4 ms·

I don't know about their selection, but most table salt here is pumped out of the ground in Windsor. When I want coarse salt I just mix some table salt with wat

I don't know about their selection, but most table salt here is pumped out of the ground in Windsor. When I want coarse salt I just mix some table salt with water and dry it like seawater. > The size of the smallest particle was 160 μm and the largest sized 980 μm. This was shocking to me, that they could miss a millimetre-scale particle of plastic in salt seems bonkers. I mean, you can more or less just filter things that size!

mentalpiracy 10y ago
Just to clarify for you, their selection study was purely sea and lake salts.
- microcolonel 10y ago
  They really ought to have put that in the title. They could have easily said "the presence of microplastics in saltwater salts from different countries".
  - mentalpiracy 10y ago
    Possibly so, but this is filed as environmental monitoring, so I think most people in the field this article is written for wouldn't have your same uncertainty. Salt derived from underground sources wouldn't be at risk of microplastics contamination.
    - mirimir 10y ago
      Well, but there might be other sources for plastic contamination, as they discuss. And there "is" nothing in the article with evidence for origin. Or even a statement like "We tested samples of lake and sea salt." Only those two lake salts are mentioned specifically. Maybe it's just an oversight, but it could also be just their assumptions. Maybe it's really "We tested samples of salt that were presumably produced from lake water and seawater."
- mirimir 10y ago
  OK, so I just went back and read carefully about that point. I don't think that they actually say clearly that they looked only at sea and lake salt. They talk about contamination pathways for sea and lake salt. And they mention lake salt from Malaysia and Iran. But Methods has: > A total of 17 brands of salt from Australia, France, Iran, Japan, Malaysia, New Zealand, Portugal, and South Africa were purchased from a Malaysian market.
  - mentalpiracy 10y ago
    Very first paragraph of the introduction. > Accordingly, it is expected that products originating from the contaminated water bodies are also loaded with MPs. This sentence is the entire premise of the study. Testing non-waterbody-derived salts would not provide any valid data in pursuit of that hypothesis. Furthermore the entire body of the abstract, introduction, and discussion discusses marine microparticles, impacts on aquatic health, and whatnot.
    - wodenokoto 10y ago
      It would give us a baseline. E.g, does the salt get contaminated with MP through production and packaging?
    - PhasmaFelis 10y ago
      That confirms that they assume all their table salt is from water. I have only skimmed the article, so I may be missing something, but the only origin information I saw was country of origin and that they "were purchased from a Malaysian market". If the researchers actually confirmed that each brand came from water and not a mine, they don't mention that that I can see. If I've missed something, please let me know.
  - pilsetnieks 10y ago
    To be honest, I wonder if "purchased from a Malaysian market" might not be a factor here, and if the products are truly from Australia, France, Japan, New Zealand, Portugal, etc.
mentalpiracy 10y ago
Sorry for double comment, just wanted to mention a thought about the filtration: You can filter them - and they certainly do - but with sea and lake salts the filtration is mainly to screen out sediments such as sand grains and bits of shell. Naturally, the filtering is a costly process and the filters need to be discarded after a certain level - I imagine there is a cost-control factor here, where screening at a 1mm threshold catches 99.9% of sediments to make the product reach a certain purity level and more thresholds are not worth the money. Further screening is probably not cost effective - and seeing from the results of the study, plastic microparticles are not a source of concern.
- microcolonel 10y ago
  Maybe centrifuges would be a good candidate to augment/replace filtration.
  - jrapdx3 10y ago
    I thought of that too, but the expense of operation is very likely not worth it to the producers. The low level of plastic contamination would not seem likely to produce health hazards.
  - rleigh 10y ago
    Not at industrial scale for fine plastic particulates. It's OK for continuous removal of denser coarse particles > 1mm but wouldn't be good for separating plastics with approximately neutral density since it wouldn't separate efficiently. Big industrial centrifuges are static (no moving parts) and operate purely by high speed liquid flow in a spiral path (like spinning a bucket of sand and water where the heavy particles collect in the centre). In the brewing industry we use Kieselguhr (perlite) filtration with filters like this: https://www.ryebeckltd.com/current-equipment/schenk-kieselguhr-filter https://www.ryebeckltd.com/current-equipment/schenk-kieselgu.... These can sterile filter particles as small as 1 micron and are density-independent. These work by having a steel plate with fine slots upon which you deposit a coarse bed of filter material, and then you dose kieselguhr into the liquid flow passing through, and this gradually builds up on top of the coarse bed to create an ultrafine filter. The ultrafine filter increases in depth over time, and this prevents blinding (blocking) of the filter as filtered particulates accumulate. While used to remove yeast and other particulates in brewing to create "bright" beer, it can be applied to most liquid filtration problems, and at high flow rates (30000 litres/hr); and you can run multiple filters in parallel to further increase the flow rates. We also used kieselguhr in research labs for fine filtration--just add the powder to regular filter paper.
mirimir 10y ago
Well, they could dissolve, filter and evaporate. But that would be energy expensive. I'm guessing that they crush and fractionate by size. Air flow separation could do it, but nobody cares enough.
wodenokoto 10y ago
I sometimes buy "himalayan salt" which are coarse salt in almost pebble sizes (presumably from the himalaya) and I actually found a pebble in a package once. Well above 2 square millimetres.
- mchannon 10y ago
  This bit of genius branding is also highly misleading. Himalayan salt (found frequently in warehouse clubs) is a product of Pakistan and is produced >100 mi from the nearest portion of the Himalayas. I still use and enjoy some on occasion.

