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Hazard Prevention Strategies in the Histopathology Lab
Manuelito A. Madrid, MD, FPSP
The laboratory is a ‘hazardous’ place
Hstopathology personnel work with: Potentially infectious and radioactive
tissues Potentially flammable, explosive, toxic,
and carcinogenic reagents Fairly complex electrical equipments Sharps, glasses, hot liquids Repetitive motions (Potentially irate doctors and patients!)
Laboratory environment
There is less chance of an accident occurring in a clean, tidy laboratory.
Good ventilation for removal of toxic and noxious fumes
Sufficient space for personnel, equipment and supplies
Smooth flow of traffic and easy communication
Work Practice Controls Handwashing
In ample running water liquid soap dispenser preferred
Cleaning work areas from clutter and work surfaces with disinfectants
No eating, drinking, smoking in area Job rotation minimizes repetitive tasks Orientation, training, continuing
education Warning signage of potential hazards
Chemical hazard warnings
Personal Protective Equipment (PPE), barriers, and procedures
Gloves must be worn when doing procedures with high risk of hand
contamination (staining, dissecting). preparing liquid stains/reagents from
powder form. open cuts/skin conditions are present that
increases infection risk from accidental contamination.
when mopping up a spill.
PPE, barriers, and procedures
Gowns and laboratory coats Masks: cutting bone, gross dissection
or activity that induces aerosolization Protective goggles and safety glasses Eyewash station and shower Safety goggles and face shields
splashing with infectious or corrosive liquids e.g. during staining procedures.
Avoid recapping of needles/sharps
Emergency showerEye wash station
Engineering Controls Puncture-resistant containers for
disposal/transport of needles/sharps Including broken glass, slides, coverslips
Color-coded biohazard bags (yellow) Splash guards Centrifuge safety buckets Biological safety cabinets and fume
hoods Mechanical pipetting devices Computer wrist/arm pads
Sharps container
Equipment hazards Each instrument should meet electrical
safety specifications and have written instructions regarding use
Well grounded electrical outlets with stable voltage.
Emergency power supply (brownouts) Maintenance: refrigerating/ heating
elements Wiring by qualified, skilled electrician Frequent inspection of continuously-run
equipment
Equipment hazards Mechanical
Centrifuge: balanced load, increase rotor speed slowly, allow to stop before opening lid
Periodic evaluation to assure proper functioning at all times
Documentation:1. date of inspection, validation, or
performance evaluation2. significant action to remedy deficiencies3. daily temperature recordings for all
temperature-controlled equipment
Chemical Hazard Plan Each chemical compound used should have
a materials safety data sheet (MSDS) on file specifies the nature, toxicity, and safety
precautions to be taken when handling the compound. Must be in ENGLISH.
Maintain inventory of all chemicals with chemical and common name
Manufacturer must assess and supply info about chemical/physical hazards (flammability, explosive, aerosol, flashpoint)
Ensure labels are not defaced or removed and post appropriate warning
Cabinet for storage of chemicals
Orderly chemical storage
Storage practices for flammables and combustibles
Bulk storage of flammable gases or liquids away from sources of heat. Ex. ether, acetone, xylene, alcohol
Withdraw an amount from main batch good only for 2 days
Bulk storage of concentrated acids should be at or near floor level, properly identified
Fire extinguishers; fire alarms CO2: for flammable liquids, chemicals, oil
and grease, electrical equipment SODA: wood, paper, rag, glowing embers
Fire alarm
Fire extinguisher
location
Infection hazards Exposure of personnel to infection can
occur by aerosolization of tissues, needlestick injury, scalpel/blade wounds, and mucocutaneous exposure during specimen processing.
In general, actual incidence of transmission of infectious agents from unfixed surgical specimens to personnel is extremely low.
Infection hazards
Risk of infection depends on Pathogen or microorganism involved Type of exposure (wound, aerosol, mouth) Amount of blood involved Amount of virus in exposed blood
If exposed to blood, immediately Wash with soap and water Flush splashes to nose, mouth, skin with
water Irrigate eyes with clean water, saline, or
sterile irrigants
Hepatitis B Virus (HBV)
All personnel should be vaccinated. After needlestick injury, seroconversion
rate is 30% from HBeAg(+) blood and <6% from HBeAg(--) blood in non-vaccinated individuals.
Mucocutaneous exposure can also occur. Postexposure prophylaxis (HBV hyper-
immune globulin and vaccine) non-vaccinated individuals or vaccinated
persons with low antibody titers. Treatment provides about 75% protection
if instituted within 7 days (1 week)
Hepatitis C Virus (HCV)
Risk is approximately 1-8% for HCV transmission after a needlestick injury. The risk after skin or mucous membrane
exposure is likely to be very low. Post-exposure treatment (immune
globulin) not effective If there is potential exposure, person
should be monitored for infection in order to start treatment as early as possible.
