PLEASE USE CAUTION WHEN HANDLING INDICATING DESICCANTS
Background
Cobalt
(II) chloride, the blue indicator in self-indicating silica gel and calcium sulfate desiccants (e.g., Drierite),
has been revealed to be a confirmed animal carcinogen at relatively high
doses. A European Commission Directive
(98/98/EC) reclassified cobalt chloride as a potential carcinogen by inhalation. The International Agency for Research on
Cancer (IARC) indicates there is limited
evidence for carcinogenicity of cobalt (II) chloride in experimental
animals, and has assigned cobalt and cobalt compounds as possibly carcinogenic to humans (group
2B).
It is
important to note that the EC directive was for the pure chemical, whereas
self-indicating desiccants contain only about 1% w/w cobalt chloride, and this
is confined within the desiccant material itself. The risk of exposure to the
products that we use in the field and laboratory is considered insignificant provided the materials do not become powdered
or crushed to the extent that the resulting dust becomes easily airborne.
Procedural Precautions
Since there is a finite health risk associated with
blue indicating desiccants when handling the material and being exposed to the
dust, the following safety precautions shall be adopted immediately by all
Clean Air Engineering employees.
1.
Pure self-indicating
(blue) desiccants should be handled in the fume hood whenever there is a
significant risk of generating dust.
This includes the task of mixing indicating silica gel with the
non-indicating gel to prepare the field product, and when adding or replacing
desiccant materials in desiccators.
2.
Dusty silica gel or Drierite-type desiccants should be gradually removed from
service. Materials should be placed in a
tough plastic bag and sealed prior to disposal into the municipal waste stream.
3.
Self-indicating
desiccants should not be powdered/crushed or handled
in any way likely to cause significant dust exposure.
4.
If there is any concern
that handling a desiccant may create an inhalable
dust cloud, and no fume hood is available, then use a regular dust mask or dust
respirator while working with the material.
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