Metallic Poisoning

Metallic poisons are inorganic irritant poisons that cause acute as well as chronic toxicity in human beings. These inorganic elements are usually not poisonous in their metallic form but cause toxic effects when combined with other elements to form salts or other compounds.

Metals are naturally occurring solid (usually) substances that are present in the Earth’s crust. Chemically they are the elements that form positively charged ions or cations by losing electrons.

There are a number of sources of metallic poisons, including- Untreated industrial waste disposal in water, the release of poisonous gases containing heavy metals, the use of pesticides in the agriculture industry, contaminated food products, metallic compounds present in certain medicines, mining, etc.

Metallic poisons when comes in contact with the human body, they act as irritants for the skin, gastrointestinal tract, respiratory system, and nervous system. In fact, there are some metals that act as accumulative poisons, which do not get excreted from the body but accumulate in a certain part of the body (hair, nails, etc.) over a period of time and cause chronic poisoning.

Here in this article, we have discussed the commonly encountered metallic poisons in forensic toxicology. Let’s explore each one of them:

Common Metallic Poisons

1. Arsenic

• Common Hindi Names: Somalkar, Sankhyal
• Characteristics: Elemental arsenic is a grey substance, insoluble in water.
• Toxic Compounds: Arsenic oxide (As₂O₃ ), Arsenic disulfide (As₂S₂ ), Arsenic trisulphide (As₂S₃), Copper compounds of Arsenic
• Source: Well water, soil, Shellfishes, etc.
• Target organ or system: Gastrointestinal tract (GIT),
• Clinical manifestations: In acute poisoning– Irritation in GIT, burning sensation nausea, vomiting with bile and blood, diarrhea, and anal irritation. Chronic poisoning– nausea, loss of appetite, diarrhea, inflammation in mucous membranes, bronchial catarrh, skin irritation with vesicular eruption, Mee’s lines (white bands) observed on the nails of hands and toes, tingling and numbness of the hands and legs, etc.
• Treatment: Acute poisoning– Stomach wash, freshly precipitated hydrated ferric oxide as an antidote, dimercaprol to treat systemic effects, and parenteral fluids. Chronic poisoning– Dimercaprol injection, vitamin B complex, sodium thiosulphate, and other symptomatic treatments.
• Fatal Dose and Fatal Period: Acute poisoning– 120-200 mg of arsenic can cause fatality in 2 to 3 hours (narcotic form) or 12 to 48 hours (gastrointestinal form). C
• Autopsy findings: Acute poisoning– Sunken eyeballs, stomach shows red velvet appearance, fatty regenerative appearance in the liver, submucous petechial hemorrhages, etc. Chronic poisoning- Kidney damage, liver damage, bone-marrow depression, etc.
• Medicolegal aspect: Arsenic is most prevalent in homicidal and accidental poisoning. It is also used as cattle poison.

2. Copper

• Common Hindi Names: Tamba
• Characteristics: Metallic copper is not poisonous but its salts are toxic. The salts show attractively colored crystals
• Toxic Compounds: Copper sulfate (blue vitriol), Copper subacetate (Verdigris)
• Source: Food cooked in a contaminated copper utensil, contaminated water, pesticides, etc.
• Target Organ or System: Gastrointestinal tract
• Clinical Manifestations: Acute poisoning– Burning sensation in the stomach with pain, vomiting, diarrhea, uremia, etc. Chronic poisoning– Metallic taste in the mouth, green lines in the gums at the base of teeth, nausea, vomiting, anemia, etc.
• Treatment: Acute poisoning– Stomach wash with 1% solution of potassium ferrocyanide, albumins, penicillamine, and EDTA. Chronic poisoning– Symptomatic treatment.
• Fatal Dose and Fatal Period: 30 gm of copper sulfate or subacetate may cause fatality in 12-24 hours or 3-5 days.
• Autopsy Findings: Acute poisoning– the yellowish appearance of skin similar to jaundice, greenish-blue froth around the mouth, fatty liver, congested mucosal membranes, etc. Chronic poisoning– hemochromatosis (bronzed diabetes), parenchymatous injuries to the heart, liver, and kidney.
• Medicolegal Aspect: Accidental and suicidal poisoning are common. Homicidal poisoning is not encountered as copper salts are easily recognized by their color.

3. Mercury

• Common Hindi Names: Para
• Characteristics: It is a lustrous liquid that exists in its metallic form. Its salts are also present in things like mercury switches, cinnabar, or vermilion (all indoor). Metallic mercury is not poisonous but its salts and vapors are highly toxic.
• Toxic Compounds: Mercuric sulfide, mercuric chloride, mercurous chloride,
• Source: Thermometers, barometers, mercury switches, vermilion, bleaching creams, pesticides, etc.
• Target Organ or System: Gastrointestinal tract
• Clinical Manifestations: Acute poisoning– constriction in the throat, metallic taste, nausea, mouth, and tongue turns grayish in appearance, sighing respiration, convulsions, etc. Chronic poisoning– excessive salivation, painful swollen gums, loosening of teeth, nephritis, Mercuria lentis (discoloration of the eye), hatter’s shake, erethism, etc.
• Treatment: Acute poisoning– 5% solution of sodium formaldehyde sulphoxylate for stomach wash, egg albumin for gastric lavage or emesis, activated charcoal, etc.
• Fatal Dose and Fatal Period: 1-2 gm sublimate of mercury may cause death in 3-5 days.
• Autopsy Findings: Acute poisoning– White coloration of the tongue, inflammation in GIT, nephritis, subendocardial hemorrhages in the heart, etc. Chronic poisoning– Necrosis in the large intestine, kidney damage, fatty degeneration of the heart and liver.
• Medicolegal Aspect: Accidental poisoning is the most common. Soluble salts of mercury used as vaginal douches, antiseptic tablets, etc can cause poisoning.

