Heterocycles Group – information sheet

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Overview

  • The Government of Canada conducted a science-based evaluation, called a screening assessment, of 3 substances in the Heterocycles 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.
  • The ecological hazard and exposure potentials of the substances in the Heterocycles Group were classified using the Ecological Risk Classification of Organic Substances Approach.
  • 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 current levels of exposure.

About these substances

  • The screening assessment focuses on 3 of the 7 substances referred to collectively under the Chemicals Management Plan (CMP) as the Heterocycles Group. The substances addressed in the screening assessment are methenamine, morpholine, and the substance with the Chemical Abstracts Service Registry Number (CAS RN) 4174-09-8.
  • 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; however assessment activities associated with use of ETU as a pesticide are ongoing, therefore the conclusion for ETU will be provided in a separate screening assessment.
  • Three other substances in the Heterocycles Group were determined to be of low concern to both human health and the environment through other approaches. Conclusions for CAS RNs 132-65-0, 28984-69-2, and 68909-18-2 are provided in the Screening Assessment for Substances Identified as Being of Low Concern using the Ecological Risk Classification of Organic Substances and the Threshold of Toxicological Concern (TTC)-based Approach for Certain Substances.
  • According to information gathered by the Government, methenamine, morpholine, and CAS RN 4174-09-8 are man-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 low or negligible.
  • Canadians may also be exposed to ETU through their diet, including drinking water, as a result of crop treatment using ethylene bis-dithiocarbamate fungicides that break down to ETU; however, these sources of exposure to ETU are being addressed under the PCPA as part of Health Canada's re-evaluation of ethylene bis-dithiocarbamate fungicides.
  • 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 Ecological Risk Classification of Organic Substances 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 this assessment.
  • Morpholine was identified as having potential adverse effects on the thyroid.
  • According to information considered under the Ecological Risk Classification of Organic Substances 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 Ecological Risk Classification of Organic Substances Approach, methenamine, morpholine, and CAS RN 4174-09-8 are considered unlikely to cause ecological harm.
  • The Government of Canada published the Final Screening Assessment for the Heterocycles Group on June 8, 2019.

Screening assessment conclusions

  • As a result of this assessment, the Government concluded that methenamine, morpholine, and CAS RN 4174-09-8 are not harmful to human health at current levels of exposure.
  • The Government also concluded that these 3 substances are not entering the environment at levels that are harmful to the environment.

Related information

  • 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.
  • 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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