Household Chemicals Reach Waterways Through Drains
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- Prof Stuart Khan, a water quality expert at the University of Sydney, says thousands of different chemicals flow through household drains into the sewerage system, including herbicides, pesticides, detergents, chlorine bleaches and antibacterial agents like triclosan.
- A recent study of indoor dust and soil samples from across Victoria detected trace metals, PFAS, pesticides, fossil fuel combustion products, and pharmaceuticals including antibiotics, antidepressants and anti-inflammatories — though most were below toxic thresholds.
- Sydney Water's Ben Armstrong says only the "three Ps" — pee, poo and toilet paper — should be flushed, while sinks and showers should receive nothing more than soap suds and water.
- Melbourne Water's Jess Walker states "if it's not rainwater, it doesn't belong in a storm water drain," since stormwater typically runs untreated into creeks, rivers and oceans.
- Khan notes that Sydney's sewage is discharged through three ocean outfalls — Malabar, Bondi and North Head — with "quite limited treatment," leaving many chemicals "barely removed at all."
- PFAS compounds are "very, very slow to naturally degrade — potentially hundreds of years for some of these chemicals to degrade in the environment," Khan says.
- The shift to phosphorus-free detergents has measurably reduced phosphate discharge into the environment, demonstrating that consumer choices can scale, per Khan.
Why it matters: Households are the front line of water pollution: Sydney's ocean outfalls receive largely untreated sewage, and PFAS can persist for centuries once it reaches waterways, meaning everyday disposal decisions by millions of households accumulate into long-tail environmental contamination that current treatment systems were never designed to strip out.
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