risk doesn't lie in the CI, and could be anywhere outside the CI, including 1 (no effect).

Here's the main point. Increase the significance level slightly, say to 97% (if this is a 95% CI, or 92% if this is a 90%, etc). Then a CI that large and that close to 1 at the left edge will turn into a CI that includes 1. The effect is not significant at all at that level. It wouldn't be saying the true effect is significant with some probability or whatever you seemed to be interpreting CIs to say. It would be saying there's no effect.

This is markedly different from the case of cigarettes, where the p-values are astronomically small. Since earlier comments seem to compare these chemical to cigarettes.

So if you're handed a pint of water laced with PFAS, you're going to drink it without a care?

Well that depends on the concentration and how much you're willing to pay me

not sure why you need to be paid to drink water that we allegedly don't know is harmful, but go ahead and price your ask per concentration

feel free to develop a formula, if you so desire

My point is the highlight that harm, concentration, risk, and damage or not binary but magnitudes. One molecule for glass is negligible and a Pure Glass would be suicide.

correct, and you should price the different concentrations you're willing to imbibe, so communities already ingesting them can apply the same pricing structure to calculate damages for unwilling exposure

If I believe the headlines, that’s all the water we are drinking.

Levels experienced in the real world by real people, or a contrived example?

We agree table salt (sodium chloride) is generally safe to eat, right? Like, you probably sprinkle it on your food and what not? If I asked you to chug a gallon of water that was 26% salt by weight, you're going to drink it without care? No? I guess you should stop eating foods with sodium chloride!

There's loads of things I use in every day life that I wouldn't want to ingest in odd quantities. I handle gasoline and paint thinner and dishwashing detergents and hand soap every now and then but if you tried to get me to even drink a teaspoon of it I'd probably turn you down. Is the rule now if you wouldn't drink a glass of it you should never handle it in any way?

By the way, please do not drink that 26% salt brine. It will do very terrible things to your body and probably significantly hurt you.

It's one thing to make an academic case in an online forum, that PFAS are not detrimental (at low levels) to human health. But when it gets down to it, would you rather avoid PFAS, or you just don't think they're a problem?

> Is the rule now if you wouldn't drink a glass of it you should never handle it in any way?

Some things are not safe at any level. Lead (Pb) for example. So what about PFAS? Does it accumulate in the body? What are the effects of long-term ingestion?

My question was intended to see just how serious people were, who were making the argument that PFAS weren't a thing to be concerned about.

Sure, I would like to avoid PFAS on things that I regularly eat like takeout containers and the like. I'd probably not go for the Scotchgard coating on my next couch as fibers from the couch's fabric usually get flung into the air and I end up breathing in small tiny amounts and it's a high contact thing overall. But if PFAS improved engine seals means my car will last longer, then sure that sounds great.

I'd avoid drinking a glass of motor oil as well, but I still prefer having my car lubricated at the end of the day.

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