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Mining and EnvironmentNews

Management of hazardous chemicals in mining – mercury

By Abigail Makumbe – Branch Manager for Curechem Bulawayo – Friday 22 May 2020

LOCAL – HARARE (Mining Index) – MERCURY is a naturally occurring metallic element, which at room temperature and in its pure form is a silvery-white liquid. It is widely used in gold mining.

Abigail Makumbe – Branch Manager Curechem Bulawayo

Mercury is also found in a range of other products, including dental amalgam, electrical switches, batteries, fluorescent light tubes, biocides, pesticides, herbicides and fungicides, pigments and dyes, and wood and leather preservatives.

Risk to human health and the Minamata Convention

The Minamata Convention on Mercury is an international treaty designed to protect human health and the environment from emissions and releases of mercury and mercury compounds.

Its aim is to enhance the reduction of mercury pollution over the next few decades. In summary it includes controls and reductions across a range of products, processes and industries where mercury is used, released or emitted.

The treaty also addresses the direct mining of mercury, its export and import, its safe storage and its disposal once it becomes waste.

The Minamata Convention is intended to help identify populations at risk, boost medical care, better training of medical staff, and treatment of effects among other things. It is envisaged that in the future, use of mercury can be completely banned but at present there are some countries which are exempted from the ban.

Mercury is very toxic. Hence the serious steps such as the Minamata Convention.

High doses can be fatal to humans, but even relatively low doses can have serious impacts on the body’s systems.

The harmful effects of exposure largely depend on both the way people are exposed and the type of mercury they are exposed to.

It can enter the human body through the mouth, nose, eyes and skin. Very little enters the body after swallowing small amounts of elemental mercury, whereas after breathing elemental mercury vapour about 80 percent enters the blood from the lungs.

Inorganic mercury compounds do not vaporise and so are not generally breathed in, and only small amounts may pass through the skin. If swallowed, up to 40 percent may enter the body.

Breathing in elemental mercury vapour for a short time affects the nervous system and lungs leading to tremors, walking difficulties, chest pains and breathlessness.

After longer periods, the lining of the mouth and lungs may be damaged.

Kidney damage may also occur as well as stomach irritation, nausea, vomiting and diarrhoea.

Eating food or drink contaminated with inorganic mercury damages the kidneys, stomach, intestines and nervous system.

Mercury has been linked with possible effects on the cardiovascular, immune and reproductive systems.

Methyl mercury can cross the placenta in pregnant women and can affect mental development in unborn babies.

Artisanal miners handling hazardous chemical without proper PPE

Contamination of clothing and cleaning equipment can also occur when dealing with spillages and skin absorption of mercury may occur.

Risks of mercury to the environment are many. Mercury can change into methyl mercury, the most toxic form of mercury.

It can build up in plants and animals, and accumulate along the food chain, particularly in fish and other aquatic life.

Birds die due to mercury poison

Low levels of mercury in surface waters can lead to high concentrations in insects, fish and birds, resulting in very toxic contamination in parts of the ecosystem.

Contamination of water bodies by mercury

Mercury can contaminate groundwater, which feeds rivers and is also used for drinking water supplies.

How can miners handle mercury in a safe manner?

Mercury can be handled safely by personnel, although its use should be eliminated or minimised wherever possible. Safe handling tips where its use is unavoidable includes the following.

Always wear gloves when working with mercury.

  1. Never use a mercury thermometer in a laboratory oven. Avoid using mercury thermometers at all.
  2. Do not leave open containers of mercury in hot areas as it will form mercury vapour.
  3. Do not keep excess mercury.
  4. Use a glass, plastic or steel tray to contain any spills that might occur.
  5. Glass or plastic vessels should have a secondary steel or plastic container around them in case the vessel fails/breaks.
  6. Do not use mercury where it could contact a hot surface and vaporize.
  7. Avoid inhaling mercury vapour and use suitable gloves when working with it.
  8. Put mercury waste in a special waste container, do not combine it with other wastes and do not dispose of it down a sink.
  9. Do not wear gold or silver jewellery when working with mercury.
  10. As always, read the material safety data sheet (MSDS) for mercury before using mercury.
  11. Access to mercury should be restricted to a locked cabinet or room, and only used by those who have been given suitable and sufficient training and protective clothing.

Dealing with spillages

With proper control and training, elemental mercury can be safely used in various settings. However, when spilled or misused, it can present a significant hazard. The following actions can be taken in case of a mercury spillage.

  1. Make an on-the-spot assessment of the severity of the spill. Seek assistance whenever necessary.
  2. Wear gloves. Collect as much mercury as possible using a 5ml or 10ml syringe. Experimentation will be necessary to find the best angle to draw the heavy mercury into the tube.
  3. Use a piece of card to gather the droplets together if they are finely divided.
  4. Collect any broken glass and other debris into a suitable container.
  5. Use card rather than gloved hands if there is broken glass.
  6. Small pieces of broken glass which are uncontaminated by mercury are best disposed of in a sharps disposal box.
  7. Mercury spill kits are available commercially; they should normally only be used by a competent person.
  8. Put the syringe and any other container into which contaminated debris has been collected into double plastic bags. Tie the necks of the bags, label the package “Danger — Mercury. Do not touch,” and put it in a safe place pending collection.
  9. Do not use a vacuum cleaner on residual mercury; this can produce high vapour concentrations.
  10. Sulphur powder can be used to mop up mercury droplets: dust it on the area & gather up
  11. Only dispose of mercury as hazardous waste.
  12. Report and investigate the incident.
  13. Mercury can be recycled by using the retort method which is basically distillation to separate impurities by vaporising the mercury in closed circuit & re-collecting it by cooling.

Miners must always be in possession of a valid Environmental Management Agency (EMA) Hazardous Chemicals Storage and Use licence. ENDS// www.miningindex.co.zw

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