Safety

Histology work exposes the eyes, skin and airway to fixatives, clearing agents and unfixed tissue. Protective equipment is chosen for the specific hazard rather than worn out of habit: a face shield over eye protection whenever formalin is poured or a fresh specimen is opened, a fluid-resistant gown with cuffed sleeves at the grossing bench, and a glove material matched to the chemical being handled. Technologists are expected to inspect equipment before use, remove it in an order that keeps contamination off the skin, and never carry it into clean areas such as the reading room or staff lunch room.

Hand hygiene in histology guards against two things at once: biological material from unfixed specimens and chemical residue from dyes, solvents and fixatives. Gloves are removed without touching their outer surface, and hands are washed whenever they are visibly soiled, whenever chemical contact is suspected, before leaving the department, and before eating. Alcohol rubs are convenient for organisms but do nothing to remove dye or solvent residue from skin. Food, drink, cosmetics and contact lens handling stay out of the technical area entirely, and lab coats stay behind when staff go to the cafeteria.

Anything leaving the laboratory by road, rail or air falls under Transportation of Dangerous Goods requirements, and histology ships plenty: fresh tissue to reference centres, blocks and slides for consultation, and bulk formalin or solvent waste. The common case is a diagnostic specimen classified as a Category B biological substance, which travels under triple packaging with a leak-proof primary receptacle, absorbent, a rigid outer box and the diamond marking. Technologists who classify, pack, label or sign shipping documents must hold current training and work to the written procedure rather than improvising with whatever container is at hand.

Engineering controls do the heavy lifting on chemical exposure in histology, and they only work when used as designed. Grossing is done on a ducted or downdraft station with the specimen inside the capture zone; solvent decanting and dye weighing happen in a fume enclosure with the sash at the marked height; processors, stainers and coverslippers are vented or fitted with carbon filtration that must be changed on schedule. Technologists check airflow indicators before starting, keep hoods free of stored bottles that disturb airflow, and stop work when an alarm or a failed indicator says the control is not performing.

Histology stocks an unusually hazardous shelf: flammable xylene and alcohols, corrosive acids used for decalcification, oxidisers, silver salts, mercury-containing fixatives and dry dye powders that become airborne when weighed. Safe practice means storing flammables in an approved cabinet, segregating incompatible classes, keeping picric acid hydrated, and using labelled containers. Every container decanted for workplace use carries a workplace label naming the product, giving safe-handling precautions and pointing to the safety data sheet. Technologists are expected to read the data sheet before first use of a reagent and to know which sections carry exposure limits, spill guidance and disposal requirements.

The recurring injuries in histology come from blades and from unfixed tissue. Microtome and cryostat knives are treated as live sharps from the moment they leave the dispenser: loaded with the guard in place, covered whenever the operator's hands go near the stage, and discarded into a rigid sharps container rather than a waste bin. The handwheel is locked before blocks are changed or debris is cleared. Fresh, unfixed tissue is handled as potentially infectious throughout, with cutting done to avoid aerosols and splashes, and any known high-risk case flagged so that the appropriate containment is arranged before the specimen arrives.

Disinfection in histology has to account for surfaces that are cold, oily with paraffin, or coated in dried reagent, none of which behave like a clean bench top. Cryostats used for unfixed tissue are defrosted, cleared of section debris and disinfected at room temperature, because chemical disinfectants are unreliable at cryostat operating temperatures. Blood spills are treated with a suitable chlorine-releasing agent at the concentration the laboratory validates, and prion-suspect work follows a separate, far more aggressive protocol. Technologists follow the manufacturer's compatibility guidance so that a disinfectant does not corrode optics, cutting stages or instrument housings.

[IMAGE] Unfixed lymph node has been sectioned in the cryostat shown for an urgent intra-operative case, leaving tissue debris in the chamber. The instrument must now be decontaminated. What condition has to be met for the disinfectant to be effective?

AChill the chamber further firstBSpray while the chamber is coldCAllow the chamber to warm upDFlood the chamber with formalin

The value of emergency equipment lies in reaching it quickly and using it long enough. A chemical splash to the eye means fifteen minutes at the eyewash with the eyelids held open, followed by medical assessment; skin contact means the safety shower and removal of contaminated clothing while the water runs. Aisles to that equipment stay clear and the units are flushed on a schedule. For fire, unexpected vapour release or a container found in a degraded state, the response is to alert others, restrict access and escalate rather than to attempt a fix. Technologists know their evacuation route and their alarm points before an incident happens.

Every histology laboratory keeps a formaldehyde spill kit and a solvent spill kit, and staff need to know which one to open and where the line sits between a spill they may clean and one that triggers evacuation. Small formalin spills are covered with a neutralising or absorbing agent applied from the perimeter toward the middle, so the puddle is not pushed outward, then swept up and treated as hazardous waste. Solvent spills demand ignition sources off and ventilation increased before anything else. Large volumes, unknown chemicals or a spill in a poorly ventilated space mean evacuate, restrict entry and call for help.

Reporting exists so that the same event does not happen to the next person, which is why near misses are documented as carefully as injuries. A technologist completes the occurrence report during the shift in which the event happened, describing what occurred, what was being done at the time, the chemical or agent involved and any equipment that failed. Exposures are also reported to the supervisor and to occupational health so that follow-up such as serology or medical assessment is arranged. The report belongs in the laboratory's safety record and is reviewed for trends; it never goes into the patient's chart.

Microtomy is among the most repetitive tasks in the laboratory: hours of one-handed wheel rotation with the neck flexed over the block, followed by microscope work and embedding at a hot plate. Poor set-up produces shoulder, wrist and neck injuries that end careers. The workstation is adjusted so the handwheel sits near elbow height with the forearm supported, the chair gives lumbar support with the feet flat or on a rest, and the microscope eyepieces come up to the eyes rather than the head coming down. Technologists rotate tasks, take short breaks and report early symptoms instead of working through them.

Safety systems in Canadian laboratories rely on the people doing the work raising problems early. A technologist who notices a failing fume hood, a missing guard, a chemical stored beside something incompatible, an empty eyewash or a colleague working without protection is expected to act: stop the unsafe task, make the hazard visible by tagging equipment out of service, and tell the supervisor or the joint health and safety committee so it is logged and fixed. Workers also hold the right to refuse work they reasonably believe is dangerous. Concerns are raised through the process rather than worked around quietly.