Mercury: The Silent Poison Behind Gold Mining—Its Chemistry, Industrial Uses, Role in Ghana’s Galamsey Crisis, and Its Devastating Effects on Human Health
Introduction
Mercury is one of the most fascinating yet dangerous elements known to science. It is the only metal that exists naturally as a liquid at room temperature, making it unique among all metallic elements. For centuries, mercury has played an important role in medicine, manufacturing, mining, scientific research, electrical engineering, and chemical industries. Ancient civilisations admired it for its unusual appearance and physical properties, while modern industries valued it for its ability to conduct electricity and form alloys with other metals.
Despite its industrial usefulness, mercury is now recognised as one of the most toxic substances released into the environment. The World Health Organization (WHO) classifies mercury as one of the top ten chemicals of major public health concern because of its persistence, ability to travel long distances in the atmosphere, and tendency to accumulate in living organisms. In Ghana, the widespread use of mercury in illegal small-scale gold mining (galamsey) has transformed a valuable industrial chemical into a major environmental and public health crisis.
The Origin and Discovery of Mercury
Mercury has been known to mankind for more than 3,500 years. Archaeological evidence suggests that the ancient Egyptians, Chinese, Greeks, Romans, Persians, and Indians all knew about mercury and used it for various purposes.
The Romans extracted mercury mainly from cinnabar, a bright red mineral composed primarily of mercury sulphide (HgS). Heating cinnabar in the presence of oxygen releases mercury vapour, which is then condensed into liquid mercury.
Mercury’s Latin name, Hydrargyrum, means “liquid silver”, derived from the Greek words ‘hydor’ (water) and ‘argyros’ (silver). Its chemical symbol Hg comes from this Latin name.
Chemical Composition of Mercury
Mercury is a naturally occurring metallic element.
Its scientific properties include:
Chemical Symbol: Hg
Atomic Number: 80
Atomic Mass: 200.59 atomic mass units
Group: 12
Period: 6
Block: d-block
Category: Transition Metal
State at Room Temperature: Liquid
Color: Silvery-white
Melting Point: –38.83°C
Boiling Point: 356.73°C
Density: 13.53 g/cm³
Mercury is an excellent conductor of electricity but a poor conductor of heat compared with most metals.
One remarkable property of mercury is its ability to dissolve many metals, forming amalgams. This property is the basis for its use in gold extraction.
Mercury on the Periodic Table
Mercury occupies Group 12 and Period 6 of the periodic table.
It belongs to the family of metals that includes the following:
Zinc (Zn)
Cadmium (Cd)
Mercury (Hg)
Unlike zinc and cadmium, mercury remains liquid under normal environmental conditions because of the unusually weak bonding between its atoms.
Isotopes of Mercury
Mercury possesses seven stable naturally occurring isotopes:
Hg-196
Hg-198
Hg-199
Hg-200
Hg-201
Hg-202
Hg-204
In addition to these, scientists have identified more than 40 radioactive isotopes that are used mainly in scientific research and nuclear studies.
Natural Sources of Mercury
Mercury occurs naturally in the following:
Volcanic rocks
Igneous rocks
Sedimentary rocks
Ocean sediments
Soil
Underground mineral deposits
Natural processes releasing mercury include the following:
Volcanic eruptions
Forest fires
Weathering of rocks
Geothermal activity
Human activities now account for a large proportion of mercury released into the environment.
Industrial and Commercial Uses of Mercury
Historically, mercury has had numerous industrial applications.
1. Gold Mining
Mercury is widely used to extract gold because it forms an amalgam with gold particles.
The amalgam is heated, causing mercury to evaporate and leaving behind pure gold.
This remains the primary reason mercury is extensively used in artisanal and illegal mining.
2. Electrical Industry
Mercury has been used in the following:
Electrical switches
Thermostats
Relays
Mercury-vapor lamps
Fluorescent bulbs
3. Scientific Instruments
Mercury was traditionally used in the following:
Thermometers
Barometers
Manometers
Laboratory instruments
Many countries have now phased out mercury thermometers because of health concerns.
4. Chemical Manufacturing
Mercury compounds have been used in manufacturing:
Chlorine
Caustic soda
Industrial catalysts
Batteries
Pigments
5. Dentistry
Dental amalgam fillings contain mercury mixed with:
Silver
Tin
Copper
Although still used in some settings, many countries are reducing their use.
6. Pharmaceuticals
Historically, mercury compounds were used in:
Antiseptics
Vaccines (as preservatives in some formulations)
Skin creams
Traditional medicines
Most of these uses have now been discontinued because of toxicity concerns.
7. Currency and Coin Production
Mercury has occasionally been used during the refining and purification of precious metals employed in minting high-value coins. Historically, mercury amalgamation was also used to recover gold and silver for coinage and bullion production. However, mercury is not used to manufacture modern paper money or polymer banknotes, which are produced from cotton-based fibres or specialised polymers using printing technologies rather than mercury.
Mercury and Galamsey in Ghana
Mercury is the chemical most commonly associated with illegal small-scale mining (galamsey) in Ghana.
After excavating gold-bearing soil, miners wash the sediments until tiny gold particles remain.
Liquid mercury is then poured into the concentrate.
Mercury rapidly binds with the gold, forming a gold-mercury amalgam.
The amalgam is heated using charcoal fires or gas burners.
As the amalgam is heated:
Mercury vapor escapes into the atmosphere.
Gold remains behind.
The mercury vapour is inhaled by miners and nearby communities.
