The quality of our drinking water is a major determinant of our health and wellbeing. It is important to consider not only the presence of pathogens or contaminants, but also the routine addition of chemicals that may cause us harm. Chlorine is a chemical typically used as a disinfectant in public water supplies as an effective way to reduce the level of pathogenic bacteria in our drinking water. (1)

Unfortunately, this chemical, and other common chemical disinfectants, may have a damaging impact on our bodies’ beneficial bacteria as well.

When chlorine is used as a water treatment, it combines with organic matter to form compounds called trihalomethanes (THMs), also known as disinfectant byproducts. One of the most common THMs formed is chloroform, which is a known carcinogen. (2) Other THMs formed include the di- and trichloramines formed when chloramine is used as a disinfecting agent. (3) These compounds are toxic when consumed, inhaled, or applied to the skin.

Research conducted on the health effects of chlorinated drinking water have demonstrated a variety of toxicity issues. Several studies have found that communities using chlorinated or chloraminated drinking water have an increased risk of bladder, kidney, and rectal cancers. (4, 5, 6) THMs from chemically treated water have been associated with a variety of poor birth outcomes, such as spontaneous abortion, birth defects, and low birth weight. (7) Chlorine and chloramine vapors are associated with greater risk of asthma, and may damage the mucosal lining of the respiratory tract. (8) Free radicals in chlorinated water have been linked to liver malfunction, weakening of the immune system and pre-arteriosclerotic changes in arteries. (9)

While there hasn’t been substantial research on the topic, it’s reasonable to assume that chlorinated water adversely affects beneficial intestinal flora. Chlorine is a powerful antimicrobial agent, and is an effective pesticide against many different strains of bacteria. (10) The compounds in disinfected water may be able to reach the gut not only through our drinking water, but also through daily showers and baths.

A recent post at the Food Renegade blog (11) brought this disturbing theory to light, not only highlighting the harmful effects of chlorinated drinking water, but emphasizing the possibly greater effect that showers and baths could have on our intestinal flora. As we know, there’s a strong connection between asthma, acne, autoimmune conditions and the health of our gut flora. We might speculate that dysbiosis induced or made worse by excess chlorine exposure could contribute to these conditions.

Showering and bathing in chlorinated water may expose us to even more chlorine and its byproducts than drinking this disinfected water.

While our bodies can filter out much of the chlorine from our drinking water, the THMs and other disinfectant byproducts we inhale during showers and baths may be much more harmful, since the chlorine gas we inhale enters directly into our blood stream. (12)

Therefore, even if you filter your drinking water, the amount of toxins you are exposed to from your daily shower or bath, through inhalation or skin absorption, may be cause for greater concern.

Research has demonstrated that the cancer risk associated with chlorinated water may actually be due to showering and bathing, rather than drinking the disinfected water. (13, 14) This suggests that many health risks of chlorine may be specifically related to dermal and inhalation exposure. In fact, the chloroform dose from a single, ten minute shower is equal to, and possibly greater than, that from the average two liters of water ingestion on a daily basis. (15, 16)

Therefore, the filtration of your shower and bath water may be even more important than the water you drink.

Chlorine filtration is fairly simple, provided you use some level of technology to remove it from your shower or bath water. There are resources on the Food Renegade blog about where to find chlorine-filtering shower heads and bath filters. (17) This includes the Rainshow’r Shower Filter and the Crystal Ball Bath Dechlorinator, both sold by the Radiant Life Company.

I’d like to point out that chlorine isn’t in everyone’s water supply, but there is another disinfectant that is also of concern. I checked my local water company’s website, and discovered they use chloramine (chlorine + ammonia) to disinfect the water supply. (17)

Chloramine exposure may be even more damaging to the lung epithelium than chlorine, and may release ammonia as another toxic byproduct as well.

The filters that remove chlorine don’t necessarily remove chloramine.

Chloramine can be removed for drinking water purposes by a carbon block or activated carbon filter that can be installed on a kitchen faucet. Also, both chlorine and chloramine can be removed for bathing purposes by dissolving Vitamin C in the bath water. One 1000 mg Vitamin C tablet will neutralize chloramine in an average bathtub. (18)

There are no shower filters on the market that completely remove chloramine. (19) There are, however, whole house water filters that remove chlorine, chloramine, and other contaminants. Unfortunately, they’re quite expensive and thus may not be an option for many people.

Vitamin C shower filters may be a good choice for those looking for an inexpensive way to reduce the chloramine (and chlorine) content of their showers.

Vitamin C is an effective dechlorination agent, removing up to 99% of chlorine and chloramine, and vitamin C filters are much less expensive than the whole house filter featured above. The disadvantage to using them is they’re not as durable or effective as a whole house filtration system, and you would need a separate filter for each shower outlet in the house.

Other simple methods to reduce exposure to chlorine and chloramine include: taking shorter or less frequent showers, avoiding excessively hot showers (since high heat increases the amount of steam), and shutting the water off while soaping up. These techniques will help decrease your exposure if filtration or dechlorination is not an option.

I recommend you check with your local water supply company to determine what disinfecting agents they use to sanitize your tap water. You can then use that information to make a decision about which shower filter is most appropriate for you and your family. Until we know more about how chlorinated water affects our health, and especially our beneficial gut flora, it seems prudent to keep chlorine and chloramine exposure to a minimum.