Is Chlorine in Water Bad for You? Health Effects Explained

No. At the levels a city puts in tap water, chlorine is not bad for you to drink: most tap water carries a quarter or less of the 4 ppm safe limit. What chlorine does do is react with organic matter in the water to form byproducts that matter over many years, and it dries out skin and hair.

I live on city water here in Maryland, and I have a carbon tank and a softener on my own house. That is a comfort choice, not a medical one. Below I keep the two apart: what the EPA, CDC and WHO say chlorine does to your body, what the research says about the byproducts, and the few cases where removing it is a must.

Is chlorine in tap water safe to drink?

Yes, at the levels a utility uses. The CDC says chlorine or chloramine levels up to 4 mg/L are considered safe in drinking water and unlikely to make people sick. EPA's limit for each is 4.0 mg/L. EPA calls it the maximum residual disinfectant level: the most disinfectant a utility is allowed to leave in the water. Its goal, the level below which there is no known or expected risk to health, is also 4.

The World Health Organization's guideline is a little higher, 5 mg/L, and WHO calls it conservative: the 2-year rodent study behind it found no dose that caused harm. WHO also says chlorine is present in most disinfected drinking water at 0.2 to 1 mg/L. Here is where your tap sits next to the limits and next to a pool:

What too much chlorine does

Above the 4.0 mg/L limit, the health effects EPA lists for chlorine are eye and nose irritation and stomach discomfort; for chloramine, EPA adds anemia. If you are worried about how your water is affecting your health, the CDC's advice is to talk to your doctor.

In this video I say chlorine is a carcinogen and that city water is not safe to drink. I said both too strongly. Chlorine itself is not classified as a cause of cancer: WHO reports that the International Agency for Research on Cancer puts hypochlorites in Group 3, "not classifiable as to their carcinogenicity to humans." The cancer link is to the disinfection byproducts, and the CDC considers tap water within the 4 mg/L limit safe to drink.

Chlorine byproducts are the real concern

When chlorine reacts with naturally occurring organic matter in water, it creates compounds like trihalomethanes (THMs) and haloacetic acids (HAAs). EPA limits both, and its own words for the risk are careful: byproducts, if consumed in excess of EPA's standard over many years, may increase health risks.

How big is that risk? Men whose water averaged more than 50 ppb of THMs over 40 years had about 1.4 times the odds of bladder cancer of men whose water had almost none. Women showed no link. That comes from a pooled analysis of six studies with 2,806 bladder cancer patients; "almost none" means 1 ppb or less.

For pregnancy, EPA's 2006 byproduct rule cites possible associations between chlorinated water and miscarriage, low birth weight and birth defects, and says the results have been mixed. EPA calls it a potential hazard concern. The CDC adds that chloramine makes fewer byproducts than chlorine.

Where your water report shows byproducts

Your utility has to deliver an annual water quality report, called the Consumer Confidence Report, by July 1 each year. The CDC says it shows which disinfectant your utility uses, its level, and the byproduct levels. If a system goes over a byproduct limit, it has to notify every customer. How to read your water quality report walks through the page line by line, and TTHMs in drinking water covers what a high number means.

Is a chlorinated shower worse than drinking?

A 10-minute shower put more THMs into people's blood than drinking a liter of tap water, in a study by CDC researchers. Blood levels were highest after the shower and lowest after the drink. The study named bathing and showering as important routes of THM exposure. A follow-up with 100 people found that the chloroform in the shower air was the strongest predictor of the chloroform in their blood afterward.

What that does to your health is less settled. Minnesota's health department says there is limited information about the risks of breathing in or touching byproducts in the shower, and that the chlorine itself in tap water is too low to cause breathing problems.

You can smell it, though. When I first moved into my house, we had a big garden tub we used every night, and before the filtration went in you could smell the chlorine coming off the water. A kitchen filter or a fridge filter covers what you drink. It does nothing for the shower or the tub.

What chlorine does to skin and hair

Chlorine can make your skin dry and itchy, and it can dry out your hair. Allergists say chlorine dries skin, and the itchy red reaction it causes is irritation, not an allergy. It can also irritate skin that is already inflamed; allergists call the reaction irritant dermatitis.

