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 and the environment.
When needed, the Government implements risk management measures under CEPA and other federal acts to help prevent or reduce potential harm.
Substances in the Siloxanes Group are associated with health effects; however, at levels of exposure considered in the assessment, the Government concluded that these substances are not harmful to human health or to the environment.
The assessment focused on 5 of 7 substances referred to collectively under the third phase of the Chemicals Management Plan (CMP) as the Siloxanes Group. The 5 substances are: cyclotrisiloxane (D3), divinyltetramethyldisiloxane (dvTMDS) and 3 linear siloxanes: hexamethyldisiloxane (L2), decamethyltetrasiloxane (L4), and dodecamethylpentasiloxane (L5).
octamethylcyclotetrasiloxane (D4; CAS RN 556-67-2)
decamethylcyclopentasiloxane (D5; CAS RN 541-02-6), and
dodecamethylcyclohexasiloxane (D6; CAS RN 540-97-6).
Accordingly, cyclomethicone is considered to have been addressed through the screening assessments of D4, D5, and D6 in 2008 and the revised conclusion regarding D5 in 2012, and is not subject to further risk assessment at this time. In those assessments, D5 and D6 were concluded as not harmful to human health or the environment while D4 was concluded as harmful to the environment, but not to human health.
Three substances in this group (L2, L4, and L5) are also components of dimethicone (CAS RN 9006-65-9). The risk to human and ecological health from dimethicone was assessed in the second phase of polymer rapid screeningand included the uses of L4 and L5 in cosmetics and L5 in drugs.
L2, L5, and dvTMDS do not occur naturally in the environment; however, L4 and D3 are found in plants.
According to information gathered by the Government, L2 is used in products available to consumers such as cosmetics, electronics, medical devices, and anti-freeze and de-icing products. There are no uses of L4 identified as an individual substance. L5 is used in industrial applications, such as paints and coatings. D3 is also used in products available to consumers, such as cosmetics, and adhesives and sealants. DvTMDS is used in the manufacture of polymers and other compounds and may be used in food packaging materials.
Human and ecological exposures
The assessment indicated that people in Canada may be exposed to the linear siloxanes (L2, L4 and L5) and D3 from the environment, mainly through indoor air.
Exposure to L5 may also occur from eating fish. Eating baked goods made in silicone baking moulds, as well as eating fish, may result in exposure to D3 while inhalation exposure to residual D3 from the use of silicone baking moulds may also occur.
Regarding products available to consumers, the main sources of exposure were from self-care products that contain L2 and D3 (L2 may be present in nail polish drying drops and bandage adhesive remover while D3 may be in body makeup and diaper cream).
Exposure of people in Canada to dvTMDS was not expected.
According to information considered under the ERC Approach, the substances in the Siloxanes Group were identified as having low ecological exposure potential.
In laboratory studies, L2 was found to affect the liver, testes, and lungs, whereas L4 was found to affect the liver.
There were limited health effects (hazard) data for L5, therefore, a comparative approach using similar chemicals, called read-across, was used for assessing potential health effects for L5. Effects on the liver, testes, and lungs were expected to be the important or critical effects for L5.
Laboratory studies indicated that D3 is associated with effects on the liver, and decreased food consumption and body weight.
Effects on human health were not identified for dvTMDS.
According to information considered under the ERC Approach, L2, L5, and D3 were identified as having a low ecological hazard potential, while L4 and dvTMDS were identified as having a moderate ecological hazard potential. This was based on factors such as their toxicity and potential to accumulate in aquatic organisms.
Consideration of subpopulations who may have greater susceptibility or greater exposure
There are groups of individuals within the Canadian population who, due to greater susceptibility or greater exposure, may be more vulnerable to experiencing adverse health effects from exposure to substances.
Certain subpopulations are routinely considered throughout the assessment process, such as infants and children and people of reproductive age. For instance, age-specific exposures are routinely estimated and developmental and reproductive toxicity studies are evaluated for potential health effects. These subpopulations were taken into account in the risk assessment outcomes of substances in the Siloxanes Group.
Risk assessment outcomes
Assessments focus on information critical to determining whether substances are harmful to human health or the environment under CEPA. This is done by considering scientific information, including information, if available, on subpopulations who may have greater susceptibility or greater exposure, vulnerable environments and cumulative effects and by incorporating a weight of evidence approach and precaution.
Based upon a comparison of levels to which Canadians may be exposed to L2, L4, L5, and D3, and levels associated with health effects, it was determined that the risk to human health for these substances is low.
Exposure to dvTMDS was not expected; therefore, the risk to human health from this substance was also considered to be low.
Based upon the outcome of the ERC Approach, L2, L4, L5, D3, and dvTMDS are considered unlikely to be causing ecological harm at levels of exposure considered in the assessment.
The Government concluded that the 5 substances in the Siloxanes Group (D3, dvTMDS, L2, L4, and L5) are not harmful to human health at levels of exposure considered in the assessment, and that they are not entering the environment at levels that are harmful.
Substances in the Siloxanes Group may be found in products available to consumers. People in Canada should follow any safety warnings and directions related to the product and dispose of products responsibly.
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