Toluene diisocyanate (TDI) airway effects and dose-responses in different animal models

Area of Science:

• Toxicology
• Occupational Health
• Inhalation Exposure Science

Background:

• Toluene diisocyanate (TDI) is a common industrial chemical with known respiratory effects.
• Numerous studies have investigated TDI's impact on respiratory systems in various animal models.
• Existing protocols for respiratory sensitization testing lack broad consensus, leading to diverse methodologies.

Purpose of the Study:

• To review and synthesize data from inhalation studies on TDI focusing on respiratory irritation and sensitization.
• To identify threshold or dose-response information from available literature.
• To establish a clearer understanding of TDI's effects as a model respiratory sensitizer.

Main Methods:

• Literature review of inhalation exposure studies involving TDI.
• Data collection focused on studies providing threshold or dose-response information for respiratory irritation and sensitization.
• Exclusion of mechanistic studies unless directly relevant to threshold data.

Main Results:

• Respiratory irritation and sensitization induced by TDI appear to be interdependent phenomena.
• Both irritation and sensitization effects of TDI are demonstrated to be threshold phenomena.
• Across species, the majority of No Observed Adverse Effect Concentrations (NOAECs) for respiratory sensitization fall within the 0.005 to 0.03 ppm range.

Conclusions:

• TDI-induced respiratory irritation and sensitization are linked and occur above specific exposure thresholds.
• The identified NOAECs provide crucial data for risk assessment and establishing safe exposure limits for TDI.
• Further standardization of respiratory sensitization testing protocols is warranted.