Pat Kendall
Colorado State University
Quick
Facts
- Water
is our most essential nutrient.
- Water
contains different amounts of dissolved inorganic
and organic compounds.
- The
Environmental Protection Agency regulates public
water systems.
- The
Colorado Department of Health regulates bottled
or vended water if the water does not leave Colorado.
The Food and Drug Administration regulates if the
water is involved in interstate commerce.
|
People
can survive days, weeks or months without food, but only about
four days without water. The body uses water for digestion,
absorption, circulation, transporting nutrients, building
tissues, carrying away waste and maintaining body temperature.
The
average adult consumes and excretes about 10 cups of water
daily. Adults should drink six to eight cups of liquids per
day. Although most of this liquid should come from beverages,
food supplies some water. Our bodies make water as a by-product
in the breakdown of fats, sugars and proteins to energy.
Water
is always two parts hydrogen to one part oxygen. Beyond that,
its composition depends on where it comes from, how it is
processed and handled. Water can be hard or soft, natural
or modified, bottled or tap, carbonated or still. About one-half
of our water comes from underground water tables (groundwater)
and one-half from surface water in rivers, lakes and reservoirs.
The
hardness of water relates to the amount of calcium, magnesium
and sometimes iron in the water. The more minerals present,
the harder the water. Soft water may contain sodium and other
minerals or chemicals; however, it contains very little calcium,
magnesium or iron. Many people prefer soft water because it
makes soap lather better, gets clothes cleaner and leaves
less of a ring around the tub. Some municipalities and individuals
remove calcium and magnesium, both essential nutrients, and
add sodium in an ion-exchange process to soften their water.
The harder the water, the more sodium that must be added in
exchange for calcium and magnesium ions to soften the water.
This process has drawbacks from a nutritional standpoint.
First,
soft water is more likely to dissolve certain metals from
pipes than hard water. These metals include cadmium and lead,
which are potentially toxic. Second, soft water may be a significant
source of sodium for those who need to restrict their sodium
intake for health reasons. Approximately 75 milligrams of
sodium is added to each quart of water per 10 g.p.g. (grains
per gallon) hardness. Finally, there is epidemiological evidence
to suggest a lower incidence of heart disease in communities
with hard water. The Environmental Protection Agency (EPA)
doesn't set a mandatory upper limit for sodium in water, but
suggests an upper limit of 20 milligrams per liter (quart)
to protect individuals on sodium-restricted diets.
If you
use a water softener, two ways to avoid excess sodium in drinking
water are: 1) use low sodium bottled water, and 2) install
a separate faucet in the kitchen for unsoftened water.
Along
with differences in mineral composition, water contains different
levels of microorganisms. Bacteriological tests are available
to determine if water is bacteriologically safe for human
consumption. Contact the county health department for information
on how and where such tests are performed. Chlorination and
filtration are effective controls for most bacteria. However,
a tiny one-celled parasite not readily killed by chlorination,
Giardia lamblia, deserves special discussion. Over the past
several years, giardia has become an increasingly common problem
in rural and mountain communities with inadequate filtration
systems. Giardia is mostly found in surface waters such as
mountain streams and lakes, not groundwater. Because one cannot
see, taste, or smell giardia, it is best not to drink water
directly from mountain streams or lakes.
Once
ingested, the giardia cyst develops into a trophozoite that
attaches to the wall of the small intestine. Disease symptoms
usually include diarrhea with cramping and gas, dehydration,
weakness and loss of appetite. Symptoms may take seven to
10 days to appear and last up to six weeks. Most people are
unaware at the time of ingestion that they have been infected.
Laboratory
identification can confirm the disease by diagnosis of the
organism in the stool. The disease is curable with prescribed
medication. If untreated, the symptoms may disappear on their
own and reoccur intermittently over a period of months.
Treatment
also can help prevent spread of the disease between people
and between pets and people. For example, in a Colorado Department
of Health study, person-to-person contacts within families
or between small children in day care centers were responsible
for 46 percent of the 360 cases investigated. In fact, only
15 percent of the respondents had ingested stream or lake
water in the three weeks prior to the onset of symptoms.
Prevention
is the best solution. Always wash your hands after changing
diapers and performing other hygiene activities. Wash children's
hands frequently. Thoroughly clean change surfaces after diapering.
It's
best to carry your own water on camping or backpacking trips.
