no. 9.307 |
Drinking water quality and health
by P. Kendall1Quick 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 under the Safe Drinking Water Act.
- 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.
Hard vs. Soft Water
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) doesnt 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.
Giardia and Other Microorganisms
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. 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.
Prevention is the best solution. Always wash your hands after changing
diapers and performing other hygiene activities. Wash childrens
hands frequently. Thoroughly clean change surfaces after diapering.
Its 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.
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
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 50 years of fluoridation, only
two-thirds fo the U.S. population is served by drinking water with optimal
levels of fluoride. 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, including cancer. However, a recent study found a lower cancer incidence
in areas with high fluoride concentrations in the drinking water.
Tooth decay is on the decline in the United States. The decline is occuring
in fluoridated and to a lesser extent in non-fluoridated areas. Fluoride
treatments, fluoridated toothpaste, dental sealants, 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
Lead is a toxic heavy metal known to turn up in drinking water. A 1986
EPA survey estimated that 40 million Americans (one in five) were using
drinking water that contained potentially hazardous levels of lead. This
finding led to changes in the Safe Drinking Water Act to require the use
of lead-free pipe, solder, and flux in the installation or
repair of home and commercial plumbing connected to public water systems.
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 the nationwide 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 currently requires that public utilities ensure that lead levels
at the customers tap not exceed 15 parts per billion (ppb) in at
least 90 percent of the homes sampled. Water systems that exceed such
levels are 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. Consumers
can follow a number of simple practices to help reduce the level of lead
at the tap.
- 1. Cook with and drink only cold water. Hot water tends to dissolve more
lead from pipes.
2. Dont 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.
3. 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.
4. If lead levels remain high, consider bottled water for drinking and cooking purposes.
Nitrate
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 measured as nitrogen (N). The MCL for nitrite is 1 mg/l measured at nitrogen.
Sulfate
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.
A list of contaminants currently monitored by public drinking water systems, maximum contaminant levels (MCL), common sources and potential health effects from exposure above the MCL can be found at www.epa.gov/safewater/mcl.htm.
Sulfate
Sulfates occur naturally in groundwater combined with calcium, magnesium
and sodium as sulfate salts. Sulfate content in excess of 250 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.
Organic Chemicals
The term organic chemical includes such products as pesticides,
herbicides, petroleum products and industrial solvents. 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 more than 50 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 these chemicals may cause various problems
including increased risk of cancer, impaired nervous system or damage
to the heart. In low doses, organic chemicals may have cumulative effects,
but less is known about their nature or magnitude.
Radon
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 20,000 lung-cancer deaths each year. While most deaths are
from radon accumulated in houses from seepage through cracks and holes
in the foundation, some 160 deaths per year are attributed to radon from
household water. Showering, dish-washing and laundering agitate water
and release radon into the air.
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.
References
- E.P.A. Lead in Your Drinking Water. Washington D.C.: Environmental Protection Agency, Public Information Center, 1993. Available at www.epa.gov/safewater/Pubs/lead1.htm.
- Fundingsland, S. and D. Lundstrom. Drinking Water and Health. Pub. 27, HEA, NDSU Extension Service, North Dakota State University, Fargo, ND 58105, June, 1988.
- Steiner, G. Cancer Incidence Rates and Environmental Factors: An Ecological Study. Journal of Environ, Pathology, Toxicology, Oncology. 2002; 21(3)205-12.
- National Academy of Sciences. Risk Assessment of Radon in Drinking Water. Washington D.C.: National Academy Press. 1999. Available at http://books.nap.edu/html/radon/.
1Colorado State University Extension food science and human nutrition specialist and professor, food science and human nutrition. 10/92. Revised 2/03.
Colorado State University, U.S. Department of Agriculture, and Colorado counties cooperating. CSU Extension programs are available to all without discrimination. No endorsement of products mentioned is intended nor is criticism implied of products not mentioned.
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