Microplastics have transitioned from a niche topic in marine biology to a primary concern for homeowners evaluating their tap water quality. As testing techniques grow more sensitive, scientists are detecting microscopic plastic particles in tap water, bottled water, rivers, and even inside the human body.

While headlines can sound alarming, the scientific understanding of human health risks is still evolving. This article provides a clear, factual breakdown of what microplastics are, where they originate, what research shows about their presence in drinking water, and how water filtration systems perform against them.

1. What Are Microplastics and Nanoplastics?

Plastic does not readily biodegrade; instead, environmental exposure to sunlight, wind, and wave action breaks it down into progressively smaller fragments. Plastic contaminants in water are generally classified into two primary size categories:

• Microplastics: synthetic solid plastic particles ranging from 1 micrometer (µm) up to 5 millimeters (mm) in size (about the size of a pencil eraser).
• Nanoplastics: plastic particles smaller than 1 micrometer (under 1,000 nanometers). Because of their sub-micron scale, nanoplastics are invisible under standard optical microscopes and require advanced chemical imaging technology to detect.

Primary Sources of Contamination

Microplastics enter the water supply through several everyday human activities and industrial processes:

• Synthetic Clothing Fibers: Washing synthetic garments (such as polyester, nylon, or acrylic fleece) sheds thousands of microfibers per laundry load. Wastewater treatment facilities capture many, but not all, of these fibers before effluent is discharged into waterways.
• Tire Wear and Road Runoff: Friction between vehicle tires (made of synthetic rubber compounds) and road surfaces generates tiny rubber-plastic particles. Rain washes this debris into storm drains and local surface waters.
• Degraded Plastic Waste: Single-use plastic packaging, bags, and bottles left in landfills or rivers slowly break down into fragments and microfibers over time.
• Cosmetics Microbeads: Historically added as exfoliants in facial scrubs and toothpaste, polyethylene microbeads washed down household drains. Although federal law banned intentionally added microbeads in wash-off cosmetics via the Microbead-Free Waters Act of 2015, older residues persist in environmental sediments.

2. What Studies Have Found in Drinking Water

As scientific instrumentation has advanced, researchers have shifted from studying ocean waters to testing tap and bottled water directly.

• Tap Water Contamination (Kosuth et al., 2018): In a global study published in PLOS ONE, researchers tested 159 tap water samples from around the world. The study found that 81% of tap water samples contained anthropogenic particles — nearly all of them fibers — with an average concentration of 5.45 particles per liter.
• Bottled Water Microplastics (Mason et al., 2018): A groundbreaking study by researchers at the State University of New York at Fredonia analyzed 259 individual bottles of water across 11 global brands (published in Frontiers in Chemistry). The team detected plastic particles in 93% of the tested bottles, averaging 325 particles per liter (including particles down to 6.5 µm). Polypropylene, the polymer frequently used to manufacture bottle caps, accounted for 54% of the identified particles, suggesting the packaging process itself contributes contamination.
• Bottled Water Nanoplastics (Qian et al., 2024): Utilizing single-particle Stimulated Raman Scattering (SRS) microscopy, researchers from Columbia and Rutgers Universities published a landmark study in PNAS. They found that bottled water contained an average of ~240,000 plastic particles per liter — roughly 90% of which were nanoplastics under 1 micrometer in size, which earlier analytical methods were unable to count. (That headline count has since drawn a published critique over laboratory blank methods, which the authors have answered; the exact number is debated, but the finding that bottled water carries far more plastic particles than tap water is not.)

3. Potential Health Effects: What Science Knows (and Does Not Know)

Understanding how microplastics affect human health requires distinguishing between detection and toxicity. Scientists have confirmed where particles go, but long-term health consequences remain an active field of study.

Where Particles Have Been Detected in the Body

Peer-reviewed studies have detected microplastics and nanoplastics in human blood, lung tissue, placenta tissue, and stool samples. Recent autopsy studies have also detected particles in cardiovascular tissue and human brain tissue samples.

The Current Scientific Consensus

• Biological Absorption: Larger microplastics (above roughly 150 micrometers) are generally not absorbed by the human gastrointestinal tract and pass through the body. However, smaller particles — particularly sub-micron nanoplastics — possess the theoretical capability to cross biological membranes, such as the gut lining or blood-brain barrier.
• Toxicity Concerns: Researchers are actively investigating two main areas of concern: cellular toxicity caused by physical particle irritation, and chemical exposure from plastic additives (such as phthalates or bisphenols) leaching into tissues.
• Current Status: In its public health evaluations, the World Health Organization (WHO) concluded that while routine monitoring is sensible, the current scientific evidence does not show a clear, quantified health risk from consuming microplastics at current levels in drinking water. Health institutions emphasize that more standardized research is required before firm conclusions can be drawn.

4. Regulatory Status: EPA Standards and Regulations

To evaluate your drinking water accurately, it is essential to understand federal and state regulatory frameworks.