If this is not practical, the next best solution is to boil
the water. Although giardia cysts are killed at temperatures
of 131 degrees F, boiling for one minute at sea level and
up to five minutes at 10,000 feet is recommended to eliminate
other microorganisms that might be more heat resistant than
giardia. Giardia also will not survive in water held at 59
degrees F for 30 minutes if one iodine tablet has been added
per quart. Filters are available, but are expensive and inconvenient.
Furthermore, many products marketed for backpackers are not
effective in filtering out the tiny giardia cysts.
Protection
is the key to the control of giardiasis. Since feces can contain
the organism, bury waste 8 inches deep and at least 100 feet
away from natural waters. Dogs, like people, can get infected
with giardia. Unless carefully controlled, dogs can contaminate
the water and continue the chain of infection from animals
to humans.
Fluoride
is found naturally in Colorado water supplies in different
amounts. The dental benefits of fluoridated water are well
documented. Fluoride concentrations of 1.0 milligrams per
liter or greater will reduce the incidence of dental cavities.
However, concentrations over 2.0 milligrams per liter can
darken tooth enamel causing fluorosis.
The
American Dental Association and the American Medical Association
endorse fluoridation. Yet, after more than 40 years of fluoridation,
nearly 40 percent of tap water remains unfluoridated. Opponents
have long argued that fluoridation violates individual rights,
certain religious beliefs that ban medications, and does not
prevent tooth decay. They also claim it promotes a variety
of ills. A recent study in which male (but not female) rats
given water with high levels of sodium fluoride developed
a rare bone cancer, added fuel to their concerns. Proponents
counter that fluoridation is not a form of medication, but
an adjustment of an essential nutrient to a level favorable
to health. What that level is and whether or not it should
come from fluoridated drinking water will be at the crux of
the next round of debates.
Tooth
decay is on the decline in the United States (50 percent decline
in the last 20 years). The decline is occurring in fluoridated
and to a lesser extent in non-fluoridated areas. Fluoride
treatments, fluoridated toothpaste, better diets and improved
oral hygiene are all factors.
Like
most elements, fluoride appears to be both beneficial to health
and potentially toxic. The goal is to determine the optimum
level and then decide how best to achieve that level. The
EPA currently sets the maximum allowable level of sodium fluoride
in drinking water (natural or added) at 4 milligrams per liter
(4 parts per million) and the maximum recommended level at
2 milligrams per liter. The EPA reviews drinking water standards
every three years.
Lead
is a toxic heavy metal known to turn up in drinking water.
Recent data indicate that levels formerly safe may threaten
health, especially among infants and children. In an 1986
EPA survey, an estimated 40 million Americans (one in five)
were using drinking water that contained potentially hazardous
levels of lead.
Acute
lead poisoning can cause severe brain damage and death. The
effects of chronic, low-level exposure, however, are more
subtle. The developing nervous systems of fetuses, infants,
and children are particularly vulnerable. Recent studies show
that lead exposure at a young age can cause permanent learning
disabilities and hyperactive behavior. Low-level lead exposure
also is associated with elevated blood pressure, chronic anemia,
and peripheral nerve damage.
Natural
water usually contains very little lead. Contamination generally
occurs in the water distribution system or in the pipes of
a home or facility. Lead pipes, brass faucets and lead solder
used to join copper pipes are the culprits. If your home was
built before 1986 when a nation-wide ban on lead pipes and
lead solder went into effect, it is likely to have lead-soldered
plumbing.
The
severity of lead contamination depends in part on how "corrosive"
your water is. Soft or acidic water is more likely to corrode
plumbing and fixtures, leaching out lead. According to the
EPA, about 80 percent of public water utilities deliver water
that is moderately or highly corrosive.
The
EPA is changing the focus of its lead regulation from a maximum
contaminant level of 50 parts-per-billion at the tap to imposed
treatment if more than 10 percent of collected samples from
a water system exceed 15 parts-per-billion lead. Water systems
that exceed such levels will be required to implement corrosion
control measures to reduce leaching of lead into water. Techniques
such as adding lime (calcium oxide) to reduce water acidity
can greatly reduce lead levels at the tap. A number of other
simple practices also can help reduce the level of lead at
the tap.
- Cook
with and drink only cold water. Hot water tends to dissolve
more lead from pipes.
