Paracelsus, knows as father of toxicology wrote, “All things are poison, and nothing is without poison; only the dose permits something not to be poisonous.”
Poisoning can be caused by Chemical toxicants, Biological toxicants and Physical toxicants. Poisoning can effect the entire organism, specific organs or cells. The routes through which poison enter the body are oral, dermal or by inhalation.
As said by Paracelsus a specific dosage or above is required to cause poisoning. This dosage is measured in LD50 value for dermal and oral toxicity and LC50 value for inhalation toxicity.
Let’s understand the basic concepts of LD50 and LC50 values.
LD50 = Lethal Dosage. Dosage required to kill 50 percent of the test animals, dosage, measured in mg/kg body weight.
LC50 = Lethal concentration. Dosage required to kill 50 percent of test animals, dosage measured in mg/per liter of volume of air.
The word “toxic” has the same meaning as “poisonous” in IMDG Code. Toxic substances, liquids and solids, are classified under Class 6.1 and toxic gases under Class 2.3.
Definitions and properties according to IMDG Code
LD50 (median lethal dose) for acute oral toxicity is the statistically derived single dose of a substance that can be expected to cause death within 14 days in 50 per cent of young adult albino rats when administered by the oral route. The LD50 value is expressed in terms of mass of test substance per mass of test animal (mg/kg).
LD50 for acute dermal toxicity is that dose of the substance which, administered by continuous contact for 24 hours with the bare skin of the albino rabbit, is most likely to cause death within 14 days in one half of the animals tested. The number of animals tested shall be sufficient to give a statistically significant result and be in conformity with good pharmacological practices. The result is expressed in milligrams per kilogram body mass.
LC50 for acute toxicity on inhalation is that concentration of vapour, mist or dust which, administered by continuous inhalation to both male and female young adult albino rats for one hour, is most likely to cause death within 14 days in one half of the animals tested. A solid substance shall be tested if at least 10% (by mass) of its total mass is likely to be dust in the respirable range, such as the aerodynamic diameter of that particle fraction is 10 microns or less. A liquid substance shall be tested if a mist is likely to be generated in a leakage of the transport containment. For both solid and liquid substances, more than 90% (by mass) of a specimen prepared for inhalation toxicity testing shall be in the respirable range as defined above. The result is expressed in milligrams per litre of air for dusts and mists or in millilitres per cubic metre of air (parts per million) for vapours.
Class 6.1, Toxic substances for packing purposes been assigned with packing groups according to the degree of their toxic hazards in transport.
Packing group I: substances and preparations presenting a high toxicity risk;
Packing group II: substances and preparations presenting a medium toxicity risk;
Packing group III: substances and preparations presenting a low toxicity risk.