Ethylene thiourea (ETU) - information sheet

2-Imidazolidinethione
CAS Registry Number 96-45-7

Publications summarized:

• Final Screening Assessment for 2-Imidazolidinethione (Ethylene thiourea) (published on January 14, 2023). Public comments received on the draft screening assessment of the Heterocycles Group were considered and a summary of the comments with Government responses was published.
• Associated notice: Canada Gazette, Part I: Vol. 157, No. 2 – January 14, 2023

On this page

• Overview
• About this substance
• Human and ecological exposures
• Key health and ecological effects (hazard)
• Consideration of subpopulations who may be more susceptible or highly exposed
• Risk assessment outcomes
  • Screening assessment conclusions
• Preventive actions and risk reduction
  • Where to find updates
• Related resources

Overview

• The Government of Canada conducts risk assessments of substances under the Canadian Environmental Protection Act, 1999 (CEPA 1999) to determine whether they present or may present a risk to human health or to the environment.
• 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.
• The ecological hazard and exposure potentials of ethylene thiourea (ETU) were classified using the Ecological Risk Classification of Organic Substances (ERC) Approach.
• ETU is considered to have health effects of concern (potential to cause cancer, and reproductive and developmental effects); however, at levels of exposure considered in the assessment, the Government concluded that this substance is not harmful to human health or to the environment.

About this substance

• The screening assessment focused on 2-imidazolidinethione, commonly referred to as ethylene thiourea (ETU), which was assessed under the third phase of the Chemicals Management Plan (CMP).
• ETU was originally included in the draft screening assessment for the Heterocycles Group. To better align with the re-evaluation of certain pesticides, this substance was assessed separately.
• ETU is a degradation product, metabolite and residual in ethylene bis-dithiocarbamate fungicides. ETU does not occur naturally in the environment.
• According to information gathered by the Government, this substance is mainly used in Canada in plastic and rubber materials, in formed automotive parts, in vehicle imports, and in fabric, textile and leather articles.

Human and ecological exposures

• The screening assessment indicated that Canadians may be exposed to ETU mainly through their diet, including drinking water, as a result of crop treatment using ethylene bis-dithiocarbamate fungicides that break down to ETU. These sources of exposure to ETU have been addressed under the Pest Control Products Act as part of Health Canada's Pest Management Regulatory Agency (PMRA) re-evaluation of ethylene bis-dithiocarbamate fungicides> and were not characterized further.
• The general population may also be exposed through dermal contact (through the skin) to residual ETU through migration from rubber products.
• The assessment considered the results of human biomonitoring studies, which measure substances in blood, urine or other human tissues and fluids (such as breast milk, nails or hair). The information on measured levels in humans is important for estimating exposure to Canadians.
• According to the information considered under the ERC Approach, ETU was identified as having low ecological exposure potential.

Key health and ecological effects (hazard)

• To help inform the health effects characterization in the screening assessment, international and national data reports were considered, among other sources of information. This included the re-evaluation by the PMRA and summarized health effects data from United States Environmental Protection Agency (U.S. EPA), United States National Toxicology Program, International Agency for Research on Cancer (IARC) and the European Chemicals Agency (ECHA).
• ETU is classified as a probable human carcinogen by the U.S. EPA. In addition, it has been classified as a substance that may damage the unborn child under the ECHA Globally Harmonised System (GHS).
• ETU was also identified through laboratory studies as having effects on the thyroid.
• According to information considered under the ERC Approach, ETU was identified as having a low ecological hazard potential.

Consideration of subpopulations who may be more susceptible or highly exposed

• 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 screening assessment process, such as infants, children, and people of reproductive age. For instance, age-specific exposures are routinely estimated and developmental and reproductive toxicity studies are evaluated for potential adverse health effects. These subpopulations were taken into account in the risk assessment outcomes of ETU.

Risk assessment outcomes

• Based upon a comparison of levels to which Canadians may be exposed to ETU from rubber products and the levels associated with health effects, for both non-cancer and cancer effects, the risk to human health for this substance is low.
• Based upon the outcome of the ERC Approach, ETU is considered unlikely to be causing ecological harm.

Screening assessment conclusions

• The Government concluded that ETU is not harmful to human health at levels of exposure considered in the assessment, and that this substance is not entering the environment at levels that are harmful.

Preventive actions and risk reduction

• Although ETU is not considered to be harmful to human health or the environment at current levels of exposure, this substance is considered to have health effects of concern (potential to cause cancer, and reproductive and developmental toxicity). Therefore, there may be a concern if exposures to this substance were to increase.
• For this reason, the Government may consider this substance, in future information gathering initiatives, to track changes in exposure or use patterns.

Where to find updates

• Updates on this substance can be found on the timeline for ETU.
• Updates on information gathering initiatives and additional information on the risk management of substances addressed under the CMP are available.
• 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

• ETU may be found in products available to consumers. Canadians should follow any safety warnings and directions related to the product and dispose of products responsibly according to municipal or local guidelines.
• The screening assessment focused on potential risks from exposure of the general population of Canada. Hazards related to chemicals used in the workplace are defined within the Workplace Hazardous Materials Information System (WHMIS). For information concerning workplace health and safety and what steps to take in the workplace, Canadians should consult their employer or the Occupational Health and Safety Regulator in their jurisdiction.