- Don't
drink the first water out of your tap in the morning. Let
the water run for about one minute until a change in temperature
occurs.
- For
private wells, consider water treatment devices such as
calcite filters that reduce acidity and make water less
corrosive. Certain point-of-purchase treatment devices (e.g.,
some ion-exchange filters, reverse osmosis devices and distillation
units) also can remove lead.
- If
lead levels remain high, consider bottled water for drinking
and cooking purposes.
Nitrates
may be found naturally in water or may enter water supplies
through a number of sources (fertilizers, animal wastes, septic
systems). High nitrate-containing water is a serious health
concern for pregnant women and infants under the age of 6
months. Bacteria in the infants' digestive tracts may convert
the relatively harmless nitrate to nitrite. In turn, the nitrite
combines with some of the hemoglobin in blood to form methemoglobin
that cannot transport oxygen. To protect those at risk, the
Maximum Contaminant Level (MCL) for nitrate in water is 45
mg/l as nitrate (NO3) or 10 mg/l as nitrogen (N).
The MCL for nitrite is 1 mg/l.
Sulfates
occur naturally in groundwater combined with calcium, magnesium
and sodium as sulfate salts. Sulfate content in excess of
250 to 500 ppm (mg/l) may give water a bitter taste and have
a laxative effect on individuals not adapted to the water.
Water
that smells like rotten eggs has a high level of hydrogen
sulfide gas. The gas may occur naturally in water near oil
or gas fields or as the result of bacterial contamination.
To test for bacterial contamination contact the county health
department or a commercial testing lab.
The
term "organic chemical" includes such products as pesticides,
herbicides, petroleum products and industrial solvents. Although
most have not been routinely monitored, hundreds of different
organic chemicals have been found in drinking water from accidental
spills, improper disposal or non-point movement through soils
to groundwater. Today, municipalities are required to monitor
an increasing list of organic chemicals under the Safe-Drinking-Water
Act.
As with
other contaminants, the danger from organic chemicals in water
is hard to assess. In high doses and pure form some of these
chemicals may promote cancer, impair the nervous system or
damage the heart. In low doses, organic chemicals may have
cumulative effects, but so far not much is known about their
nature or magnitude.
Once
groundwater is contaminated, cleanup of that groundwater is
extremely difficult. If the water is unsuitable for human
use, it also may be unsuitable for agricultural uses and alternative
sources of water may need to be found. Organic chemicals and
groundwater contamination is an area where much research is
needed. In the meantime, the prudent use and disposal of all
chemicals (agricultural, industrial, home and garden) can
go a long way to protect the environment and groundwater from
contamination.
Radon
is a radioactive gas, a decay product of uranium, that can
dissolve into water supplies. The gas also is found in rocks
and soils that contain granite, shale, phosphate, and pitchblende.
It is odorless, colorless and tasteless.
The
EPA considers radon to be a major potential health threat,
causing an estimated 10,000 to 40,000 lung-cancer deaths each
year. While most deaths are from radon accumulated in houses
from seepage through cracks and holes in the foundation, 30
to 1,800 deaths per year are attributed to radon from household
water. Showering, dish-washing and laundering agitate water
and release radon into the air. The EPA estimates that at
least 8 million people may have high radon levels in their
water supply. Radon is most likely to be present in water
from private wells or from small community systems. Large
systems usually provide some kind of water treatment that
aerates the water and disperses any radon gas that may be
present.
Before
you test your water for radon, test the air. If your indoor
radon level is high and you use groundwater, test your water.
If the air level is low, there is no need to test your water.
Test results are expressed in picocuries of radon per liter
of water (pCi/l). In general 10,000 pCi/l of radon in water
contributes roughly 1 pCi/l of airborne radon throughout the
house. EPA currently advises consumers to take action at total
household air levels of 4 pCi/l. For waterborne radon, a simple
step is to make sure your bathroom, laundry and kitchen are
well ventilated. At moderate levels, this may adequately reduce
your exposure to waterborne radon. However if you use a private
well that has high levels of radon, water treatment devices
such as granular activated carbon units and home aerators
may be warranted.
The
growing uneasiness over the purity of tap water has led many
Americans to install waste treatment devices, such as filters
or distillers. See Service in Action 9.728 Drinking water
treatment devices: filters and 9.729 Drinking water treatment
devices: distillers.
