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What are diisocyanates?

Diisocyanates are a family of chemicals which includes:

What are they used for?

Diisocyanates are used to make urethane plastics, including rigid and flexible foams, urethane coatings (in paints), and two-part adhesives.

What do they look like?

Diisocyanates are generally found as a liquid combined with other chemicals and have a sharp, pungent, irritating odor.  They may also be found as white to light yellow crystalline flakes (NDI).

What are possible health hazards?

Diisocyanates can cause a wide range of health effects.

Heavy diisocyanate exposures have also been linked with neurological problems.  Prolonged exposure to diisocyanates at low levels has caused reduced breathing capacity and an increase in bronchitis and influenza.

Several animal studies have been conducted to determine if TDI causes cancer.  Animals fed TDI developed cancer, but animals exposed via inhalation did not.  The National Institute for Occupational Safety and Health (NIOSH) has determined that TDI should be classified as a potential human carcinogen.  Therefore, exposure to TDI should be reduced to the lowest possible concentrations.

What precautions can be taken?

Successful control of diisocyanate hazards requires a comprehensive program.  Key elements of such a program are as follows:

What regulations are there?



    TWA*                       Ceiling**

TDI:                             0.02 ppm

MDI:        –                   0.02 ppm

HDI:        –                        –

NDI:        –                        –

IPDI:       –                        –



      TWA*                          Ceiling**

0.005 ppm                         0.02 ppm

0.005 ppm                         0.02 ppm

0.005 ppm                         0.02 ppm

0.005 ppm                         0.02 ppm

*  TWA – Time-Weighted Average over an eight-hour work shift

** STEL – 15-minute Time-Weighted Average Exposure

*** Ca – Carcinogenic:  NIOSH has determined this to be a potential human carcinogen, and as such exposure should be limited to the lowest possible concentration.