Nearly every public water system in the United States uses either chlorine or chloramine to disinfect tap water. This isn’t some hidden conspiracy. It’s the reason waterborne diseases like cholera, typhoid, and dysentery are virtually nonexistent in developed countries. Water disinfection is one of the most important public health achievements of the past 150 years.

But there’s a trade-off. The same chemicals that kill dangerous pathogens also react with organic matter in the water to create disinfection byproducts (DBPs), and some of those byproducts are associated with health risks, including cancer and reproductive problems. The question isn’t whether to disinfect water (the answer to that is clearly yes). The question, and the one NonToxicLab focuses on here, is how to handle what the disinfection process leaves behind.

Chlorine vs. Chloramine: What’s the Difference?

Chlorine

Free chlorine (hypochlorous acid) has been used in U.S. water treatment since 1908. It’s effective, inexpensive, and easy to manage. Chlorine kills most waterborne pathogens quickly and leaves a measurable residual in the water that continues to protect against contamination as water travels through distribution pipes to your home.

The characteristic taste and smell of tap water is usually chlorine. The EPA allows up to 4 milligrams per liter (mg/L) as a maximum residual disinfectant level (MRDL), though most systems operate well below that. Typical levels at your tap range from 0.2 to 2.0 mg/L.

Chloramine

Chloramine is formed by combining chlorine with ammonia. About one in five Americans now gets chloramine-treated water, and that number is growing. Washington D.C., San Francisco, Denver, Philadelphia, and many other major cities use chloramine.

Utilities switch to chloramine for several reasons:

Longer-lasting residual. Chloramine doesn’t dissipate as quickly as free chlorine, which makes it better at maintaining disinfection throughout long distribution systems.

Fewer regulated byproducts. Chloramine produces lower levels of trihalomethanes (THMs) and haloacetic acids (HAAs), the two classes of disinfection byproducts that are currently regulated by the EPA. This helps utilities meet tightening EPA standards.

Reduced taste and odor. Many people find chloramine-treated water has a less noticeable chemical taste than heavily chlorinated water.

The problem is that chloramine, while producing fewer of the regulated byproducts, generates a different set of unregulated byproducts, including nitrosamines (some of which are potent carcinogens) and iodinated disinfection byproducts. The full health implications of these newer byproducts are still being studied.

Disinfection Byproducts: The Real Concern

When chlorine or chloramine reacts with natural organic matter (plant material, algae residues, dissolved organics) in the water, it creates a cocktail of chemical byproducts. Over 700 different DBPs have been identified, but only 11 are currently regulated by the EPA.

Trihalomethanes (THMs)

The most studied class of DBPs. The four regulated THMs are chloroform, bromodichloromethane, dibromochloromethane, and bromoform. The EPA’s maximum contaminant level for total trihalomethanes is 80 parts per billion (ppb).

THMs are volatile, which means they off-gas from water. You’re exposed not just by drinking tap water but also by breathing in shower steam, running a dishwasher, and even from a running faucet. A 10-minute hot shower can expose you to as much THM as drinking two liters of the same water, according to research published in Environmental Science & Technology.

Dr. Peter Attia has noted that the inhalation and dermal absorption pathways during showering are underappreciated exposure routes for chlorine and its byproducts. He has pointed out that people who filter their drinking water but shower in unfiltered water are addressing only part of the equation. A good shower filter helps with the other part.

Haloacetic Acids (HAAs)

The second regulated class of DBPs. Five HAAs are regulated (known as HAA5), with a combined maximum contaminant level of 60 ppb. HAAs don’t off-gas as easily as THMs, so ingestion is the primary exposure route.

Unregulated Byproducts

Here’s where it gets complicated. The 11 regulated DBPs represent a small fraction of the total. Among the unregulated byproducts:

  • Nitrosamines (particularly NDMA), which are potent carcinogens. Chloramine disinfection produces more nitrosamines than free chlorine.
  • Iodinated DBPs, which are more toxic than their chlorinated counterparts but appear at lower concentrations.
  • Halonitromethanes and haloacetonitriles, which have been shown to be more genotoxic than the regulated THMs in laboratory studies.

Research published in Environmental Science & Technology has found that the unregulated byproducts may pose a greater aggregate health risk than the regulated ones. This doesn’t mean your tap water is unsafe. It means the regulatory framework hasn’t caught up with the science.

Health Effects

Cancer

The association between chlorinated water and cancer has been studied for decades. A meta-analysis published in the Journal of Environmental Sciences found a statistically significant association between long-term consumption of chlorinated water and bladder cancer. The risk increase was modest (approximately 20-40% higher risk with the highest exposures), but given how many people drink chlorinated water, the population-level impact is significant.

Colorectal cancer has also been associated with long-term DBP exposure in some epidemiological studies, though the evidence is less consistent than for bladder cancer.

Reproductive Effects

Several studies have found associations between high THM levels in drinking water and adverse reproductive outcomes, including:

  • Increased risk of small-for-gestational-age births
  • Some studies suggest associations with miscarriage, though findings are mixed
  • Possible effects on fetal growth

A 2016 review in Environmental Health Perspectives concluded that the evidence for reproductive effects was suggestive but not yet definitive, and called for more research.

Respiratory Effects

Chlorine and THMs in shower steam and indoor pools can irritate the respiratory system. Competitive swimmers and people who take long hot showers in heavily chlorinated water report higher rates of respiratory symptoms. Research on indoor pool workers has found measurable effects on lung function.

