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Comment by wyldfire | Hacker News Reader

> most of the affected kids ... didn’t have enormous amounts of lead in their bloodstreams, and only two percent had a "high" level. But as the researchers note in their paper, there's no such thing as a safe amount of lead to have in your system.

It's possible that more sensitive instruments will allow us to eventually conclude "this small amount X of lead is safe to have ...". But it makes sense to take this seriously. We know lead is bad and we know lots of environmental exposure to lead exists.

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The point is that "detectable" says more about the instrument than anything else.

If there's no science that says "one atom of lead anywhere in your body is bad", then saying "detectable" is meaningless.

I mean, if you said "we found a detectable number of bullets in half of children", now that would be bad.

I think the real point is that detectable levels with modern instruments that are used for such measurements (≥1.0 μg/dL)* is considered bad.

*Another poster noted this level.

> If there's no science that says "one atom of lead anywhere in your body is bad", then saying "detectable" is meaningless.

It would be meaningless on that case too.

Also meaningless is saying that 2% of the kids have a high level of lead, without saying what "high" means.

> Also meaningless is saying that 2% of the kids have a high level of lead, without saying what "high" means.

Oh, that's simple - it's defined as above the 98th percentile.

(I kid, I hope...)

Actually, the CDC defines the 5ug/DL as high based on being the 97.5%ile [1] in children... so you're not kidding...

But if only 2% of children have lead levels that were originally defined based on the worst 2.5%, that's a 20% reduction, so great news!?

[1] https://www.cdc.gov/nceh/lead/prevention/blood-lead-levels.h...

Still, I'm not sure the article uses the CDC definition. Going on with the complaint, the article is meaningless.

Did they find a problem? An improvement? Nothing? Nobody can tell by reading it alone.

Amazing.

I might be mistaken here, but from what I've read on lead, we already know relatively well what amount of lead is safe, according to body weight etc. We also know that our bodies can deal with these small amounts, by actually getting rid of some of it. Maybe someone with more knowledge on the matter can chime in?

Total lead tells you your symptoms today. But it accrues so you'd need to know in advance your future lead intake to know if this small amount today will be a big impact tomorrow. Basically its unknowable so its practical to say that no amount is safe. There probably does exist a low enough level that the body can even clear it but there isn't any will to define it.

My understanding is that all detectable amounts currently have known negative effects when studied. The Action levels are set based on what is possible to address in an individual child.

Lead exists in the environment. It would be impractical to impossible to eliminate it entirely from the blood streams of most people. However certain areas have extremely dangerous concentrations such as dirt near major roads/old buildings, water in certain areas, and lead paints.

Lead pipes are an interesting one where it is simply impractical to replace all the pipes and remove lead in old cities. Hence as long as the calcification holds there is no action on the small amount of lead which leaks into the pipes.

In the US at least, were it structured as an infrastructure project on a city by city basis, it would actually be extremely possible to strip out lead pipes and replace them with something modern.

The problem is that pipe ownership in a domestic home is the property of the homeowner, and there's no political will to do that kind of massive wealth transfer from the public coffers to the improved infrastructure of millions of individual properties. But while it wouldn't be inexpensive, it's on par with other expenditures the federal government makes for federal projects.

That statement has the exact same problem. With sufficiently sensitive tests you might in theory be able to detect the negative effects of a single lead atom.

What we really want to know is: how big of a deal is this really?

Does a single atom have known negative effects?

There are unlikely to be people in the US with blood levels less than 1 order of magnitude less than the EPA action threshold. Lead is in your drinking water, food, and if you lived near anything with leaded - your air.

We used to use lead based pesticides at the dawn of the 20th century, if you eat any food grown in the midwest you are exposing yourself to reasonably large quantities of lead.

Actually, you dont need to replace the pipes. They can actually line them in place. Of course then people might have concerns about the chemical makeup of the liners (basically plastic), but it's hard to say what other alternatives are out there.

It's noise. Worry about teaching kids to look both ways etc before obsessing about this one, is my advice.

I taught my kids to look both ways. Now what do I do?

etc

So, I'd agree that there are lead levels too low to be worth worrying about. But I recall a clever study a while back where a researcher noticed that children found to be in the top decile of lead exposure got lead abatement for their homes or apartments by the city. The researchers compared them to the previous second decile (now first decile) and found a pretty significant effect size on life outcomes. This was done on poor people in city centers so the lead levels were high compared to, say, suburbanites but there are lead levels many kids in the US are exposed to that are actually a big deal.

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