Human Immunodeficiency Virus (HIV)
0.3% of persons seroconvert after a needlestick exposure, 0.1% after mucocutaneous exposure, and <0.1% after skin exposure. HIV can be cultured from cadavers hours
to days after death Post-exposure treatment with antiviral
agents can decrease the risk of seroconversion by 81% Treatment should start ASAP, as it may be
less effective after 2-3 days.
Tuberculosis (TB)
Can be transmitted not only as aerosol but also percutaneously
Risk of transmission of TB in performance of autopsy and frozen section is documented Must wear mask when working with fresh
or unfixed specimens that are suspected or known to be infected
Use of coolant aerosol spray in frozen section discouraged
Formalin probably kills TB
SARS and CJD
Risk for severe acute respiratory syndrome (SARS) low for personnel, except when performing autopsies. Suspected cases handled as for HBV All tissues should be promptly fixed and
cryostat decontaminated Creutzfeldt-Jacob disease (CJD)
Present in formalin-fixed and paraffin embedded tissues for years
CJD transmission to pathologists and histotechnologist is documented
CJD-infected specimen
Decontamination procedure Double-gloving; processing formalin-fixed
tissue on a table covered by plastic sheet To deactivate infectivity, soak tissue
blocks in conc. formic acid for 1hr, then fresh 10% buffered formalin for at least 48hrs.
All instruments and gloves used must be decontaminated. Immerse in 2N NaOH for 1hr.
Tissue remnants, cutting debris, used formalin, plastic sheet should be discarded in a plastic container to be cremated as infectious hospital waste.
Infection control in the section
Universal precautions: treat all tissues as potentially infectious
PPE and puncture-proof used-sharps box Dissecting instruments in Lysol solution Water baths: wash, rinse, dry daily Cutting boards: disinfectant (cover overnight) Autotechnicon: wash/dry beakers once/wk Tissue cassettes: remove wax, place in
detergent bath, wash clean, scald, towel dry Wet tissue: store in 10% formalin in leak-proof
container. After 4 weeks, incinerate. Disinfect daily: sink, knobs, handles, phones No smoking, no eating, no drinking
Infection control in the section
Fresh tissues potentially infective; all specimens placed in fixative ASAP.
Formalin effectively inactivates viruses (including HIV and HBV) and reduces infectivity of mycobacteria.
Frozen section on potentially infectious cases may be done but should be avoided if cytologic preparations can be used or intra-operative diagnosis is not needed. Freezing does not inactivate infectious agents.
Air-dried slides should be considered potentially infectious. Any smears submitted for evaluation must be fixed in alcohol.
Decontamination
Common decontamination agent – 10% solution (volume/volume with tap water, made daily) of household bleach makes a very effective/economical disinfectant, inactivating HBV in 10min & HIV in 2min
Prewashing removes concentrated amounts of protein
All laboratory surfaces must be made of nonporous material, allowing for easy cleaning and decontamination
Common Histopath-specific hazards
Fixatives: formalin Severe eye and skin irritant. Pungent
fumes require good ventilation. Sensitizer by skin and respiratory contact. Toxic by ingestion and inhalation. Corrosive. Carcinogenic. Work in well ventilated area, wear goggles, gloves, and lab coat.
Sodium azide: reagent preservative Flush solutions down the drain with lots of
water (tendency for the azide to form metal azides in the plumbing). These are also explosive.
Histopathology-specific hazards
Benzidine, benzene, anthracene, and naphthol containing compounds: carcinogens, use with caution
Cytology: clean cytocentrifuge daily; use capped tubes to spin samples
Decalcification: formalin fixed tissues should be washed
well before decalcifying in HNO3 due to danger of forming carcinogenic fumes of bis-chloromethyl ether.
Histopathology-specific hazards
Frozen section: fresh material may be infectious. Sterilize
cabinet and microtome before cleaning. Paraffin wax processing:
rotary processors’ drawback: high rate of solvent evaporation, with risk of toxic and potentially explosive fumes in air.
Microtomy: use blade guards Most common site of injury is the non-
dominant hand. Reusable but contaminated equipment should be decontaminated with bleach.
Radiation Safety
Radioactive specimens ex. sentinel lymph nodes(SLN) may be received Dose of 0.4-1.0 milliCurie(mCi) 99m
technetium–sulfur colloid is typically used
Mean radiation dose (MRD) to skin of hand of surgeon during biopsy is about 10mrem. MRD to pathology staff exposed to these
specimens much lower than that of surgeon due to shorter time handling the specimens. Source: Am J Surg Pathol 24(11):1549–1551, 2000
Half-life of Tc99m is 6hrs, and radiation levels decrease to background levels after 10 half-lives (60hrs). SLN samples and related surgical materials
can be disposed of through ordinary medical waste disposal methods 60hrs after surgery.
