Safety in the laboratory

● Each laboratory should have a written manual of safe laboratory practices which should be followed at all times.

● The laboratory should have a first-aid box (see section 3.8.2) and at least one staff member trained in first aid.

● The laboratory should be a work area only; visitors should be restricted.

● No food or drink should be consumed in the laboratory.

● Wear protective clothing and remove it before leaving the laboratory.

● Always consider any laboratory specimen as potentially infectious and handle it carefully; wear protective gloves.

● Place all specimens safely on a bench or in a rack to prevent spillage or breakage.

● Take great care when collecting and processing blood samples as they may harbour infective agents (e.g. hepatitis B virus, parasites, etc.).

● Do not contaminate yourself or the work areas with any specimen.

● Do not pipette blood or other body fluids or any reagents by mouth.

● Cover all cuts with an impervious dressing (plaster).

● Dispose of used needles and lancets safely in a “sharps” container. (Sharps con- tainers can be made from plastic bottles with a screw top in which a hole is made.) Once filled, containers should be autoclaved or soaked in disinfectant before burning or burying in a deep pit (see sections 3.6.2 and 3.6.3).

● Cover any spilled material or broken culture tubes with a cloth soaked in disinfectant (see section 3.5.4) and leave for 30 min. Then use a stiff brush or sheet of cardboard to sweep it into a disposable specimen container.

● At the end of the day swab the benches with a cloth soaked in disinfectant (see section 3.5.4).

● Wash your hands well after handling infective material and before leaving the laboratory.

Specimens may be disposed of:

— in cardboard cartons or plastic pots that can be destroyed (stools, sputum);

— in glass jars and bottles that can be cleaned, sterilized and used again (see sections 3.5.1, 3.5.2 and 3.5.5).

Disposable containers must not be reused.

1. Precautions to prevent accidents

Handling acids and alkalis

Diluting concentrated sulfuric acid with water

Always add the concentrated sulfuric acid to the water drop by drop, stirring the mixture after each drop. Do this in a sink whenever possible. Never pour the water into the sulfuric acid because of the danger of splashing due to the explosive evapo- ration of water while mixing.

Bottles of acids and alkalis

Keep bottles of acids and alkalis on the lower shelves of the cupboards. When you take a bottle out make sure your hand is dry and hold the bottle firmly upright. Do not keep acids and alkalis in bottles with ground glass stoppers (they may get stuck).

Pipetting

Use small measuring cylinders for measuring acids and alkalis. If more accurate measurement is required, use a pipette with a rubber safety bulb attached. Pipette slowly, watching the level of the liquid.

Heating glassware and liquids

Test-tubes

Never heat the bottom of a test-tube; the liquid inside might sputter. Heat the middle of the tube, shaking gently. The mouth of the tube should be facing away from you and any other person, towards an empty work space or a sink.

Heat-resistant glass

Only heat-resistant glassware and porcelain receptacles can be heated over a Bunsen flame. Ordinary glass will break.

Flammable liquids

Only small quantities of flammable liquids such as ether, ethanol, acetone, benzene and toluene should be kept in the laboratory.

War ning: Ether will ignite at a distance of several metres from a flame. Never place a bottle of ether on a workbench where there is an open flame.

Propane and butane gas burners

When lighting a gas burner, always light the match and hold it to the burner before turning on the gas tap. Turn off the main valves of all bottles of butane gas every evening. Replace the rubber connecting pipes once a year.

2. First aid in laboratory accidents

Accidents in the medical laboratory may have various causes:

● Acids or alkalis: splashes on the skin or in the eyes, swallowing.

● Toxic substances.

● Heat: naked flames, hot liquids, flammable liquids, explosions.

● Injuries involving infectious material, electric shocks, etc.

First-aid equipment

● First-aid box (see below)

● Sodium carbonate, 5% solution (reagent no. 52)

● Sodium bicarbonate, 2% solution (reagent no. 50) (in an eyedrop bottle)

● Boric acid, saturated solution (reagent no. 12) (in an eyedrop bottle)

● Acetic acid, 5% solution (reagent no. 1)

● Cotton wool and gauze

● Mercurochrome and tincture of iodine.

The above items should be readily available in the laboratory. They must not be kept in a locked cupboard. The solutions should be kept in plastic bottles.

First-aid box

The first-aid box should contain the following:

● An instruction sheet giving general guidance

● Individually wrapped sterile adhesive dressings in a variety of sizes

● Sterile eye-pads with bandages for attachment

● Triangular bandages

● Sterile dressings for serious wounds

● A selection of sterile unmedicated dressings for minor wounds

● Safety-pins

● A bottle containing eye drops

● A first-aid manual.

The contents of the first-aid box should be replenished immediately after use and inspected regularly to ensure that they remain in satisfactory condition.

Corrosive injuries from acids

Acids such as nitric acid, sulfuric acid, chromic acid, hydrochloric acid, acetic acid and trichloroacetic acid can cause corrosive injuries. It is therefore essential to take immediate action in the event of an accident.

In all cases: Wash the affected area immediately with large quantities of water.

Acid splashes on the skin

● Wash the affected area thoroughly and repeatedly with large quantities of water.

● Bathe the affected skin with cotton wool soaked in a 5% solution of sodium carbonate.