Most miners do not use:
Respirators
Protective gloves
Protective clothing
Vapor recovery systems
As a result, they are exposed to dangerously high levels of mercury.
Mercury Pollution of Land
Mercury released during galamsey contaminates surrounding soils.
Effects include:
Death of soil microorganisms
Loss of soil fertility
Reduced agricultural productivity
Destruction of vegetation
Long-term contamination lasting decades
Reduced biodiversity
Because mercury does not biodegrade, contaminated land can remain hazardous for generations.
Mercury Pollution of Rivers
During washing, excess mercury enters nearby rivers and streams.
Examples include:
River Pra
River Offin
River Ankobra
River Birim
River Tano
Inside water bodies, microorganisms convert elemental mercury into methylmercury, an organic form that is even more toxic.
Methylmercury accumulates in:
Fish
Shellfish
Aquatic plants
Humans then ingest methylmercury through contaminated food, leading to bioaccumulation and biomagnification along the food chain.
Mercury Poisoning and the Human Body
Mercury enters the body through:
Inhalation of vapor
Drinking contaminated water
Eating contaminated fish
Skin absorption (to a much lesser extent than inhalation or ingestion)
It easily crosses:
The blood-brain barrier
The placenta
The fetal nervous system
This makes unborn babies particularly vulnerable.
SYSTEMS PATHOLOGY
Mercury affects virtually every organ system. Below are its major effects across the thirteen commonly taught body systems.
1. Nervous System
The nervous system is the principal target. Mercury can cause tremors, numbness, tingling, poor coordination, memory loss, irritability, anxiety, depression, headaches, difficulty concentrating, peripheral neuropathy, and, in severe cases, seizures or coma. Developing foetal and childhood brains are especially susceptible.
2. Cardiovascular System
Exposure has been associated with elevated blood pressure, endothelial dysfunction, oxidative stress, and an increased risk of cardiovascular disease. Very high exposures can contribute to abnormal heart rhythms.
3. Respiratory System
Inhaling mercury vapour may cause coughing, chest tightness, shortness of breath, inflammation of the airways, and chemical pneumonitis. Severe exposure can lead to acute lung injury.
4. Digestive (Gastrointestinal) System
Mercury poisoning may produce nausea, vomiting, abdominal pain, diarrhoea, loss of appetite, mouth ulcers, inflamed gums, and excessive salivation, depending on the form of mercury involved.
5. Urinary (Renal) System
The kidneys accumulate mercury and are highly vulnerable to injury. Toxicity may result in protein leakage into the urine, reduced kidney function, and, in severe cases, kidney failure.
6. Musculoskeletal System
People with mercury toxicity may develop muscle weakness, muscle wasting, tremors, reduced grip strength, joint discomfort, and impaired coordination due to nerve and muscle involvement.
7. Skeletal System
Mercury does not primarily target bone, but long-term exposure may interfere with bone remodelling and normal mineral metabolism. Secondary effects from kidney damage can also adversely affect bone health.
8. Endocrine System
Mercury may disrupt hormone regulation and interfere with thyroid function, adrenal activity, glucose metabolism, and reproductive hormones by affecting endocrine signalling pathways.
9. Reproductive System
Mercury exposure has been linked to reduced fertility, impaired sperm quality, menstrual disturbances, pregnancy complications, miscarriage, and developmental problems in the foetus because mercury crosses the placenta.
10. Integumentary (Skin) System
Exposure may cause skin irritation, rashes, allergic contact dermatitis, and discolouration. Certain mercury-containing skin-lightening creams have caused systemic mercury poisoning after prolonged use.
11. Immune (Lymphatic) System
Mercury can alter immune responses, trigger autoimmune reactions in susceptible individuals, and impair the body’s ability to regulate inflammation.
12. Sensory Organs (Eyes and Ears)
Chronic exposure may impair vision and hearing, including constricted visual fields, reduced visual acuity, tinnitus, and balance problems resulting from nervous system damage.
13. Hematologic (Blood) System
Mercury can increase oxidative stress within blood cells and, in some circumstances, contribute to anaemia or altered immune cell function, although the blood is not its primary target.
The Future Without Mercury
Recognising the dangers of mercury, many countries have adopted the Minamata Convention on Mercury, an international treaty aimed at reducing mercury emissions, restricting trade, and promoting safer alternatives in mining and industry. Ghana is a party to the convention and has committed to reducing mercury use in artisanal and small-scale gold mining through formalisation, education, and cleaner gold recovery technologies.
Conclusion
Mercury is a remarkable element whose unusual physical and chemical properties have made it valuable in science, industry, and mining for thousands of years. Its ability to form amalgams with gold revolutionised gold extraction and continues to make it attractive to artisanal miners. Yet these same properties have also made mercury one of the world’s most dangerous environmental pollutants.
In Ghana, the widespread use of mercury in galamsey has contaminated rivers, degraded farmland, harmed wildlife, and exposed miners and surrounding communities to significant health risks. Once released, mercury can persist in the environment, transform into the even more toxic methylmercury, and move through aquatic food chains until it reaches humans. Its effects are most pronounced on the nervous system but extend to the kidneys, lungs, cardiovascular system, reproductive health, endocrine function, and many other organ systems.
Reducing mercury pollution will require stronger enforcement of mining regulations, wider adoption of mercury-free gold recovery methods, environmental restoration, and sustained public education. Protecting Ghana’s people and ecosystems depends on balancing the economic importance of gold with the imperative to safeguard public health and the environment for future generations.