One in four US households likely exceed new soil lead guidance levels
agupubs.onlinelibrary.wiley.com
agupubs.onlinelibrary.wiley.com
Continually ratcheting up the safety level to spur continuous improvement is great in principle. But what I think this does in practice is mean that people are no longer able to evaluate soil lead levels appropiately. What does 400ppm mean versus say 1600ppm? They are both "bad" according to the US EPA now but one is clearly worse. If 10% of soil area is above your limit it is easier to allocate your limited resources to fix it than if 25% is. At 25%, with the same resources maybe you just throw up your hands and walk away from the problem.
There's similar problems with air quality limits. When the WHO says there is "no safe limit" they simulatenously misunderstand odds ratios and give a lot of people a great excuse to stop worrying about a problem they now think is unfixable.
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".
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.
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?
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
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."
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.
Yes, that especially.
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).
> With the Clean Air and Clean Water Acts, US policy began severely limiting the production and use of lead in infrastructure and consumer products, including water pipes, paint, and gasoline that have been historical sources of lead entry into the environment.
Curious about deteriorating gas stations and underground oil tanks.
Oh yes, cover the thing up and let someone else deal with it. The same strategy employed for years with lead paint.
We can either spend billions covering it up over and over again, or we can deal with it once and be done.
What does this mean? Dismantling the community and replacing everything above the bedrock?
Is this a random guess or based on anything?
What rate does it remove at? You’ll need to depopulate a quarter of American housing during that period. Are we sure none of the lead will emerge in the volatiles from burning?
You would definitely need to look into the lead coming out the chimney; if it does, you just dry the material and accept less concentration. (Or use a more complex technology like a molten salt reactor to keep it from escaping the chimney, but if it's eg concentrating in the leaves, drying it out is probably almost as effective as burning it.)
You only need to kick people out of their homes if the soil is so dangerous they can't live there anyway. You're not disturbing the soil more than gardening would.
There would definitely be huge challenges, my main point is that it's a naive assumption that you necessarily have to relocate people to remediate the soil. It doesn't necessarily have to work quickly as much as steadily. If you can do it in 10 years by relocating people and 100 years without, it probably makes sense to go the slow route and the soil will get less and less dangerous all the time.
If you're curious, you might look up bioremediation and biomining.
The article is specifically about unsafe lead levels.
> If you can do it in 10 years by relocating people and 100 years without, it probably makes sense to go the slow route and the soil will get less and less dangerous all the time
Versus just covering it up? What kind of cost-benefit analysis does that pass?
All kinds of toxic substances exist below the top soil. I agree it would be nice if we could poof away the problem. But given its scale, that’s not a real option. (For context, if we can do this we can solve the housing crisis.)
Is that a good use of resources? I don't have the data to form that opinion, and I'm not going to gather it for a casual Internet conversation, so I just don't know.
Capping leaded soil isn't great, in that you can't look at dirt and guess that it's old enough to probably be bad the way you can with paint or tile, and many plants tend to have deep roots that'll suck the lead right back up to the surface.
That said, so long as it is disclosed properly to future occupants, it's better than doing a bad job (accidentally or otherwise) and telling everyone it's been taken care of.
If lead paint is sequestered, it poses no threat. When you start trying to scrape all of it off and replace it is the point at which you've now exposed yourself and everyone that might inhale some of that dust.
Same thing with asbestos. As long as it's somewhere that you won't inhale/ingest it, there isn't a problem. Asbestos brake pads, problem. Asbestos siding on a house, only a problem if you're doing construction that disrupts it.
Similarly, if you have a location with high levels of lead in the dirt or are concerned about it, perhaps you should import soil and do some raised bed planting.