Methylenediphenyl Diisocyanate and Diamine (MDI/MDA) substances - information sheet

Updated August 29, 2020

The Final Screening Assessment for the MDI/MDA Substance Grouping was published on June 10, 2017 under the Substance Groupings Initiative of the Chemicals Management Plan (CMP). The assessment is summarized in this information sheet. The section in this information sheet entitled "Preventive actions and reducing risk" communicates updates in risk management activities, namely:

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  • The Government of Canada conducted a science-based screening assessment under the Canadian Environmental Protection Act, 1999 (CEPA 1999) to address the potential for harm to Canadians and to the environment from 5 MDI and 2 MDA substances.
  • Under CEPA 1999, the risk posed by a substance is determined by considering both its hazardous properties (its potential to cause adverse human health or ecological effects) and the amount of exposure there is to people or the environment.
  • As a result of this screening assessment, the Government concluded that the 5 MDI substances are harmful to human health, but not to the environment. The 2 MDA substances were concluded to not be harmful to human health or the environment at levels of exposure considered in the assessment.

About these substances

  • The screening assessment focused on 5 methylenediphenyl diisocyanate substances (MDIs) and 2 methylenediphenyl diamine substances (MDAs), making up the MDI/MDA Substance Grouping.
  • These 7 MDIs and MDAs were assessed together due to their similarities in chemical structure, properties, and use patterns.
  • The substances in this grouping are man-made chemicals that are not expected to occur naturally in the environment.
  • The major use of 4,4'-MDI, pMDI, and of mixed MDI is in the manufacture of polyurethanes and polyurethane products, such as adhesives, coatings, insulation foams, flexible packaging laminate, and foam slabs used in furniture. They are used as adhesives in the production of engineered wood products, such as oriented strand board (wood panel used in construction).
  • MDIs are also used in do-it-yourself (DIY) adhesive, sealant and insulating products, such as spray polyurethane foam (SPF) products.
  • Globally, MDAs are used mostly in the production of MDIs.

Human and ecological exposures

  • The assessment indicated that exposure of Canadians to MDIs is expected to result primarily during the use of products containing unreacted or "free" MDIs, such as adhesives and sealants, including spray polyurethane foam products.
  • Exposure of Canadians to MDAs from the environment is expected to be low as they are not manufactured in Canada and their use is limited to a few industrial applications. Moreover, exposure to MDAs from the use of products available to consumers is not expected.
  • In Canada, MDIs have the potential to be released to the environment, primarily to air, during industrial uses such as in the production of engineered wood and polyurethane products.
  • Release of MDIs to air may also result in deposition to soil and/or surface waters in the area surrounding the release site.
  • MDAs are not expected to be released to the environment; however, small quantities of MDAs may form through the breakdown of MDIs when reacting with water in the environment.

Key health and ecological effects (hazard)

  • On the basis of available information and international classifications, the critical effects used for characterizing the risk to human health from exposure to MDIs were carcinogenicity (potential to cause cancer), respiratory effects including respiratory sensitization as well as dermal sensitization. Sensitization can result in breathing problems or effects on the skin.
  • The critical effect used to characterize risk to human health for 4,4′-MDA and pMDA was carcinogenicity (potential to cause cancer).
  • For the ecological assessment, aquatic studies suggest that both 4,4′-MDI and pMDI have low toxicity to aquatic species. MDIs also have low toxicity to the tested soil invertebrate species and plants.
  • Studies suggest that 4,4'-MDA is moderately to highly toxic to various aquatic organisms including algae, microorganisms, invertebrates, and fish. 4,4′-MDA shows low to moderate toxicity to soil organisms and plants and is moderately toxic to sediment-dwelling organisms and birds.

