Thallium Poisoning - Causes, Symptoms, Diagnosis, Treatment, and Prevention

What Is Thallium?

Thallium is a tasteless, odorless heavy bluish-white metal usually obtained from smelting other metals as a by-product. It is found with bromine, iodine, fluorine, and chlorine, and its most natural form is present as thallic and thallic compounds. Thallium is used in making switches, electronic devices, and in some medical procedures. It was also used in making rat and ant poison sometimes back. However, thallium can cause severe chronic toxicity in the body as it can get readily absorbed through skin and inhalation.

What Are the Uses of Thallium Metal?

Uses of thallium metal include:

• Thallium in detecting gamma radiations.

• It is used in the manufacturing of optical lasers and other equipment.

• Thallium is used for glass manufacturing.

• Thallium poison is still used for killing rats and ants.

• Mercury lamps and radioisotopes are also made up of thallium.

• Thallium acts as a catalyst in various organic reactions.

• It is also used in photoelectric cells in electronic industries.

How Is Thallium Distributed in the Environment?

Thallium is present in the environment in various forms, but its concentration is deficient. But due to human activities like industrial processes, smelting or burning of coal, the concentration of thallium in the environment has increased, and the traces can be seen in the following forms:

• Sediments and soil.

• Food chain and plants.

• Terrestrial and aquatic animals.

• Thallium in peasant water resources.

How Can We Get Thallium Exposure?

Thallium poisoning can occur through skin absorption or direct inhalation; even a small amount of thallium exposure can cause death. Although a lethal or safe dose for humans is considered to be 50 to 20 mg/kg, prolonged exposure can cause severe chronic poisoning and severe toxic effects. Sources of exposure include:

• Shellfish and fish that we eat can be contaminated with thallium toxicants.

• Substance abusers of cocaine or heroin can get thallium poisoning, and people who use some herbal products.

• Rat poison contains thallium; therefore, accidental or intentional (suicidal) ingestion can cause thallium poisoning.

• Workers in fuel-smelting plants and people cleaning ducts for maintenance can ingest thallium particles and get exposed.

• People living near garbage dumps and hazardous waste sites can be exposed to thallium through contaminated air and soil.

• Cigarette smoking.

What Are the Signs and Symptoms of Thallium Poisoning?

• During the initial hours of acute thallium exposure, nausea, vomiting, and abdominal pain occur, and stool with blood can sometimes be seen.

• The person may also have symptoms like hallucinations, anxiety, confusion, psychosis, and delirium.

• Depression, aggression, changes in personality, and agitated behavior can also be seen.

• Color vision (Diplopia) defects also occur, and the image is sometimes reduced.

• Respiratory disorders like pleuritic chest pain and shortening of breath are also seen.

• Hair loss, disturbed vision, lack of appetite, depression, headache, and tiredness is seen in patients with chronic toxicity.

How Is the Examination for Thallium Poisoning in the Body Done?

• Abdominal Examination - Initial assessment shows hyperactive bowel, tenderness

• Neurological Examination - The symptoms usually develop within two to four days of exposure. The examination includes assessing the neurological system (visual field defects and cranial nerves). Neuropathy is also observed in the periphery with paraesthesia and tenderness on the foot and legs. In addition, facial nerve palsy, drooping eyelids, loss of eyebrows, keratitis, and loss of eyebrows can be seen.

• Dermatological Examination - These symptoms develop over two to three weeks of thallium exposure causing skin rashes and hair loss due to hair follicle atrophy affecting eyebrows, scalp, and eyelashes. After a few months of thallium poisoning, white lines (Mees’ lines) on the nails can also be seen, which is common in arsenic poisoning. Other symptoms include dark pigmentation on the scalp, stomatitis, redness of the tongue tip, palmar erythema, glossitis, eczematous lesion, and hair discoloration.

What Are the Diagnostic Approaches for Investigating Thallium Toxicity?

• Assay For Urine - Thallium concentration is a helpful and accurate method to check thallium poisoning in the body. Urine appears green in color.

• Blood chemistry is also investigated for anemia and renal functioning.

• Heavy metal ingestion can be seen through abdominal X-rays showing opacity.

• ECG (electrocardiogram) is also done to check for cardiac arrhythmia.

• An electrophysiology test can check abnormalities in the nerves of the feet.

What Is the Differential Diagnosis for Thallium Toxicity?

• Mercury and arsenic toxicity.

• Organophosphate poisoning.

• Thiamine deficiency.

• Diabetic polyneuritis.

• Vasculitis.

• Isoniazid poisoning.

What Are the Ways to Treat Thallium Poisoning?

Several ways can help treat thallium poisoning, including:

• Initial stabilization is done by accessing the cardiovascular system, airway passage, and breathing.

• Contaminated clothes are also removed to eliminate the source of exposure.

• Exposure within 30 minutes can be treated with gastric decontamination with the help of Prussian blue and activated charcoal treatment.

• Prussian blue treatment must be continued for up to 24 hours until urine thallium concentration returns to average values.

• Haemodialysis and hemoperfusion can also help treat thallium poisoning, which is helpful in case of delayed diagnosis of the exposure.

• Skin exposure or contact must be washed immediately with water and soap.

• Urine and blood test should be done a week thrice to monitor thallium concentration in the body with regular follow-ups.

• A person showing significant symptoms of thallium poisoning must be admitted to the hospital as soon as possible.

What Is the Prognosis for Thallium Poisoning?

• A person may have impaired visual ability and neurological disorders.

• Psychosis, depression, and dementia may occur due to severe toxicity.

• Fetal abnormalities can also occur due to exposure during pregnancy.

• Long-term peripheral neuropathy and other neurological disorders can be seen if treatment is not provided on time during exposure incidents.

Conclusion

Thallium poisoning or exposure is more prevalent in developing countries due to a lack of safe work practices, and people still use rat poisons containing thallium. The primary human life threats are contaminated food, soil, occupational exposures, and a toxic environment. Thallium is a highly poisonous substance that causes degenerative changes in the body and adverse health conditions, but neurological disorders are more severe with thallium poisoning. Therefore, preventive measures must be taken to minimize the effect and everyday exposure to thallium substances.