Mercury

Hazards associated with mercury and disposal methods.

What are the hazards?

Mercury vapour, and most compounds of mercury, are toxic to the human nervous system and act as cumulative poisons. The developing brains of foetuses and infants are especially sensitive to mercury’s toxic effects. Because mercury vapours are readily absorbed through the lungs into the bloodstream, they are particularly hazardous. Exposure to mercury vapours can occur when mercury containing products (such as thermometers, sphygmamometers and fluorescent lamps) are broken.

Whilst spills such as that from a broken thermometer do not pose a high risk, the area of the spill should be cordoned off and the spill cleaned up immediately to prevent spread and secondary exposures. Mercury vapours are heavier than air and may linger in higher concentrations at the site of the spill.

The factors that determine how severe the health effects are from mercury exposure include:

• The dose (concentration of mercury vapour in the air);
• The age of the person exposed (the foetus is the most susceptible);
• The duration of exposure;
• The route of exposure - inhalation, ingestion, dermal contact, etc.; and
• The health of the person exposed.

Symptoms include:

• tremors;
• emotional changes (e.g., mood swings, irritability, nervousness, excessive shyness);
• neuromuscular changes (such as weakness, muscle atrophy, twitching);
• headaches;
• insomnia;
• disturbances in sensations;
• changes in nerve responses;
• performance deficits on tests of cognitive function.

At higher exposures there may be kidney effects, respiratory failure and death.

It cannot be stressed strongly enough however that such symptoms would only manifest following prolonged exposure to fairly high concentrations of mercury in air e.g. during lamp manufacture or mercury distillation.

Precautions when using mercury

Where mercury is used, the following precautions should be observed:

• Keep mercury surfaces covered to prevent evaporation.
• Ensure good ventilation of the working area.
• Carry out manipulations of mercury over a tray which will contain spills. The surface of the tray should be smooth and impervious.
• Clean up spilled mercury, at once.
• If a mercury hazard is suspected, arrange with the School Safety Adviser for airborne concentrations of mercury vapour to be measured.
• Alcohol thermometers must be used in preference to mercury thermometers where ever practical, this especially so when a thermometer is to be left in a heating block where history has shown that they are vulnerable to knocks and breakage.

Cleaning up following the spillage of mercury

• The room should be vacated and ventilated for at least 15 minutes.
• Specialist spill kits are available from many laboratory supply companies. RS Components Ltd, VWR International Ltd and BOC Ltd are all on the University SciQuest online ordering system and can supply mercury spill kits.
• Wear a facefit tested half mask respirator with mercury filters, disposable over trousers and nitrile gloves. Guidance on facefit testing can be found at Facefit testing.
• Do not use a vacuum cleaner, but rather clean up using light strokes with a brush aiming to avoid creating and inhaling airborne dust. Disposable gloves should be worn and all particles, the brush and glass fragments placed in a cardboard box.
• Wipe the area with a damp cloth, then add that to the box, as well as the disposable over trousers and seal it.
• Only remove the half mask respirator once box is sealed.
• Mercury is hazardous waste therefore the box should not be disposed of in the general waste bin. Instead it must be contained appropriately and disposed of via the University’s designated Hazardous Waste contractor. Lab waste guidance on Waste and Recycling website

Distillation of mercury

The distillation of mercury has ceased in this University, should the reinstatement of this procedure be contemplated it may only be carried out in a dedicated room and within an efficient and dedicated fume cupboard, under appropriate supervision and only after prior consultation and agreement with the Health and Safety Department.