Chloral hydrate - information sheet

1,1-Ethanediol, 2,2,2-trichloro-
CAS Registry Number 302-17-0

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  • The Government of Canada conducted a science-based evaluation of chloral hydrate, called a screening assessment, 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 or to 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.
  • In the case of chloral hydrate, the substance has hazardous properties; however, exposure to Canadians is low. It is concluded that chloral hydrate is not harmful to human health or to the environment.

About this substance

  • This screening assessment focuses on the substance 1,1-Ethanediol, 2,2,2-trichloro-, also called chloral hydrate.
  • This substance was assessed as part of the third phase of the Chemicals Management Plan (CMP) and was classified as having a low exposure and hazard potential using the Ecological Risk Classification of Organic Substances Approach. More information on the exposure and hazard classifications can be found in that approach document.
  • Chloral hydrate does not occur naturally in the environment. In Canada, chloral hydrate is primarily found as a disinfection by-product in chlorinated drinking water.
  • Chloral hydrate is used as an active ingredient in prescription drugs used as sedatives and hypnotics, and as a medicinal ingredient in natural health products licensed as homeopathic medicines.
  • It is also used in industrial metal plating.
  • Based on the most recent data, most commercial chloral hydrate is imported into Canada although a small quantity is manufactured in the country.

Exposure of Canadians and the environment

  • Canadians may primarily be exposed to chloral hydrate from its presence as a disinfection by-product in drinking water, although these exposures are considered to be minimal.
  • Exposure of Canadians is not expected to occur from the use of chloral hydrate in the metal plating industry.
  • Chloral hydrate was classified as having a low ecological exposure potential.

Key health and ecological effects (hazard)

  • Chloral hydrate was previously assessed by Health Canada through the Federal-Provincial-Territorial Committee on Drinking Water and a Guidance Document on Chloral Hydrate in Drinking Water was published. The important or “critical” effects considered for human health are adverse effects on the liver. This information was used as the basis of this screening assessment.
  • The guidance document determined that the amount of chloral hydrate found in drinking water is well below the level at which health effects may be observed. More recent drinking water surveys further confirm this finding.
  • Chloral hydrate was classified as having a low ecological hazard potential. 

Risk assessment outcomes

  • The Ecological Risk Classification of Organic Substances Approach was used to characterize whether or not chloral hydrate poses an ecological risk as a result of potential releases of the substance to the environment. Through this approach, chloral hydrate was identified as having a low potential to cause ecological harm.
  • On the basis of the information presented in this assessment, the risk to human health from chloral hydrate is low and there is low risk of harm to organisms and the broader integrity of the environment.
  • The Government of Canada published the Final Screening Assessment for Chloral Hydrate on October 7, 2017.

Screening assessment conclusions

  • As a result of this assessment, the Government concluded that chloral hydrate is not entering the environment at levels that are harmful to the environment.
  • The Government also concluded that chloral hydrate is not harmful to human health at current levels of exposure. 

Preventive actions and reducing risk

  • A health-based value of 0.2 milligrams per litre for chloral hydrate in drinking water was derived by the Federal-Provincial-Territorial Committee on Drinking Water (and published by Health Canada). However, this value was not established as a guideline, as levels of chloral hydrate in Canadian drinking water are much lower.
  • Although chloral hydrate is not considered to be harmful to human health at current levels of exposure, this substance is considered to have a health effect of concern based on its potential to cause cancer. Therefore, it may be of concern for human health if exposure to this substance were to increase.
  • The Government will consider gathering information to track trends in commercial activities and changes in use patterns for chloral hydrate, which will include future information gathering initiatives, such as a mandatory survey under section 71 of CEPA 1999.  

Important to know

  • Chloral hydrate can be found in certain products available to consumers. To protect themselves and the environment, Canadians should follow any safety warnings and directions on product labels and dispose of products responsibly.  
  • To help minimize exposure, some disinfection by-products in drinking water can be removed by using an activated carbon filter. It is important to follow the manufacturer's instructions for these filters.
  • Canadians who may be exposed to chloral hydrate in the workplace should 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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