A team of scientists have discovered what's inside thousands of slimy, black balls that washed up on Sydney, Australia's famously sunny beaches -- and it's more disgusting than first thought.
A few weeks ago, thousands of sticky, round blobs washed ashore on at least six beaches after lifeguards first spotted them at Coogee Beach, which left scientists puzzled about the origin and formation of the debris.
While the mysterious substance was originally thought to be toxic tar balls formed from weathered oil, researchers from the University of New South Wales say it's actually much more revolting.
"Our analyses show that the material is not natural and cannot be attributed solely to an oil spill," Associate Professor Jon Beves, who led the investigation, said in a statement. "It is most consistent with human generated waste."
The analysis determined the sticky spheres are actually a mixture of "hundreds of different components" -- including raw sewage, cooking fat, soap scum, pesticides, PFAS chemicals, steroidal compounds, antihypertensive medications and veterinary drugs.
Researchers used a combination of standard and advanced chemical analytical techniques to reveal the composition and potential sources of the material.
Radiocarbon dating of the samples indicated that the interior of the balls contained about 70% modern carbon and 30% fossil carbon, while the surface was made up of approximately 85% modern carbon and 15% fossil carbon. Modern carbon includes carbon derived from plants and animals, as opposed to fossil fuels.
Elemental analysis, X-ray fluorescence and energy-dispersive X-ray spectroscopy also revealed significant levels of calcium and other metals. Additional spectroscopy tests revealed that atoms and molecules in a sample matched those found in soap scum and cooking oil, reinforcing the presence of domestic waste material.
The analysis also revealed the presence of alkanes typical of diesel fuel, fatty acids and other compounds commonly found in used cooking oils and soap. Additionally, perfluoroalkyl substances (the forever chemicals known as PFAS), steroidal compounds, antihypertensive medications, pesticides, and veterinary drugs were detected, consistent with contamination from sewage and industrial runoff.
Markers of human fecal waste, such as epicoprostanol and recreational drug residues like THC (from marijuana) and methamphetamine, were also identified – consistent with contributions from domestic sources.
Researchers say the presence of fats, oils, and high calcium levels in the black balls suggests they could potentially be related to fat, oil and grease (FOG) blobs commonly formed in sewage systems. 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 FOG 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," Beves said.
The exact origin of the washed up balls remains uncertain, but researchers say they used "deductive reasoning to trace the likely source to human waste."
"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 fecal waste... 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," said Professor William Alexander Donald, an analytical chemist involved in the research.
Sydney Water has reported no known issues with its water treatment plants, so the origin of the balls remains unsolved.