Personnel monitoring devices (film badges) not necessary for pathology staff because of the low levels of radioactivity, rapid decay, and limited exposure time.
Source: Am J Surg Pathol 24(11): 1549–1551, 2000
Radiation Safety
Other considerations All personnel handling these specimens,
including couriers, must be aware that the specimens contain low levels of radioactivity.
The specimen should be sent promptly to the laboratory in sealed containers labeled with: Caution – Radioactive Material
Protective wear (disposable gloves, surgical scrubs, plastic aprons) should be worn when handling the specimens.
Gross examination should be delayed for at least 6hrs from time of surgery
Radiation Safety
Other considerations Quarantine primary tumor excision at least
24hrs due to its higher radioactivity level compared with SLN.
Frozen Section: amount of radioactive material in specimen shavings limited or low, no special precautions recommended and no need for a dedicated cryostat.
Specimen should be held in a secure location to prevent unauthorized access and premature disposal.
Labels indicating radioactive materials should be removed before disposal.
Radiation Safety
Treatment of samples/reagents before disposal
Presept tablet (strong hypochlorite) Efficient disinfectant containing sodium
dichloroisocyanurate (NaDCC) in an effervescent base
Dissolved in water, it is effective through the entire biocidal spectrum (all bacteria, viruses, fungi, algae, and protozoa)
Highly resistant to inactivation by organic soilage
Compact and stable in storage Compatible with detergents
Disposition of instruments, trash, and specimen after dissection Needles, blades, and other sharp
disposable objects promptly discarded into appropriate containers.
Trash items soiled with blood or other potentially infectious materials discarded into designated biohazard containers in the cutting area.
Upon completion of the dissection, the specimen should be stored in a container with adequate formalin, securely closed to prevent leakage, accurately labeled and placed in the vented storage cabinet.
Garbage disposal and cleaning the section
The laboratory must have a method for disposal of hazardous wastes. Health care facilities processing tissues
often contract this to a waste management company.
Tissues collected should be stored in formalin and may be disposed by incineration or by putting them through a "tissue grinder" attached to a large sink (similar to a large garbage disposal unit).
Garbage disposal and cleaning the section
Daily cleaning of the histopathology section should be done. Wax on the floor should be removed with
a metal spatula. Garbage should be collected everyday.
The collected garbage in each “trashcan” should be sealed and place in a big yellow bag and labeled the date it was collected.
Garbage should be discarded after 2 days from the date it was collected. Just in case tissue, request form, or
specimen containers are inadvertently thrown
Rational waste segregation
Disposal of tissues Schedule disposal of surgical tissues
and body fluids. Only those samples with official report
are to be discarded. Samples for disposal are removed
from formalin and placed in a doubled yellow plastic bag with a newspaper underneath to absorb the formalin.
The plastic bag should be labeled “for disposal” and must be endorsed to the assigned housekeeper.
Disposal of chemicals
Formalin Formalin stock solution is stored in a cool
and dry place in a tightly capped container.
Prepared 10% formalin is stored in a tightly capped container with a faucet for easy retrieval.
All used formalin (10%) is disposed of properly in the sink with a continuous flow of running tap water (at least 5 minutes) depending on the volume of formalin being disposed of.
Disposal of chemicals
Xylene and toluene Stock solution of both Xylene and Toluene
are placed in a cool and dry place. Used Xylene and Toluene are stored
separately in a tightly capped container labeled as “used xylene/toluene – for disposal”.
Once the container is full, the chemicals are disposed of accordingly.
Disposal of chemicals
Alcohols (ethanol and methanol) Stock solutions are stored in a cool and
dry place away from flammable materials. All used alcohols are disposed thru the
sink with continuous flow of running tap water.
Staff training and preparedness
Safety standard operating procedure (SOP) Manual should define the hazards and safe working procedures for the department.
Safety training program should be part of the continuing education lectures given periodically as new recruits come in.
Regular safety inspections (at least annually).
Staff training and preparedness
Staff must be familiar with the location and operation of the ff emergency items in the lab: First aid kit Fire extinguisher Eyewash station and Emergency shower Spill Kit (minor chemical/biologic spills
<1L) Evacuation procedures and exits
for disasters and major spills Hotline numbers for emergency
Chemical spills kit & procedure
Safety information flyers
Emergency route
Documentation
Laboratory safety manual Incident report logbook:
Investigate and record all accidents to prevent same occurrence in the future.
Safety training program Fire extinguishers, spill kits, first aid Evacuation procedures
Equipment maintenance checks Ex. calibration, temperature, company
preventive maintenance MSDS: preferably bound and in
alphabetical order
Thanks (again) for the attention
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