Site-restricted Heavy Fuel Oils (Site-restricted HFOs)

CAS Registry Numbers:

  • 64741-45-3
  • 64741-61-3
  • 64741-80-6
  • 68333-22-2
  • 68333-27-7
  • 68476-32-4
  • 68478-17-1

What are they?

  • Heavy fuel oils, also known as HFOs, are a category of complex petroleum mixtures. Their composition varies with the source of crude oil or bitumen, and the processing steps involved.
  • HFOs are composed of varying lengths of carbon atom chains, ranging between 20 and 50 carbon atoms.
  • HFOs are considered to be of Unknown or Variable composition, Complex reaction products or Biological materials (UVCBs).
  • Site-restricted HFOs are not expected to be transported off petroleum refinery and upgrader facility sites.

How are they used?

  • HFOs are used in final heavy fuel products or as an intermediate product of distillate or residue (leftover from the manufacturing process) derived from refinery distillation or cracking units.
  • While site-restricted HFOs are not expected to leave petroleum facilities, the final fuel product usually consists of a mixture of HFOs as well as higher-quality hydrocarbons.

Why did the Government of Canada assess them?

  • These HFOs were included in the Petroleum Sector Stream Approach (Stream 1) under the Chemicals Management Plan for the screening assessment of potential risks to the environment and to human health.
  • Prior to their assessment by the Government of Canada, these seven site-restricted HFOs were identified as a potential concern for human health based on their classification by international organizations as substances that may cause cancer, and based on a moderate or high potential for exposure (not including workplace exposures) to the general population of Canada.
  • Some were also identified as a potential concern to the environment based on available information regarding possible persistence, accumulation in organisms and potential to cause harm to non-human organisms.

How are Canadians exposed to them?

  • The general population is not expected to be exposed to site-restricted HFOs since they are not expected to be transported off petroleum refinery or upgrader facility sites.

How are they released into the environment?

  • The HFOs considered in this report have been identified as site-restricted (in other words, they are not expected to be transported off refinery or upgrader facility sites); they are either consumed on site or blended into substances leaving the site under different CAS Registry Numbers (which will also be addressed under the Chemicals Management Plan).
  • Releases of site-restricted HFOs are captured into a closed system and then returned to the processing facility for re-use or they are sent to the facility wastewater treatment plant where they are removed from the wastewater.

What are the results of the assessment?

  • The Government of Canada has conducted a science-based evaluation of site-restricted HFOs, called a screening assessment.
  • Screening assessments address the potential for harm to the general population of Canada (not including workplace exposures) and the environment.
  • Results of the final screening assessment indicate that these site-restricted HFOs are not expected to be transported off petroleum refinery or upgrader facility sites.
  • The Government of Canada has therefore concluded that these site-restricted HFOs are not entering the environment in a quantity or under conditions that constitute a danger to the environment.
  • The Government of Canada has also concluded that these site-restricted HFOs are not harmful to the health of the general population as exposure is not expected.
  • HFOs that are not site-restricted and substances into which site-restricted HFOs may be blended will be addressed at a later stage under the Chemicals Management Plan.

What is the Government of Canada doing?

  • Exposure of the general population of Canada to these site-restricted HFOs is currently not expected and the Government of Canada is proposing action to limit the potential for future exposure.
  • The final screening assessment report was published on September 10, 2011.

What can Canadians do?

  • The health risks associated with a chemical depend on the hazard (its potential to cause health effects) and the dose (the amount of chemical to which you are exposed). Site-restricted HFOs are not presently a concern for the environment or human health as exposure is not expected.
  • Canadians who may be exposed to HFOs in the workplace should consult with their occupational health and safety representative about safe handling practices, applicable laws and requirements under the Workplace Hazardous Materials Information System.
Site-restricted HFOs assessed by the Government of Canada
CAS RN DSL Name
64741-45-3 Residues (petroleum), atm. tower
64741-61-3 Distillates (petroleum), heavy catalytic cracked
64741-80-6 Residues (petroleum), thermal cracked
68333-22-2 Residues (petroleum), atmospheric
68333-27-7 Distillates (petroleum), hydrodesulfurized intermediate catalytic cracked
68476-32-4 Fuel oil, residues-straight-run gas oils, high-sulfur
68478-17-1 Residues (petroleum), heavy coker gas oil and vacuum gas oil
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