Introduction
● Mercury also known as Quicksilver and Liquid silver.
● Mercury in elemental or metallic form is a liquid metal, silvery luster and volatile at room temperature.
● Metallic mercury is not considered to be poisonous but under certain conditions it may undergo some chemical changes in the body and may acts as poison.
● The vapours of mercury are poisonous.
● Soluble salts of mercury such as nitrate, sulphate or mercury chloride or oxide are highly poisonous.
● Mercuric salts include mercuric chloride (corrosive sublimate) which is a white crystalline corrosive powder. It is also known as corrosive sublimate.
● Mercuric oxide is a red crystalline powder that turns yellow when treated with caustic soda or potash. It is insoluble in water.
● Mercury sulfide (vermilion or sindoor) which is a red crystalline powder.
● Mercuric Sulphate is white in colour and acts as a corrosive.
● Mercurous salt is mercurous chloride (calomel) which is fibrous and heavy. It is sold in market as vas Kapoor.
● Mercury exists in three forms that include-
● Elemental mercury – Hgo – vapours are toxic.
● Inorganic mercury and Organic mercury.
● Inorganic salts are of two types that includes- Mercuric (bivalent Hg++) which is more poisonous and other is Mercurous (monovalent Hg+ ) which are less poisonous.
● Organic compounds of mercury are more toxic than inorganic compounds and are – Ethyl Mercury, Methyl Mercury and Mercurochrome. The most toxic compound of mercury is methyl mercury.
Uses
Mercury is used in industry for making-
● Barometer, thermometer, etc.
● Ceramics
● Dry cell batteries
● Electrical appliances (mercury switches.
● Explosives and fireworks
● Fluorescent and mercury vapour lamps.
Mercury is used for medicine and dentistry in following ways-
● Antiseptic and disinfectant.
● Dental amalgam
● Diuretic
● Purgative
● It is also used in gastroenterology equipment.
● It is also used as fingerprint powder for developing latent fingerprint.
It is also used in/as –
● Electroplating
● Embalming
● Fabric softener Fungicide
● Felt hats
● Gold and silver extraction
● Grain preservative
● Paints
● Pesticides
● Taxidermy
Fatal Dose
● The amount of ingested mercury that would be fatal to a man is 100 grams.
● For Mercuric chloride: 0.5 to 1 gm/70 kg
● For Mercurous chloride : 1.5 to 2 gm/70 kg
● For Mercuric cyanide – 0.6 to 1.3 gm
● Mercuric chloride – 1 gm
● For Mercuric nitrate – 4 gm
Fatal Period
● 3 to 5 days
● Death may takes place within a few hours of ingestion of the poison.
Absorption, Metabolism and Excretion
● After inhalation, Elemental mercury is readily absorbed through alveolar membrane and enters the blood.
● Mercury slats are absorbed through skin, GIT mucosa, vaginal mucosa and bladder. Organic compounds can pass placental barrier and cause fetal toxicity.
● In blood, mercury is converted into mercuric ions and causes renal tubular damage during excretion.
● In CNS, mercury acts on cerebellum, temporal lobe, basal ganglia and corpus callosum.
● Both organic and inorganic mercury can be absorbed through intact skin.
● Mercury gets deposited in liver, kidneys, spleen and bone.
● Mercury is excreted in urine, feces and bile with eneterohepatic circulation.
Mode of Action
Mercury compounds act by inactivating sulphydril enzymes causing interference with cellular metabolism.
Sign and Symptoms
A. Poisoning with elemental mercury and inorganic salts-
A. Acute poisoning
Inhalation –
- Breathlessness
- Cough
- Fever, chills (metal fume fever)
- Headache
- Blurring of vision
- Non-cardiogenic pulmonary edema
- Convulsions
- Ataxia
- Delirium.
Injection
● Subcutaneous or intramuscular injection of mercury causes abscess formation with ulceration.
● Intravenous administration results in thrombophlebitis, granuloma formation and pulmonary embolism.
● Intra-arterial administration results in peripheral embolism with ischemia and gangrene.
Ingestion
- Metallic taste
- Abdominal pain
- Vomiting
- Shock
- Corrosion of mouth and tongue.
- Hematemesis
- Renal failure
- Pulmonary edema
- Urine – pinkish in colour
- Glossitis and ulcerative gingivitis
- Loosening of teeth
- Necrosis of jaw
- Membranous colitis
Management
● Airway assessment and stabilisation.
● Antero-posterior and lateral chest radiographs that visualise the neck, chest, and abdomen.
● Patients with batteries in the airway or lower respiratory tract require emergency removal via bronchoscopy.
B. Poisoning by organic compounds shows-
- Dysarthria
- Ataxia
- Paraesthesia
- Neuropathy
- Diminished visual and auditory activity.
- Mental deterioration.
- Chorea
- Minimata disease
C. Chronic poisoning
● Also called as hydrargyrism, mercurialism.
● Excessive salivation (Ptyalism, Sialorrhea).
● Metallic taste
● Anorexia
● Insomnia
● Headache
● Gingivitis
● Halitosis
● Blue line on gums.
