Mysterious substance found in Sydney street sparks concern
A Sydney woman was concerned after noticing a strange substance on the side of the road where school kids often walk through.
Standing in the gutter looking down at the ground, the Sutherland Shire resident in Sydney's south, photographed the alarming find which had leaked into the grass and onto the gutter.
"Any idea what this might be coming up through the ground by the looks of things," she wrote on Facebook.
"School kids walk past through it. Concerning??"
While many urged the woman to contact Sydney Water, others said the brightly coloured reddish-brown liquid resembled iron or rust.
"I'm sure that's iron, lots of places where the ground got really soaked are still releasing and this is common, I could be wrong tho," one said.
Another explained it was "iron ochre" a "byproduct of the iron in the clay soil in the local area."
"Groundwater with high iron. Not cross-connected. With the amount of water we've had the water table has risen dramatically, give it a few days or weeks for the water table to drop," another shared.
Strange, brown substance explained
Speaking to Yahoo News Australia, Dr William W. Bennett, Associate Professor in Environmental Chemistry at Griffith University, confirmed the liquid is "most likely iron oxide".
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"[This] can form when groundwater comes into contact with oxygen in the atmosphere," he said.
"Iron is not a particularly toxic element, especially in the form of iron oxides. In fact, iron is one of the most common elements in the Earth's crust."
Some people in the comments had thought the iron could be dangerous for humans, particularly kids.
Dr Bennett explained that it's a "natural process" and although it looks strange at first, "it poses no risk to humans".
However, the professor noted that while iron oxide itself has low toxicity and isn't harmful to humans, there's always a risk of contamination in water run-off, which could prove toxic.
"There's always the possibility of other contaminants or microbiological hazards in natural waters such as this," he said. So kids and pets should avoid ingesting the water, he said.
Common find around homes
Other people said they've spotted the same substance at the homes, commonly on driveways and on rocks around the property.
This is because iron is naturally present in soil. When it migrates along with the water towards the drainage system and comes in contact with the atmosphere, it forms a sludge of iron hydroxide.
"I have it coming off our sandstone rocks on patio probs from sandstone under the ground," one said.
"We have it on the driveway too, coming via rocks and clay," revealed another.
While it's not harmful to humans, it can cause damage to pipes and plumbing systems.
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