Working with Hazardous Chemicals

Personal protective equipmentSpecial conditions

Routes of chemical exposure

Part 1:

• Personal Protective Equipment (PPE)

Standard Lab Dress

• Have as little bare skin as possible• No loose hair, necklaces, neckties• No loose clothing (i.e. sleeves)• No rings, watches

• Key: Easy to remove clothes or wash skin if chemical contamination or fire occur

Proper use of lab coats

• Always wear lab coats.– To protect skin and clothes from

contamination – To prevent spread of contamination outside of

lab• Won’t protect against corrosives

– USE APRON• Fit: should not be too loose, unbuttoned, or have

rolled sleevesShould not be laundered at home. Should

not be worn outside of lab. http://cdn.shopify.com/s/files/1/0041/4632/files/new-lab-coat.jpg?1263858434

Appropriate Lab Footwear

• CLOSED TOE. NOT WOVEN.– Protect against spills – Broken glass

• Lab shoes vs. street shoes– Disposable shoe covers

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Laboratory Gloves: Purpose

• Gloves serve a wide range of purposes: – protection against chemicals– against biologicals– against punctures– against temperature extremes

• No single glove can do all this and still be flexible enough to use in fine manipulations

Choosing Laboratory Gloves

• Consult chemical resistance chart for glove– degradation rate: tendency of chemical to physically

change properties of glove on contact– permeation rate: tendency of chemical to penetrate– breakthrough rate: time required for chemical

spilled on outside of glove to be detected on inside surface

Proper Glove Use

• Can double glove with two different glove types for extra protection

• Choose thickest gloves which allow dexterity to perform task

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Proper Glove Use (con.)

• Check for holes or tears• Keep cuts bandaged• Keep nails short• Make sure gloves cover wrists• Change regularly and after contact with hazardous materials• Remove gloves so that skin contact does not occur with outside

glove surface• Wash hands after glove use or if contamination is expected• Do not touch doorknobs, lights, etc. with gloves on

Eye Protection

• Safety glasses with side shields– small chemical splashes

• Goggles– large splashes and caustics

• Face shields– explosion

• good for UV protection. Wear eyewear underneath.

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http://www.labsafety.com/images/xl/TASCO-9000-Face-Shield-LSS-_i_LBN67630_01S.jpg

Other types of PPE

• Ear protection– ear plugs or ear muffs– protect against sonication noise

• Masks– filter dust and aerosols– protect against minor splashes– Will not protect against biological

infectious agents

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Other PPE (con.)

• Respirators– protect against toxic

fumes– must have training to

use• Self-contained breathing

apparatus– contains own air supply– when user must work

in highly toxic fumes

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Part 2:

• Working in special conditions

Working with glass

• Check glassware prior to heating or centrifuging or otherwise stressing glass

• Place mat in bottom of sink prior to washing glassware

Working with sharps

• Never leave these sitting on benchtops where someone may accidentally get hurt

• Always scrape or cut away from body• Recap needles by placing cap on

benchtop and inserting needle to prevent punctures

• Dispose of sharps in specially labeled container

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Working with gas cylinders

Gases mostly non-toxic and nonflammable

Danger comes from risk of explosion or falling

• Wear eye protection• Attach cylinders to wall• Transport cylinders one at a time in a cart secured

by a strap• Keep safety cap on during movement• Know about hazards of gas prior to use• Never direct stream of gas at anyone

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Working with heat

• Bunsen burners• don’t leave flame unattended• Don’t leave flame where someone may reach over it• Keep flame visible

• Hot plates• Leave note that it is hot after use

• Hot liquids• Never heat a closed container• Watch for superheated liquids

• In case of minor burns, flood skin with cold water for 10 – 15 minutes

Laboratory Fires

Most common source of fire = ignition of flammable organic liquids and vapors

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Preventing Laboratory Fires

• Keep minimum amount of flammables• Keep open solvents away from flame• Store flammables in appropriate cabinets• Use water baths or hot plates instead of Bunsen burners• Limit ignition sources: sparks, static electricity• Never leave flame unattended• Marked heated hot plates• Reduce electrical hazards

Extinguishing Laboratory Fires

• NEED FUEL, HEAT, OXYGEN TO GET FIRE– TAKE ONE AWAY AND IT

EXTINGUISHES

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Types of Extinguishers

• Class A = paper, cloth, wood – Use water or multipurpose dry chemical

• Class B = organic solvents, gases, paints– DO NOT USE WATER– Carbon dioxide or foam to remove oxygen

• Class C = electrical– DO NOT USE WATER. May cause electrocution.– Use carbon dioxide or dry foam

• Class D = combustible metals– Need special extinguisher approved for source metal.

