How does Thallium get into your water?
Thallium is a soft, malleable gray metal that was previously widely used in rat poisons and insecticides and commonly sold over the counter. Thallium itself and compounds containing the element are highly toxic. It is particularly dangerous because compounds containing Thallium are colorless, odorless, and tasteless.
Because of this high toxicity, the World Health Organization (WHO) recommends against the use of Thallium in rodent and insect poisons. However, poisons containing Thallium are still in use in some parts of the world. Small amounts of Thallium are normally found in the earth's crust and atmosphere. It is also present in small amounts in cigarette smoke. An average of 23 ppb of Thallium in surface water and 11 ppb in groundwater have been found to be hazardous.
Since Thallium compounds mix easily with water, you can be exposed. But only if you live near a chemical waste site where Thallium emissions have contaminated the local water supplies.
Thallium has many industrial uses, and certain isotopes of Thallium are used in the medical imaging industry.
The Health Implications of Thallium
Thallium can be absorbed by our skin. It can also be ingested or inhaled.
If a significant amount (significant poisoning is usually defined as ingesting over 1 gram of Thallium, or over 8 milligrams per kilogram of body weight) of Thallium enters the body, symptoms of Thallium poisoning start to develop.
Why does Thallium kill you?
Tl+ behaves chemically in a very similar manner to Na+ and K+ ions, and when present in the body it can replace these ions within cells.
Since these ions are essential for nerve functions, it is therefore no surprise that victims of Thallium poisoning often suffer neurological symptoms and side effects.
The presence of Thallium impairs the ability of your cells to produce nerve impulses. Which often end up killing untreated patients through either respiratory paralysis or circulatory disruption.
Thallium takes very little to become fatal.
The lethal dose of Thallium sulfate for an adult is thought to range from 500 mg to 1 g.
Is there an antidote?
Yes, the antidote, rather surprisingly, is to ingest a cyanide-based molecule called Prussian Blue Fe7(CN)18, three times a day for 2 weeks.
Prussian Blue is more commonly known as a pigment with a dark blue colour and was the first modern synthetic pigment.
It is insoluble in water, but can still be used in paint as it has a very fine colloidal dispersion.
So has it been used for murder?
Of course, but we’ll come on to that later.
From the 1700s to the 1900s it was actually used as a rather poor medical treatment for ringworm – a fungal infection of the skin which results in an itchy, round rash.
Ringworm is transmitted by physical contact with an infected individual and is said to affect 20% of the population at any given time.
Thallium sulfate often proved too toxic for the patient, but at least it did kill the ringworm before it killed the patient!
In the 1920s Thallium sulfate found widespread use as a pesticide. But this was not without its controversies; in the South American country of Guyana, more than 40 people died from its misuse.
The reason was that the pesticide, which was left lying around in an attempt to kill rats, where it was absorbed by plants, and then entered the food chain, increasing in concentration ‘bio-accumulation’, until it was eventually ingested by humans via the consumption of meat and vegetables.
It was also found that Thallium sulfate had the unfortunate side effect of inhibiting the growth of plants by stopping germination, which reduced crop yields.
And in Israel its use as a rodenticide is blamed for wiping out the brown fish owl – a local bird of prey that used to eat fish.
The Thallium compound had seeped into the rivers and lakes and poisoned the fish, which were then eaten by the owls who all died.
So I suppose they stopped using it as a pesticide…?
Not immediately, despite Thallium sulfate’s known toxicity its use was not discontinued in Guyana until 1987.
Another problem is that the only way to identify patients with thallium poisoning was through blood and urine testing, and this was done only in Guyana’s Hospital in its capital Georgetown.
Of the 2,400 people who had either their blood or urine tested, a shocking 77% tested positive for Thallium poisoning, showing just how widespread the Thallium poisoning had affected the local population and environment.
What are the symptoms of Thallium poisoning?
Thallium sulfate poisoning, much like the deceptive appearance of the compound itself, has initial symptoms typical of a winter virus. This generally means that poisoning is mistaken for a common cold or flu.
The symptoms are generally seen in the hours immediately after exposure and can include severe stomach aches as well as diarrhea.
2-5 days after exposure to Thallium the body’s response takes a more neurological turn with numbness and tingling, felt especially on the palms and soles of the feet.
This is followed in the weeks after exposure with the growth of a dark pigment at the root of hair leading to baldness.
There is also an increase in neurological symptoms such as comas and blindness.
These symptoms can sometimes also appear in the days immediately after exposure dependent on the quantity ingested.
The compound also affects the heart. Initially increasing heart rate and later possibly causing circulatory disturbances that can lead to death.
The time that the compound will take to kill you depends on many factors and ranges from as little as 6 days or up to 8 weeks.
Thallium poisoning can be treated.
Effective treatment to prevent absorption of Thallium is available if therapy is begun within six hours following ingestion.The antidote against Thallium (known as Potassium Ferrihexacyanoferrate, or Prussian blue or Berlin blue) works by sequestering Thallium molecules and preventing their absorption by the intestine.
Other treatments that may be successful for victims of Thallium poisoning include dialysis and medications to increase the kidneys' excretion of Thallium.
