The toxic spill in Vancouver's English Bay has been identified as bunker fuel, otherwise known as residual fuel oil.

According to the oil industry's material data sheets, the oil is a complex blend of hydrocarbons derived from various refinery streams, usually residue from the oil refinery processes. It is recommended for use in marine diesel engines, boilers, furnaces and other combustion equipment.

The safety data sheet recorded by Shell Marine Fuel Oil in 2013, lists a number of hazards associated with the combustible material, including the possible presence of hydrogen sulphide, which is not only harmful if inhaled, but has a vapour that can also be trapped in clothing.

The list of possible effects are listed as:

Harmful if inhaled

Suspected of damaging fertility or the unborn child

May cause damage to organs or organ systems through prolonged or repeated exposure

May cause cancer

The fuel is also, according to Shell's data, extremely dangerous for the marine environment.