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In our lab we have three forms of zinc. We were initially experimenting with these three forms to optimize our application. We have "zinc shot", "mossy zinc", and "zinc granules". The granules are ~20 mesh. I am tasked with creating chemical standard operating procedures (SOPs) for all reagents that are considered "particularly hazardous". Zinc granules are considered particularly hazardous by our University and is an "acute toxin to aquatic life with lasting effects" in a recent safety data sheet (SDS) while zinc shot and mossy zinc are not considered hazardous by our University or on comparable recent SDSs. I see zinc powder is also considered toxic. To me this suggests particle size dictates toxicity, but why? I understand surface area influences the rate of reactions but if the effects are long lasting, then why are all forms of zinc not considered to be an aquatic life toxin?

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    $\begingroup$ Fisher's SDS from 2015 for mossy zinc states it is "toxic to aquatic life;" and their one for zinc shot, 2018 states "very toxic to aquatic life with long lasting effects." Something's amiss. $\endgroup$
    – Todd Minehardt
    May 25, 2021 at 21:02
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    $\begingroup$ Also, see the dated but still-relevant EPA publication on Ambient Water Quality Criteria for Zinc for more details. $\endgroup$
    – Todd Minehardt
    May 25, 2021 at 21:06
  • $\begingroup$ It seems unusual because for one thing a great many tons of zinc rich paints have been, and are being used . I have been retired for awhile but i remember seeing no caution signs on the zinc powder ( typically -400 mesh/screen) used to mix these coatings. These zinc rich primers are a mainstay in many industries with apparently no problems. $\endgroup$ May 26, 2021 at 0:18
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    $\begingroup$ @blacksmith37 They are problems. Here's just one MSDS for a zinc-rich primer. It's "aquatic acute" and the rest of the (M)SDS is hardly encouraging. I suspect that back in the day we didn't know and/or didn't care about handling things that later turned out to be "problematic," such as DDT, leaded gasoline, benzene, tobacco, etc. $\endgroup$
    – Todd Minehardt
    May 26, 2021 at 0:29
  • $\begingroup$ So older people who lived with galvanized plumbing are all going to die ? $\endgroup$ May 26, 2021 at 16:11

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The key to toxicity is concentration, which is related to how rapidly the material disperses (or concentrates) in the environment. Which is also related to water type (fresh or salt) and temperature. MSDS sheets are a bit of a joke. They are worded in a way that fends off lawyers rather than gives detailed useful toxicity data. Consider this MSDS for Sodium Chloride

Bear in mind this useful advice when using it at home: "Eye Protection Wear safety glasses with side shields (or goggles) (European standard - EN 166). Hand Protection Protective gloves"

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    $\begingroup$ NaCl SDS quote - “Keep away from food”. So perhaps you allude to a more appropriate question. How can students and labs inform themselves of the true toxicity or lack there of for any given chemical. $\endgroup$
    – ajschauer
    May 27, 2021 at 1:13
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    $\begingroup$ @ajschauer Yes. I am having the same problem working with Tungsten Carbide powder. Useless MSDS - and toxicology reports focus on tool grinding and composites with Nickel/Cobalt composites. The best I can assume is "don't eat it, don't breath it, but otherwise mostly harmless" $\endgroup$ May 27, 2021 at 9:33

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