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Comment by refurb | Hacker News Reader

This is a very insightful comment.

Analytical techniques have rapidly improved over the past few decades. Our limit of detection has gone from tens of parts per million (ppm) to fractions of parts per trillion (ppt) for many analytes.

That's a million fold better detection level.

So in the past you might test drinking water and say there is no lead present. You test using techniques today and you'll find lead is present. But the level hasn't changed.

At the sensitivity of parts per trillion you'll find the presence of toxins in damn near everything.

People forget that toxins like lead, arsenic are naturally occurring.

And pushing "acceptable levels" down as detection improves needs to be done based on proven biological effect, not "no level is safe".

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The level chosen seems like a reasonable level to put up a flag. 200ppm is a level where an active gardener could cause excess exposure by growing leafy vegetables-- so that being the point where you warn people there's a potential problem and they should consider where to plant and what to grow.

If you told me my soil lead content was 200ppm, I would change my gardening practices and-- even though it may be a little overprotective-- cover contaminated soils where my kids play most.

(Now, if you told me that only 1/8th of homes would be affected if you set the level to 250ppm, maybe I'd say 250ppm would be a more appropriate level to balance the number of people warned; but if it's not a huge increment in the number warned, 200ppm seems appropriate-- that is, the tradeoff isn't just between direct harms and direct benefits but also, as grandparent seems to state, in helping people judge relative levels of risk accurately).

But what amounts to excess exposure is also getting lowered all the time. Also people grew lettuce to obtain lead. People like the taste of foods high in heavy metals, their absence is the reason why vegetables turned into tasteless plant mass.

I think these guidelines are also a political problem. They need to balance risk, communication, and what is feasible given the resources available and threat level. That’s not an easy thing to do. Still I am deeply skeptical that the people publishing these guidelines are considering these aspects effectively when their lead guideline puts 25% of residential areas in the US “at risk”.

The EPA's position is "there is no safe level of exposure to lead" in drinking water.

But the question is - is that based on science? And if detection methods continue to improve, will we hold to that statement? Will we tell people not to drink water that contains 0.00001 parts per trillion?

There clearly is some level of lead exposure where the level of effect cannot be distinguished from an individual not exposed.

A blood lead level of 1 ug/dl is enough to increase ADHD symptoms in children[1]. Children absorb lead more readily than adults and lead bioaccumulates. The CDC's action level for childhood BLL is 3.5ug/dl.

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4892926/

Holy uncontrolled confounding factors Batman!

No. Look at the actual results - the problematic behavior peaks at 5mcg/dl. They are simply too disabled to be impulsive below that. Ritalin actually appears to replace or allow an otherwise lead dependent process.

You will always see a difference, because it's essential, so every little but makes you less deficient. That is all they did, they never determined which way it is better. It's only assumed to be better - that the protein won't get activated is better, the way you look is supposedly better, the way you think is supposedly better. Even though people got ugly, sick, and the world is in "polycrisis"

Two options:

1. People drink water containing let's say 1 part per trillion lead. We test it, we can't measure that, we say it's fine. The people drinking it are in fact fine.

2. People drink water containing let's say 1 part per trillion lead. We test it, we can't measure that, we say it's fine. The people drinking it incur brain damage, but because we can't measure the thing causing it, we don't correlate it with anything.

How do we distinguish these cases?

Lead is an essential nutrient. Among other things, it's essential for calmodulin, which is a highly conserved protein. There is no eucaryotic life without it. This, and the absence of other "heavy metals" is incorrectly blamed on global warming.

Interesting. Can you point me to further reading on essential heavy metals in eukaryotes and what is understood about the the dietary levels needed?

https://pubmed.ncbi.nlm.nih.gov/10996673/

Thanks for this. Interesting and surprising, that Pb ++ can substitute so well for Ca ++ in calmodulin. Do you have any thing supporting lead being an essential nutrient? I've not seen anything here or searching showing Lead is essential for eukaryotic life, and that is what I'm really interesting in exploring. Also, understanding the mechanism of any lead toxicity in the context if its essential functions would be of great interest.

It doesn't substitute well, it's outright several orders of magnitude more effective at it than calcium. There is no good reason to believe it isn't the correct one.

It's also found in all historical bones, and strongly (positively) correlates with social status, as well as with prosperity population wise. Very high levels have been found in Neanderthal teeth. https://www.science.org/doi/10.1126/sciadv.aau9483

Pb binds with greater affinity, but is that good? calmodulin is generally though to be regulated by changes in calcium levels. higher affinity cation could inhibit that function, no?

That interpretation of the historical data goes counter to the authors view that the lead levels may be anecdotal due to location of a lead mine, and lead levels were not found in an individual from a different site.

"Periods of lead exposure during the childhoods of these two French Neanderthals are remarkable, as biogenic lead bands were not apparent in the ~100-ka-old Belgian individual discussed above, and decades of research have shown that there is no safe level for lead in humans and other animals."

Pb binds with greater affinity, but is that good?

Why would you assume that the metal that binds it with the greatest affinity isn't supposed to be there? It isn't uncommon that another atom can activate a protein, albeit poorly.

I did my own research, it is certainly essential. It's why moss has dissapeared, for example.

calmodulin is generally though to be regulated by changes in calcium levels.

Presumably in error.

biogenic lead bands were not apparent in the ~100-ka-old Belgian individual discussed above

No such data is shown, they measured a 5.4ka individual, in addition to the neanderthals.

decades of research have shown that there is no safe level for lead in humans and other animals

They got their indices the wrong way round. I don't deny there is a difference, I claim that the healthy state is with lead present.

I appreciate you entertaining my questions. That said, I cannot get past the massive body of evidence supporting the toxicity of lead on a number of systems (blood, neural, kidney etc) from a vast number of sources over many years. Kudos on doing your own research, but I'd suggest caution in applying it. Cheers.

neural

Yes, that especially.

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