- The problem with chlorine and DBPs
- Showering and chloroform exposure
- The health effects of unfiltered shower water
- Benefits of a shower filter
- Things to look out for when buying a shower filter
- Shower filter brand comparison
A whole home water filtration system is an ideal way to filter all of the water you use at home. Whether it’s your drinking water, or the water you shower and bathe in, there are filter options available. Isn’t filtering your shower water a little overkill? Isn’t it enough to just filter your drinking water? While I was also skeptical at first, a little research has convinced me of the benefits of filtering shower water. In this post, I’ll take a look at those benefits and offer my recommendations for the best shower filter systems available.
The first thing to understand about the water you shower and bathe in is that it is normally pre-treated with chemicals such as chlorine to kill potential pathogens. Sadly, these chemicals do not magically disappear after use. Instead, the water you’re using to get clean likely contains residues of chlorine and other disinfection by-products (DBPs).
The problem with chlorine and DBPs
Showering in unfiltered water usually means exposing your body to disinfection by-products (DBPs), typically in the form of chloroform. Chloroform is a trihalomethane that exists at room temperature as a clear, colorless, heavy liquid with a specific odor you probably recognize from public swimming pools.
Chloroform is the most common trihalomethane in the water supply and is present both in tap water and well water. Swimming pools that rely on chlorination for disinfection also contain trihalomethanes as by-products. Chloroform is light sensitive and degrades in the presence of light and air. Chloroform concentrations in water systems are inconsistent and trihalomethane concentrations rise as water remains in the distribution system (R).
Other trihalomethanes include: bromodichloromethane, dibromochloromethane, and bromoform. Shower water may also be contaminated with haloacetic acids (HAAs; monochloroacetic acid, monobromoacetic acid, dibromoacetic acid, dichloroacetic acid, and trichloroacetic acid). Human exposure to these substances comes via ingestion, inhalation, and contact with the skin. And, rather worryingly, using hot water when showering, bathing, or doing the dishes appears to increase absorption.
So, while it’s smart to filter the water you drink, it may be even smarter to prioritize filtering your shower water.
Showering and chloroform exposure
The average adults is exposed to 0.199 to 1.89 μg of chloroform per kg of body weight every day, according to the World Health Organization. Other estimates suggest that exposure could be higher than 3.0 μg/kg of body weight if you account for chloroform inhalation from air and ingestion from food (R, R). Chloroform is found in food, drinking water, and in the air. The largest single source of exposure, however, seems to be showering and bathing.
Daily showering and bathing in unfiltered water increases chloroform exposure both through inhalation and through the skin. This is thought to add 0.36 to 3.4 μg/kg daily, with studies showing increased chloroform concentrations in the blood after using household water for showering, bathing, and even for doing the dishes by hand (R, R). Specifically, blood chloroform concentrations increased by 2 to 7 times after showering; in one study, water levels of chloroform were 8 and 85 parts per billion, while blood concentrations after showering were 57 and 280 ppt (ng/L) (R).
One reason why showering and bathing seem to increase chloroform levels so significantly is that you absorb more chloroform through your skin from hot water. At bath-water temperatures of 30°C, volunteers in one study exhaled 0.2 μg of chloroform, versus 7 μg at the highest temperature (40°C) (R). In another study, the absorption of cytotoxic DBPs haloacetonitriles and chloral hydrate (CH) in human skin increased by approximately 50% to 170% when water temperatures increased from 25°C to 40°C (R).
Shockingly, one small study found that swimming for a couple of hours in a chlorinated pool could raise the average concentration of chloroform in breath to as much as 371 μg/m3 (R). Worryingly, chloroform and other potential contaminants in shower water, such as benzene, have been shown to pass through the placenta to an unborn fetus where they accumulate at a higher level than in maternal blood (R).
The health effects of unfiltered shower water
Why does it matter how much chloroform and other DBPs are in your water? Well, for a start, higher levels of trihalomethanes have been linked to a higher rate of certain types of cancer, particularly cancer of the urinary bladder and rectum, and possibly colon cancer (R). Indeed, the US Department of Health and Human Services included concerns over chlorinated water and cancer in the 14th Edition of their Report on Carcinogens, National Toxicology Program.
