OECD 433: Acute inhalation study (fixed concentration)
The OECD 433 procedure assesses the impact of acute inhalation, allowing GHS classification of toxicity of a chemical. It tests moderate concentrations with an endpoint of signs of evident toxicity rather than mortality.
QSAR, read-across information on similar substances, and other factors are used to determine the starting concentration and confirm whether the test is appropriate.
A sighting study is often done with one gender each to determine the concentration and identify whether one sex is more sensitive to the chemical. Clinical observations for each model are made regularly over 14 days, in particular monitoring for signs of evident toxicity (tremors, hypoactivity, irregular respiration or weight loss >10%). If no adverse signs are observed, the protocol is repeated with additional models at higher concentrations until one or more signs occur in a model, ending the observation.
Concentrations, observations and euthanasias are reported.