The Government of Canada conducted a science-based evaluation, called a screening assessment of 4 substances in the Thiols Group to address the potential for harm to Canadians and to the environment.
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.
Although some of these substances are associated with human health and/or ecological effects, the risk to Canadians and the environment is low at current levels of exposure. Therefore, it is concluded 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 4 of 6 substances referred to collectively under the Chemicals Management Plan (CMP) as the Thiols Group. The substances addressed in this screening assessment are dimethyl sulfide, benzyl disulfide, tert-dodecyl mercaptan, and grapefruit mercaptan.
The Government gathers information on substances, including details on their commercial status in Canada, to support the risk assessment and management of substances under the CMP.
Dimethyl sulfide and benzyl disulphide occur naturally in a variety of foods and grapefruit mercaptan is naturally present in grapefruit juice.
In Canada, dimethyl sulfide, benzyl disulfide and grapefruit mercaptan may be used as food flavouring agents. Dimethyl sulfide is used as an odorant in natural gas.
tert-Dodecyl mercaptan may be used in the manufacture of some food packaging materials. It can also be found in products available to consumers, such as paints and coatings, vinyl floor coverings, paper products, as well as in plastics, and rubber and metal materials.
Exposure of Canadians and the environment
Canadians may be exposed to dimethyl sulfide, benzyl disulfide and grapefruit mercaptan through natural presence in food or use as a food flavouring agent.
Canadians may be exposed to dimethyl sulfide from the environment (for example, outdoor air); however, this exposure is expected to be limited. tert-Dodecyl mercaptan may be used in the manufacture of some food packaging materials in Canada; however, this exposure is considered to be negligible. Exposure to tert-dodecyl mercaptan may also occur as a result of using some paint and coatings products available to consumers.
These 4 substances were identified by the Ecological Risk Classification of Organic Substances Approach as having low ecological exposure potential.
Key health and ecological effects (hazard)
To identify human health effects, international reports on these substances were reviewed.
The JECFA evaluated the safety of dimethyl sulfide, benzyl disulfide, and grapefruit mercaptan, and determined that the substances were of no safety concern in relation to their potential use as food flavouring agents.
The Ecological Risk Classification of Organic Substances Approach identified dimethyl sulfide as having a low ecological hazard potential.
Benzyl disulfide and tert-dodecyl mercaptan were identified as having moderate ecological hazard potential based on their ecotoxicity and potential to cause adverse effects in aquatic food webs due to their bioaccumulation potential.
Grapefruit mercaptan was identified as having a high ecological hazard potential based on its level of ecotoxicity and potential to cause adverse effects in aquatic food webs due to its bioaccumulation potential.
Risk assessment outcomes
Based upon the consideration of international assessments, the risk to human health from dimethyl sulfide, benzyl disulfide, and grapefruit mercaptan is considered to be low.
Based upon a comparison of levels to which Canadians may be exposed and the levels associated with health effects, the risk to human health from tert-dodecyl mercaptan is considered to be low.
The Ecological Risk Classification of Organic Substances Approach characterized these 4 substances as posing a low risk of harm to the environment, based on current low levels of exposure.
As a result of this assessment, the Government concluded that these 4 substances are not harmful to human health at current levels of exposure.
The Government also concluded that these 4 substances are not entering the environment at levels that are harmful to the environment.
Important to know
tert-Dodecyl mercaptan can 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).