Is there an EPA Maximum Contaminant Level (MCL) for microplastics?
No. There is currently no enforceable EPA drinking water standard or Maximum Contaminant Level (MCL) for microplastics or nanoplastics under the Safe Drinking Water Act. Public water utilities are not legally required to test for or report microplastic concentrations.

Regulatory Outlook:
The EPA has included microplastics on its draft Contaminant Candidate List 6 (CCL 6), published in April 2026. The CCL is a watchlist of unregulated contaminants known or anticipated to occur in public water systems. Inclusion on this list prioritizes federal research into standardized testing methodologies, occurrence, and toxicology, which represents the initial administrative step toward potential future regulation. Microplastics are often discussed alongside PFAS — the forever chemicals — as the two emerging contaminant stories in drinking water; you can read our full breakdown in PFAS in Drinking Water.

5. Particle Sizes vs. Filter Micron Ratings

Selecting the right water filter requires comparing particle dimensions against filter pore sizes. Particle dimensions are measured in micrometers (µm), commonly called microns (1 micron = 0.001 millimeters).

Size Reference Scale

• Human Hair Diameter: ~70 µm
• Fine Beach Sand: ~100 µm
• Microplastics: 1 µm to 5,000 µm (5 mm)
• Nanoplastics: under 1 µm (under 1,000 nanometers)

Absolute vs. Nominal Micron Ratings

When shopping for water treatment filters, understanding the difference between rating types is critical:

• Nominal Micron Rating: Per the Water Quality Association (WQA), a nominal rating means the filter traps about 85% of particles at the specified size. A 1-micron nominal filter still lets roughly 15% of 1-micron particles pass through.
• Absolute Micron Rating: Represents a verified physical barrier where the filter rejects 99.9% or more of particles at or above that specified micron size under laboratory test conditions.

6. What Removes Microplastics: Filter Types and Pore Sizes

Water treatment technologies vary in their ability to capture microplastics based on physical pore size and filtration mechanics.

Sediment Filters

Typical Pore Size / Rating: 1 µm to 50 µm

Microplastic Removal Capability: Moderate to High (traps larger fragments and synthetic fibers)

Nanoplastic Removal Capability: None (nanoplastics pass straight through)

Carbon Block Filters

Typical Pore Size / Rating: 0.5 µm to 10 µm

Microplastic Removal Capability: High (captures most microplastics 0.5 µm and larger via physical straining and adsorption)

Nanoplastic Removal Capability: Low to None (sub-micron particles bypass carbon pores)

Reverse Osmosis (RO)

Typical Pore Size / Rating: ~0.0001 µm

Microplastic Removal Capability: Very High (~99%+ physical rejection)

Nanoplastic Removal Capability: High (rejects sub-micron particles down to ionic levels)

Important Note on Certifications

There is no standalone standard written only for microplastics — but that does not mean no certification exists. Microplastics Reduction is a certified claim under NSF/ANSI 401, the standard for emerging compounds, and real products carry it today, certified by NSF and by IAPMO R and T. When you shop, that claim — Microplastics Reduction under NSF/ANSI 401 — is the one to look for, and you can confirm any product listing in the certifier own directory before you buy.

The size-based claim still matters too: Particulate Reduction, Class I, under NSF/ANSI 42 covers particles of 0.5 to 1 µm (at least 85% reduction) — rust-and-sediment territory originally, but the same physical size range as larger microplastics. Be wary of any brand advertising a special microplastic certified logo outside these standards; check the claim against the NSF/ANSI 401 listing instead.

7. Regional Findings: Microplastics in New Jersey Waterways

Local research in New Jersey highlights how microplastics move through state water infrastructure and natural surface waters.

• NJ DEP Wastewater and Surface Water Analysis (2026): A May 2026 study published by the New Jersey Department of Environmental Protection (NJ DEP) Division of Science and Research, with Rutgers University researchers, evaluated microplastic concentrations across four municipal Wastewater Treatment Plants (WWTPs) and receiving water bodies.
• Findings: The study identified particles ranging in size from 140 µm to 5,000 µm in wastewater. Influent entering the plants averaged 33 microplastic particles per liter, and the plants removed 84–93% of microplastics by the end of treatment, with treated effluent averaging about 1.4 particles per liter. Nearby surface waters averaged between 1.0 (upstream) and 1.5 (downstream) microplastic particles per liter, showing that treated discharge and stormwater runoff continually introduce synthetic polymers into New Jersey rivers and watershed systems; the most common polymers identified in the wastewater itself were polypropylene (35%) and polyester (23%).

Summary and Practical Takeaways

1. Tap water contains significantly fewer microplastic particles than bottled water. Bottled water packaging sheds substantial quantities of micro- and nanoplastics into the liquid.
2. Reverse Osmosis (RO) and sub-micron Carbon Block filters (0.5 µm absolute) are the most effective home filtration methods for capturing microscopic plastic debris.
3. A microplastics certification does exist — look for a Microplastics Reduction claim under NSF/ANSI 401, verified in the certifier directory, or a certified Class I particulate reduction (0.5–1 µm) under NSF/ANSI 42, or an RO system, for the strongest documented performance.

