Sydney Harbour ‘fluorescent green substance’ leak confirmed to be non-toxic

A spill that turned parts of Sydney Harbour bright green has been found to be non-toxic, but the origin will likely remain a mystery.

Resident observed a “fluorescent green substance” in the water at Milson Park bay in the harbourside suburb of Kirribilli on Wednesday afternoon.

Fire and Rescue NSW crews, council rangers and engineers were called in to plug a drainage system with spill socks and managed to clear any traces of green water by early evening.

The event had no negative environmental impact, Fire and Rescue NSW Superintendent Adam Dewberry said.

“I can confirm to you is that it’s not toxic,” he told AAP.

“I had a look down there this morning. There’s no marine life that’s ... dead.

“There’s no staining or marks on any of the wharfs or the boats that are in the bay.”

Authorities believe the colour was probably caused by fluorescein, an odourless substance used to dye water in plumbing networks for diagnostic tests.

But given the number of potential sources around the area, Dewberry said it was unlikely they would be able to determine its origin.

“There’s extremely old buildings in construction, there’s new buildings, there’s sewer systems or stormwater systems all throughout,” he said.

“Was it a plumber, was it a prank? I don’t know, just don’t know.”

Dewberry said community members he had interacted with at the scene showed little concern about the spill, due to the lack of any signs of environmental damage.

Residents had observed the colour hours before emergency services were called.

“I would say there was more of an interest from the community, not an element of concern,” he said.

“They went, ‘Oh, it’s green’.”