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Consumer’s Guide to Showerhead Water Filters
Many people regard a long, hot shower as one of
life’s unalloyed pleasures. The gentle liquid pelting…the soothing hot steam…the
billowing cloud of toxic chlorine gas—whoa! Something’s wrong with this picture,
but fortunately it can be made right with a relatively simple technical fix.
The fix is a filter for your showerhead. Shower
filters have become much more popular in recent years as evidence continues to
mount that the chlorine added as a disinfectant to public water systems is a
health hazard, and that many people may be getting much more exposure to
chlorine and its toxic byproducts by inhaling it in the shower than by drinking
it in their tap water. Chlorine and other chemicals are evaporated from hot
shower water and easily inhaled, not only in the close confines of the shower
but also in the bathroom, where other members of your family can be exposed as
well. The pores of your skin also open up from the steam and allow increased
absorption of waterborne pollutants. One estimate is that you can be exposed to
as much water pollution during a twenty-minute hot shower as by drinking two
quarts of tap water per day.
Is Chlorine a Hidden Menace in Your Shower?
Even if you can’t smell its pungent odor,
chlorine may be a hidden menace in your shower, causing ailments ranging from
headaches to neurotoxic reactions. In the digestive tract chlorine can upset the
balance of intestinal flora and promote candida or other infections. Researchers
have suggested that chlorine and its toxic byproducts may be responsible for an
increased risk of heart disease, allergic reactions, and spontaneous abortions.
Studies indicate that consumption of chlorinated water is linked to
significantly increased rates of bladder, colon, and rectal cancer. One recent
researcher has even noted that chlorine-related toxins may be proven in the
future to be "the most important environmental carcinogens in terms of the
number of attributable cancers per year."
In addition to its adverse effects on health,
chlorine has unwanted topical and cosmetic actions on hair and skin. Anyone who
has spent too much time in an overly chlorinated pool can attest to chlorine’s
ability to irritate the eyes and aggravate mucous membranes in the nose and
throat. Chlorine bonds with proteins in the hair, making it dry and brittle and
causing color to be washed out. Chlorine strips skin of its natural oils,
leaving it dry, itchy, and prematurely aged.
Chlorine has its place, as we’ll see, but that
place should not be in your shower.
Chlorine: A Versatile Germ-Killer
A greenish-yellow gaseous element that readily
dissolves in water, chlorine may seem to be an unlikely health hazard—after all,
water treatment officials routinely add it to the public drinking supply
throughout the United States. They do this for a good reason: since it began to
be used as a disinfectant almost two centuries ago, chlorine has probably saved
hundreds of thousands of lives because of its ability to destroy harmful
bacteria, viruses, and other pathogens.
Chlorine disinfection was recognized as a
potential lifesaver as early as the 1820s by European physicians who were
concerned about the extremely high rates of post-birth deaths in hospital
maternity wards. Well before Pasteur’s work in the early 1860s convincingly
established the germ theory for transmitting disease, a number of pioneering
physicians had begun to use chlorine to disinfect hospital rooms. Some concerned
physicians also had doctors wash their hands in a chlorine solution before they
examined patients. Such practices dramatically reduced maternal mortality from
puerperal fever, a highly contagious streptococcus infection of the uterus after
birth, which was killing as many as one in six recently delivered mothers in
some hospitals. In hindsight we know that many if not most of these deaths were
from bacterial infections induced by "the examining finger"—doctors and medical
students at the time routinely went directly from dissecting cadavers to probing
the genitals of women.
Chlorine began to be used in U.S. water systems
in the early 1900s because it killed the salmonella bacteria that were causing
outbreaks of typhoid fever, and the vibrio bacteria responsible for cholera.
Chlorine is now used in approximately 75 percent of public water systems in the
U.S. to prevent waterborne diseases. It is added routinely in many areas to
prevent bacterial growth in water mains. Water systems with leaky and aging
pipes and other infrastructure are especially prone to contamination by
microorganisms, such as from fecal matter from leaky septic systems. Water
officials often add chlorine in higher amounts during the summer, when the risk
of bacterial contamination of water increases. If a routine water test suggests
a potential bacterial contamination, public water may be spiked with
higher-than-average levels of chlorine, in some instances up to 8 parts per
Most people can smell residual chlorine at a
concentration of about 3-4 ppm. If you’re not sure whether your drinking water
is being treated with chlorine, check with your local water officials.
A Double-Edged Tool
Although chlorine has no doubt saved many lives
by preventing deadly diseases, its toxicity toward microorganisms is a
double-edged tool. Although relatively small amounts are used to disinfect water
supplies, even low concentrations of chlorine are clearly detrimental to human
and animal health. It is widely considered an air pollutant at a mere 1 ppm.
Inhaling high levels, like 600 ppm, for 10 minutes can be fatal, a fact that
militaries recognized back in World War One, when chlorine was used to make
poisonous gas weapons. Chlorine is also toxic and irritating to the skin.
