Toluene Diisocyanates Profile
INDUSTRIAL CHEMICALS – POSSIBLE CARCINOGEN (IARC 2B)
Contents
Toluene Diisocyanates Profile
General Information
Toluene diisocyanates (TDI) are colourless to pale yellow liquids, solids, or crystals with a distinctive and pungent odour.[1] They are highly reactive compounds widely used to manufacture polyurethane foams and coatings.[2] TDI are typically available as a mixture of two isomers: 2,4-TDI isomer (80%) and 2,6-TDI isomer (20%).[1]
TDI may also be referred to as 2,4- or 2,6-diisocyanato-1-methylbenzene.[3] There are numerous other synonyms and product names; see the Hazardous Substances Data Bank (HSDB) for more information.[2]
TDI have been classified by the International Agency for Research on Cancer (IARC) as Group 2B, possibly carcinogenic to
humans.[4] Administration of TDI in animal experiments caused benign liver, mammary-gland, and pancreatic tumours in rats and mice.[1] Exposure also caused both benign and malignant tumours in blood vessels and subcutaneous tissues in rats and mice.[1] 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.[1,4]
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.[5] It is a potent skin and respiratory sensitizer, and a well-known cause of occupational asthma.[4,6,7] TDI can also cause hypersensitivity pneumonitis and chronic bronchitis.[4]
Regulations and Guidelines
Occupational exposure limits (OEL)[8,9,10,11,12,13,14,15,16,17,18,19,20,21,22]
| Canadian Jurisdictions | OEL (ppm) |
|---|---|
| Canada Labour Code | 0.001 [ifv, sk, dsen, rsen] 0.005 [stel, ifv, sk, dsen, rsen,] |
| AB, ON | 0.005 0.02 [c] |
| BC | 0.005 [sk, dsen, rsen] 0.01 [c, sk, dsen, rsen] |
| MB, NL, PE, NS | 0.001 [ifv, sk, dsen, rsen] 0.005 [stel, ifv, sk, dsen, rsen,] |
| NU, NT, SK, NB | 0.005 [sen] 0.02 [stel] |
| QC | 0.005 [sen, em] 0.02 [stel, sen, em] |
| YT | 0.02 [c] |
| Other Jurisdiction | OEL (ppm) |
| ACGIH 2020 TLV | 0.001 [ifv, sk, dsen, rsen] 0.005 [stel, ifv, sk, dsen, rsen] |
ppm = parts per million
ifv = inhalable fraction and vapour
sk = easily absorbed through the skin
dsen = dermal sensitization
rsen = respiratory sensitization
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 and standards*
| Jurisdiction | Limit | Year |
|---|---|---|
| Ontario Ambient Air Quality Criteria | 24-hour: 0.2 µg/m3 | 2016[23] |
| Government of Canada’s Indoor Air Reference Levels | 0.008 µg/m3 (critical effect: decreased lung function) | 2018[24] |
| Ontario’s Air Pollution – Local Air Quality Regulation | 24-hour standard: 0.2 µg/m3; Prohibited discharge into the air if the concentration of TDI exceeds the standard | 2020[25] |
| Cosmetic Ingredients Hotlist | Not Permitted | 2011[26] |
µg/m3 = micrograms per cubic metre
*Standards are legislated and legally enforceable, while guidelines (including Ontario ambient air quality criteria) describe concentrations of contaminants in the environment (e.g. air, water) that are protective against adverse health, environmental, or aesthetic (e.g. odour) effects
Canadian agencies/organizations
| Agency | Designation/Position | Year |
|---|---|---|
| Health Canada | 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) | 2006[27] |
| Challenge to Industry | Batch 1 | 2007[28] |
| CEPA | Schedule 1, paragraph ‘c’ | 2010[2] |
| Environment Canada’s National Pollutant Release Inventory | NPRI Part (Threshold Category): 1B, Reportable to NPRI if manufactured, processed, or otherwise used at quantities greater than: 100 kg. Total of all isomers, including, but not limited to, isomers with CAS RN 354-12-1, 354-15-4 and 354-21-2 | 2016[29] |
| PMRA List of Formulants | List 4B: List 4B contains formulants, some of which may be toxic, for which there are sufficient data to reasonably conclude that the specific use pattern of the pest control product will not adversely affect public health and the environment. | 2020[30] |
DSL = domestic substance list
CEPA = Canadian Environmental Protection Act
PMRA = Pest Management Regulatory Agency
TDI were not included in other Canadian government guidelines, standards, or chemical listings reviewed.