Crypto’s in the news this week — 14 people got sick from a hotel pool in Washington, and the pool was clean, well-maintained, no violations on record. That’s the thing about Cryptosporidium: chlorine doesn’t stop it. These are the same parasites behind every “boil water” notice you’ve ever seen. Giardia and Cryptosporidium — “Crypto” — are microscopic parasites that cause intestinal illness, and Crypto has one nasty trick: its protective shell shrugs off the chlorine your utility uses to disinfect the water.

What they are

Single-celled parasites spread through human and animal waste. When conditions turn bad, they form hard-shelled cysts (Giardia) and oocysts (Crypto) that survive in cold water for months. It takes as few as one to ten organisms to cause infection. Symptoms: diarrhea, nausea, vomiting, fever — miserable for a healthy adult, dangerous for the immunocompromised.

Where they come from

Surface water — lakes, rivers, reservoirs — contaminated by wildlife, livestock, or sewage overflows. Wells under the influence of surface water can carry them too. After heavy rain or flooding, the risk spikes. This is why utilities drawing from surface water must filter and disinfect to strict federal standards.

The health picture, honestly

For healthy people, giardiasis and cryptosporidiosis are usually self-limiting — a week or two of misery. For infants, the elderly, and anyone immunocompromised, Crypto can be life-threatening. There’s no MCL for either — the EPA regulates them through treatment requirements instead: utilities must achieve 99.9% removal or inactivation of Giardia and 99% of Crypto.

How to test

Specialized lab testing exists but isn’t routine for homeowners. Practically: if your utility issues a boil-water advisory, assume the worst. Well owners after floods or with surface-water influence should test for total coliform as a screening indicator and talk to their health department.

What removes them

Three proven answers: boiling (a rolling boil for 1 minute kills both — the CDC’s gold standard), absolute 1-micron filtration, and UV disinfection (very effective against both, including chlorine-resistant Crypto). Reverse osmosis removes them easily. Note the word absolute: a filter labeled “absolute 1 micron” is tested to block everything above that size. A filter labeled “nominal 1 micron” or just “1 micron” is not — the CDC specifically warns that nominal filters may NOT remove Crypto. NSF Standard 53 or 58 certification for cyst reduction is what you look for on the box.

What does NOT remove them

Chlorine and chloramine at normal municipal levels — Crypto is virtually unaffected. Standard carbon pitchers, water softeners, and sediment filters with loose micron ratings. “Effective against Giardia” on a label doesn’t mean effective against Crypto.

If a boil-water advisory hits your town

Don’t use your drinking water system during the advisory. Put whole-home filters in bypass mode — bacteria can linger in the filter media and in POE tanks. It might not cause trouble right away, but they’re susceptible to harboring it. After the advisory lifts, flush through the spigot — not the shower head — before putting anything back in service. If a shower head filter was used during the advisory, replace it just like the other filters. And if your RO was used, assume the prefilters and membrane are fouled — replace them and disinfect the tank as a precaution.

What I’d buy: a point-of-use filter certified to NSF 53 or 58 for cyst reduction with an ABSOLUTE (not nominal) 1-micron rating — or an under-sink reverse osmosis unit, which handles cysts plus everything dissolved. For whole-house protection on a private well, a properly sized UV system validated for Crypto inactivation.

This is the article where the micron rating lesson matters most: absolute versus nominal is the difference between protected and exposed. Read the label. If it doesn’t say “absolute,” it doesn’t count.

Curious what’s in your tap? Start with What’s In Your Water?

Chloramine in Drinking Water

If your tap water smells a little like a swimming pool but your utility says they don’t use chlorine — they’re probably using chloramine. It’s the disinfectant of choice for a growing number of water systems, and it’s a tougher customer than chlorine when it comes to filtration.

What it is. Chloramine (usually monochloramine) is made by combining chlorine with ammonia. Utilities have used it since the 1930s, and its use has grown because it lasts longer in the distribution system and forms fewer disinfection byproducts (like TTHMs and HAA5) than free chlorine. Over 68 million Americans drank chloraminated water as of the last big survey, and the number has only grown.

Where it comes from. Your utility, on purpose. If your annual water quality report lists a disinfectant residual and mentions chloramine — or your utility sent a notice about switching disinfectants — that’s your answer. This is a city-water topic.

The health picture, honestly. The EPA caps chloramine at 4.0 mg/L (measured as chlorine), and water meeting that standard is considered safe to drink, cook with, and bathe in. Above that level, eye and nose irritation, stomach discomfort, and anemia are the reported effects. Two groups must remove it completely: kidney dialysis patients (it must never enter the bloodstream) and aquarium owners (it’s lethal to fish). Everyone else — it’s a taste, smell, and peace-of-mind issue more than a health emergency.

How to test. Your utility’s report tells you whether they use chloramine and at what residual. Home test kits for total chlorine will pick it up. If your water smells like a pool but tests low for free chlorine, suspect chloramine.