A 2013 study in South Korea also found a significant association between exposure to trihalomethanes from showering and the lifetime risk of cancer, with up to a 10-fold increase in risk when ingesting shower water (R).
Concern over DBPs and lead contamination in tap water in Flint, Michigan, made national and international news a few years ago when the city switched its water supply and inadvertently exposed nearly 100,000 residents to potentially unsafe water. Research subsequently revealed that children under 5 who used tap water during this time had much higher levels of lead and DBPs than normal, with potentially life-long consequences for health as well as for their immediate growth and development. Residents were advised to drink filtered water or, in the case of those who were pregnant, to drink bottled water. This advisory seemingly ignored the science showing showering and bathing in unfiltered water to be the greatest source of trihalomethane exposure in the home.
Even before we get to that stage, though, unfiltered shower water could be damaging your skin and hair. If your shower water is hard, i.e. if it has a high mineral content, it can leave a residue on your skin and make skin feel dry and irritated. Hard water can also leave hair feeling dry and looking dull, and cause scalp flakiness, thanks to minerals such as calcium, magnesium, silica, and iron. Over time, this may cause hard to break more easily and could increase unwanted frizz. Exposure to chloroform and other DBPs might even reduce your ability to synthesize vitamin D. That’s because these DBPs can strip the skin of a variety of natural substances, including cholesterol esters that form previtamin D (R).
Not only does chloroform in shower water strip the skin of its natural oils, reducing the skin’s natural barrier to infection, shower water pipes also appear to have a higher level of bacterial contamination than kitchen tap water pipes, at least according to one study (R). This may be because less frequent use leads to biofilm formation. Opportunistic pathogens in this water, such as Legionella spp., mycobacteria, Pseudomonas aeruginosa, and free-living amobae (FLA) pose a risk to human health, especially for anybody who is immunocompromised, including young children and seniors (R).
The absorption of some chemicals also increased with the addition of two common surfactants found in shampoos and soaps, sodium lauryl sulfate (SLS) and sodium laureth sulfate (SLES) (R). These surfactants disrupt the stratum corneum, i.e. the layer of the skin that provides the main barrier protecting us against environmental contaminates. Disruption of the stratum corneum means that the skin has a harder time maintaining moisture levels. It also reduces the skin’s ability to keep pathogens and irritants out. As such, showering in unfiltered hot water while using products containing SLS or SLES can dry out your skin and cause irritation. This may also exacerbate skin conditions such as psoriasis and eczema.
Benefits of a shower filter
All in all, installing a complete home water filtration system, or single fixture water filters for your shower and bath water could have benefits including:
- Reducing skin irritation and dryness
- Relieving psoriasis and eczema
- Reducing scalp flakiness
- Improving hair shine and healthier
- Reducing frizziness
- Reducing exposure to opportunistic pathogens
- Lowering your risk of some cancers.
Shower filters can effectively eliminate or reduce contaminants like chlorine and other DBPs. They are also relatively inexpensive, especially compared to hair treatments, skin treatments, and medical costs. They are also super simple to install. For most products, just unscrew your current shower head, screw in the filter, then screw the shower head into the filter. Easy!
Things to look out for when buying a shower filter
When looking for a shower filter, check for certification by our old friends at the National Sanitation Foundation (NSF). An NSF/ANSI 42 certification means that the filter reduces aesthetic impurities such as chlorine and taste or odor. NSF/ANSI 177 certification is for shower filters that attach directly to the pipe in front of the showerhead and reduce free available chlorine.
You’ll probably notice that some shower filters mention vitamin C, which might seem a little odd. There’s good reason for this, however. Vitamin C (as sodium ascorbate or ascorbic acid) rapidly neutralizes chlorine. As such, vitamin C has become quite popular with sanitation engineers who need to quickly and safely dechlorinate waste water.
