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I am examining a material safety data sheet that reports on trivalent and hexavalent chromium in chemical films. It covers each type where it is used in a product individually.

Is there a practical difference in safety between the two, such that they should be reported separately?

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    $\begingroup$ Sure, and a great one. Chromium (III) is just another light metal cation, almost as harmless as iron (II, III). Chromium (VI) is acutely toxic. $\endgroup$ – Ivan Neretin Apr 23 '18 at 22:00
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Since you're referencing an SDS, I'm assuming your talking about the occupational environment, in which case it makes sense to talk about occupational exposure limits. The American Conference of Governmental Industrial Hygienists (ACGIH) has established non-enforceable Threshold Limit Values (TLVs) for different oxidation states of Chromium:

  • Chromium VI - 0.0002 mg/m3
  • Chromium III - 0.003 mg/m3
  • Chromium metal - 0.5 mg/m3

These values refer to the maximum recommended 8-hour time weighted average exposure concentration for a given substance. A lower number means someone is allowed less exposure; a higher number means someone is allowed a greater amount of exposure.

Depending on your product and process, it may make sense to look at measuring exposure to each of the different oxidation states. Particularly for chromium VI, because the exposure limit is so low, it's doesn't take much to overexpose someone.

Note also that if you're in the US, OSHA has a limit for Chromium VI of 0.005 mg/m3. If you exceed this limit, there are a ton of requirements that kick in. See 29 CFR 1910.1026 for more information.

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Hexavalent chromium is a genotoxic carcinogen. Due to the similarity of the chromate(VI) and sulfate ions, it is transported around the body via the sulfate channels. Due to this it is a major health hazard. Trivalent chromium on the other hand is not generally regarded as a health hazard due to its poor solubility in water. With this information you should report both separately.

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  • $\begingroup$ Thank you for providing these details. I'm now curious why trivalent chromium would even be mentioned in a hazardous materials report. $\endgroup$ – Jim Apr 24 '18 at 14:50
  • $\begingroup$ Possible irritant effect maybe? $\endgroup$ – David Wyn Williams Apr 24 '18 at 15:25

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