Chlorine is an effective bacteria-killer in part
because it is so reactive. Free chlorine in water oxidizes and kills
microorganisms, and it also readily combines with other chemicals, such as
carbon, to form toxic compounds such as carbon tetrachloride. When organic
matter such as leaves fall into a reservoir, they decay and release organic
compounds into the water. As chlorine combines with these, it forms water
pollutants known as trihalomethanes (THMs). These highly toxic chlorination
byproducts include chloroform and trichloroethylene (TCE). If chlorine is
present in water, in all likelihood the volatile chemicals chloroform and TCE
are as well.
Don’t Underestimate Shower
Until the mid-1980s, most studies that looked at
adverse effects from waterborne contaminants considered people’s exposure
through only one route: drinking. Research conducted since then, however, has
demonstrated that this was a very one-dimensional approach to the issue.
Trichloroethylene and chloroform in particular may be much more worrisome as
water toxins that are inhaled or absorbed through the skin. Both TCE and
chloroform are readily absorbed from the lungs into the blood. A number of
recent studies have added to the weight of concern:
According to a 1999 study conducted by
researchers at the Environmental and Occupational Health Sciences Institute in
Piscataway, N.J., "Strong relationships were identified between the THM breath
concentrations collected after a shower and both the THM water concentration
and the THM exposure from a shower."
A 1998 study conducted in Taiwan compared the
cancer risk at three major metropolitan areas with chloroform exposure during
showering. The researchers considered exposure from all three major routes:
ingestion, inhalation, and skin absorption. They concluded that a ten-minute
shower would result in chloroform exposure with a 3:4:3 ratio (ingestion,
inhalation, skin absorption); for a 20-minute shower the ratio was 1:7:2. In
other words, those who were taking 20-minute showers were getting 90 percent
of their exposure to chloroform from the shower. The researchers also
determined that the cancer risk was almost thirteen times as high for a person
who took a 20-minute shower in the area with the highest chloroform
concentrations in the water compared to the risk for a person who took a
ten-minute shower in the area with the lowest concentration.
According to the authors of a 1996 study, "The
volatilization of volatile organic chemicals during domestic water usage can
result in significant indoor air concentrations, and the subsequent inhalation
of these contaminants is an important route of exposure….The simulated daily
exposure is well described by a simplified equation that is a function of the
amount of time the individual spends in the shower, the bath, and the
bathroom; the total water usage in the home; and the fraction of time the
individual is at home."
The authors of another 1996 study set up an
experimental shower to measure the release of toxins. At 104 degrees F., a
common shower temperature, volatilization was found to be approximately 80
percent for TCE and 60 percent for chloroform. According to the researchers,
"The temperature of the water typically had a dominant effect on the total
release of each of the three chemicals from the shower water to the air."
The National Academy of Sciences estimated in
1986 that up to 1,000 Americans die each year from cancers resulting from
drinking water; but the figure may be many times higher when you consider
people’s exposure to these chemicals from inhaling them while taking showers.
New Shower Filter Technology
Chlorine’s adverse health effects has caused the
administrators of public water systems, and the owners of private and public
swimming pools, to explore alternative, less toxic methods of germ control. New
technologies such as the use of ozone may eventually replace chlorine, but in
the meantime consumers can rely on water filters. Whole-house systems can remove
chlorine in shower water, as well as various other contaminants, but the
simplest and most cost-effective solution for many people is to install a filter
for the showerhead.
In recent years a new type of showerhead filter,
dubbed KDF, has become available. The filter medium is made from a copper zinc
alloy, which works by attracting chloride ions and converting them to zinc
chloride. Effective showerhead filters can remove chlorine to less than 0.1 ppm
and reduce dirt, rust, and bad odors, leaving your shower water looking and
smelling fresh and clean. High-output showerhead filters are available with
replaceable and reversible (that is, able to operate in either direction) filter
cartridges. (Periodic reversing of the filter ensures balanced filtration and
back-flushes the cartridge as it is filtering.)
Adding a filter to your showerhead can make that
long, hot shower the unalloyed pleasure it ought to be.
Girodino, N.J, and J.B. Andelman, "Characterization
of the emission of trichloroethylene, chloroform, and
1,2-dibromo-3-chloropropane in a full-size, experimental shower," J Expo
Anal Environ Epidemiol, 6(4):413-23, 1996 Oct-Dec
Kuo, H.W., et al., "Estimates of cancer risk from
chloroform exposure during showering in Taiwan," Sci Total Environ,
218(1):1-7, 1998 Jul 11
Weisel, C.P., et al., "Exposure estimates to
disinfection by-products of chlorinated drinking water," Environ Health
Perspect, 107(2):103-10, 1999 Feb
Wilkes, C.R., et al., "Modeling the effects of water
usage and co-behavior on inhalation exposures to contaminants volatilized from
household water," J Expo Anal Environ Epidemiol, 6(4):393-412, 1996
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