This method provides information on health hazard likely to arise from short-term
exposure to a test article (gas, vapour or aerosol/particulate test article) by inhalation.
The revised Test Guideline describes two studies: a traditional LC50 protocol and
a Concentration x Time (C x t) protocol. It can be used to estimate a median lethal
concentration (LC50), non-lethal threshold concentration (LC01) and slope, and to
identify possible sex susceptibility. This Test Guideline enables a test article quantitative
risk assessment and classification according to the Globally Harmonized System for
the Classification and Labelling of Chemicals. In the traditional LC50 protocol, animals
are exposed to one limit concentration or to three concentrations, at least, for a
predetermined duration, generally of 4 hours. Usually 10 animals should be used for
each concentration. In the C x T protocol, animals are exposed to one limit concentration
or a series of concentrations over multiple time durations. Usually 2 animals per
C x t interval are used. Animals (the preferred species is the rat) should be observed
for at least 14 days. The study includes measurements (including weighing), daily
and detailed observations, as well as gross necropsy.