What removes it. Here’s the key point: standard carbon is slow and incomplete against chloramine — you need catalytic carbon. Catalytic carbon breaks the chlorine-ammonia bond far more effectively than regular GAC. A whole-house catalytic carbon system is the standard answer. Reverse osmosis also removes it effectively at the drinking-water tap. UV is an established technology for chloramine removal in dialysis and pharmaceutical settings.

What does NOT remove it. Standard pitcher filters and fridge filters — they’re built for chlorine, not chloramine, and contact time is too short. Boiling doesn’t reliably remove it. Letting water sit out, which works for chlorine, barely dents chloramine — that’s exactly why utilities switched to it.

What I’d buy

Treatment type: a whole-house catalytic carbon system, NSF or WQA listed, at the point of entry. Not standard carbon — catalytic. That’s the difference between actually removing chloramine and just hoping. For drinking water only, an under-sink RO works.

Chloramine isn’t the villain some corners of the internet make it out to be — it’s a legitimate disinfectant with real benefits. But if you want it out of your water, you need the right carbon for the job. Regular carbon won’t cut it.

Curious what’s in your tap? Start with What’s In Your Water?

Benzene in Drinking Water

If there’s a gas station, an old factory, or a leaking underground fuel tank anywhere near your well, keep reading. Benzene is the one that shows up when petroleum gets into groundwater — and it’s the nastiest of the bunch.

What it is. Benzene is a volatile organic compound — a building block of gasoline and a feedstock for plastics, resins, and synthetic fibers. It’s a known human carcinogen. Not a “maybe,” not “suggestive” — the occupational evidence settled that decades ago, and the cancer it causes is leukemia. That “known carcinogen” label is a hazard classification — it says benzene can cause cancer, not how much risk any given dose carries.

Where it comes from. Gasoline, mostly. Leaking underground storage tanks at gas stations are the classic source: a slow drip of fuel into the soil becomes a plume in the groundwater. Petroleum refineries, chemical plants, and hazardous waste sites round out the list. If your well sits downhill from any of those, test.

The health picture, honestly. Long-term exposure above the legal limit is linked to leukemia and other blood cancers, plus anemia and immune system damage. At high doses it causes dizziness and headaches first — and because it’s volatile, it gets into you through the air in your home too, not just the glass. The EPA’s legal limit is 5 parts per billion, with a health goal of zero. Some states go further — California and Florida hold it to 1 ppb.

How to test. A lab test for VOCs (EPA Method 524.2) from a state-certified lab. On city water, check your annual water quality report first. On a well near gas stations, industrial sites, or known spill areas — test, don’t guess.

What removes it. Granular activated carbon (GAC) plus aeration — that’s the EPA-approved combo. A whole-house carbon system at the point where water enters the home, sized for your flow rate and maintained on schedule. For serious contamination, packed tower aeration strips it out before carbon polishes what’s left.

What does NOT remove it. Here’s the one that surprises people: reverse osmosis does NOT reliably remove benzene — the solvent can dissolve into the RO membrane and migrate through to the treated water. Standard pitcher filters are the wrong scale for this. Boiling just drives it into the air. Water softeners, UV, chlorine — nothing.

What I’d buy

Treatment type: a whole-house granular activated carbon system, NSF or WQA listed, sized for your home and installed at the point of entry. Carbon works — but only until it’s exhausted, so replace it on schedule and retest to prove it.

Benzene is the real deal as contaminants go. But it’s also very treatable — carbon and aeration have been doing this job for decades. Test, treat the whole house, verify. That’s the order.

Curious what’s in your tap? Start with What’s In Your Water?

Fluoride might be the most argued-about thing in drinking water. One side calls it a public-health triumph that prevents cavities; the other side wants it out of the water completely. Both sides are loud — and if you’re stuck in the middle, it’s hard to know what to believe.

So let’s clear it up: they’re arguing about different doses. At 0.7 milligrams per liter — the level U.S. health authorities recommend for community water systems — fluoride prevents tooth decay, and that’s well supported. At much higher levels, it does real harm: stained, pitted teeth in kids, and stiff, painful joints over decades. Same substance, different dose. Dose is the whole argument.

This article is about the high end — too much fluoride — because that’s the end where filtration matters. Nobody needs a filter for 0.7 mg/L.

What it is

Fluoride is a naturally occurring mineral — one of the most abundant elements on earth. It gets into water two ways: it dissolves out of rock and soil into groundwater, or a water utility adds it deliberately to prevent tooth decay. About two-thirds of Americans on public water systems drink fluoridated water.

Where too much comes from

Mostly geology. In regions with fluoride-rich rock formations — parts of Texas, the Southwest, and scattered pockets elsewhere — private wells can test at 2, 3, even 4+ mg/L straight out of the ground. On public water, utilities target 0.7 mg/L, so excess fluoride is mainly a private-well story.

