Potential Hazards in the Histology lab
Carl G T du Toit
B.Sc. Hons (Biochemistry)
Introduction
Laboratory hazards are many and diverse and may consist of poisons; infectious agents; flammable,
explosive, or radioactive materials; moving machinery; extreme temperatures; lasers, strong magnetic
fields or high voltage. In laboratories where unsafe circumstances might exist, safety measures are vital.
Rules exist to reduce the individual's risk, and safety equipment is used to safeguard the lab user from
harm or to aid in reacting to an emergency. (http://en.wikipedia.org/wiki/Laboratory)
Potential Hazards in the Histology lab
The business of histology is the preparation of tissue specimens for the diagnosis of cancers and other
diseases. A wide variety of tasks are performed there that involve the use of hazardous chemicals, sharpedged implements and blades, and substances that can make even walking more dangerous. Besides
having to be careful around hot melted wax, residue of this substance on the floors can create a slip
hazard. (Scungio 2011)
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Table 1 Potential Hazards in the Histology lab, their causes and possible remedies.
Type
Fire hazard
Cause
Inflammable solutions i.e.,
alcohol, ether, toluene and
xylene
Remedy
Keep minimal stocks of
inflammables in the lab.
Keep larger volumes of
inflammables in cool well
ventilated store.
Keep inflammables away from
open flames.
Treatment of
Accidents
Small fires extinguish with wet
cloth or CO2 fire
extinguisher.
Large fires Evacuated lab
immediately and call
fire brigade.
Fire extinguishers should be
readily available.
Smoking is prohibited.
Poisonous,
erosive and
corrosive
reagents
Specimens
Formaldehyde, Methyl
alcohol, cyanide
components, arsenic salts,
mercury, oxalates,
nitroprussides, zinc salts,
lead, barium and iodine
salts, acryl amide, aromatic
amines.
Fresh tissue is bio-hazardous
i.e., tissue from patient with
tuberculosis, CreutzfeldtJakob disease (CJD), HIV or
other infectious diseases.
Correct labelling of containers.
Education of staff on which
reagents are toxic.
General safe lab practises should
be adhered to:
Wear PPE / Personal Protective
Equipment (lab coat, gloves, and
face protection).
Clean spillages
immediately.
Treat acid burns by
neutralizing with
weak alkalis and
rinsing with large
volumes of water.
Work in a fume cupboard.
ALWAYS add acid to
water, NEVER water
to acid.
No mouth pipetting.
Contact physician.
Use PPE and exercise standard
safety precautions when handling
fresh tissue.
Maintain open communication
with the sites that provide the
specimens.
If certain infectious diseases are
suspected inform staff so that
precautions can be taken.
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Type
Sharp tools
Cause
Remedy
Treatment of
Accidents
Changing the scalpel blade
and handling these tools can
be dangerous if not done
correctly.
Cutting tools such as scissors or
scalpels should not be left lying on
grossing boards where a swipe of
a hand while working could create
exposure.
Access the extent of
cut and treat
accordingly.
Contact physician.
Place these items in an upright
holder to avoid injuries.
The cutting blade inside of a
cryostat or a microtome is
extremely sharp and many
injuries can occur when
working with these
instruments or when
performing maintenance.
Never replace scalpel blades by
hand, use an automatic scalpel
blade remover.
Cryostat and microtome blades
should never be manipulated by
hand.
Use knife-guards whenever
possible, and use a magnet-tipped
tool or metal mesh gloves to
remove used blades.
Perform cleaning and
maintenance with the blade
removed and place a new blade
inside using rubber-tipped forceps
or metal mesh gloves.
Radiation
Radioactive material such as
prostate seeds or sentinel
lymph nodes
If radioactive tissue is being
handled, the amount of
radioactivity is generally low, but
specimens should be handled
quickly, and seeds used for
treatment should be placed in
lead-lined containers. Leave
specimen in formalin for 24 hrs.
With so many safety hazards, it should be clear that no employee should perform tasks in the histology
laboratory without proper safety training. (Scungio 2011)
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Carl G T du Toit
A practical look at safety
A common process in histology is the processing of fresh tissue specimens. Tissues must be processed
quickly. The first step is gross examination on a cutting board. Next the specimen is fixed, embedded and
sliced on a microtome so that tissue slides can be prepared. The staining of the slides follows with the
pathologist completing the process through slide examination.
There are safety hazards to consider in every step mentioned above:

Most specimens are received in a 10% Formalin solution. Formaldehyde is the most common
chemical used in fixation of tissue and is poisonous.

