Disposal of Zenker's Fluid
Zenker's Fluid has 2 significantly hazardous ingredients: hexavalent
chromium (from potassium dichromate), which is a carcinogen, and
mercury (from mercuric chloride). Mercury forms highly toxic organic
compounds once it is released into the environment. Additionally,
acetic acid lowers the pH below acceptable limits for drain disposal.
If you add formaldehyde (Helly's fluid), you have a third significantly
Carmen, check your provincial ministry of the environment for the
definitive word on acceptable disposal practices. How others dispose
of this solution does not matter, because you don't know if their
method is legitimate in their locale, much less in your community.
Mercury creates an especially troublesome problem. In addition to the
fixative itself, all stations on the processor through at least the
last alcohol contain environmentally significant amounts of mercury and
must be treated as mercury waste. Then, during staining, you remove
mercury deposits. The iodine, thiosulfate and all rinse solutions
involved with these are also mercury-containing hazardous waste. From
just a few specimens each week you can generate enormous quantities of
In the United States there is a concerted effort between the American
Hospital Association and the Environmental Protection Agency to
eliminate ALL sources of mercury waste from medical facilities. After
the elimination of mercury-containing instrumentation, histological
waste is the next most significant source.
Some eastern Canadian provinces were joining this effort several years
Here is another thought if the foregoing is not enough to stop using
Zenker's, B-5 and similar fixatives: Mercuric salts complex with metal
parts in pipes, stainers and processors. Long after you stop using
these fixatives your equipment and plumbing will continue to leach
measurable quantities of this dangerous metal. Labs in New England
have had to have their equipment and pipes hauled off to mercury-secure
landfills before they could come into compliance with "zero tolerance"
restrictions on wastewater.
Alternative fixatives must be used if we are to conduct laboratory work
responsibly. Will these solutions produce absolutely identical
results? No, they cannot, because they do not have the same
ingredients. However, many substitutes offer excellent, highly
acceptable (and sometimes better) results, often with more convenience
and lower cost. Everybody (and the environment) wins, except the
hazardous waste hauler. The fact that many, many labs have made the
switch is evidence enough that it can be done.
I implore everyone who would ask how to dispose of mercuric fixatives
to change the question to "What are you HistoNetters using in place of
mercury?" Get in touch with those who succeeded, not the naysayers
whose pathologists refused to change.
Richard Dapson, Ph.D.
1020 Harts Lake Road
Battle Creek, MI 49015
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