Sales
of bottled water have increased dramatically over the last
few years. Bottled-water companies and public water systems
often battle over the relative merits of their products. EPA
regulates public water systems. FDA regulates bottled water
that crosses state lines. Bottled or vended water that stays
in Colorado falls under the jurisdiction of the Colorado State
Department of Health.
Public
water systems generally are disinfected with chlorine. Bottled
water is commonly disinfected by ozone treatment. Ozone is
a high-strength oxygen that quickly reverts to normal oxygen.
It is a strong oxidant, like chlorine, but does not add taste
like chlorine does. The length of time chlorine and ozone
remain active in water depends on many factors, including
temperature. Chlorine usually provides residual disinfection
throughout the public-water distribution system. Ozone provides
a residual disinfection for a limited time. However, bottled
water may be in distribution for several weeks and storage
conditions, especially temperature, may adversely affect quality.
In terms of bacterial content, it is questionable as to whether
bottled water is better than most municipal tap water.
Bottled
water often is purchased for its good taste. However, taste
does not always indicate safeness. At the concentrations present
in drinking water, most harmful substances (including some
disease-causing microorganisms, nitrates, trace amounts of
lead and mercury, and some pesticides and organic materials)
have no taste. Differences in taste among bottled waters generally
are due to differing amounts of carbon dioxide, calcium, iron
compounds, sodium, and other minerals and mineral salts. Differences
also may be due to the amount and type of processing.
Mineral-free
water or distilled water is treated to remove the minerals
that occur naturally in water. Almost all sodium is removed
by these processes. The resulting water is rather flat and
tasteless for drinking because of the lack of minerals.
Drinking
water comes from municipal water systems, wells or springs.
It often is treated by reverse osmosis to remove bacteria
and other pathogens and most pesticides. The resulting water
is purified but still contains some dissolved solids.
Natural
water comes from unprotected well or spring systems and
is bottled without extensive treatment. Because it is almost
exclusively groundwater, it usually contains a range of minerals
and is, therefore, quite flavorful. Spring water is ground
water that has risen naturally to the surface. Artesian spring
water also rises under its own pressure, but only after it
has been reached by drilling.
Mineral
water is simply water that contains minerals - which is
true of virtually all water except distilled water.
Natural
mineral water contains just the minerals present in the
water as it comes from the ground. Mineral water can be still
or sparkling. The carbon dioxide that causes carbonation also
can be natural or added during bottling.
As for
contaminants, bottled water generally rates as good as but
no better than municipal water supplies used for comparison
purposes. If you do purchase bottled or vended water, purchase
from a quality retailer who handles enough volume to rotate
stock. If you have concerns about locally vended water, contact
your county health department or the Colorado Department of
Health, (303) 692-2000.
- E.P.A.
Lead in Drinking Water: Should you be concerned? Environmental
Protection Agency, Public Information Center, Waterside
Mall, 410 M St., SW, Washington D.C.
- Follett,
R.H. and J.R. Self. Domestic water quality criteria. Colorado
State University Cooperative Extension, Service in Action,
.513, Fort Collins, CO 1989.
- Fundingsland,
S. and D. Lundstrom. Drinking Water and Health. Pub. 27,
HEA, NDSU Extension Service, North Dakota State University,
Fargo, ND 58105, June, 1988.
- Shelton,
T. Interpreting Drinking Water Quality Analysis - What Do
the Numbers Mean? Pub. E127, Rutgers Cooperative Extension,
Cook College, Rutgers University, New Brunswick, NJ 08903,
1989.
- Stewart,
J., A. Lemley, S. Hogan, R. Weismiller. Health Effects of
Drinking Water Contaminants. Water Quality Fact Sheet 2,
Cornell University and University of Maryland, Rev. 1988-89.
- The
Pollutants that Matter Most: Lead, Radon, Nitrate. Consumer
Reports, p. 30-32, January, 1990.
Disclaimer
and Reproduction Information: Information in NASD does not
represent NIOSH policy. Information included in NASD appears
by permission of the author and/or copyright holder. More
NASD Review: 04/2002
Service
in Action 9.307, Cooperative Extension, Colorado State University.
Published May 1991. Revised October 1992. Copyright 1992.
For more information, contact your county Cooperative Extension
office.
Colorado State University Cooperative Extension food science
and human nutrition specialist and professor, food science
and human nutrition.
|