ABC of Safety in the Biological Sciences




Fresh tissues may be brought into the histopathology laboratory for urgent sectioning (also see Frozen Sections), culture followed by routine histology, immunohistochemistry (including lymphocyte surface markers), impression smears, enzyme assay, tissue culture, because the correct fixative was not available (such as glutaraldehyde for electron microscopy) or the specimen was simply not placed in fixative.

Before processing any tissue, determine the exact test required and ensure that enough clinical information has been provided so that any associated risks can be identified. In any case all tissues must be deemed potentially infectious and handled with great care. Appropriate protective clothing should be worn and all equipment (including the cryostat) in contact with fresh tissue should be disinfected immediately after use. Check the outside of specimen containers for contamination.

Infections which can be transmitted to laboratory staff from handling fresh tissues include the following:

  • Hepatitis B
  • Tuberculosis
  • Prions.

If safe work practices are adhered to occupational hazards will be minimised.

  • treat all human tissue as potentially infectious even if received in fixative. It can take up to 12 hours for formalin to penetrate 1 cm into dense tissue. Until the fixative has reached all of the tissue any potential infecting agent remains viable. Prions are not inactivated by formalin.
  • wear protective clothing at all times, protect your skin, eyes and mouth.
  • cover open wounds or broken skin.
  • use disposable instruments wherever possible.
  • clean instruments in cold water (reduces the aerosol hazard) then soak in disinfectant (0.5% sodium hypochlorite or 70% ethyl alcohol are recommended).
  • work on a clean surface. Mop up spills immediately and disinfect the surface with 0.5% sodium hypochlorite solution.
  • place all material for disposal in clearly labelled, adequate containers (see waste disposal procedures chapter 1.1).


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