On Tue, 22 Dec 1998, Sharon F. Vogt wrote:

> Back to DAB, if you add copper or something to intensify or alter the
> color of the end-product before rinsing away the DAB, would that solution
> do anything to alter the mutagenic characteristics of the DAB in the
> waste solution?
                                               23rd Dec 1998

   Who knows, and does it matter? Mutagenicity is tested in bacteria.
   It's a simple test: do they or don't they make a certain enzyme
   after exposure to the compound? Carcinogenicity is induction of
   malignant change in animals: quite a time-consuming test, typically
   done in susceptible strains of mouse. Human carcinogenicity is
   deduced from epidemiological data - takes years to collect, and
   tobacco farmers and company directors still argue that P < 0.0001
   is not significant! Lots of everyday "harmless" substances are
   carcinogenic in mice but not convincingly so in man. Conversely,
   adverse effects of compounds have been picked up first in humans.
   The thalidomide tragedy would not have happened if more thorough
   animal testing had been done.

   The "mutagenic" argument is based on the belief that all
   known animal carcinogens are mutagenic to bacteria. (If someone
   has found an exception please shout.) This statement is
   equivalent to saying, "All convicted criminals have been
   fingerprinted." So have all convicted murderers. You don't need
   a PhD in philosophy to see the flaw in the argument that
   everyone who has been fingerprinted is a murderer until proved
   otherwise. The converse is also untrue: I'm guessing, but probably
   most abortionists have never been fingerprinted.

   Safety is always important in the laboratory, but the simple
   principle of "be well informed and don't take chances" has become
   the life work of some of those who have made their careers in
   this field. As we all know, they impose restrictions that often
   are (a) based on insufficient or ludicrously irrelevant data, and
   (b) impossible to enforce, even if enforcement were warranted.
   It is assumed that everyone is Hep-B and HIV positive, so no "body
   fluids" can legally enter the public drains. There are no laws
   to restrict spitting on the public roads and sidewalks - a current
   cult of teenagers and a well recognized cause of dissemination of
   tubercle bacilli, which cause a disease that's on the increase
   and still kills many people.

   'nuff said! Let's just put this safety stuff in a reasonable
   perspective.

   Merry Christmas to one and all,

 John A. Kiernan,
 Department of Anatomy & Cell Biology,
 The University of Western Ontario,
 LONDON,  Canada  N6A 5C1