"one must differentiate between exposure channels"
I think this is a mistake, though.
I mean, yes, exposure "channels" are absolutely important, but its the (false) assumption that one "safe channel" lowers the general risk of the other channels being an issue.
Your particular example mentions powder - what happens to the substance after it is crushed in a landfill? Or involved in a high speed collision, exposed to high heat, uv rays, microwaved, etc.
Potential harm should include the risk posed by all channels as a function how likely they are to be in that state. If the likelyhood is at 100% over any "reasonable" period of time, then you don't get to ignore the effects of that "channel".
Worse, if any of the channels are difficult to detect, then the risk should be compounded - I know about wood dust and can both easily see it and am amply aware when it is an issue and can take precautions. I'm not sure I can even identify the material you mention nor would be able to distinguish it from just "normal" dust.
I think this is a mistake, though.
I mean, yes, exposure "channels" are absolutely important, but its the (false) assumption that one "safe channel" lowers the general risk of the other channels being an issue.
Your particular example mentions powder - what happens to the substance after it is crushed in a landfill? Or involved in a high speed collision, exposed to high heat, uv rays, microwaved, etc.
Potential harm should include the risk posed by all channels as a function how likely they are to be in that state. If the likelyhood is at 100% over any "reasonable" period of time, then you don't get to ignore the effects of that "channel".
Worse, if any of the channels are difficult to detect, then the risk should be compounded - I know about wood dust and can both easily see it and am amply aware when it is an issue and can take precautions. I'm not sure I can even identify the material you mention nor would be able to distinguish it from just "normal" dust.