Histotechnology - Lecture 1 - Safety in the Histology Department

What are the 6 most common safety protocols in the Histology department? (Even though all hospitals establish their own safety protocols)

a) Practice standard precautions - Treat everything as infectious

b) Wear proper PPE

c) Do NOT touch “clean” areas with gloves

d) Wash hands frequently

e) Disinfect all instruments

f) Minimize chemical contact

What is the first step when responding to a chemical spill in the histology lab?

Notify your supervisor

What PPE is essential when handling formalin-fixed tissues?

Safety glasses, nitrile gloves, lap coat (all of the above)

What is a basic safety rule in any laboratory?

The proper labelling of chemicals

What is a significant hazard when working with xylene in the histology lab?

Fire hazard

What is the primary health risk associated with prolonged exposure to formeldehyde?

Respiratory issues

What are exposure limits in the context of laboratory safety?

The maximum amount of concentration from a chemical that workers can be exposed to

What are some possible hazards in histology?

• infection

• needle-stick injury

• cuts

• carcinogenic agents

• flammable chemicals (xylene)

• allergenic agents

• physical hazards (microtome)

What two types of SOP’s MUST be in place when detailing an exposure control plan?

Institutional and Laboratory SOPS

What should the SOP’s exposure control plan be detailing?

• Housekeeping details (how garbage is removed)

• PPE

• Waste disposal

What tasks in the histology lab may expose one to blood or potentially infectious materials?

• Frozen sectioning

• Autopsy

• Gross dissection

• Cytology preparation

What are the four major classes of hazards in the histology lab?

1. Biological/Infectious

2. Technical

3. Chemical

4. Health/physical

What are 5 potential Biological/Infectious hazards?

1. Mycobacterium tuberculosis (TB)

2. HIV, HBV, HCV

3. Creutzfeldt-Jakob disease (CJD)

4. Infectious aerosols

5. Infectious wastes

What specimens are not considered infectious unless visible blood is present?

Sputum, stool, vomitus

What is always required when dealing with potential TB?

Respiratory protection - N95 mask

What is the mode of transmission for TB?

Airborne and droplet nuclei

What is the inoculation period for TB?

10 bacilli via inhalation

What is the incubation period for TB?

1-3 months from exposure

What 5 disinfectants is TB susceptible too?

1. 5% Phenol

2. Glutaraldehyde

3. Iodine w/ high concentration

4. Formaldehyde (longer contact time)

5. 1% bleach (longer contact time)

What is TB inactivated by?

Moist heat 121 degrees for 15 mins

What is the infectious dose for HIV?

It is very low, small amount entering bloodstream or mucus membranes can result in infection

What is the incubation period for HIV?

6 months to 7 years

What 4 disinfectants is HIV susceptible to?

1. 1% bleach

2. 2% Glutaraldehyde

3. Formaldehyde

4. Ethanol

What decreases the reactivity of HIV to below detectable amounts?

Heating specimen at 56-60 degrees (pasteurization)

When is HIV destroyed outside of the host?

Within several hours

What are direct contact hazards in regards to HIV?

Skin (un-intact skin), mucous membranes (mouth, nose, eyes), accidental percutaneous (through skin) injuries

What are the two forms of pathogenicity?

• Symptomatic (looks like you got it)

• Asymptomatic (doesn’t look like you got it)

What is the infectious dose for HBV?

Unknown, one mL of blood can contain 102-109 HBV particles (not a lot)

What is HBV’s mode of transmission?

Through percutaneous or permucosal exposure with infected body fluids

What is the incubation period for HBV?

24-180 days (2-3 months)

Is HIV and HBV stable or fragile?

HIV is fragile, HBV is stable

What 4 disinfectants is HBV susceptible too?

1. 1% bleach

2. 2% Alkalinized glutaraldehyde

3. Formaldehyde

4. 70% ethanol

What is the most frequently encountered lab associated infection?

HBV

What type of disease is CJD?

Prion disease - Prions are abnormal proteins that can cause disease

How does CJD affect one?

CJD affects nervous tissue, causes changes to the white matter of the brain called spongiform encephalopathy

How is CJD transmissible?

Transplants, exposure to brain tissue and CSF

How long can it take CJD for symptoms to appear?

It can take up to 20 years

How do you destroy a prion?

They are very resistant to destruction and basically have to be incinerated

What 4 things are prions susceptible too?

1. Autoclave for one hour at 121 degrees, 132-134 degrees is preferred

2. 5% sodium hypochlorite (bleach) for two hours (destroys instrument)

3. Concentrated formic acid for 1 hour

4. 1N sodium hydroxide for 1 hour

What are the 3 classifications of CJD?

1. Sporadic - unknown cause

2. Familial - genetic predisposition

3. Iatrogenic - accidental contamination

Can standard fixation kill CJD microorganisms?

False

What is vCJD associated with?

Associated with eating meat from cows infected with “bovine spongiform encephalopathy” (BSE) = “known as mad cow disease”

What to disinfect steel instruments with after possible CJD exposure?

2N NaOH for 1 hour

In regards to infectious aerosols, should cryogenic sprays be used on frozen sections or poorly fixed tissue?

No

In regards to waste tissue specimens, how should all materials that came into contact with tissue be disposed of?