Even a little bit of chlorine residue in treated waste water can have devastating effects on local wildlife. Happily, vitamin C is not toxic to wildlife and does not lower the dissolved oxygen in water as much as sulfur-based chemicals. Ascorbic acid is mildly acidic and reacts with chlorine to form hydrochloric acid. Don’t worry, though, this has a negligible effect on the pH of the water exiting your shower head. And, if a system uses sodium ascorbate, this is neutral and does not affect the water pH.
Confused? Well, to make things even easier, here’s a quick round-up of some of the best shower filter systems available.
Shower filter brand comparison
|Culligan Wall-Mount Filtered Showerhead|
|Raindrops Shower Head with Filter|
|Propur ProMax (Top Recommendation)|
|OPUS Aroma Sense Aromatherapy Vitamin C Handheld|
This chrome-finish patented filter not only filters chlorine and sulfur, it also filters bacteria and offers five spray settings. Easy to install (without any tools needed), the Culligan is certified by NSF International against ANSI Standard 177. And, if you’re concerned about water conservation, you’ll be happy that this showerhead meets the EPA Water Sense certification standard of maximum 2.0 gallons per minute or less.
If you’re looking for something a little more stylish, the Raindrops filter is a great option. This shower head has a six-step filtration system that softens hard water, removes chlorine, heavy metal, fluoride, bacteria, lead, and mercury. It may also help remove copper, iron, and other metals. This makes the Raindrops system a good option if you have well water that turns your shower blue or red. Raindrops six-step system is certified by National Sanitation Foundation as ANSI 42. This means it can reduce aesthetic impurities such as chlorine and taste or odor.
Again, this shower filter does not require tools to install and is quick and simple to screw on. Once in place, the filter lasts for around 6 months.
The Propur ProMax reduces or removes over 200 potential contaminants, including volatile oil compounds (VOCs), lead, fluoride, heavy metals, pesticides, DBPs, chloramines, herbicides, pharmaceuticals, and micro-organisms, among other things. How do I know? Well, this system has been independently tested and the results published online here.
Going above and beyond, the Propur ProMax is certified to NSF 53. This means it can reduce contaminants to support better health.
There are several options for this filter system, including a standard white plastic model, a chrome filter, and a wall-mounted or wand style set-up. Filter changes are recommended every 6-9 months and it’s easy to install!
The Berkey KDSF is made by the same folks who make the countertop gravity water filters I’ve written about here. Their shower filter system is a little different, however. This filter comprises a calcium, copper, and zinc blend that causes a chemical reaction to convert chlorine into chloride. Chloride molecules are larger and can’t be absorbed by the skin.
Berkey claim that the system reduces up to 95% of chlorine, as well as reducing hydrogen sulfide, limescale, mold, algae, bacteria, and heavy metals like lead, mercury, and iron. As far as I can tell, though, it’s not been certified. The Berkey shower head is also not quite so stylish as the countertop models, but does have mist, spray, and massage settings. You can also just buy the filter and use it with your existing shower head.
The major advantage for the Berkey shower filter is that the filters last for up to a year. This system also has a back-flow attachment you can use to flush out the filter to get rid of sediment build-up.
A favorite with spa fans, the OPUS Aroma Sense provides chlorine and trihalomethane filtration, replenishment with vitamin C, and aromatherapy courtesy of a lemon oil cartridge. This handheld shower filter also helps you conserve water while maintaining good water pressure.
As mentioned above, vitamin C (as ascorbic acid or sodium ascorbate) can quickly neutralize chlorine. So, although this system doesn’t seem to be certified, its mechanism for chlorine removal is scientifically sound.
I’ve included this model here, despite its lack of certification chops, because it is one of the few handheld options available. If you’re going for a wall-mounted filter, I’d strongly suggest choosing the Propur ProMax, Raindrops, or Culligan over the OPUS, however. You should also note that the cartridges on the handheld system need to be changed very 30-45 days and the wall-mounted version needs changing every 60-90 days.
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