FRESH evidence has emerged that potentially toxic coal dust has already contaminated sediments near Hay Point, and could be spread widely across the Great Barrier Reef lagoon.
The study by James Cook University was handed to a Senate inquiry examining the reef's management during a committee hearing in Townsville today.
Based on an analysis of existing data on polynuclear aromatic hydrocarbons (PAHs) in coal dust, the study had what were described in the hearing as "damning findings".
Comparing the extent of the particles at Hay Point found in 2011, the 2014 study revealed the local sediments were "already contaminated with coal residues" that exceed national water quality guidelines.
"This demonstrates that the sources of the PAHs are coastal. The suspended sediments carry coal dust offshore during the normal cycles of re-suspension and tidal transport processes," study author Dr Kathryn Burns wrote.
"The concentrations reported here are for samples collected in 2009 and 2010 before the current expansion of the coal ports began.
"If the ports are greatly expanded, then it can be expected, so will the PAH contamination of the Great Barrier Reef lagoon."
Long-time reef scientist Dr Terry Hughes presented the study, saying it found the "toxic chemicals" already exceeded Australian standards and it was unlikely the existing dust could be cleaned up.
However, Great Barrier Reef Marine Park Authority chairman and chief executive Dr Russell Reichelt said he did not consider it to be a "toxic material".
He said the nature of the coal dust particles was such that it might not present an actual toxic threat to corals, but that coal dust, especially near loaders at ports, was a risk for smothering seagrass.
But he did confirm that the particles were "spread at very fine levels across the continental shelf" on which the reef sits.
The Senate inquiry is expected to report to parliament in August.