Aqueous Toxicology Register

Under-Sink RO Contaminant Rejection Index

Evaluating physical membrane rejection versus carbon adsorption across the six most prevalent neurotoxic, synthetic, and inorganic contaminants documented in American municipal and private well drinking water.

Synthetic Fluorinated OrganicsNSF/ANSI 58 & 53

PFAS & PFOA (Forever Chemicals)

Activated carbon pitchers become saturated within 30 days and leach PFAS back into water. High-pressure RO membranes provide non-permeable steric rejection.

📏 Particle Size: 0.001 - 0.002 microns

⚖️ EPA Limit: 4.0 ppt (Strict Maximum)

🛡️ RO Rejection: 98.5% - 99.2%

⚠️ Carbon Only: 40% - 70% (Depletes rapidly)

⚠️ Health Risk: Bioaccumulation, thyroid disruption, hepatic toxicity and carcinogenic risk.

Neurotoxic Heavy MetalNSF/ANSI 58

Dissolved Lead (Pb²⁺ Ions)

Lead leaches from legacy brass fixtures and solder lines inside home plumbing. RO thin-film composite membranes reject divalent lead ions by electrical charge repulsion.

📏 Particle Size: 0.0003 microns (Ionic)

⚖️ EPA Limit: 15 ppb (Action Level; Safe Level = 0)

🛡️ RO Rejection: 98.0% - 99.5%

⚠️ Carbon Only: Variable (Only specialized catalytic carbon)

⚠️ Health Risk: Irreversible pediatric neurological damage, cognitive deficit, and adult hypertension.

Naturally Occurring MetalloidNSF/ANSI 58

Inorganic Arsenic (As-III & As-V)

Common in rural deep private wells. Pentavalent Arsenic (As-V) is efficiently blocked by RO. Trivalent Arsenic (As-III) requires pre-chlorination to convert to As-V for complete rejection.

📏 Particle Size: 0.0004 microns

⚖️ EPA Limit: 10 ppb (Maximum Contaminant Level)

🛡️ RO Rejection: 95.0% - 98.0% (For Arsenic-V)

⚠️ Carbon Only: < 10% (Virtually ineffective)

⚠️ Health Risk: Arsenicosis, skin lesions, cardiovascular disease, and bladder/lung cancers.

Dissolved Inorganic AnionNSF/ANSI 58

Municipal Fluoride (F⁻)

Standard countertop carbon pitchers completely fail on fluoride. Only Reverse Osmosis, bone char, or activated alumina can remove fluoride at the molecular level.

📏 Particle Size: 0.00013 microns (Ionic Radius)

⚖️ EPA Limit: 4.0 ppm (Secondary standard: 2.0 ppm)

🛡️ RO Rejection: 92.0% - 96.0%

⚠️ Carbon Only: 0% (Carbon cannot capture fluoride ions)

⚠️ Health Risk: Dental and skeletal fluorosis, pineal calcification concerns.

Synthetic Polymer FragmentsNSF/ANSI 401 & 58

Micro & Nano-Plastics

Nano-plastics slip through municipal sand filters and standard home sediment cartidges. A 0.0001-micron RO pore barrier creates an impenetrable physical block.

📏 Particle Size: 0.001 - 5.0 microns

⚖️ EPA Limit: Unregulated (Emerging Contaminant)

🛡️ RO Rejection: > 99.9% (Absolute Barrier)

⚠️ Carbon Only: 60% - 85% (Micro scale only)

⚠️ Health Risk: Endocrine disruption, cellular inflammation, chemical carrier effects.

Disinfection Chemical ByproductsNSF/ANSI 53 & 58

Total Trihalomethanes (TTHMs)

Formed when chlorine added by city water plants reacts with organic matter. Dual-stage carbon pre-filters followed by RO eliminate both free chlorine and volatile TTHMs.

📏 Particle Size: 0.0008 microns

⚖️ EPA Limit: 80 ppb (Annual Average)

🛡️ RO Rejection: > 99.0% (Combined RO + Carbon Block)

⚠️ Carbon Only: 80% - 95% (When carbon is fresh)

⚠️ Health Risk: Liver, kidney, and central nervous system damage; potential cancer risk.