Industrial Chemicals– Possible Carcinogen (IARC 2B)
CAS No. 26471-62-5
Photo: Wikimedia Commons
IARC Monograph Vol. 71, 1999 (Group 2B)
Toluene diisocyanates (TDI) are colourless to pale yellow liquids, solids, or crystals with a distinctive and pungent odour. They are highly reactive compounds widely used to manufacture polyurethane foams and coatings. TDI are typically available as a mixture of two isomers: 2,4-TDI isomer (80%) and 2,6-TDI isomer (20%).
TDI may also be referred to as 2,4- or 2,6-diisocyanato-1-methylbenzene. There are numerous other synonyms and product names; see the Hazardous Substances Data Bank (HSDB) for more information.
TDI have been classified by the International Agency for Research on Cancer (IARC) as Group 2B, possibly carcinogenic to humans. Administration of TDI in animal experiments caused benign liver, mammary-gland, and pancreatic tumours in rats and mice. Exposure also caused both benign and malignant tumours in blood vessels and subcutaneous tissues in rats and mice. Epidemiological studies looking specifically at TDI exposure and human cancer are limited; other studies that included TDI as an exposure did not identify strong and consistent associations between TDI exposure and cancer in humans.[2,5]
The toxicity of TDI has been recognized for many years. Exposure to high levels of TDI severely irritates the skin, eyes, and nose, and causes nervous system effects. It is a potent skin and respiratory sensitizer, and a well-known cause of occupational asthma.[5,7,8] TDI can also cause hypersensitivity pneumonitis and chronic bronchitis.
stel = short term exposure limit (15 min. maximum)
c = ceiling (not to be exceeded at any time)
ACGIH = American Conference of Governmental Industrial Hygienists
TLV = threshold limit value
Canadian Environmental Guidelines
Ontario Ambient Air Quality Criteria
24 hour 0.2 µg/m3
Cosmetic Ingredients Hotlist
µg/m3 = micrograms per cubic metre
TDI were not included in other Canadian environmental guidelines reviewed.[11,12,13,14,15,16,17]
DSL – high priority substance with greatest potential for exposure (for mixed isomers) and intermediate potential for exposure (for 2,4-TDI and 2,6-TDI individually)
Challenge to Industry
Recommended to be added to the toxic substances list
Toluene diisocyanates were not included in other Canadian government chemical listings reviewed.[20,21]
DSL = domestic substance list
CEPA = Canadian Environmental Protection Act
Toluene diisocyanates are used to prepare polyurethane foams, elastomers, and coatings. Polyurethane foam is used in furniture, bedding, refrigerators, laminate flooring and roofing, truck and trailer insulation, and in cargo containers. Polyurethane elastomers are used in coated fabrics and clay-pipe seals. Polyurethane coatings are used in floor finishes, wood finishes and sealers, and coatings for aircraft, tank trucks, truck trailers, and truck fleets.
TDI are also used as a cross-linking agent for nylon-6 and as a hardener in polyurethane adhesives.
Canadian Production and Trade
Toluene diisocyanates are not produced in Canada, but they are imported and used extensively to manufacture a number of the products listed above.[3,22] Approximately 97% of TDI consumption in Canada occurs in the flexible foam production sector.
Production and Trade
180 t of 'isocyanates'
22,907 t of 'isocyanates'
t = tonne
Workers may be exposed during all phases of toluene diisocyanate manufacture and use. Inhalation and dermal contact are the most important routes of occupational exposure.
CAREX Canada estimates that approximately 24,000 Canadians are exposed to TDI in their workplaces. The largest industrial groups exposed are plastic product manufacturing, automotive repair and maintenance, motor vehicle parts manufacturing, and furniture and cabinet making. The largest occupational groups exposed include plastic processing machine operators, followed by labourers in rubber and plastics manufacturing, automotive service technicians, plastic product assemblers, finishers, and inspectors, and motor vehicle assemblers.
Other important occupations exposed include adhesive workers, insulators, lacquer applicators, organic chemical synthesizers, paint and urethane foam sprayers, ship builders, textile processors, and wire coating workers. Potential for exposure also exists with processes involving heating (welding, soldering, or hot-wire cutting) polyurethane products.
The most important route of environmental exposure to toluene diisocyanates is inhalation. Dermal exposure via some consumer products is also possible. In Canada, most industrial releases of TDI are into the air. Long range atmospheric transport is unlikely due to the short half-life of TDI in the environment (approximately two days).
In Canada, a potential source of TDI exposure to the general population is industrial releases during urethane foam manufacture and processing. The estimated annual average concentration of TDI in close proximity to a foam manufacturing facility in Canada is 1.06 µg/m3. Other potential sources of TDI exposure include: industrial releases from manufacturing, using, or disposing of other TDI-based products; and the use of consumer products such as polyurethane foams, varnishes, adhesives, and sealants. Most Canadian releases of TDI to the environment occur in Ontario.
In 2011, Environment Canada released a P2 Planning Notice, in which specific owners or operators of a facility within the polyurethane and other foam sector are required to limit their on-site releases of TDI to air below 100 kg/year, or maintain ambient levels below 0.2 µg/m3. All facility owners and operators have been compliant with the plan. This may influence the overall reduction of releases of these substances to the environment.
Searches of Environment Canada's National Pollutant Release Inventory (NPRI) and the US Household Products Database yielded the following results on current potential for exposure to TDI in Canada:
NPRI and US Household Products Database
Substance name: 'Toluene-2,4-diisocyanate'
Released into Environment
Specialized freight trucking, plastic, paint, coating and adhesive manufacturing, other chemical product manufacturing (6 facilities)
plastic product manufacturing, motor vehicle part manufacturing, waste treatment and disposal, resin, rubber, synthetic fibre and filament manufacturing (15 facilities)
Sent to off-site recycling
t = tonne
US Household Products 2015
Sealants (8), cement/concrete (1), hair dye (1)
Our team has performed a detailed scan of exposure control resources and assembled a compilation of key publications and resources. These are organized by type of exposure (environmental or occupational) and by specificity (general or carcinogen-specific). Please visit our Exposures Reduction Resources page to view.
We also recommend exploring the Prevention Policies Directory, a freely-accessible online tool offering information on policies related to cancer and chronic disease prevention. Providing summaries of the policies and direct access to the policy documents, the Directory allows users to search by carcinogen, risk factor, jurisdiction, geographical location, and document type. Click here to learn more about policies specific to toluene diisocyanates in the Directory. For questions about this resource, please contact a member of the Prevention Team at the Canadian Partnership Against Cancer at firstname.lastname@example.org.