Main Uses
Toluene diisocyanates are used to prepare polyurethane foams, elastomers, and coatings.[4] Polyurethane foam is used in furniture, bedding, refrigerators, laminate flooring and roofing, truck and trailer insulation, and in cargo containers.[1] Polyurethane elastomers are used in coated fabrics and clay-pipe seals.[4] Polyurethane coatings are used in floor finishes, wood finishes and sealers, and coatings for aircraft, tank trucks, truck trailers, and truck fleets.[4]
TDI are also used as a cross-linking agent for nylon-6 and as a hardener in polyurethane adhesives.[4]
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.[2,31] Approximately 97% of TDI consumption in Canada occurs in the flexible foam production sector.[2]
Production and trade
| Activity | Quantity | Year |
|---|---|---|
| Export | 481 t of ‘isocyanates’ | 2021[32] |
| Import | 35,135 t of ‘isocyanates’ | 2021[32] |
t = tonne
Environmental Exposures Overview
The most important route of environmental exposure to toluene diisocyanates is inhalation. Dermal exposure via some consumer products is also possible.[2] 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).[2]
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.[33]
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.[34]
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
| NPRI 2015[35] | ||
|---|---|---|
| Substance name: ‘Toluene-2,4-diisocyanate’ | ||
| Category | Quantity | Industry |
| Released into Environment | 0.190 t | Specialized freight trucking, plastic, paint, coating and adhesive manufacturing, other chemical product manufacturing (6 facilities) |
| Disposed of | 0.672 t | |
| Sent to off-site recycling | None | |
| Substance name: ‘Toluene-2,6-diisocyanate’ | ||
| Category | Quantity | Industry |
| Released into Environment | 0.000129 | Specialized freight trucking, plastic, paint, coating and adhesive manufacturing (3 facilities) |
| Disposed of | 0.06 t | |
| Sent to off-site recycling | None | |
| Substance name: ‘Toluene diisocyanate (mixed isomers)’ | ||
| Category | Quantity | Industry |
| Released into Environment | 0.138 t | plastic product manufacturing, motor vehicle part manufacturing, waste treatment and disposal, resin, rubber, synthetic fibre and filament manufacturing (15 facilities) |
| Disposed of | 1.751 t | |
| Sent to off-site recycling | None | |
t = tonne
| US Household Products 2015[36] | ||
|---|---|---|
| Search Term | Quantity | Product Type |
| ‘Toluene diisocyanate’ | 10 | Sealants (8), cement/concrete (1), hair dye (1) |
Occupational Exposures Overview
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.[1]
CAREX Canada estimates that approximately 16,000 Canadians are exposed to TDI in their workplaces.The largest industrial groups exposed are automotive repair and maintenance, plastic product manufacturing, and motor vehicle parts manufacturing.
The largest occupational groups exposed include automotive service technicians, truck and bus mechanics, and mechanical repairers; plastics processing machine operators; motor vehicle body repairers; and plastic products assemblers (finishers and inspectors). 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.[1] Potential for exposure also exists with processes involving heating (welding, soldering, or hot-wire cutting) polyurethane products.
For more information, see the occupational exposure estimate for TDI.
Sources
Other Resources
- International Programme on Chemical Safety (IPCS) INCHEM. Environmental Health Criteria 75, Toluene Diisocyanates
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