The odor threshold is 0.4 ppm in about half of the subjects. It may be released to the environment as fugitive emissions and from stack exhaust during the production, transport, and use of TDI in the manufacture of polyurethane foam products and coatings as well as from spills. Much of the enviromental fate and monitoring data does not distinguish between the isomers of toluene diisocyanate, however, since the types of reactions are similar, some of the data presented below is for the commercial TDI mixture. If spilled on wet land, TDI is rapidly degraded. If released into water, a crust forms around the liquid TDI and concentrations of TDI hydrolyze in the aqueous environment in approximately a day.
Human exposure is primarily occupational via inhalation and dermal contact.
The TDI solidified and the area was covered with sand. No TDI was detected in a connecting brook 10 days after the spill . After 6 years, only TDI-derived polyureas were found at the site . The reaction product was largely polyureas . When low concns of TDI are released into model river or seaway systems, it is hydrolyzed within a day .