The risks posed by a substance are determined by both its hazardous properties (potential to cause adverse human health or ecological effects) and the amount or extent of exposure to people or the environment.
When needed, the Government implements risk management measures under CEPA and other federal acts to help prevent or reduce potential harm.
As a result of the screening assessment, the 5 MDI substances were concluded to be harmful to human health, but not to the environment at levels of exposure considered in the assessment. Risk management actions were taken for the protection of human health.
These 7 MDIs and MDAs were assessed together due to their similarities in chemical structure, properties, and use patterns.
These substances are not expected to occur naturally in the environment.
According to information gathered by the Government, 4,4'-MDI, pMDI, and mixed MDI are primarily used 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.
Human and ecological exposures
The screening assessment indicated that people living in Canada may be exposed to MDIs from the use of products containing unreacted or "free" MDIs, such as adhesives and sealants, including SPF products.
Exposure of people living in Canada to MDAs from the environment is expected to be low as these substances 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)
To help inform the health effects characterization in the screening assessment, international data reports on these substances were considered, among other sources of information.
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 ability to cause cancer), respiratory effects including respiratory sensitization, and 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 ability 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
Based upon a comparison of levels to which people living in Canada may be exposed to the 5 MDIs from the use of certain low-pressure, two-component SPF products, and levels associated with critical effects, it was determined that these substances may pose a risk to human health. The risk to human health from 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.
Screening assessment conclusions
The Government concluded that the 5 MDIs are harmful to human health at levels of exposure considered in the assessment. It is also concluded that the 2 MDAs are not harmful to human health at levels 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.
Preventive actions and risk reduction
The 5 MDI substances were added to Schedule 1 to CEPA. Adding a substance to Schedule 1 does not restrict its use, manufacture or import. Rather, it enables the Government to take risk management actions under CEPA.
The Government published the Proposed Risk Management Approach for MDIs on June 10, 2017 for a 60-day public comment period. The following actions were taken to address concerns for human health:
Although 4,4’-MDA and pMDA are not considered to be harmful to human health at exposure levels at the time of the assessment, these substances are considered to have health effects of concern due to their potential to cause cancer. There may be a concern if exposures were to increase.
This requires that the Government be notified of certain proposed new activities related to these substances, and that the new activity be assessed for potential risks to human health and the environment before being undertaken.
The order outlines the definition of a significant new activity in relation to 4,4’-MDA and pMDA, as well as the information that needs to be provided to the Government for assessment before the new activity is undertaken.
Information about SNAc provisions applied to substances, including new notices and orders, and those already published, can be found in the SNAc publications dataset.
Use the Substances Search tool to find substances that are referenced in certain legislative or regulatory instruments or on Government of Canada websites.
Related resources
The 5 MDI and 2 MDA substances may be found in products available to consumers. People living in Canada should follow any safety warnings and directions related to the product and dispose of products responsibly.
Visit Healthy Home for information on chemical safety in and around the home.
Assessments conducted under CEPA focus on risks of exposure of the general population. Hazards related to chemicals used in the workplace are defined within the Workplace Hazardous Materials Information System (WHMIS). If a substance is harmful to the general population, it could also be of concern for individuals in situations where a higher volume of the substance is used or where the substance is used for a longer duration (for example, the workplace). The Government of Canada recognizes that it is the responsibility of the federal, provincial and territorial occupational health and safety organizations to coordinate legislation for the safe use of chemicals in the workplace. We are working to support this role by integrating the information, tools, and technical expertise of the CMP and Health Canada’s Workplace Hazardous Products Program.