Eczema cuts both ways. Eczema groups say pool water can irritate some people with eczema. The National Eczema Association also recommends bleach baths for eczema, two to three times a week after talking to a dermatologist, to help reduce inflammation and itch, and its recipe card says that bath has about the chlorine level of an average swimming pool. So chlorine can irritate eczema that is already there. If baths or showers seem to make yours flare, that is a question for your dermatologist.

Can you be allergic to chlorine?

Almost never. The American College of Allergy, Asthma and Immunology says you can't be allergic to chlorine, but you can be sensitive to it: the itchy, red skin or hives is irritant dermatitis. A Cleveland Clinic allergist says true chlorine allergy is extremely rare and that irritant dermatitis is what he sees 99% of the time.

Those allergists are talking about pools, and a pool carries more chlorine than your shower. The CDC wants at least 1 ppm in a pool and at least 3 in a hot tub, while most tap water runs 0.2 to 1 (the levels table above). Minnesota's health department says tap water carries far less chlorine than a swimming pool, so skin irritation from it is expected to be rare.

The sharp "chlorine" smell at an indoor pool is probably chloramines, made when chlorine meets sweat and pee, and those are what give swimmers red eyes, rashes and coughing. The CDC says the chloramines that form in pool water are different from the chloramine your utility may add to tap water.

A caller in New Jersey told me that after he called the city about the chlorine smell, "my body's been itching more lately." He had been in that house 23 years and never had it before. If that sounds like you, ask your utility whether they changed their disinfectant, and see an allergist; that is the allergists' own advice for a suspected chlorine sensitivity.

What chlorine does to hair

The hair warnings from dermatologists are about pool swimming. Chlorine dissolves the oils that coat each hair, which means more split ends and breakage, and it can dull or fade color-treated hair. In the video I say it can change the color of your hair depending on what type of hair you have. Dermatologists say the green tint on blond, bleached or gray hair comes from copper that chlorine-dried hair soaks up, not from the chlorine itself.

Chlorine vs chloramine in tap water

More than one in five Americans drink water treated with chloramine, which is chlorine with ammonia added so it keeps disinfecting longer in the pipes. The two behave differently in your house:

Your water quality report says which one your utility uses. A pool and spa test kit can read free and total chlorine; total minus free is the combined chlorine. Some utilities switch between the two at different times of the year, so a summer reading and a winter reading can differ. How to test for chlorine in tap water explains what your numbers mean, and Chloramine vs chlorine covers why your filter cares.

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Who needs chlorine removed from water

The CDC says the low levels of disinfectant allowed in tap water do not make people sick, so for most households removing chlorine is about taste, smell and comfort. A few cases are different:

How to remove chlorine from your house

Activated carbon takes chlorine, chloramine and some chlorine byproducts out of water. For chloramine, catalytic carbon works faster than standard carbon. Carbon filters for water: the complete guide covers everything else carbon does and does not remove. Here is what each option covers:

The simplest way to get chlorine out of the whole house is one of the 2.5 cubic foot or 1.5 cubic foot non-backwashing upflow carbon tanks. The 2.5 is what most homes get; the 1.5 is for smaller homes. Both hold Centaur catalytic carbon, which Calgon Carbon makes from bituminous coal and sells for chloramine removal, and neither needs a drain or electricity. You change the carbon about every 5 years (a little sooner in the 1.5), at $295 per cubic foot. Best whole house carbon filter goes through which tank fits which house, and you can compare them all on the whole house chlorine filters page.

What ships: the tank, the Clack in/out head with a bypass valve, a fill funnel, and the carbon in 1 cubic foot boxes (two for the 2.5, one for the 1.5), loaded into the tank at install. With no drain and no electricity, the install is an inlet and an outlet, about an hour or two of a plumber's time, and I recommend having a plumber do it. I'm a phone call away for your plumber at 800-460-5810, and if you'd rather do it yourself, text me at 443-277-2204 with any questions.

If you rent, or a whole-house system is not in the budget, a fridge filter with carbon in it or bottled water covers what you drink. Some people add a shower head filter from Amazon for the shower; we don't sell them, and we recommend filtering the whole house. An uncovered pitcher in the fridge for a few hours lets the chlorine smell leave, but it does nothing for chloramine.

If your city water is also hard, the carbon filter and water softener package pairs the 2.5 cubic foot tank with a 64,000 grain softener for $3,795. Carbon filter and water softener: do you need both? explains when you do.

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