3 ms·

It should be pointed out that some of the natural levels of heavy metals are somewhat toxic as well.

ziddoap 1y ago
This is pointed out in the article: "“The widespread distribution of cadmium contamination comes from both natural and anthropogenic sources,”" "“Geochemically, certain parent rock materials [substrate below the ground], such as black shales, contain high levels of cadmium, leading to elevated concentrations in the soil due to weathering.”" "However, the study does not assign blame to either natural or human causes."
- Robotbeat 1y ago
  Yeah, natural or human caused, it’s toxic. Sometimes in modernity, we forget that Nature Herself is massively dangerous.
  - hilbert42 1y ago
    Right, both Nature and life itself are dangerous, they conspire together and eventually kill us. :-)
hilbert42 1y ago
Right, for example naturally occurring arsenic, which is commonly found in soils across large areas of the planet, can be dangerous if concentrated. To put that into perspective, I recall seeing one estimate that put the typical levels of arsenic in a cubic meter of soil that if concentrated would kill the average human. Now, a cubic meter of soil is a very large amount, so the effective concentration is what actually counts. How relevant to human health is this 'typical' amount/quantity? Well, I don't know as it's not my field. I'd suggest however it cannot have a big effect on human health as we've lived and evolved for hundreds of millennia with that level of arsenic in soils—that's long before anthropogenic sources would have had time to kick in. That said, we know that in some locations natural arsenic levels are high enough to cause significant health problems, in fact sometimes concentrations are so high as to be life-threatening. Such high levels are especially dangerous when leached out of rocks and soils and they end up in water supplies (contaminated bore water being the main culprit, it's a well-known problem).
- dyauspitr 1y ago
  That’s why I only buy basmati rice from India because it has by far some of the lowest levels of arsenic in the world.
  - sevensor 1y ago
    I’d heard US rice was heavily contaminated with arsenic due to having been planted in regions that formerly grew cotton. And cotton was once treated with arsenates to control boll weevil (https://a-c-s.confex.com/a-c-s/2005am/techprogram/P4552.HTM https://a-c-s.confex.com/a-c-s/2005am/techprogram/P4552.HTM) I was surprised not to see this reflected in the map
    - dyauspitr 1y ago
      US, Chinese and Bangladeshi rice have the highest levels. Especially in brown rice. Strangely California white basmati has relatively low levels.
      - toast0 1y ago
        California rice having low levels fits with sevensor's theory about boll weevil control with arsenates on fields used for cotton and later for rice. This report [1] says that boll weevils weren't an issue in California cotton fields, and that likely means arsenates wouldn't have been used, so if those fields switch to rice, they won't have high levels of arsenic from previous insecticide application. https://apps1.cdfa.ca.gov/FertilizerResearch/docs/Cotton_Production_CA.pdf https://apps1.cdfa.ca.gov/FertilizerResearch/docs/Cotton_Pro...
- RetroTechie 1y ago
  > Now, a cubic meter of soil is a very large amount, so the effective concentration is what actually counts. What counts is how much winds up in humans' bodies. And halfway: how much winds up in crops grown in such areas. There is no 1:1 relation between [concentration in the soil] and [concentration in crops grown in that soil]. Some plants are known to be strong accumulators of certain elements/compounds. And some plants could be low in X even if soil they're from is high in X. So the only way to be sure is have crop samples chemically analyzed.

This is pointed out in the article: "“The widespread distribution of cadmium contamination comes from both natural and anthropogenic sources,”" "“Geochemically, certain parent rock materials [substrate below the ground], such as black shales, contain high levels of cadmium, leading to elevated concentrations in the soil due to weathering.”" "However, the study does not assign blame to either natural or human causes."

Robotbeat 1y ago
Yeah, natural or human caused, it’s toxic. Sometimes in modernity, we forget that Nature Herself is massively dangerous.
- hilbert42 1y ago
  Right, both Nature and life itself are dangerous, they conspire together and eventually kill us. :-)

hilbert42 1y ago

Right, for example naturally occurring arsenic, which is commonly found in soils across large areas of the planet, can be dangerous if concentrated. To put that into perspective, I recall seeing one estimate that put the typical levels of arsenic in a cubic meter of soil that if concentrated would kill the average human. Now, a cubic meter of soil is a very large amount, so the effective concentration is what actually counts. How relevant to human health is this 'typical' amount/quantity? Well, I don't know as it's not my field. I'd suggest however it cannot have a big effect on human health as we've lived and evolved for hundreds of millennia with that level of arsenic in soils—that's long before anthropogenic sources would have had time to kick in. That said, we know that in some locations natural arsenic levels are high enough to cause significant health problems, in fact sometimes concentrations are so high as to be life-threatening. Such high levels are especially dangerous when leached out of rocks and soils and they end up in water supplies (contaminated bore water being the main culprit, it's a well-known problem).

dyauspitr 1y ago
That’s why I only buy basmati rice from India because it has by far some of the lowest levels of arsenic in the world.
- sevensor 1y ago
  I’d heard US rice was heavily contaminated with arsenic due to having been planted in regions that formerly grew cotton. And cotton was once treated with arsenates to control boll weevil (https://a-c-s.confex.com/a-c-s/2005am/techprogram/P4552.HTM https://a-c-s.confex.com/a-c-s/2005am/techprogram/P4552.HTM) I was surprised not to see this reflected in the map
  - dyauspitr 1y ago
    US, Chinese and Bangladeshi rice have the highest levels. Especially in brown rice. Strangely California white basmati has relatively low levels.
    - toast0 1y ago
      California rice having low levels fits with sevensor's theory about boll weevil control with arsenates on fields used for cotton and later for rice. This report [1] says that boll weevils weren't an issue in California cotton fields, and that likely means arsenates wouldn't have been used, so if those fields switch to rice, they won't have high levels of arsenic from previous insecticide application. https://apps1.cdfa.ca.gov/FertilizerResearch/docs/Cotton_Production_CA.pdf https://apps1.cdfa.ca.gov/FertilizerResearch/docs/Cotton_Pro...
RetroTechie 1y ago
> Now, a cubic meter of soil is a very large amount, so the effective concentration is what actually counts. What counts is how much winds up in humans' bodies. And halfway: how much winds up in crops grown in such areas. There is no 1:1 relation between [concentration in the soil] and [concentration in crops grown in that soil]. Some plants are known to be strong accumulators of certain elements/compounds. And some plants could be low in X even if soil they're from is high in X. So the only way to be sure is have crop samples chemically analyzed.