In a BIOHAZARDOUS bag with a biohazard warning

What are the four classifications of infectious waste?

1. Pathologic material specimens

2. Blood

3. Microbiological or Culture specimens

4. Sharp objects

What methods is recommended for all waste except pathological waste?

Steam sterilization or incineration, only incineration for pathologic

Can blood be poured down the drain?

Yes

What are some hazards within the category of mechanical hazards?

• knife blades

• razors

• scalpels                   sharps container for disposal

• needles

• glass

• electrical

What is an engineering control?

What we put in place to get rid of the hazards

What must be preformed on all electrical equipment within the lab?

Grounding, condition of wires checked periodically, extension cords surge protected, must all be documented

What are the two classes of chemical hazards?

1. Physical

2. Health

3 examples of Physical Chemical hazards?

Flammable, explosive, oxidizers

5 examples of Health Chemical hazards?

Carcinogens, sensitizers, toxins, corrosives, irritants

What is PEL?

Permissible exposure limit - Maximum allowable airborne concentration of a chemical that a worker may be exposed to in a 8hr workday, 5 days a week, for a lifetime without receiving damaging effects

What is TWA?

Time Weighted Average - The average exposure to a chemical workers may be exposed to without adverse effects over a period such as 8hr day or 40 hr week

What is STEL?

Short Term Exposure Limit - The measurement of exposure over a short period of time (15 mins) where the worst exposure occurs (STEL always higher than TWA)

What is CL?

Ceiling Limit - Maximum permissible instantaneous exposure to a chemical during any part of the work shift. Reserved for very dangerous substances

What is the TWA for formaldehyde?

0.75 ppm - average 8hr work shift)

What is the action level for formaldehyde?

0.5 ppm calculated for 8hr TWA

What must occur if intial TWA is greater than 0.5 ppm?

Monitoring must be done every 6 months to look for improvement

When formaldehyde levels are at or above action level or STEL in areas what must be done?

Must be stated and respirators must be worn

Does a TWA greater than 0.5 ppm but WITHIN stel limits require monitoring?

No, only if theres an employee present with symptoms

What 3 things must chemicals be evaluated for?

1. Carcinogenic potential

2. Reproductive toxicity

3. Acute toxicity

What are the five health hazards?

1. Biohazards

2. Irritants

3. Corrosive chemicals

4. Sensitizers

5. Carcinogens

Define biohazard:

Has potential to cause disease in humans

Define irritants:

Reversible inflammatory damage effecting site of contact

Define Corrosives:

Irreversible damage, physical and health hazard (acid)

Define Sensitizers:

Causes allergic reactions

Define Carcinogens:

Can cause cancer

What 4 carcinogens can cause cancer?

Benzene (replaced with xylene now), formaldehyde, chromic acid, chloroform

What 3 dyes (aromatic compounds) are also carcinogenic?

1. Basic fuchsin

2. Auramine

3. Ponceau 2R

What are 4 physical hazards?

1. Combustibles (needs help to catch on fire)

2. Flammables (can catch on it’s on)

3. Explosives

4. Oxidizers

Is it better to choose a combustible product over a flammable product?

Yes

How do combustibles catch on fire?

When they’re FP (flashpoint) is at or over the specified temperature

What has lower FP combustibles or flammables?

Flammables, vapours must be carefully controlled

Most common explosive?

Picric acid, some silvers

What is an oxidizer?

They can initiate/promote combustion in any other material

What is an insidious chemical hazard?

Hazards that develop gradually, and are very subtle but in a HARMFUL way

What are 3 examples of insidious chemical hazards?

1. Ethers

2. Mercury

3. Picric acid

How are ethers insidious chemicals?

They progress with exposure to air and are accelerated by light, and oxidize to form peroxides

How is mercury a insidious chemical hazard?

Liquid mercury releases vapors at levels exceeding exposure limits

How does one store picric acid?

Store wet always, never dry

What must be present for hazard identification?

·      Chemical containers MUST contain correct labels

·      Signage must be available where specific reagents are used

·      Data sheets (DS) must be available for ALL chemicals

What is toxic dose?

Lowest dose of a substance that can result in a toxic effect by means other than inhalation

What does “toxic concentration low” mean?

If toxic by inhalation

What is LD50?

Calculated dose of a chemical expected to cause death of 50% of an experimental animal population by exposure by any route except inhalation

What are three toxic chemical examples?

1. Formaldehyde

2. Metallic compounds – mercury, chromium, Ag

3. Hydrocarbons: xylene and toluene

What inhalation concentrations of formaldehyde result in difficulty breathing?

10-20 ppm

What can inhalations above 20 ppm cause?

Pulmonary edema (fluid in lung)

What can 0.5-2.0 ppm of formaldehyde cause?

Irritation of eyes, nose, throat

What can chronic exposure to formaldehyde cause?

Respiratory issues

What occurs when formaldehyde reacts with HCL?

Produces ether vapor which is very carcinogenic

Is formaldehyde a sensitizing agent?

yes

Is formaldehyde flammable?

Yes flammable liquid and vapours

Potassium Dichromate:

• Carcinogen

• Corrosive

• Sensitizer

• Oxidizing agent

• Non-flammabe

Methanol:

Highly flammable

Osmium Tetroxide:

Not explosive or fire hazard, just very toxic