Acid splashes in the eye

● Wash the eye immediately with large quantities of water sprayed from a polyethylene bottle (or rubber bulb) for 15 min (Fig. 3.76); squirt the water into the corner of the eye near the nose. Alternatively, wash the eye with running water from a tap (Fig. 3.77). Ask the patient to close the eye that is not affected.

● After washing, put 4 drops of a 2% solution of sodium bicarbonate into the eye.

● Send for a physician. Continue to apply bicarbonate solution to the eye until the physician arrives.

Fig. 3.76 Rinsing the eye using a polyethylene bottle

Fig. 3.77 Rinsing the eye under the tap

Swallowing acids

If acid is accidentally swallowed:

● Send for a physician.

● Make the patient drink some milk immediately (alternatively, two egg whites mixed with 500 ml of water may be given). If neither of these is available, the patient should drink ordinary water.

● Make the patient gargle with the milk.

● Give the patient three or four glasses of ordinary water.

● If the lips and tongue are burned by the acid:

— rinse thoroughly with water, then

— bathe with a 2% solution of sodium bicarbonate.

Note: Always pipette acids using a rubber safety bulb, never by mouth.

Corrosive injuries from alkalis

Alkalis such as sodium hydroxide, potassium hydroxide and ammonium hydroxide can also cause corrosive injuries. Such injuries may be more serious than those caused by acids.

In all cases: Wash the affected area immediately with large quantities of water.

Alkali splashes on the skin

● Wash the affected area thoroughly and repeatedly with water.

● Bathe the affected skin with cotton wool soaked in a 5% solution of acetic acid (or undiluted vinegar or lemon juice).

Alkali splashes in the eye

● Wash the eye immediately with large quantities of water sprayed from a polyethylene bottle (or rubber bulb); squirt the water into the corner of the eye near the nose (see Fig. 3.76). Alternatively, wash the eye with running water from a tap (see Fig. 3.77).

● After washing the eye with water, bathe it with a saturated solution of boric acid.

● Send for a physician. Continue to apply boric acid solution to the eye until the physician arrives.

Swallowing alkalis

If alkali is accidentally swallowed:

● Send for a physician.

● Immediately make the patient drink a 5% solution of acetic acid (or lemon juice or vinegar diluted 1 part vinegar to 3 parts water).

● Make the patient gargle with the same acid solution.

● Give the patient three or four glasses of ordinary water.

● If the lips and tongue are burned by the alkali:

— rinse throughly with water, then

— bathe with a 5% solution of acetic acid.

Poisoning

This can be caused by:

— inhaling toxic vapours or gases (e.g. chloroform)

— accidental swallowing of a poisonous solution.

In all cases:

● Send for a physician or qualified nurse, specifying the toxic substance involved.

● Place the victim in the open air while waiting for the physician or nurse.

Burns caused by heat

These fall into two categories:

● Severe burns (e.g. burns caused when burning ether or boiling water is spilled over the victim).

● Minor burns (e.g. burns caused by hot glassware or a Bunsen flame).

Severe burns

● If the victim is on fire (e.g. splashed with burning ether or other flammable solvents), roll him or her in a blanket to extinguish the flames.

● Inform the physician on duty at the casualty department immediately, specifying that a patient with severe burns will have to be moved.

● Lay the victim on the ground. Do not remove any clothing. Cover the patient if he or she is cold.

● Do not apply any treatment to the burns: this must be left to the physician.

Minor burns

● Plunge the affected part into cold water or a mixture of ice and water to soothe the pain.

● Apply mercurochrome or tincture of iodine to the burn.

● Apply a dry gauze dressing loosely.

● If the burn becomes infected or does not heal, refer the patient to a physician.

Note: Never tear off blisters that form over burns!

Injuries caused by broken glass

Clean glass

● Disinfect the skin in the normal way (using, for example, mercurochrome or tincture of iodine).

● If the cut is minor, cover it with a sterile adhesive dressing (ready-made type).

● If the cut bleeds profusely, stop the bleeding by pressing down on it with a sterile compress. Refer the patient to the casualty department.

● If the cut bleeds heavily with the blood spurting out at intervals, try to stop the bleeding by pressing down on it with a sterile compress and send for a physician or qualified nurse.

● Continue to press on the covered wound while waiting for the physician or nurse. (He or she will decide whether a tourniquet should be applied.)

Glass containing infected material

Glassware containing stools, pus, bacterial cultures, etc.:

● Check whether the cut is bleeding; if not, squeeze hard to make it bleed for several minutes.

● Bathe the whole area (the edges of the cut and inside the cut) with tincture of iodine or a surgical antiseptic (see Table 3.1, page 84).

● Wash the whole area thoroughly with soapy water.

● Bathe the area again with tincture of iodine.

● Refer the victim to the physician if the material involved is known to be infective (e.g. bacterial cultures, pus).

Electric shocks

Alternating electric current (120 V or 220 V) is usually used in the laboratory. Electric shocks may occur when faulty equipment is being handled, particularly with wet hands. The symptoms are fainting, asphyxia and cardiac arrest.

● Before doing anything else, cut off the electricity at the main fuse.

● Send for a physician.

● In case of a cardiac arrest, massage the heart externally if necessary and begin giving artificial respiration.