Is forty times an extremely small number still negligible? (asking not out of skepticism but curiousness)
40 times greater chance of a comet hitting you on the head? Still gonna be negligible and you probably shouldn't be too concerned.
40 times more lead in your eggs? Well, you should really be aiming for zero lead in your eggs and lead poisoning can happen over time (My cousins got lead poisoning from old plates and bowls). If you have chickens, you are probably being fed a consistent diet of eggs. So yeah, it might very well be a concern.
Is this 40x the chance of getting hit by a comet, or 40 games of Russian roulette.
The study talks about increased blood lead levels ~1 to 1.4 μg/dL. Now how risky is that? The CDC has alert levels for children of 5 ug/dL, recently revised from 10 ug/uL.
What the measurable impact is from 5ug, let alone 1 ug is hotly debated because it is so difficult to asses.
Here is the study they cross reference:
>Our IEUBK model predictions suggested that consuming one egg per day with a lead concentration less than 100 μg/kg, in addition to the model’s default lead exposure from diet and all other sources, would result in estimated GM blood-lead concentration increases of less than 1 μg/dL in children. However, daily consumption of one egg with the highest lead concentration we found in eggs from NYC community gardens (167 μg/kg) would increase GM blood-lead concentrations by 1 to 1.4 μg/dL, and daily consumption of one egg with 300 μg/kg lead would increase GM blood-lead concentrations by as much as 2.4 μg/dL, well above the 1 μg/dL guideline.
The IEUBK model output was also used to estimate the number of eggs children could consume without excessively increasing blood-lead concentrations. Among children 1 – 6 years of age, the model output suggested that an increase in dietary lead intake of up to 5.6 μg/day for 1 to 2 year olds (and slightly larger increases – as much as 7.6 μg/day – for older children), would raise GM blood-lead concentrations by less than 1 μg/dL. This intake translates into the consumption of about 6 medium eggs/day at 20 μg/kg lead, 2.5 eggs/day at 50 μg/kg, or 1.2 eggs/day at 100 μg/kg.
These evaluations implied that, overall, the lead concentrations we found in eggs from NYC community gardens were not likely to significantly increase lead exposure or to pose a significant health risk. However, frequent consumption of eggs with the highest lead concentration we found could significantly increase lead exposure, and chickens exposed to higher concentrations of lead in soil are likely to produce eggs with higher concentrations of lead. This exposure pathway could potentially be significant in some gardens, and it should not be ignored
[1] https://www.who.int/news-room/fact-sheets/detail/lead-poison...
> Some studies suggest that the current OSHA PEL and NIOSH REL may be too high to protect against certain health effects.
"Some studies suggest that the current OSHA PEL and NIOSH REL may be too high to protect against certain health effects"
The reason we have non-zero "official" threshold values is for practical reasons: In our times and on this earth right now it simply is not possible. The values are set so that medical people are kind of okay with it - any damages are too subtle and not too obvious (e.g. less IQ as well as most small issues nicely also correlate with age so it can always be attributed to aging, and proving for an individual (and not just statistically for a lot of people without being able to say anything about each individual) that some issue was caused by or was contributed to by e.g. lead is impossible (we can't tag all the atoms and follow them around and see what they do, and even if we could do the first part perfectly, the following those atoms, we still would not know what they actually do just from knowing where they've been, even less so how the local bio-chemistry deals with consequences longer term than we can observe). So we need to have a limit that is low enough to not cause medical alarm bells to go off, but high enough to not bankrupt government and industry if they were told they had to clean it all up. Which, quite frankly, they can't at this point.
Last time I heard about China they have an already huge and increasing problem with heavy metals on large parts of their agricultural lands... (Example, two links of many randomly chosen: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6239058/ or https://www.chinawaterrisk.org/resources/analysis-reviews/he...) and the West had a lot of time where nobody cared about pollution one bit, during and after industrial revolution. The "superfund sites" (https://en.wikipedia.org/wiki/List_of_Superfund_sites) are just the biggest concentrations. Oh and then there's coal - burning it also has been releasing heavy metals such as mercury for a long time, and it's still going on.
Oh and by the way, please nobody blame "capitalism". I grew up in East Germany, near ash mountains and a river clearly unsuitable to even be touched by a human, everything was dirty and gray. I did not even live in one of the known polluted places (e.g. Bitterfeld). After reunification everything was cleaned up with Western money and methods - ash mountains gone, the river is clear and has nice water plants showing it's really healthy, etc. East Germany under capitalism is A LOT cleaner than under socialism. I say this because in sooo many discussions about the environment always somebody blames capitalism, but it's deeper and orthogonal to whatever system is used I think. People do or don't care about their environment, if it was just about economic pressure, you have them in all systems, because all systems need to produce something.