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).
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 bacteria
- Reducing chloroform exposure
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!
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.
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.
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).
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.