The health picture, honestly

Three numbers matter. At 0.7 mg/L, you’re in the cavity-prevention zone — that’s the target. At 2.0 mg/L — the EPA’s secondary standard — children under nine can develop dental fluorosis: white streaks, brown staining, or pitting of the teeth as they form. It’s cosmetic, but it’s permanent. At 4.0 mg/L — the EPA’s enforceable legal limit — decades of exposure can cause skeletal fluorosis: stiff, painful joints and, in severe cases, weakened bones. That’s the line the law draws, and it’s there for a reason.

How to test

If you’re on city water, your utility’s annual water quality report lists the fluoride level — look it up before spending a dime. On a private well, get a lab test; fluoride is cheap to analyze and most state-certified labs run it for a few dollars. Home test strips exist but they’re rough estimates — fine for a first sniff, not for decisions.

What removes it

Here’s where I have to be blunt, because this is the trap: your standard pitcher filter does not remove fluoride. Not Brita-style carbon, not fridge filters, not faucet mounts — plain carbon doesn’t catch dissolved fluoride ions, period. What actually works:

• Reverse osmosis. The proven home answer — removes 80–99% of fluoride along with most everything else dissolved in the water. Under-sink unit, done.
• Distillation. Boils water and condenses the steam, leaving fluoride behind. Near-total removal, but slow and energy-hungry.
• Activated alumina. A specialty filter media that grabs fluoride ions. Effective (up to ~90%) but finicky — it wants slightly acidic water and regular media replacement.
• Bone char carbon. Charred animal bone — sounds odd, works well. Not for everyone, for obvious reasons.

What does NOT remove it

Standard carbon pitchers and filters. Water softeners. UV light. Chlorine. And boiling — boiling water down concentrates fluoride as the water evaporates. If your plan was “I’ll just boil it,” that’s backwards.

What I’d buy

Treatment type: an under-sink reverse osmosis unit — it’s the straightforward, proven way to take fluoride out of drinking and cooking water without turning it into a science project. Test first so you know your starting number, then retest after install to confirm where you landed.

The bottom line

Fluoride is one of those rare topics where both sides have a point: the right amount protects teeth, too much causes real harm. The answer isn’t fear — it’s a number. Get tested, know your level, and act on that instead of guessing.

Start here: What’s In Your Water? — learn how to read your water report and test your own tap.

If you grew up anywhere near factories, dry cleaners, or a military base, there’s a decent chance you’ve heard of this one. Trichloroethylene — TCE for short — is an industrial solvent that was used everywhere for decades: degreasing metal parts, dry cleaning, making refrigerants and adhesives. Some of the most famous water contamination cases in American history, like Camp Lejeune, involve TCE. The EPA restricted or banned most uses of it in 2024, but the stuff it spilled decades ago is still sitting in groundwater today. It breaks down slowly, so old messes are still old problems.

Here’s the thing about TCE: it’s a volatile organic compound. That means it doesn’t just stay in the water — it can evaporate out of it, including into the air inside a home from contaminated groundwater. So people near a plume can get exposed through drinking water, through showering in it, and through vapor getting indoors. Three ways in, not one. That matters when we talk about how to fix it.

The health picture

I’ll be straight with you, and I’ll frame this right: the International Agency for Research on Cancer lists TCE in Group 1. IARC groups are hazard classifications — they say whether something can cause cancer, not how much risk a given dose carries. Group 1 doesn’t mean “dangerous at any dose.”

With that understood: worker studies show higher rates of kidney cancer among people exposed to high levels of TCE over long periods, with some evidence for non-Hodgkin lymphoma and liver cancer too. High exposures can cause dizziness, headaches, nausea, confusion, and damage to the liver and kidneys. Animal studies link it to developmental effects, including fetal heart defects from exposure early in pregnancy. The EPA set the legal limit in public drinking water at 5 parts per billion, and its stated goal for TCE in drinking water is zero — meaning below the legal limit is fine, but less is always better.

How to test

TCE is a job for a lab, not a test strip. Ask for a VOC panel (EPA Method 524.2) from a state-certified lab. Who should test? If you’re on a private well anywhere near industrial sites, old factories, dry cleaners, or known cleanup sites, yes. If you’re on city water, your utility tests for it and reports the numbers in your annual water quality report — check what yours says. Private wells near known contamination areas are the real exposure stories with TCE.

What removes it

Good news: TCE is one of the contaminants where treatment is proven. Whole-house granular activated carbon filtration is the standard recommendation — state health departments point to carbon filtration first for residential TCE. For well water with significant contamination, aeration (packed tower aeration) is highly effective because TCE is volatile and wants to leave the water; utilities pair it with carbon to catch what’s left. Reverse osmosis also removes it. Whatever system you use, have it installed by a pro, retest after install, and keep up with filter changes — a saturated carbon filter stops doing its job.

What does NOT remove it

This is the important part. A water softener does nothing for TCE. UV light does nothing for it. Chlorine does nothing for it. And boiling? Boiling drives it into the air, which can turn a water problem into an air problem. A point-of-use pitcher on the kitchen counter is the wrong scale for a contaminant you can also absorb in the shower — TCE is a whole-house problem, not a drinking-glass problem.

