The Government of Canada conducted a science-based evaluation, called a screening assessment, to address the potential for harm to Canadians and to the environment from substances in the Siloxanes Group.
Under the Canadian Environmental Protection Act, 1999 (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 and the environment. A substance may have hazardous properties; however, the risk to human health or to the environment may be low depending upon the level of exposure.
The 7 substances in the Siloxanes Group are associated with some health effects; however, the risk to human health is low.They are also considered to have a low potential to cause ecological harm. Therefore, it is proposed that these substances are not harmful to human health or to the environment at current levels of exposure.
About these substances
This screening assessment focuses on 6 of 7 substances referred to collectively under the Chemicals Management Plan (CMP) as the Siloxanes Group. The 6 substances addressed in this screening assessment are hexamethyldisiloxane (L2), decamethyltetrasiloxane (L4), dodecamethylpentasiloxane (L5), cyclotrisiloxane (D3), divinyltetramethyldisiloxane (dvTMDS), and cyclomethicone.
Cyclomethicone is primarily comprised of 3 substances previously assessed (octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6)) in the Challenge initiative of the CMP. Accordingly, the human health risk characterization for cyclomethicone has been evaluated as part of the D4, D5, and D6 assessments, and no significant new studies or subsequent international reviews were identified that could impact the previous assessment conclusions for human health. As a result of these assessments, D4, D5, and D6 were concluded not harmful to human health. The substances in the Siloxanes Group do not occur naturally in the environment.
According to information gathered by the Government, L2, L4, L5, and D3 may be used in Canada in products available to consumers such as cosmetics, natural health products, electronics, medical devices, adhesives and sealants.
L5 is also used in sunscreens, and cyclomethicone is used in various products available to consumers, including cosmetics.
DvTMDS may be used as a component in the manufacture of polymers and other compounds, which are used in food packaging materials.
Human and ecological exposures
The main source of exposure of Canadians to L2, L4, L5, and D3 from environmental media is indoor air, while exposure to D3 may also occur from eating fish.
Exposure to these 4 substances may also occur from the use of products available to consumers, such as cosmetics and sunscreens. Exposure of Canadians to dvTMDS is expected to be negligible.
According to information considered under the Ecological Risk Classification of Organic Substances approach, the substances in the Siloxanes Group were identified as having low ecological exposure potential.
Key health and ecological effects (hazard)
Available information indicates that L2 affects the liver, testes, and lungs, whereas L4 affects the liver.
There were limited health effects (hazard) data for L4 and L5, therefore, a comparative approach using similar chemicals, called read-across, was used for assessing potential health effects. Using available data, effects on the liver, testes, and lungs were expected to be the important or “critical” effects.
D3 results in effects including decreased food consumption, body weight, and liver weight.
No effects on human health have been identified for dvTMDS.
According to information considered under the Ecological Risk Classification of Organic Substances approach, substances in the Siloxanes Group were identified as having a low to moderate ecological hazard potential. This was based on factors such as the mechanism of action causing hazardous effects, toxicity limits, bioavailability, and chemical and biological activity.
Risk assessment outcomes
Based upon a comparison of levels to which Canadians may be exposed to L2, L4, L5, D3, and dvTMDS, and levels associated with health effects, the risk to human health for these substances is considered to be low. Cyclomethicone is not considered to be harmful to human health based on the conclusions from the D4, D5, and D6 screening assessments.
Based upon the outcome of the Ecological Risk Classification of Organic Substances approach, L2, L4, L5, D3, dvTMDS, and cyclomethicone are considered unlikely to be causing ecological harm.
As a result of this assessment, the Government is proposing that these substances are not harmful to human health at current levels of exposure.
The Government is also proposing that these substances are not entering the environment at levels that are harmful to the environment.
The substances in the Siloxanes Group may be found in products available to consumers. Canadians should follow any safety warnings and directions on product labels and dispose of products responsibly.
Canadians who may be exposed to these substances in the workplace can consult with their employer and an occupational health and safety (OHS) representative about safe handling practices, applicable laws, and requirements under OHS legislation and the Workplace Hazardous Materials Information System (WHMIS).
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