Revealed: Mysterious origin of 'disgusting' black balls that washed up on Sydney beaches

7 November 2024, 16:15 | Updated: 7 November 2024, 16:17

The mystery behind thousands of black balls which plagued beaches across Sydney has finally been solved.

The sticky balls, which were first discovered on Coogee and Gordons Bay beaches last month, were originally believed to be tar balls.

Thousands began washing up on October 16, with eight beaches being forced to close amid fears over their toxicity.

But scientists have now identified their actual origins - and it's much more "disgusting" than they first thought.

Researchers from the University of New South Wales discovered that the balls are a mix of human excrement, soap scum, cooking fat and drugs.

Analysis of the balls found traces of veterinary medicine, steroids, and drugs including THC from cannabis.

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Lead investigator and associate professor Jonathan Beves said: "Our analyses show that the material is not natural and cannot be attributed solely to an oil spill.

"It is most consistent with human generated waste."

He told 9news: "They smell absolutely disgusting, they smell worse than anything you've ever smelt

"The sticky spheres contained hundreds of different components, including molecules that derive from cooking oil and soap scum, PFAS chemicals, steroidal compounds, antihypertensive medications, pesticides, and veterinary drugs."

The high levels of calcium trigger the organic chemicals to club into 'fatbergs', which are typically found in sewers.

Their discovery on the beach suggests there was a sewage leak. However, the exact source remains a mystery.

Writing in The Conversation, Professors Beves and Donald, said: "The black ball incident does highlight the broader issue of pollution along Sydney's coastline.

"Even after all we did, we cannot yet draw definitive conclusions regarding the primary source of the blobs.

"This uncertainty reflects the broader challenges faced by scientists and environmental agencies in tracking and addressing pollution in coastal areas."