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 
hazardous component.

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 
mercury waste.

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 
ago.

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.

Dick


Richard Dapson, Ph.D.
Anatech Ltd.
1020 Harts Lake Road
Battle Creek, MI  49015

269-964-6450
dickdapson@anatechltdusa.com