With the investigation of the murder case of Alexander Litvinenko, poisons have been in the news. We have read articles that list the most poisonous substances, which are classified according to their toxicity level as measured by something called LD50.
LD50 is the amount of a toxic agent that is enough to kill 50 percent of a population of animals usually within a certain time. Though this seems a cruel method, it is the best way to analyze how poisonous a given substance is, but overall toxicity is more complex than that.
Here is a list of toxins which shows higher toxicity than their LD50 values might indicate :
1. Botulinum toxins
Some of them are popularly used for reducing wrinkles and rejuvenating the aging face. The LD50 values for these seven proteins measure about 5 mg/kg.
Serious problems can occur if the botulinum toxin spreads to other areas in the body other than where it was injected.
2. Snake Toxins
Toxicity of snake venom is sometimes used to determine the extent of their danger to humans but this is inappropriate. Some snakes are regarded as the world’s most venomous snake based on LD50. Its efficiency of venom delivery, its venom yield and the change in its behavior after attacking humans are the factors considered to detect the danger of any given snake. Snakes show LD50s below 1mg/kg.
Arsenic is found in natural form on earth in small concentrations. It is present in soil, minerals and are carried to air, water and land via wind-blown dust and water run-off. Elemental arsenic shows an LD50 of around 13mg/kg. Organic arsenic is harmless. However, exposure to inorganic arsenic may lead to serious ailments such as stomach upset, chances of cancer, skin changes and lung disorders.
Polonium-210 was a media attraction when it was used to kill KGB agent-turned-Kremlin critic Alexander Ltivinenko in London in 2006. Polonium-210 is a radioactive element that is found in small concentrations in the earth’s crust. If ingested, it is lethal in extremely small doses. Less than 1 gram of silver powder is enough to kill. Once enters the blood stream, polonium’s potent effects are impossible to stop. A poisoned victim may suffer multiple organ failure as alpha radiation particles damage the liver, kidneys and bone marrow from within.
People may be exposed to mercury in any of its forms- elemental and inorganic. These forms of mercury vary in their extent of toxicity and in their effects on the nervous, digestive and immune systems, and on lungs, kidneys, skin and eyes. The LD50 values of mercury compounds are between 1mg/kg and 100 mg/kg.