I misspoke!!! Of those calcium hydroxides tested, BRS’ "pharma" product does NOT contain the highest level of arsenic. That was the other unnamed aquarium bulk product. BRS’ was the second-lowest. MS Lime contained 5X lower arsenic than BRS, but in all reality, it's a non-issue in practice. Levels of undesirables were mentioned by BRS when discussing the challenges of slurry, but in my experience, I've experienced no elevated contaminants as measured by my last ICP.
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Thanks to @BahamaLlamaCoral for the backup mic recommendation!