Andrew Huberman has discussed the importance of water quality for overall health, noting that both the chemicals intentionally added to water and their byproducts deserve attention. He has emphasized that practical filtration is one of the simpler environmental health steps you can take.

Skin and Hair

Chlorine and chloramine are oxidizing agents. They strip natural oils from skin and hair, which is why many people notice dry skin, brittle hair, or irritated scalp from showering in chlorinated water. These effects are cosmetic rather than dangerous, but they’re among the most immediately noticeable consequences of water treatment chemicals.

How to Reduce Your Exposure

You don’t need to eliminate chlorine or chloramine entirely from your water. You need to remove the disinfectant and its byproducts from the water you drink, cook with, and bathe in. Let the disinfectant do its job in the distribution system, and then filter it out at the point of use.

Drinking Water Filtration

Activated carbon filters effectively remove free chlorine and many DBPs, including THMs. This includes carbon block filters in pitchers, faucet-mount systems, and under-sink units. Carbon filtration is the most practical and affordable first step. Our water filtration guide covers the full range of options.

Chloramine is harder to remove. Standard carbon filters reduce chloramine, but much more slowly than they reduce free chlorine. For chloramine removal, look for catalytic carbon filters (which are engineered specifically for chloramine) or reverse osmosis systems. If your utility uses chloramine, a basic Brita pitcher may not be sufficient. Check our best gravity water filters for systems rated for chloramine reduction.

Reverse osmosis removes both chlorine and chloramine along with their byproducts. It’s the most thorough point-of-use option.

Dr. Rhonda Patrick has discussed the value of mineral-rich filtered water and has pointed out that RO systems remove beneficial minerals along with contaminants. She’s recommended remineralization for people using RO filtration, which is a practical consideration when choosing a system.

Shower Filtration

A shower filter with activated carbon or KDF (kinetic degradation fluxion) media reduces chlorine from shower water. This addresses the inhalation and skin absorption pathways. Chloramine is harder to filter at the flow rates typical of a shower (2 to 2.5 gallons per minute), but vitamin C (ascorbic acid) shower filters can neutralize both chlorine and chloramine. Our shower filter guide covers what works.

Whole-House Filtration

A whole-house water filter treats all water entering your home, covering every tap, shower, and appliance. This is the most thorough approach but also the most expensive. For chloramine treatment, whole-house catalytic carbon systems are the standard.

Simple Steps That Help

  • Let water sit. Free chlorine dissipates from water if you let it sit in an open container for 24 hours. This works for watering plants or filling a pet bowl. It does not work for chloramine, which is stable and doesn’t evaporate under normal conditions.
  • Shorter, cooler showers reduce your exposure to volatile DBPs in steam.
  • Ventilate your bathroom during and after showers to disperse any off-gassed chlorine.
  • Open windows when running the dishwasher, which releases chlorine-containing steam.

How to Find Out What’s in Your Water

Your water utility is required to publish an annual Consumer Confidence Report (CCR), also called a water quality report. This document lists the disinfectant used (chlorine or chloramine), residual levels, and measured DBP concentrations.

You can also search the EWG Tap Water Database by zip code to see your local utility’s test results compared against both EPA legal limits and EWG’s more stringent health guidelines.

If you want to test your own tap water, home test kits for free chlorine, total chlorine (which includes chloramine), and THMs are available. For more detailed analysis, send a sample to a certified laboratory.

Reader Questions

Is chloramine worse than chlorine?

Neither is categorically worse. Chloramine produces fewer of the currently regulated byproducts (THMs and HAAs) but more of certain unregulated ones (like nitrosamines). Chloramine is also harder to remove with standard carbon filtration and doesn’t dissipate from water by sitting. For consumers, the practical difference is that you need better filtration for chloramine-treated water.

Can I boil water to remove chlorine?

Boiling water for 15 to 20 minutes will drive off free chlorine. It’s not practical for daily use, but it works in a pinch. Boiling is not effective for chloramine, which is more chemically stable and doesn’t volatilize as easily. It also doesn’t remove DBPs that have already formed.

Is bottled water better?

Not necessarily. Bottled water isn’t required to be chlorine-free, and it may contain its own set of contaminants including microplastics from the plastic packaging. Filtered tap water in a glass or stainless steel bottle is generally the better option. Our non-toxic water bottle guide covers safe container options.

Do I need a whole-house filter?

It depends on your priorities and budget. If your main concern is drinking water quality, a countertop or under-sink filter handles that effectively. If you also want to address shower exposure and appliance use, a whole-house system is the way to go. Most people start with a drinking water filter and add shower filtration, which covers the biggest exposure routes at a reasonable cost.

Does chloramine affect fish in an aquarium?

Yes. Both chlorine and chloramine are lethal to fish and other aquatic life. Chloramine is more dangerous for aquariums because it doesn’t off-gas from water the way chlorine does. Aquarium owners using chloramine-treated water must use a dechlorinating water conditioner before adding tap water to the tank.

How do I know if my water has chlorine or chloramine?

Check your utility’s annual Consumer Confidence Report, or call your water utility directly. You can also test at home: add a standard chlorine test strip to a glass of tap water. If it reads positive for “total chlorine” but negative or low for “free chlorine,” your water contains chloramine. Many test kit manufacturers sell strips that measure both.

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