mentalpiracy 10y ago

Just to clarify for you, their selection study was purely sea and lake salts.

microcolonel 10y ago
They really ought to have put that in the title. They could have easily said "the presence of microplastics in saltwater salts from different countries".
- mentalpiracy 10y ago
  Possibly so, but this is filed as environmental monitoring, so I think most people in the field this article is written for wouldn't have your same uncertainty. Salt derived from underground sources wouldn't be at risk of microplastics contamination.
  - mirimir 10y ago
    Well, but there might be other sources for plastic contamination, as they discuss. And there "is" nothing in the article with evidence for origin. Or even a statement like "We tested samples of lake and sea salt." Only those two lake salts are mentioned specifically. Maybe it's just an oversight, but it could also be just their assumptions. Maybe it's really "We tested samples of salt that were presumably produced from lake water and seawater."
mirimir 10y ago
OK, so I just went back and read carefully about that point. I don't think that they actually say clearly that they looked only at sea and lake salt. They talk about contamination pathways for sea and lake salt. And they mention lake salt from Malaysia and Iran. But Methods has: > A total of 17 brands of salt from Australia, France, Iran, Japan, Malaysia, New Zealand, Portugal, and South Africa were purchased from a Malaysian market.
- mentalpiracy 10y ago
  Very first paragraph of the introduction. > Accordingly, it is expected that products originating from the contaminated water bodies are also loaded with MPs. This sentence is the entire premise of the study. Testing non-waterbody-derived salts would not provide any valid data in pursuit of that hypothesis. Furthermore the entire body of the abstract, introduction, and discussion discusses marine microparticles, impacts on aquatic health, and whatnot.
  - wodenokoto 10y ago
    It would give us a baseline. E.g, does the salt get contaminated with MP through production and packaging?
  - PhasmaFelis 10y ago
    That confirms that they assume all their table salt is from water. I have only skimmed the article, so I may be missing something, but the only origin information I saw was country of origin and that they "were purchased from a Malaysian market". If the researchers actually confirmed that each brand came from water and not a mine, they don't mention that that I can see. If I've missed something, please let me know.
- pilsetnieks 10y ago
  To be honest, I wonder if "purchased from a Malaysian market" might not be a factor here, and if the products are truly from Australia, France, Japan, New Zealand, Portugal, etc.

mentalpiracy 10y ago

Sorry for double comment, just wanted to mention a thought about the filtration: You can filter them - and they certainly do - but with sea and lake salts the filtration is mainly to screen out sediments such as sand grains and bits of shell. Naturally, the filtering is a costly process and the filters need to be discarded after a certain level - I imagine there is a cost-control factor here, where screening at a 1mm threshold catches 99.9% of sediments to make the product reach a certain purity level and more thresholds are not worth the money. Further screening is probably not cost effective - and seeing from the results of the study, plastic microparticles are not a source of concern.

microcolonel 10y ago
Maybe centrifuges would be a good candidate to augment/replace filtration.
- jrapdx3 10y ago
  I thought of that too, but the expense of operation is very likely not worth it to the producers. The low level of plastic contamination would not seem likely to produce health hazards.
- rleigh 10y ago
  Not at industrial scale for fine plastic particulates. It's OK for continuous removal of denser coarse particles > 1mm but wouldn't be good for separating plastics with approximately neutral density since it wouldn't separate efficiently. Big industrial centrifuges are static (no moving parts) and operate purely by high speed liquid flow in a spiral path (like spinning a bucket of sand and water where the heavy particles collect in the centre). In the brewing industry we use Kieselguhr (perlite) filtration with filters like this: https://www.ryebeckltd.com/current-equipment/schenk-kieselguhr-filter https://www.ryebeckltd.com/current-equipment/schenk-kieselgu.... These can sterile filter particles as small as 1 micron and are density-independent. These work by having a steel plate with fine slots upon which you deposit a coarse bed of filter material, and then you dose kieselguhr into the liquid flow passing through, and this gradually builds up on top of the coarse bed to create an ultrafine filter. The ultrafine filter increases in depth over time, and this prevents blinding (blocking) of the filter as filtered particulates accumulate. While used to remove yeast and other particulates in brewing to create "bright" beer, it can be applied to most liquid filtration problems, and at high flow rates (30000 litres/hr); and you can run multiple filters in parallel to further increase the flow rates. We also used kieselguhr in research labs for fine filtration--just add the powder to regular filter paper.

mirimir 10y ago

Well, they could dissolve, filter and evaporate. But that would be energy expensive. I'm guessing that they crush and fractionate by size. Air flow separation could do it, but nobody cares enough.

wodenokoto 10y ago

I sometimes buy "himalayan salt" which are coarse salt in almost pebble sizes (presumably from the himalaya) and I actually found a pebble in a package once. Well above 2 square millimetres.

mchannon 10y ago
This bit of genius branding is also highly misleading. Himalayan salt (found frequently in warehouse clubs) is a product of Pakistan and is produced >100 mi from the nearest portion of the Himalayas. I still use and enjoy some on occasion.