What I’d buy

Treatment type: a whole-house granular activated carbon filter from a certified unit (NSF or WQA listed), installed at the point where water enters the home. For a private well with high TCE readings, point-of-entry aeration ahead of carbon is the proven combo. This one’s worth getting professional help for — get the water tested before and after, and retest on a schedule.

The bottom line

If you suspect TCE anywhere near your well, don’t guess. Test it, treat the whole house, and verify with retesting. Knowledge first, filter second — that’s always the order.

Start here: What’s In Your Water? — learn how to read your water report and test your own tap.

Radium is the one contaminant in this series that makes a Geiger counter click. Radium-226 and radium-228 are radioactive isotopes — real radiation, right in the glass — and they show up in drinking water more often than most people realize. No taste, no smell, no color. You cannot sense it. Only a lab test finds it.

So let’s talk about it straight: what it is, where it comes from, and what the risk actually looks like at the levels people drink.

What it is

Radium is a naturally occurring radioactive metal. It’s born when uranium and thorium — both present in small amounts in most rocks and soil — undergo radioactive decay. Two of its isotopes matter for drinking water: radium-226 and radium-228.

Here’s the detail that matters for your body: radium behaves chemically a lot like calcium. When you drink it, your body mistakes it for calcium and deposits it in your bones, where it sits and emits radiation into the surrounding bone tissue. That’s why the health concern is specifically bone cancer — along with other cancers linked to long-term exposure.

A quick framing note, since this series covers carcinogens: IARC (the International Agency for Research on Cancer) lists both radium-226 and radium-228 as Group 1 — “carcinogenic to humans.” That classification is about hazard: it says radium can cause cancer. It does not say how much risk a given exposure carries. Group 1 does not mean “dangerous at any dose.”

Where it comes from

Erosion of natural deposits — it’s geology, not industry. Deep wells pull from rock formations where radium dissolves into the water over time. Surface water and shallow wells typically have lower levels; deep wells have higher ones. Oil and gas extraction activities can also elevate concentrations in some areas.

This isn’t a rare edge case. USGS research found that in some regions — including the mid-continental U.S. and the North Atlantic coastal region, which includes parts of New Jersey — more than 20 percent of sampled wells had radium above the federal limit. If you’re on a private well in one of those regions, radium is not a hypothetical; it’s a routine test.

The health picture, honestly

The EPA’s numbers, plainly: the maximum contaminant level (MCL) for combined radium-226/228 is 5 picocuries per liter (pCi/L), and the health goal (MCLG) is zero — EPA doesn’t consider any level risk-free, just legally acceptable below the limit.

What does the legal limit mean in real risk? EPA estimates that 1 in every 10,000 people drinking water at the MCL for a lifetime would develop cancer. That’s the honest math: a real, nonzero risk, but not a large one at the legal limit. California, for reference, set its public health goal vastly lower — 0.05 pCi/L for radium-226 and 0.019 pCi/L for radium-228 — levels so low most lab tests can’t even detect them.

The risk scales with dose and time. A little above the limit for a year is a different story than five times the limit for twenty years. This is a long-term-exposure problem, not an acute-poisoning one.

How to test

There is no home strip for radioactivity. Radium is measured in picocuries per liter — a radioactivity measurement, not a chemical one — and it takes a lab. Most people test two ways:

• Gross alpha screening. Labs often start here: a general screen for radioactive particles. If gross alpha comes back elevated, you follow up with radium-specific analysis.
• Radium-226/228 analysis. The exact measurement the EPA limit is based on.

In New Jersey, radium screening is built into the process: the state’s Private Well Testing Act requires a gross alpha test when a property with a private well changes hands, so if you bought a house on well water here, you may already have a number on file. Either way, a certified lab is the only way to know your level. Utilities on public water are required to test for it, and the results are in your annual water quality report — check it before paying for anything.

What actually removes it

The good news: radium is one of the more straightforward contaminants to remove, because as an ion it responds to proven methods. Per the WQA fact sheet and EPA guidance:

• Cation exchange (a whole-house water softener). This is the standout: a standard ion-exchange softener removes radium the same way it removes calcium and magnesium — it’s all the same exchange process. One of the rare cases where “just a water softener” is a legitimate, proven treatment.
• Reverse osmosis. An under-sink RO unit removes radium from drinking and cooking water at the tap — solid choice if you only want to treat what you drink.
• Distillation and lime softening. Both effective, though distillation is slow and energy-hungry for household use, and lime softening is a utility-scale method.

What does NOT remove it

• Boiling. Does nothing for radium — if anything, boiling water down concentrates it as the water evaporates.
• Any carbon filter — pitcher, faucet, fridge, whole-house carbon block. Carbon does not remove dissolved radium ions. Zero effect.
• A sediment filter. Screens particles, not dissolved ions.
• UV sterilization. Kills microbes; does nothing about radioactivity.
• Chlorine or chlorination. Disinfects; doesn’t touch radium.

