Acute toxicity refers to the adverse effects from either (1) exposure of a single dose of substance, (2) multiple exposures within 24 hours, or (3) inhalation exposure of 4 hours. Chemicals are categorized into one of five toxicity categories that are expressed in the numerical criteria as either LD50 (oral and dermal) or LC50 (inhalation).
So what is the difference between LD50 and LC50? LD50 is the “Lethal Dose” of material that will cause death in 50% of the tested animals within 24 hours of exposure, whereas LC50 is the “Lethal Concentration” of the chemical in air that will cause death in 50% of the tested animals in the exposure duration of 4 hours.
Substances are assigned to one of five toxicity categories, with Category 1 as the most toxic and Category 5 as the least toxic. The table below will give you a better understanding of the Acute Toxicity criteria:
Since Category 1 is the highest toxicity category, you can expect the cut-off value to be the lowest of the five categories (e.g. 5mg/kg by the oral route and 50 mg/kg by the dermal route). Unlike Category 1, substances in Category 5 have an oral and dermal LD50 in the range of 2,000 – 5,000 mg/kg, which is significantly greater than the cut-off values in Categories 1, 2, and 3, and thus less toxic.
Besides determining the toxicity and cut-off points, acute toxicity information also plays a roll in determining the proper symbols, signal words, hazard statements, and packing groups to apply. Please refer to the table below:
So, although toxicity categories tell us a lot about the substances, the information also helps determine which symbols, signal words, hazard statements, and packing groups to include in the GHS compliant SDS.