● Lassitude
● Visual blurring
● Concentric constriction of visual field (tunnel vision).
● Mercurialentis – opacities of the anterior capsule of the lens of eye due to deposition of mercury
● Ataxia – reeling gait.
● Tremors – classical manifestation of chronic mercury poisoning and is referred as “Danbury tremor”. The tremors are coarse, intentional type, interspersed with jerky movements, initially involving hands. Later it involves lip, tongue, arms and legs. The advanced condition of tremors is called as “Hatter’s shakes” (because the condition was first described among felt hat workers). In Hatter’s shakes, the tremor becomes so severe that daily activities of person are grossly impaired such as shaving, writing, holding cup etc. As the disease progresses, the most severe form of tremor are called as “Concussio mercurialis” which means no activity is possible.
● Mercurial erethism – a classical manifestation of chronic mercury poisoning characterized by cluster of psychiatric symptoms including disturbance in personality, abnormal shyness, timidity, loss of self confidence, insomnia, excitability, progressing later into delirium with hallucinations (Mad as hatter).
● Colitis
● Melanosis coli
● Mercury dermatitis from mercuric sulphide (cinnabar) as red areas of tattoo has been reported. Also contact dermatitis as occupational hazard had been noted.
● Dementia
● Renal failure
● Acrodynia (Pink disease) seen mostly in children and caused by chronic mercury exposure. It causes anorexia, insomnia, profuse sweating, skin rash, redness, vesication and desquamation (peeling) of palm, finger, sole and photophobia.
● The hands and feet become puffy, pinkish, painful, paraesthetic, perspiring and peeling (remember 6 P’s).
● Shedding of teeth and ulceration of gums.
Treatment
A. Acute Poisoning
Metallic mercury and inorganic compounds
Inhalation:
- Supportive measures.
- Chelation
Ingestion:
● In elemental mercury ingestion, take x-ray and repeat it to study the progression. If mercury gets lodged in the appendix, perform appendectomy.
● Administer laxatives.
● Demulcents for corrosive compounds such as mercuric chloride.
● Stomach wash: It may be advisable to add egg white or 5% albumin or just plain milk to the lavage fluid to bind the mercury.
● Chelation.
Injection:
● If there is abscess formation, perform repeated incisions to remove the mercury. If the globules are very minute and widely distributed in the intercellular spaces, excise the affected tissue.
● Monitor the CNS and renal functions for evidence of toxicity.
● Mercuric salts are relatively well adsorbed by activated charcoal.
● Chelation.
B. For Organic mercury:
● Supportive measures.
● Chelation is not very effective.
● In severe manifestations with acute renal failure resulting from any type of exposure, the following may be tried: haemodialysis, haemofiltration, or plasma exchange.
● Haemoperfusion is said to be ineffective.
C. Chronic Poisoning:
● Chelation therapy- BAL (British Anti Lewisite) -100 mg by deep IM, every 4 hours for 48 hours, followed by 100 mg every 8 hours for 8 to 10 days.
● DMPS ( 2,3 DiMercapto Propane-1-Sulfonate) – 5 mg/kg IV, or 6 infusions of 250 mg/day, followed by 100 mg orally twice a day for 24 days.
● DMSA (Meso 2,3 DiMercapto Succinic Acid, or Succimer) – 30 mg/kg/day orally for 5 days, followed by 20 mg/day for 14 days.
● D-Penicillamine – 250 mg qid, for adults, (20 mg/kg/day) for 5 to 10 days.
● Supportive measures
Detection and Forensic Examination
● X-ray.
● In case of Blood mercury level, Flameless atomic absorption spectrometry is best for examination. Normal level is less than 3 mcg/100 ml. If blood mercury concentrations of 5 mcg/100 ml or greater than this then Symptoms of toxicity may occur.
● Hair analysis: Hair analysis is done by cold vapour atomic absorption spectrometry.
● Urine mercury level: Urinary mercury is the best biological marker for chronic elemental or inorganic mercury exposure. Signs and symptoms of toxicity may occur at urinary mercury concentrations of 20 to 100 mcg/100 ml.
Post Mortem Findings
● Emaciated body
● Mouth, throat, stomach appear grayish with softening and corrosion with hemorrhagic areas.
● Colitis.
● Fatty degeneration in Liver and heart.
● Kidneys become pale, swollen with edema of renal cortex with necrosis of renal tubules.
Medico Legal Aspects
● Poisoning occur due to accidental consumption of mercury as-
● Folk medicine/indigenous medicine.
● Toothpaste
● Industrial exposure.
● Dental amalgam.
● Dry cell battery
● Homicide and suicide is rare but has been reported.
● Use to procure criminal abortion.
● Food poisoning (especially involving fish) through mercury compounds can give rise to manifestations skin to the Minimata disease.
References
- Dr. K.S. Narayan Reddy. The essential of forensic medicine and toxicology.34th edition.
- VV Pillay. Modern medical toxicology.4th edition.
- R.K.Sharma. Concise textbook of forensic medicine and toxicology. 3rd edition.