What I’d buy

Treatment type: a whole-house cation-exchange water softener — it’s one of the rare cases where the standard softener is the proven answer, treating every tap in the house for radium in one system. If you’d rather treat just your drinking water, an under-sink reverse osmosis unit is the proven point-of-use option. Either way, test first and confirm the treatment brought your combined radium-226/228 under the 5 pCi/L federal limit with a follow-up lab test.

The bottom line

Radium is invisible, tasteless, radioactive, and naturally in the ground — and it’s also one of the easier contaminants in this series to beat, because plain ion exchange works. The trap is never testing: the biggest risk isn’t the radium itself, it’s drinking it for decades without knowing. One lab test tells you where you stand. If you’re on a private well in radium country, that’s the single highest-value test you can run.

Start here: What’s In Your Water? — learn how to read your water report and test your own tap.

If your water smells like rotten eggs, you don’t have a mystery — you have hydrogen sulfide. It’s the most complained-about well water problem that isn’t actually dangerous. Here’s how to diagnose it and fix it.

What it is

Hydrogen sulfide (H₂S) is a gas dissolved in your water, produced when sulfur-reducing bacteria break down organic matter in low-oxygen environments — deep wells, water heaters, plumbing. Humans can smell it at absurdly low levels (around half a part per billion), which is why a tiny amount smells like a disaster. The smell is the whole problem at household levels: EPA has no primary drinking-water limit for it because typical concentrations aren’t a health threat. (At very high concentrations it’s genuinely toxic — that’s an industrial-safety issue, not a tap-water one.)

The one test that tells you where it’s coming from

Run the cold tap. Then run the hot tap. Smell both.

• Smell only in hot water: the problem is in your water heater, not your well. The magnesium anode rod (the sacrificial rod that keeps the tank from rusting) reacts with naturally occurring sulfate-reducing bacteria, making H₂S inside the tank. Common, fixable, and your well water is fine.
• Smell in cold water too: it’s coming from the well or the source water itself.

That thirty-second test saves people from buying whole-house treatment they don’t need. Hot-only smell? Start at the heater.

The honest health picture

At the levels found in household water, hydrogen sulfide is a nuisance — smell, taste, and it can tarnish silverware and corrode plumbing fixtures. It is not making you sick. Don’t let anyone sell you a treatment system on fear. Fix it for comfort and to protect your plumbing, not because it’s poisoning anyone.

What actually removes it

It depends on where it’s coming from:

Hot-water-only smell (water heater):

• Temporarily raise the heater to 160°F for a few hours to kill the bacteria, then flush (careful with scalding — turn it back down after).
• Chlorinate the heater and flush it.
• Replace the magnesium anode rod with a zinc-aluminum alloy rod, which produces far less sulfide gas.

Cold-water smell (well/source):

• Aeration — spraying or cascading the water through air strips the gas out. Simple, chemical-free, very effective.
• Oxidation + filtration — chlorine injection, hydrogen peroxide, or ozone converts H₂S to filterable sulfur particles, then a carbon or multimedia filter catches them.
• Manganese greensand filtration — oxidizes and filters in one unit.

What doesn’t

• A standard water softener — no. It swaps hardness minerals; the gas passes through.
• A plain sediment filter — no. Though here’s the micron-rating footnote: a 5-micron nominal sediment pre-filter is still worth having ahead of oxidation equipment, because sediment fouls treatment media. It protects the fix; it isn’t the fix.
• A standard carbon pitcher — no. Whole-house GAC after oxidation works; a pitcher doesn’t have the contact time.

Bottom line

Rotten-egg smell is hydrogen sulfide, it’s a comfort problem not a health crisis, and the hot-vs.-cold test tells you whether it’s a $30 anode rod or a well treatment system. Diagnose first, buy second.

Wondering what else might be in your water? Start with What’s In Your Water?

A positive bacteria test is the single most common reason a private well fails its water test. If you’ve ever gotten a lab report back with the word “coliform” on it, here’s what it actually means — and what it doesn’t.

What the test is really telling you

“Total coliform” is a family of bacteria used as an indicator, not a diagnosis. Most coliforms are harmless and live everywhere in soil and vegetation. Their presence in your water says: surface water or soil is getting in somewhere it shouldn’t — a cracked well cap, a failing septic, flooding, a well too close to a barnyard.

E. coli is the more specific one. It’s a type of fecal coliform — its presence means fecal contamination has reached your water, and where feces go, worse pathogens (Giardia, viruses, the dangerous E. coli O157:H7 strain) can follow. Most E. coli strains won’t hurt you. The test isn’t saying you’re drinking poison — it’s saying the door is open.

The honest health picture

A total-coliform positive with no E. coli: investigate and retest, don’t panic. An E. coli positive: stop drinking it until it’s resolved — switch to bottled or boiled water. People with weakened immune systems, infants, and the elderly should be the most cautious. This is straightforward stuff, not a scare story: bacteria in well water is common, well understood, and fixable.

