Inhalation Toxicology

The Globally Harmonized System (GHS) is a United Nations endorsed system for the classification of material hazards, including toxicity. The U.S. Environmental Protection Agency has also established a toxicity classification system. Current OECD testing guidelines (TGs 403, 433, 436) for inhalation toxicity outline the use of animals to determine LC-50 (concentration required to cause death of 50% of test animals).

The EpiAirway in vitro tissue model is used to determine the IC-75 value (concentration required to reduce tissue viability to 75% of vehicle control-treated tissues) of a test chemical.  This value can then be used to predict GHS or EPA classification. The model has been shown to predict GHS Acute Inhalation Toxicity Category 1 and 2 chemicals with 100% sensitivity and 43.1% specificity. It has also predicted EPA Acute Inhalation Toxicity Category I-II chemicals with 100% sensitivity and 50% specificity.


Test ModelEpiAirway
ReplicatesN=3 tissues per test condition
Exposure Time3-hour topical exposure to a predetermined 4-concentration range of test chemical, followed by a 24 hour recovery period
Assay ControlsNegative Control – Sterile DI H2O or Corn oil
Positive Control – 14mg/ml Formaldehyde
EndpointsMTT Tissue Viability Assay
Data DeliveryIC-75 Values
Predicted GHS or EPA Classification

Download the EpiAirway Inhalation Toxicity Test Protocol


(Click images to enlarge)


Jackson, et al., Prevalidation of an Acute Inhalation Toxicity Test Using the EpiAirway in vitro Human Airway Model. Applied In Vitro Toxicology 4(2): 2018

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