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 1999 and other federal acts to help prevent or reduce potential harm.
Substances in the Heterocycles Group may be associated with human health and/or ecological effects; however; the risk to human health and the environment was determined to be low at current levels of exposure. It was concluded that the substances in the Heterocycles Group are not harmful to human health or to the environment at levels of exposure considered in the assessment.
The substance 2-imidazolidinethione, commonly referred to as ethylene thiourea (ETU), was included in the Draft Screening Assessment for the Heterocycles Group published on November 11, 2017. To better align with the re-evaluation of certain pesticides, this substance was assessed separately, and the conclusions for ETU are provided in a separate screening assessment.
According to information gathered by the Government, methenamine, morpholine, and CAS RN 4174-09-8 are human made substances and do not occur naturally in the environment.
These substances are widely used in Canada.
Methenamine is used in the manufacture of resins and rubber and it is consumed during the manufacturing process. It is also used to produce certain explosives and fuel tablets, and may be used in cosmetics as a preservative.
Morpholine is used in the manufacture of rubber, pharmaceuticals, pesticides, optical brighteners, antioxidants and as an industrial solvent.
Morpholine is added to some waxes used to coat fresh produce, such as apples.
CAS RN 4174-09-8 is used to colour plastics, varnishes and coatings.
Human and ecological exposures
Methenamine, morpholine, and CAS RN 4174-09-8 may be used in certain food packaging materials in Canada; however, this exposure is considered to be negligible.
Exposure to morpholine may also occur through foods that may be treated with the substance, such as waxed apples, and from disinfectant sprays.
According to information considered under the ERC Approach, morpholine, and CAS RN 4174-09-8 were identified as having a low ecological exposure potential.
Methenamine was identified as having a high ecological exposure potential due to its ability to stay in the environment for a long time and the large use volumes reported in a recent survey.
Key health and ecological effects (hazard)
To identify human health effects for substances in the Heterocycles Group, national and international reports of data were reviewed. These assessments were used to inform the screening assessment.
For methenamine, potential developmental effects were considered to be the important or critical effects used for characterizing the risk to human health in the assessment.
Morpholine was identified as having potential adverse effects on the thyroid.
According to information considered under the ERC Approach, methenamine and morpholine were identified as having a low ecological hazard potential while CAS RN 4174-09-8 was identified as having a high ecological hazard potential, on the basis of its ecotoxicity and moderate potential to bioaccumulate in aquatic food webs.
Risk assessment outcomes
Based upon the consideration of national and international assessments, along with the information presented in the screening assessment, the risk to human health from methenamine, morpholine, and CAS RN 4174-09-8 is low.
Based upon the outcome of the ERC Approach, methenamine, morpholine, and CAS RN 4174-09-8 are considered unlikely to be causing ecological harm.
Screening assessment conclusions
The Government concluded that methenamine, morpholine, and CAS RN 4174-09-8 are not harmful to human health at levels of exposure considered in the assessment.
The Government also concluded that these 3 substances are not entering the environment at levels that are harmful to the environment.
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
Health Canada assessed the safety of the use of morpholine in apple-wax coatings and determined that such use did not present a risk to human health. It is always a good idea to wash fresh produce under running water and wipe dry. This will help remove any remaining surface pesticide residues, and more importantly, it will help to remove any dirt or bacteria that may be on the surface of the food.
Substances in the Heterocycles Group may be found in certain products available to consumers. Canadians should follow any safety warnings and directions on product labels and dispose of products responsibly according to municipal or local guidelines.