What to do when a test comes back positive

• Retest to confirm — one bad sample can be a sampling error. Use a clean, sterile bottle and follow the lab’s instructions exactly.
• Inspect the wellhead. Cracked cap? Missing screen? Water pooling around the casing? Most bacterial problems start at the top of the well, not deep underground.
• Shock-chlorinate the well — a strong chlorine dose circulated through the whole system, then flushed. This is the standard first response and it works for one-time contamination events.
• Find the source. If positives keep coming back, something structural is wrong — septic too close, surface water intrusion, a compromised casing. Disinfection treats the symptom; the source needs fixing.

What truly disinfects water (and what doesn’t)

• Chlorination — yes, the municipal standard for a century.
• UV light — yes, with a sediment pre-filter. UV can’t disinfect what it can’t see through — cloudy water shields bacteria from the light. This is where filter ratings earn their keep: a 5-micron nominal sediment cartridge ahead of the UV unit keeps the water clear enough for the light to do its job.
• Boiling — yes. A full rolling boil for one minute kills bacteria and viruses. (Note the contrast with nitrates: boiling fixes bacteria and worsens nitrate. Know which problem you have.)
• Distillation — yes.

What doesn’t:

• Standard carbon filters — no. They improve taste and remove chemicals; they don’t disinfect. A carbon filter on bacteria-positive water is decoration.
• Standard water softeners — no.
• A sediment filter alone — no. It protects your UV or RO unit; it doesn’t make water safe by itself.

A word on micron ratings, since they matter here

Bacteria run about 0.2 to 10 microns. An absolute-rated sub-micron membrane can physically block them, but the nominal-rated sediment cartridges in most homes can’t be trusted for that — “nominal” means “most of the time,” and disinfection isn’t a most-of-the-time job. For bacteria, disinfect — don’t just filter.

Bottom line

Test for coliform annually (New Jersey requires it for private wells for good reason). A positive test is a to-do list, not a tragedy: confirm it, inspect, shock, and fix the source. And put disinfection — not just filtration — between your well and your glass.

Wondering what else might be in your water? Start with What’s In Your Water?

Nitrate is the most common chemical contaminant in America’s private wells. Not lead, not PFAS — nitrate. If your water comes from a well anywhere near farmland, a septic system, or livestock, this one is worth understanding.

What it is

Nitrate (NO₃) and nitrite (NO₂) are nitrogen compounds that dissolve easily in water. The EPA’s legal limit is 10 milligrams per liter measured as nitrogen — you’ll see it written “10 mg/L as N.” That number exists for one clear reason, which I’ll get to below.

Where it comes from

Mostly from the surface, working its way down. Synthetic fertilizers and manure spread on fields, septic system drain fields, feedlots, wastewater — rain and irrigation carry the nitrogen down into groundwater. Shallow wells in agricultural areas are the most exposed. This is also why New Jersey’s private-well testing law requires a nitrate test: the state knows it’s the likeliest thing to show up.

The honest health picture

The established, no-argument risk is to infants under six months: “blue baby syndrome” (methemoglobinemia). An infant’s digestive system converts nitrate to nitrite more readily, and nitrite interferes with the blood’s ability to carry oxygen. It is serious, and it is preventable — do not mix infant formula with water over the limit.

For adults, the picture is murkier. You’ll see alarming claims online; here’s the measured version. IARC (the International Agency for Research on Cancer) classifies ingested nitrate and nitrite under conditions that lead to nitrosamine formation in the body as Group 2A — “probably carcinogenic.” A quick framing note, since this series covers classified substances: IARC groups are hazard classifications. They say whether something can cause cancer, not how much risk a given exposure carries. Group 2A does not mean “dangerous at any dose.” The science on adult risk at typical exposures is still debated. What isn’t debated: infants and pregnant women should take the limit seriously.

How to test

A lab test for “nitrate as nitrogen,” usually $20–40 from a certified lab. Test once a year if you’re near farms or septic systems, and retest after heavy flooding — runoff spikes levels. If you’ve never tested your well for nitrate, that test is overdue.

What actually removes it

• Reverse osmosis — yes, effective.
• Anion exchange (nitrate-selective resin) — yes, the whole-house option.
• Distillation — yes.

What doesn’t — and the dangerous myth

• Boiling does NOT remove nitrate. It makes it worse. Water evaporates, nitrate stays, concentration goes up. This is the single most important sentence in this article: if your water is high in nitrate, boiling it for your baby’s formula concentrates the very thing you’re worried about.
• Standard carbon filters — no.
• Standard water softeners — no (they swap calcium for sodium; nitrate sails through).
• UV light — no. UV kills bacteria; it doesn’t touch dissolved chemicals.

Bottom line

Nitrate is common, testable, and fixable — but only by the right equipment. If you’re on a well, test for it. If it’s over 10 mg/L as N, an RO unit at the kitchen sink handles drinking and cooking water, and that’s the honest, proportionate fix.

Wondering what else might be in your water? Start with What’s In Your Water?