Working with extreme cold

• Contact with extreme cold (-78 degrees Celsius or below) causes skin burns– Cryogenic liquids can not be used with ordinary lab

glass or plastic. Stored in Dewar vacuum glass flasks.

• Dry ice = solid– Use eye protection to chip large blocks– Do not lean too far into chest for long periods. This

can cause suffocation.

• Liquid nitrogen (-198 degrees Celsius) – Very hazardous to dispense. Never do this without

training.

Working safely with electricity

• Keep hands dry• Be sure equipment is grounded• Keep area under equipment dry• Check cords to see if in good condition

Working with UV light

UV-B AND UV-C light in labs can damage skin and eyes

• Always wear approved eye protection• Cover skin• Do not direct UV light at coworkers• Use a face shield if necessary• Use germicidal lamp only when area not in use

Working with autoclaves

Autoclaves are sterilization devices that use high pressure and very high temperature

• Do not use chipped glassware• Be sure plastics are autoclavable• Make sure inside of autoclave is at atmospheric pressure before

opening door• Wear eye and hand protection• Stand back when opening door• Release pressure slowly for liquids to prevent boilover• Let autoclaved liquids sit 10 minutes prior to removal to prevent

boilover

Part 3:

• Routes of entry for chemical exposure

Routes of entry for toxic chemicals

• Inhalation• Skin and eye contact• Ingestion• Injection

• Most likely in lab = skin contact and inhalation

Measuring chemical toxicity

Chemicals differ in:– Toxic dose– Route of toxicity

• LD50 (lethal dose – 50%)– amount of chemical causing

death in 50% of test animals– LD50 is recorded in grams

chemical / kilograms body weight

http://www.chem.duke.edu/~bonk/Chem8304/LD50.GIF

Levels of toxicity

• LD50 depends upon route of exposure– High toxicity = <500 milligrams / kg by ingestion or injection– High toxicity = < 1 gram / kg by skin contact

• LC50 (lethal concentration)– concentration of chemical in air that will kill 50% of exposed

animals.– Expressed in ppm. – <2000 ppm inhalation = highly toxic.

Toxicity by inhalation

Reactions range from mild discomfort to burning to asphyxiation

• For volatile chemicals, can NOT estimate exposure by odor. Therefore, you should limit your exposure by working in a fume hood.

ACGIH limits of exposure• American Conference of

Governmental Industrial Hygienists (ACGIH) has set limits of exposure– OSHA adopted these

and set as regulated limits.

• Threshold Limit Value (TLV) = airborne concentration for a chemical that most healthy workers can safely be exposed to for 8 hours per day repeatedly with no adverse effects. ( can be averaged over the course of the day)

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ACGIH limits of exposure

• TLV-STEL (short term exposure limit) = air concentration at which only 15 continuous minutes of exposure is allowed up to 4 times per 8 hour day

• TLC-C (Ceiling exposure limit) = airborne values must never exceed this value.

Consequences of skin contact with a hazardous chemical

• No harm• Rashes, burns, other skin

irritations• Penetration of skin = allergic

sensitization• Penetration of skin and entry into

bloodstream resulting in systemic toxicity

• Skin is normally a barrier but entry at hair follicles, sweat glands, cuts and abrasions can occur

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Toxicity by ingestion

• Touching face with contaminated hands, chewing on pencils, etc.

LD lo = lowest dose of chemical reported to cause a human death

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Use of a fume hood: when is it required?

Whenever using chemicals that:• Are volatile• Have unpleasant smells• Have TLV lower than 50 ppm in

air

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Fume hood terminology

Sash: window that is impact-resistant and can be raised and lowered

Baffles: direct air flow

Airfoils: reduce turbulence in air flow

Face velocity: rate of air flow into entrance of hood

Types of fume hoods

• Fumes hoods can be “constant air volume” (changing sash height changes the face velocity)

• Can also be variable air volume which means relatively constant face velocity.

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Fume hood use and maintenance

• Testing must occur at least annually. • Not all parts of a hood are equally good for working in. • Handle toxic chemicals 5 to 6 inches back from sash.

Fume hood rules of use

• Check hood function• Put all equipment in at once, check compatibility of chemicals• Do not overload hood because blocks air flow. Keep

equipment 2 inches off of hood surface• Move sash slowly and keeps hands from making sudden

movements• Keep face behind hood sash• Wear face and eye protection• Do not use infectious agents (need biological safety cabinet)

Fume hood spills

In the event of fire or spill:

1. Close sash completely

2. Leave exhaust fan ON

3. Unplug all equipment in hood (if outlets are outside sash)

4. Evacuate area