Safety & Contaminant Scope

What RO Removes (Fluoride, PFAS, Microplastics) & Health Facts

Reverse osmosis is one of the broadest residential water barriers available, yet different contaminants are stopped by different stages. Understanding what the membrane rejects versus what carbon handles prevents false confidence.

Scientific editorial illustration of water molecules passing through a semi-permeable RO membrane while larger dissolved salts, heavy metals, and microplastics are deflected — **Scientific Illustration — Semi-Permeable Membrane Separation:** Water molecules pass through the polyamide barrier under pressure while larger hydrated ions, heavy metals, and microplastics are rejected to the drain stream.

Figure 11 — Two-Layer Barrier: A TFC RO membrane relies on carbon pre- and post-filters for chlorine and small uncharged organics (VOCs), while the membrane handles dissolved salts and heavy ions.

1. Contaminant Removal Matrix (NSF/ANSI 58 & 53 Context)

Contaminant	Typical RO System Reduction	Key Condition / Limit
Fluoride	~85%–95%	Driven by the TFC membrane; maintain ≥40 psi feed pressure and replace aging membranes when TDS rejection drops.
PFAS ("Forever Chemicals")	>90%–99% (certified units)	Look for systems specifically certified under NSF/ANSI 58 or 53 for PFOA/PFOS; carbon pre/post stages provide backup polishing.
Microplastics	>99%	Membrane pore size (~0.0001 micron) is thousands of times smaller than microplastic particles; faucet housing cleanliness matters too.
Nitrates / Arsenic (V)	~80%–95%+	Check your system's NSF 58 data sheet—arsenic (III) requires pre-oxidation on well water for full removal.
Chlorine & VOCs	~95%–99% (via Carbon)	Handled by carbon blocks, not the membrane. Keep carbon swaps on a strict 6–12 month schedule.

2. "Is RO Water Bad for You?" — The Mineral Reality Check

A frequent concern is whether drinking low-TDS RO water causes mineral deficiency. Looking at actual milligram numbers puts this in perspective: drinking water—even hard tap water—supplies only a tiny fraction of daily calcium and magnesium compared with ordinary food.

Source (Typical Serving)	Calcium (mg)	Magnesium (mg)
1 Liter Standard RO Water	~0–5 mg	~0–2 mg
1 Liter Moderate Tap Water (150 ppm)	~30–40 mg	~8–12 mg
1 Cup (240 mL) Milk or Fortified Soy Milk	~300 mg	~25 mg
1 Ounce (28 g) Almonds	~75 mg	~75 mg

For healthy adults eating a normal diet, RO water does not cause mineral deficiency. If you prefer crisp mineral flavor or neutral pH for coffee, add a calcite remineralization cartridge.

3. Why Freshly Poured RO Water Sometimes Looks Cloudy

If your RO glass looks milky right after changing filters, recharging the tank, or installing a new unit, watch the glass for 30–60 seconds: if it clears from the bottom upward, it is harmless dissolved air micro-bubbles escaping under pressure—not sediment or bad filters. Also note that indoor houseplants watered exclusively with pure 0–10 ppm RO water still need occasional balanced fertilizer, because tap water's trace calcium and magnesium are removed.