Hazard

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.


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.


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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