Disgusting origins of mystery balls that shut down NSW beaches revealed

The origin of mysterious round blobs that washed ashore on Sydney beaches earlier this month, forcing their closure, is closer to being solved after scientists made a disgusting finding.

After a series of analytical tests, UNSW Science Associate Professor Jon Beves said the blobs were consistent with “human-generated waste”.

In January, nine beaches had to be closed after thousands of sticky marble-sized balls washed ashore. It came after a number of beaches were closed in 2024 when what was thought to be tar balls washed up.

Beachgoers were told to stay away from Manly, Dee Why, Long Reef, Queenscliff, Freshwater, North and South Curl Curl, North Steyne and North Narrabeen beaches.

“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,” Professor Beves said.

“We found 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.”

Using a variety of techniques, analysis by experts from UNSW, NSW Environmental Protection Authority and Randwick Council found the blobs contained fats, oils, and high calcium levels which suggest they could be similar to fat, oil, and grease (FOG) blobs commonly formed in sewage systems.

FOG blobs form through supramolecular self-assembly, where fatty molecules cluster together through weak, non-covalent interactions.

Calcium and other metal elements are known to enhance this blobbing process by binding to fatty acids and forming aggregates that don’t dissolve in water (soap scum). These masses can become dense and stable, particularly when fats encounter cool water, leading to the creation of sticky blobs.

“The black balls found at Coogee Beach have high concentrations of fatty acids, glycerides and calcium, similar to FOG deposits,” Professor William Alexander Donald, an analytical chemist involved in the research, said.

Professor Donald said analysing the balls had been a challenge.

“Carbon-14 dating suggested they weren’t purely from an oil spill, as the material was mostly modern carbon, loaded with fats, oils, and greasy molecules.

“Detecting markers of human faecal waste – like coprostanol – alongside recreational drugs like THC and industrial PFAS ‘forever chemicals’ pointed us to sewage and other sources of urban effluent as the most consistent origins.”

A Sydney Water spokesperson said there had been no issues with the normal operations at its five Sydney coastal water resource recovery facilities.

“We comply with our licences as set by the NSW Environment Protection Authority (EPA),” they said.

“Sydney Water is taking the matter seriously and is continuing to work with the EPA to investigate possible causes of the grease balls.”