Risk assessment outcomes

  • As a result of the screening assessment, it was determined that the 5 MDIs may pose a risk to human health because of possible exposure from the use of certain low-pressure two-component SPF products. The risk to human health posed by 4,4'-MDA and pMDA was considered to be low.
  • MDIs were not expected to remain in the environment for a long time or accumulate in organisms. The amounts of MDIs that may be released to the environment were below the level expected to cause harm to organisms.
  • Similarly, the amounts of MDAs that may be released to the environment were also below the level expected to cause harm to organisms.
  • The Government published the Final Screening Assessment for the MDI/MDA Substance Grouping on June 10, 2017.

Screening assessment conclusions

  • The Government concluded that the 5 MDIs are harmful to human health. The Government also concluded that the 2 MDAs are not harmful to human health, at levels of exposure considered in the assessment.
  • The Government concluded that none of these 5 MDIs or 2 MDAs are entering the environment at levels that are harmful to the environment.
  • It was determined that none of these 5 MDIs or 2 MDAs meet the persistence or bioaccumulation criteria as set out in the Persistence and Bioaccumulation Regulations of CEPA 1999.

Preventive actions and reducing risk

  • The Government published the Proposed Risk Management Approach for MDIs on June 10, 2017 for a 60-day public comment period. Comments received were considered and informed the proposed risk management summarized below.
  • The final order adding 5 MDI substances to Schedule 1 of CEPA 1999, also called the List of Toxic Substances, was published on May 15, 2019.
  • On August 29, 2020, a Code of Practice for Certain Methylenediphenyl Diisocyanates in Low-Pressure Two-Component Spray Polyurethane Foam Products was published in the Canada Gazette.
  • This code of practice aims to help reduce exposure of Canadians to MDIs that may result from using low-pressure two-component spray polyurethane foam products available to Canadians. The code outlines actions for any person who manufactures, imports, or sells these products to:
    • provide general information to users on safe use and handling
    • communicate general information concerning health and safety procedures
    • facilitate access to training materials to help promote proper use of the products
    • provide retailers with general information to help promote safe use and handling of the products.
  • The Government developed the code of practice through collaboration with stakeholders to leverage their knowledge and expertise, with the goal of developing an effective and practical risk management tool.
  • Further information and updates on risk management actions for substances managed under the CMP can be found in the risk management actions table and the two year rolling risk management activities and consultations schedule.

Additional considerations

  • Although the 2 MDAs were not concluded to be harmful to human health or the environment, there may be a concern if exposures were to increase since these substances have potential effects of concern to human health and potential negative ecological effects.
  • Therefore, in June 2017, the Government published a notice of intent to apply Significant New Activity (SNAc) provisions of CEPA 1999 to these 2 MDAs. The publication had a 60-day public comment period.
  • The SNAc would require that the Government be notified of proposed new activities related to these 2 MDAs, and that the new activity be assessed for potential risks to human health and the environment before being undertaken.

Related information

  • MDIs are present in products available to consumers. Canadians should follow any safety warnings and directions related to the products and dispose of products responsibly.
  • Visit Healthy Home for more information on chemical safety in and around the home, including information on MDIs for consumers.
  • To minimize exposure to MDIs, Canadians can consider hiring trained professional contractors to apply low-pressure two-component SPF products instead of doing it themselves. Direction from a contractor should be taken on what to do when the product is being applied, such as leaving the area, and when to re-enter.
  • If using low-pressure two-component SPF products, Canadians should carefully follow the instructions for the product and contact the manufacturer for safe use and handling information. It is important to wear the correct personal protective equipment (for example, clothing and recommended respiratory protection) to avoid inhaling the substances or getting the product on the skin. Actions should also be taken to prepare the work area for safe use and application of the product (for example, proper ventilation).
  • The screening assessment focused on potential risks from exposure of the general population of Canada, rather than occupational exposure. Hazards related to chemicals used in the workplace are defined within the Workplace Hazardous Materials Information System. For information concerning workplace health and safety and what steps to take in the workplace, Canadians should consult their employer and/or the Occupational Health and Safety Regulator in their jurisdiction.

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