[Scouse D]

I don't think we need to be overly worried about our exposure to Silicon dioxide. This is from the HSE website for stonemasons (I tried to think of the occupation with the highest potential exposure to shitloads of silica dust). RCS is respirable Crystallise Silica.

 "If you are exposed to RCS then you are at risk of developing silicosis. This disease makes breathing more difficult and increases the risk of lung infections. Silicosis usually follows many years of exposure to RCS. Exceptionally high exposures over a few months or years can cause acute silicosis, which can cause death within months of exposure. Heavy and prolonged exposure to RCS under the conditions that produce silicosis can cause lung cancer"

[sirlockoff]

I don't think we need to be overly worried about our exposure to Silicon dioxide. This is from the HSE website for stonemasons (I tried to think of the occupation with the highest potential exposure to shitloads of silica dust). RCS is respirable Crystallise Silica.

 "If you are exposed to RCS then you are at risk of developing silicosis. This disease makes breathing more difficult and increases the risk of lung infections. Silicosis usually follows many years of exposure to RCS. Exceptionally high exposures over a few months or years can cause acute silicosis, which can cause death within months of exposure. Heavy and prolonged exposure to RCS under the conditions that produce silicosis can cause lung cancer"

that's a pass from me

[Dingdong]

I don't think we need to be overly worried about our exposure to Silicon dioxide. This is from the HSE website for stonemasons (I tried to think of the occupation with the highest potential exposure to shitloads of silica dust). RCS is respirable Crystallise Silica.

 "If you are exposed to RCS then you are at risk of developing silicosis. This disease makes breathing more difficult and increases the risk of lung infections. Silicosis usually follows many years of exposure to RCS. Exceptionally high exposures over a few months or years can cause acute silicosis, which can cause death within months of exposure. Heavy and prolonged exposure to RCS under the conditions that produce silicosis can cause lung cancer"

I can’t tell the first paragraph is sarcasm  fuck that noise. Mark, probably best you don’t expose yourself and others to this stuff mate. Really not worth it to have slightly drier skin.

[SA Chris]

Perhaps I should cut out all the shampoos, deodrants and foods (!) that use it as an additive as well.

Maybe you should. I have friends who have eczema and the like who do.

[ajh]

Really? It's the same stuff that has been in Superchalk for years.

You don't know that. It might be SiO2. It could be a Ca silicate. It could be some random contamination brought in from just about anywhere in the production process - Si isn't exactly a rare element. Without confirmation from Metolius or a much more rigorous study (the one on the first page is pretty dire, unfortunately - all it really says is climbing chalk is not very chemically pure; hardly a revelation to most people) there is no way of knowing.

If it is SiO2 then it is very, very, very unlikely to be crystalline SiO2 - this is a really important distinction that hasn't been mentioned yet although the study alludes to it. It is much more likely to be amorphous - i.e. silica gel. There isn't too much out there about the health risks of inhaling this rather than the crystalline form but there is a bit of research to suggest the risks are significantly lower (e.g. https://pubmed.ncbi.nlm.nih.gov/11876495/ and https://pubmed.ncbi.nlm.nih.gov/15279029/ which came up from a quick google).

Finally, if - if - it is SiO2, then Metolius have removed it for a reason. I'd like to know what that reason was before I started trying to make my own and sticking it in my chalk bag.

"If you are exposed to RCS then you are at risk of developing silicosis. This disease makes breathing more difficult and increases the risk of lung infections. Silicosis usually follows many years of exposure to RCS. Exceptionally high exposures over a few months or years can cause acute silicosis, which can cause death within months of exposure. Heavy and prolonged exposure to RCS under the conditions that produce silicosis can cause lung cancer"

True but why roll the dice by deliberately exposing yourself to the stuff?

[sirlockoff]

Perhaps I should cut out all the shampoos, deodrants and foods (!) that use it as an additive as well.

Maybe you should. I have friends who have eczema and the like who do.

my friends eczema flares up as soon as he uses super chalk, he hasn't tried the newer version yet

[mark20]

Really? It's the same stuff that has been in Superchalk for years.

You don't know that. It might be SiO2. It could be a Ca silicate. It could be some random contamination brought in from just about anywhere in the production process - Si isn't exactly a rare element. Without confirmation from Metolius or a much more rigorous study (the one on the first page is pretty dire, unfortunately - all it really says is climbing chalk is not very chemically pure; hardly a revelation to most people) there is no way of knowing.

If it is SiO2 then it is very, very, very unlikely to be crystalline SiO2 - this is a really important distinction that hasn't been mentioned yet although the study alludes to it. It is much more likely to be amorphous - i.e. silica gel. There isn't too much out there about the health risks of inhaling this rather than the crystalline form but there is a bit of research to suggest the risks are significantly lower (e.g. https://pubmed.ncbi.nlm.nih.gov/11876495/ and https://pubmed.ncbi.nlm.nih.gov/15279029/ which came up from a quick google).

Finally, if - if - it is SiO2, then Metolius have removed it for a reason. I'd like to know what that reason was before I started trying to make my own and sticking it in my chalk bag.

Thanks for this info.
I've had it confirmed to be SiO2, specifically "cabosil" which as you say is amorphous / fumed Silica. The stuff I  bought is 'flour' which sounds like it contains crystalline silica, so I will ditch this stuff.
They say they removed it as all other chalk manufacturers are marketing "pure chalk" etc and wanted to be in line with that. Though, obviously if it was because they thought the drying agent was unsafe I wouldn't expect them to admit it!