The toxicity of materials is assessed by their Lethal Dose 50% (LD50) or Lethal Concentration 50% (LC50). LD50 is defined as the dose at which 50 percent of the exposed test animals (generally, rats or mice) died, usually within 1-2 hours after being dosed by ingestion, injection or skin exposure. LC50 is defined as the concentration in air at which 50 percent of the test animals (generally rats or mice) died, usually within a specified time after being exposed by inhalation.

A substance is considered extremely toxic if it has an LD50 of less than 5 mgs/kg of animal body weight. To humans, this is the equivalent of a taste (less than 7 drops). It is Highly toxic if it has an LD50 of between 5 and 50 mg/kg of animal body weight to a human, this would be about a teaspoon.

Work Practices for Handling Carcinogens will vary, depending on whether it is a solid, a liquid, or a gas.