Safety and Quality Management
Chemical safety: know the numbers
Formaldehyde: the OSHA permissible exposure limit is 0.75 ppm as an 8-hour time-weighted average, the short-term exposure limit is 2 ppm for 15 minutes, and the action level is 0.5 ppm, which triggers exposure monitoring and medical surveillance. Formalin is a suspected carcinogen: use ventilated hoods or closed processors, keep a spill kit with absorbent and a neutralizer, and never mix formalin waste with oxidizers.
Other hazards: xylene is flammable and neurotoxic; picric acid is explosive when dry; mercury-containing solutions (B5, some hematoxylins) require special waste; bloodborne pathogens require standard precautions, sharps handling and an exposure control plan.
Waste: segregate hazardous chemical waste, keep formalin and xylene streams separate, label containers and maintain manifests. The chemical hygiene plan and SDS files must be accessible.
Quality management
CLIA '88 and CAP accreditation require procedure manuals, documented competency assessment, QC records, proficiency testing with investigation of failures, quality indicators, and root cause analysis with corrective and preventive action. Document and change control prevent which-SOP-is-current errors.
Traps
Confusing the TWA with the STEL; forgetting the action level entirely; treating a fume hood as a substitute for a closed system; discarding a failed QC result without investigation; and signing off competency without direct observation.
Rule of thumb: Remember 0.5 / 0.75 / 2 ppm as action level / TWA / STEL. Any threshold crossed, whether exposure or QC, demands a documented response.