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Potential Hazards in Laboratory Techniques

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Potential Hazards in Laboratory Techniques
Infection of laboratory workers is a common problem while handling microorganisms and in most of these cases, finding out the source of infection is very difficult. The problem is very severe in clinical microbiological laboratories where the microorganisms being handled are mostly pathogenic, although other research and development laboratories experience a similar problem.

Infection may occur by breathing in (inhalation) of infected aerosol, droplet nuclei or infected dust particles.

Aerosol is a cloud of small droplets of liquid in air. Most aerosols consist predominantly of droplets smaller than 0.1 run in diameter which dry within a second or so to become solid residues called droplet nuclei. These droplet nuclei are very small hence may remain airborne for up to several hours and may directly land on the upper respiratory or lower respiratory tract and initiate infection.

Invisible aerosols are generated by any action that breaks the continuity of
the surface of a liquid. Some examples include:

withdrawal of a loopful from a broth culture
bursting of the film of culture in a loop
vibration of a wire loop during an inoculation procedure.
sputtering of a charged loop during flaming
mixing of a suspension with a loop or a mixing equipment .
removal of a wet stopper, screw cap or cotton wool plug.
expulsion of residual fluid from a pipette
letting liquid fall in drops into a container instead of pouring it smoothly down a side
vigorous shaking or high speed mixing of liquid
dropping and breaking of culture plates or tubes
centrifuging of full tubes or tubes with wet rim and breakages in the centrifuge

Infective dusts which are particles small enough to remain airborne for minutes or hours can be produced by spillage of cultures onto the skin, clothing or floor.

After drying, the spillage residue is readily fragmented by minor movements into a fine dust and disseminated into the air.

Clouds of infective dust can be released by the opening of containers of freeze dried cultures or by the withdrawal of cotton wool plugs that have dried after being wetted with culture fluid.

Convectional and other air currents dispense droplet nuclei and dust particles widely within the laboratories. Particles more than 5 mm diameter are deposited in the nose and throat while smaller particles reach the bronchi and the lungs.

 
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