Waste disposal and hazard codes

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From:"Anatech Ltd." <anatech@net-link.net>
Date:Fri, 12 Mar 1999 14:49:38 -0400
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To Priscilla in Central Wyoming and all others who want to know about
disposing of hazardous waste down the drain, let me add my 2 cents' worth.

First, it matters not a bit what others are doing, even if they are doing
it with the full knowledge and permission of their wastewater treatment
officials.  This is because every treatment plant is different, and must
set its own limits on chemical waste.  You must get approval from your own

Getting permission from one's own group of officials may be a pleasant or
difficult experience, but you can ease the way a bit by being prepared.
Realize that most of them do not know what our histological chemicals are,
so provide them with the OSHA-mandated hazard codes (e.g., flammable,
corrosive, carcinogenic, etc.).  They also want to know flash point, pH,
miscibility with water and odor (if strong).

Picric acid, Bouin's and any solutions turned yellow by these substances
must never be discarded down the drain, as the picric acid can form
potentially explosive compounds with metal in the plumbing.  A plumber
twisting off a union or joint encrusted with these compounds could be
seriously injured or killed.

Precipitating heavy metals is a good way to reduce the volume of hazardous
waste (if the metal is the only hazardous component), but procedures vary
with the element.  Some metals fall out of solution at about pH 7 and stay
out as the pH is raised (most will redissolve at lower pH); others
precipitate at pH 7 but redissolve at higher pH (above 9 or 10).  Yet
others remain in solution regardless of pH.

I strongly recommend reading Prudent Practices for Disposal of Chemicals
from Laboratories (National Academy Press, Washington, DC).  Over 50 metal
ions are listed, with the proper pH range for precipitation given for each.
More specific directions are given for precipitating metals common to
histology in our book, Hazardous Materials in the Histopathology Laboratory
(3rd edition).

There is no practical way to reclaim the precipitated metal for reuse in
the laboratory.  Mercury and silver can be reclaimed, but only by
commercial entities.

On Thursday, Ann asked about hazard codes for all reagents in the
histology/cytology department.  We need more specific information here.
What did the safety officer mean by hazard codes?  There are two sets
commonly encountered in such circumstances:  OSHA codes and NFPA codes.

OSHA codes are easy:  most of them should be part of the label on the
bottles.  If not, the MSDS might list them.  If all else fails, the MSDS
should have enough information for you to determine them.  Definitions are
straightforward; see Hazardous Materials in the Histopathology Laboratory
(3rd edition), pages 107-115 for details.  Incidentally, if you do not wish
to wade through wads of MSDS's, our book also gives these codes for most
chemicals of histological/cytological interest.  This would be the quickest

If NFPA codes are desired, your problems are insurmountable.  NFPA codes
are intended to be used by firefighters involved in chemical fires or in
building fires with burning chemicals.  The codes are the hazard ratings
for select chemicals under conditions of fire (very high heat, possible
exposure to water, actual combustion).  They definitely are not the hazards
of the chemicals in normal use at room temperature.

Very few chemicals have been rated by NFPA.  Anyone wishing to determine
what the rating might be for a non-listed chemical must make informed
inferences.  NFPA definitions are rather vague and very difficult to fit to
particular reagents.  Few MSDS's contain this information for that reason.

I hope this helps.


Richard W. Dapson, Ph.D.
1020 Harts Lake Road
Battle Creek, MI  49015
800-262-8324 or 616-964-6450
Fax 616-964-8084
E-mail anatech@net-link.net

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