Some thoughts follow an abbreviated quote of your email.

On Thu, 6 Jan 2000, Cathy De Viney wrote:
> I am not a histo tech, I am the safety officer at our lab, and have a
> few questions I hope you can help with.
> When you send your paraffin blocks to other labs, do you ...
> ... mark the shipping container as a biohazard? ...
> I posed the question a few days ago about disposal of paraffin blocks.
> All but one lab disposed of them as biohazards.  Are they to be
> treated as biohazards whenever they are handled (i.e. should the histo
> techs wear gloves when they are handling the blocks)?  Or is their
> disposal as a biohazard merely a precaution to keep them from:
> {a} turning up in the wrong place (i.e. children getting them from a
> dumpster)?
> {b} public relation/perception problem re: medical waste?
____________________________

Reply:

  A paraffin block contains tissue that has passed through several
  substances that kill pretty well everything, and it is entombed in
  a solid material (wax) that is not miscible with water, or even
  with 100% alcohol. Admittedly, the prions of CJD and kuru might
  still be infective, and pose a hazard to people who manage to
  inject themselves with old paraffin blocks, or eat them after
  very thorough chewing. There could also be a danger of bacterial
  spores that survive formaldehyde, alcohol, xylene and heat. Such
  spores might infect anyone who grinds a paraffin block into a
  fine powder (which can be done, at temperatures below -10C) and
  then inhales the resulting dust.

    It is difficult to imagine a safer way to encapsulate tissue than
    routine paraffin embedding. The reason for all the "biohazard"
    nonsense is the terrifying power of laboratory safety officers
    and the even more ignorant civil servants to whom the safety
    officers report. The easy way out is always the most expensive
    one when the cheap alternative, if approved, might put some
    worthless administrator into the ranks of the unemployable.

  It is a SIGN OF PROGRESS that you, one of the Feared
  Inspectorate, ask a question on HistoNet. I hope you
  get lots of sincere answers from Those Who Do The Real Work.
  Please keep in contact and let us all know how you respond
  to the many perceived and few real concerns in the field of
  histological lab safety.

 John A. Kiernan, MB, ChB, PhD, DSc,
 Profesor, Dept of Anatomy & Cell Biology,
 The University of Western Ontario,
 LONDON,  Canada  N6A 5C1
   FAX (Department): (519) 661-3936
   E-mail: kiernan@uwo.ca