Hexachlorobutadiene (HCBD)

What is it?

Hexachlorobutadiene (HCBD) has never been commercially produced in Canada. Formerly, the substance was imported for use as a solvent, but it is no longer imported into Canada.

Where is it found and how is it used?

There are no natural sources of HCBD. HCBD is generated as a by-product during the production of certain chemicals. Most notably, HCBD is found as a contaminant at very low levels in certain chlorinated solvents which are imported and used in Canada. As a result, it may be released upon the use of these chemicals. Other possible releases of HCBD in the Canadian environment could be from hazardous landfill leachate. Long-range transport may also contribute to its presence in the Canadian environment.

What are the effects?

When HCBD is released into the environment, it tends to persist in the air, soil or water to which it was released and can accumulate in organisms. It can affect the growth and survival of aquatic organisms, notably those found in sediments.

Canadians' exposure to HCBD from environmental sources is less than the Tolerable Intake that Health Canada recommends, which is based on a benchmark dose or effect levels for non-cancer effects in the kidney. Tolerable Intake is the level of intake to which it is believed a person may be exposed daily over a lifetime without deleterious effect.

What are we doing?

On July 24, 2003, HCBD was added to Schedule 1 Canadian Environmental Protection Act, 1999. Also in 2003 Solvent Degreasing Regulations, which reduce the use and release of two chlorinated solvents: tricholorethylene and tetrachloroethylene, and the Tetrachloroethylene (Use in Dry Cleaning and Reporting) Regulations, which reduce the use and release of tetrachloroethylene, were passed. As HCBD is found as an incidental contaminant in these solvents, the reduction of their use and release also reduces the potential release of HCBD.

On February 15, 2005, it was added to Schedule 1 of the Prohibition of Certain Toxic Substances Regulations, 2005 in order to prevent its reintroduction to the Canadian market. On December 13, 2006, HCBD became the first substance placed on the Virtual Elimination List.

Health effects for any substance depend on the amount of exposure, and how that exposure occurs.