Microplastics in drinking water — what Australian homeowners need to know

What are microplastics?

Microplastics are plastic particles smaller than 5 millimetres in diameter. They exist on a huge size spectrum — from fragments visible to the naked eye all the way down to nanoplastics smaller than 1 micrometre, which are invisible and can penetrate individual cells.

They come from two main sources. Primary microplastics are intentionally manufactured at small sizes — microbeads in personal care products, plastic pellets (nurdles) used as raw material in manufacturing, and synthetic fibres shed from clothing during washing. Secondary microplastics form when larger plastic items break down through UV exposure, physical weathering, and wave action.

Once in the environment, microplastics are effectively impossible to remove at scale. They've been found in the deepest ocean trenches, in Antarctic ice cores, in remote mountain air, and in the bodies of wildlife across the food chain. In Australia, they've been detected in Great Barrier Reef waters, in Sydney Harbour sediments, and in numerous drinking water studies.

Are microplastics in Australian tap water?

Yes — microplastics have been detected in tap water samples from Australian cities, as they have in virtually every country where drinking water has been tested. A major 2017 global study analysed tap water from multiple countries and found microplastic contamination in approximately 83% of samples. Australian samples were among those tested.

To be clear about context: the concentrations found in treated town water are generally low — typically single-digit to low double-digit particles per litre. This is significantly lower than the concentrations found in some bottled waters (more on that below) and in seafood. The contamination appears to enter the water supply through a combination of atmospheric deposition, pipe infrastructure, and limitations in water treatment.

The bottled water problem

One of the more counterintuitive findings in microplastics research is that bottled water often contains more microplastics than tap water. A 2018 study by researchers at the State University of New York tested 259 bottles of water from 11 brands and 9 countries and found an average of 325 microplastic particles per litre — roughly twice the concentration found in most tap water studies.

The source appears to be the plastic bottle and cap themselves, with additional contamination during the bottling process. Switching to bottled water specifically to avoid microplastics is therefore counterproductive. A home filtration system is a more effective approach on both environmental and health grounds.

What do we know about health effects?

This is the area where honest communication is important — the science is genuinely uncertain. We know microplastics are in human bodies: they've been found in blood, lung tissue, placental tissue, breast milk, and the digestive system in multiple studies. We don't yet have definitive evidence about what harm, if any, this causes at typical real-world exposure levels.

What we do know from laboratory and animal studies:

• Microplastics can carry adsorbed chemical contaminants including plasticisers (phthalates, BPA), flame retardants, and other industrial chemicals into the body
• Nanoplastics in particular can cross biological barriers including the gut wall, the blood-brain barrier, and the placenta
• Inflammatory responses have been documented in animal models at higher concentrations than typical human exposure
• Some plastic-associated chemicals (particularly phthalates and bisphenols) are known endocrine disruptors with established health effects

The World Health Organisation's 2019 assessment concluded that microplastics in drinking water don't appear to pose a risk at current levels, but called for more research and noted significant data gaps — particularly for nanoplastics and the long-term accumulation question. That assessment is now several years old and the research landscape has moved considerably since.

The precautionary position is reasonable: the evidence for harm isn't definitive, but the evidence for absence of harm is also not definitive, and the cost of filtering is modest relative to the uncertainty.

Which water filters remove microplastics?

Unlike PFAS — where filter type matters enormously — microplastics are physical particles, which means physical filtration is effective. The key variable is pore size: you need a filter fine enough to physically block the particles.

Filter Type	Microplastic removal	Notes
Reverse Osmosis (RO)	Excellent (>99%)	RO membranes have pore sizes of 0.0001μm — far smaller than any microplastic. The most thorough solution. Also removes nanoplastics.
Carbon block (solid)	Very good (>95%)	Dense carbon block filters with sub-micron ratings physically block microplastics. Quality matters — look for 0.5μm or 1μm rated blocks. Some certified under NSF 53.
Ultrafiltration (UF)	Very good (>95%)	UF membranes (0.01–0.1μm pore size) remove microplastics effectively. Less commonly found in residential whole-home systems in Australia.
Granular Activated Carbon (GAC)	Moderate	GAC removes larger microplastic particles but the granular structure allows smaller particles to pass through gaps between granules. Less reliable than block carbon for fine particles.
Standard sediment filter (5μm)	Partial	A 5μm sediment filter removes particles larger than 5 micrometres — which includes many microplastics but misses smaller particles and all nanoplastics.
Fine sediment filter (1μm)	Good (>90% of microplastics)	A 1μm sediment filter catches the vast majority of microplastics. Won't remove nanoplastics. Good value option when combined with carbon block.
UV filtration	No effect	UV treatment targets biological contaminants. It has no effect on plastic particles.
KDF / TAC media	No effect	Neither KDF nor TAC technology has a mechanism for removing particulate matter at microplastic scales.

What about nanoplastics specifically?

Nanoplastics (particles under 1 micrometre) are the most concerning size category because they can cross cell membranes and biological barriers. They are also the hardest to remove. Only reverse osmosis reliably removes nanoplastics — standard sediment filters, carbon block, and most other filter types have effective pore sizes larger than nanoplastic particles.

If nanoplastics are a specific concern, an under-sink RO system is the practical solution. A solid carbon block filter will remove a very large proportion of microplastics but cannot guarantee nanoplastic removal.

Filtering your tap water is only part of the picture

Water is not the primary source of microplastic exposure for most people. Research estimates suggest that food — particularly seafood, salt, and foods packaged in plastic — contributes more to total microplastic ingestion than drinking water. Inhaled microplastics from synthetic textiles, dust, and outdoor air are also a significant exposure pathway.

This doesn't mean filtering drinking water isn't worthwhile — it's one of the easier controllable variables. But it's worth having realistic expectations: a whole-home water filter addresses the water ingestion pathway, not total microplastic exposure.

What to ask water filter suppliers

If microplastic removal is a priority, here are the specific questions to ask any supplier:

• What is the micron rating of your carbon block or sediment filter? Look for 1μm or 0.5μm for reliable microplastic removal. A 5μm or 10μm filter is less effective for smaller particles.
• Is the system certified under NSF 53 for cyst reduction? Cyst reduction certification (Cryptosporidium, Giardia) requires sub-1μm filtration performance and is a useful proxy for microplastic removal capability.
• Does the system include a reverse osmosis membrane? For nanoplastic removal, RO is the only reliable option.
• Are the filter ratings absolute or nominal? Absolute ratings mean the filter blocks all particles above the rated size. Nominal ratings mean it blocks most — typically 85–98% — which is less reliable.

Be cautious of suppliers who claim microplastic removal without being able to specify the filter's micron rating or provide certification documentation. Vague claims about "comprehensive filtration" or "advanced technology" without specific micron ratings are a red flag. Our consultation checklist includes questions for evaluating any supplier claim systematically.

---