4. Lead

• Common Hindi Names: Shisha
• Characteristics: It is the most toxic metal for children, reducing their IQ, slow growth, behavior disorders, etc.
• Toxic Compounds: Lead acetate, lead oxide, lead carbonate, lead tetraoxide (sindoor)
• Source: Paints, lead smelting industry, battery manufacturing industries, etc.
• Target Organ or System: Toxic for GIT, blood cells, nervous tissues, kidneys, and reproductive system.
• Clinical Manifestations: Acute poisoning– Dry throat, nausea, vomiting, colic pains in the stomach, headache, drowsiness, paralysis, lead encephalopathy, etc. Chronic poisoning– facial pallor, paralysis, anemia with punctate basophilia, a characteristic line at the top of teeth with swollen gums, renovascular and reproductive manifestations, etc.
• Treatment: Acute poisoning-1% solution of magnesium or sodium sulfate for stomach wash, morphine to treat colic pain, EDTA as an antidote, etc. Chronic poisoning– EDTA and penicillamine.
• Fatal Dose and Fatal Period: 4 gms of lead carbonate or 20 gms of lead acetate can cause death in 2-3 days.
• Autopsy Findings: Congested gastric mucosa, appearance similar to gastroenteritis, black feces in the large intestine.
• Medicolegal Aspect: Usually chronic poisoning is observed. Accidental poisoning is prevalent and also used as cattle poison.

5. Zinc

• Common Hindi Names: Jasta
• Characteristics: Zinc is a brittle hard metal used in many alloys, supplements, medicines, etc.
• Toxic Compounds: Zinc sulphate (white vitriol), zinc sulphide
• Source: Rodenticides, metallurgic processes.
• Target Organ or System: Gastro-Intestinal Tract
• Clinical Manifestations: Gastrointestinal irritation, abdominal pain, vomiting, diarrhea
• Treatment: Sodium carbonate and demulcents.
• Fatal Dose and Fatal Period: 15-90 gms of zinc sulphate can cause death within 2 hours to 5 days
• Autopsy Findings: Similar to irritant acids
• Medicolegal Aspect: Accidental and suicidal poisoning is common.

6. Thallium

• Characteristics: Thallium is soft and pliable metal, having tin-white color but tarnishes the surface on exposure to air due to the formation of the black thallous oxide.
• Toxic Compounds: Thallium sulfate, Thallium acetate, Thallium iodide
• Source: Dye industry, jewelry intimation industry, pesticides, etc.
• Target Organ or System: GIT, nervous system, and excretory system.
• Clinical Manifestations: Pain in the abdomen, features similar to gastroenteritis, hematemesis, hematochezia, Headache, Confusion, Disorientation, Paraesthesia, and hallucinations.
• Treatment: Gastric lavage with ferric Ferro cyanide (Prussian blue), Prussian blue binds thallium in the intestine and enhances its fecal excretion, hemodialysis, forced diuresis, and supportive measures.
• Fatal Dose and Fatal Period: 12 mg/kg body weight can cause death in 24 to 30 hours
• Autopsy Findings: Alopecia, stomatitis, fatty degeneration of the liver and heart, tubular necrosis, pulmonary edema, and cerebral edema.
• Medicolegal Aspect: Accidental and homicidal poisoning is common.

Conclusion

Metals are naturally occurring inorganic substances in the Earth’s crust. Though metals form an important part of the utility of human beings, some of them are highly toxic to human beings. Metallic poisons are inorganic irritants that usually cause gastrointestinal irritations and neurotoxicity. Some of the commonly encountered metallic poisons in accidental and homicidal poisoning have been discussed in this article.

Also Have a Look at:

• Cadmium Poisoning: Causes, Signs & Symptoms, and Case Studies
• Organophosphorus Poisoning: Action, Symptoms, Causes and Uses
• Ethanol: Classification, Mechanism and Forensic Examination

Frequently Asked Questions

1. How Much Mercury Will Cause Poisoning?

Mercury is a naturally occurring element that when exposed to too much amount can cause serious health concerns known as Mercury Poisoning. Mercury levels in the blood of amounts more than 100 ng/ml are associated with clear signs of Poisoning in humans.

2. What is The Slowest Acting Poison?

Thallium is the slowest-acting poison that takes weeks to kill its victims unless they are treated. Due to its colorless, odorless, and tasteless characteristics, it is also known as a prisoner’s poison. Its painful, slow-acting, and wide-ranging symptoms make it one of the most dangerous metallic poisons.

3. Which Chemical is The King of Poison?

Arsenic is known as the king of poison. John Parascandola examined it and due to its surprising history named it as poison’s king. Arsenic is called king due to its history when the kings used it to kill the members of the ruling class during the middle age due to its potency and non-traceable characteristic.