Fresh tissue is bio-hazardous, so routine laboratory PPE should be used. However, what if the
physician suspects Tuberculosis? Could there be radioactive material such as prostate seeds
present? Is this brain tissue from a patient with Creutzfeldt-Jakob disease (CJD)?

The tools are sharp. Changing the scalpel blade and handling these tools can be dangerous if not
done correctly.

The cutting blade inside of a microtome is extremely sharp and many injuries occur annually when
working with these instruments or when performing maintenance.

The process typically involves xylene, a flammable solvent with strong vapors and potential
negative health effects.
All of these hazards need to be taken into account by pathologists and other staff working in the grossing
area or microtome area of the histology laboratory. Some general practices to keep the area safe while
processing tissues:

The pungent fumes of formalin affect the eyes and mucous membranes of the nose and throat; a
good system of ventilation is therefore very important. When handling tissues fixed in formalin,
gloves should always be worn as dermatitis may be caused. Cut up tables must direct the airflow
downwards away from the operators face. The use of an enclosed system for the preparation and
dispensing of formaldehyde will also help. (Bancroft and Stevens)
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Carl G T du Toit

Use a lab coat, gloves, and face protection when handling fixed or fresh tissue. Maintain open
communication with the sites that provide the specimens. If certain diseases are suspected or if
radiation is present, staff needs to be aware so that precautions can be taken.

Cutting tools such as scissors or scalpels left lying on grossing boards could create exposure. Place
these items in an upright holder to avoid injuries. Never replace scalpel blades by hand, use an
automatic scalpel blade remover.

Cryostat and microtome blades should never be manipulated by hand. Use knife-guards whenever
possible, and use a magnet-tipped tool or metal mesh gloves to remove used blades. Perform
cleaning and maintenance with the blade removed, and place a new blade inside using rubbertipped forceps or metal mesh gloves.

Staining should be performed under a chemical fume hood or near wall ventilation to avoid xylene
vapors. Perform vapor monitoring to determine the level of xylene exposure incurred by staff in
the laboratory.
Conclusion
Laboratory staff works in a potentially dangerous environment and with hazardous materials. The
implementations of work practices and controls that will keep laboratory staff safe are vital. (Scungio
2011)
Inspections and audits should be performed regularly to evaluate hazards. An important part of such
audits is the assessment of regulatory compliance and the training of staff that has access to and/or work
in the laboratory. (http://en.wikipedia.org/wiki/Laboratory)
However, it is possible to work with samples, handle equipment and materials, and to do these things
without injury or harmful exposure. By following the general safety guidelines, and by knowing the
accrediting agency regulations, these hazards can be avoided to ensure a safe working environment for
histology staff. (Scungio 2011)
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Carl G T du Toit
References
1. Retrieved from: "http://en.wikipedia.org/wiki/Laboratory"
2. Scungio, D. J., 15 February 2011. Safety Pitfalls in Histology: Hazardous Chemicals, Sharp-Edged
Implements Make for a Dangerous Environment. [Online]. Available:
http://laboratorian.advanceweb.com/Archives/Article-Archives/Safety-Pitfalls-in-Histology.aspx
[1 August 2011]
3. Cellular Pathology I Student Learning Guide/Notes. Section II Techniques in Cellular Pathology
(p.11-16)
4. Bancroft, J.D. And Stevens, A., Theory and practice of Histological techniques. 4 th Ed.
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