The Canadian government has been keeping a tight lid on a report that says little is known about the potential toxic impacts of tar sands/oil sands production and transport on oceans, lakes, and rivers.

The report was first commissioned to address concerns raised during hearings on the Northern Gateway pipeline through British Columbia, redrafted several times since 2013, but never released until Greenpeace obtained it under access to information legislation.

Research on the toxicology of bitumen and its effects on aquatic organisms is lacking, the report says. An early draft identified 10 “knowledge gaps” about bitumen and the diluents with which it is combined so that it can flow through a pipeline.

“Very little information is available on the physical and chemical characteristics of oilsands-related products following a spill into water,” the report states. “A better understanding of the fate and behaviour of these products is critical for assessing the potential risk to aquatic organisms.”

Rather than publishing the assessment, Fisheries and Oceans Canada produced “a more complete, peer-reviewed report” that will be released in the coming months, spokesperson David Walters told Maclean’s. (h/t to Smarter Shift Content Strategist Karen Irving for tracking this story)