Drinking Water Quality and Safety
When you turn on the tap for a glass of water, do you ever wonder about the quality
or safety of that water? With drinking water, it's important to consider not just
the water itself, but how that water gets to you.
The reality is, naturally pure water doesn't exist. Water is very good at dissolving
and absorbing impurities as it flows in streams, sits in lakes, or filters through
layers of soil and rock in the ground. Some of these substances, like certain naturally
occurring minerals, are harmless. Other naturally occurring minerals and many manmade
chemicals are not. Water also contains organic matter like dirt, leaves, and microbes.
The water you drink comes from one of two sources:
Surface water found in lakes, rivers, and reservoirs
Water found in an underground aquifer and pumped from a well
Clean, safe drinking water is important for good health.
Drinking water quality differs from place to place. It depends on the condition of
its source and the treatment it gets. Sources of contaminants might be in your neighborhood
or many miles away from you in the watershed. The watershed is the land area drained
by water as it flows into the river, lake, reservoir, or aquifer.
Standards ensure safety
Public water supplies must meet quality and safety standards set by the EPA and state
governments. Your local government and private water suppliers are responsible for
maintaining the quality of the water that flows to your tap. They are required to
test and treat the water. They must also maintain the systems that deliver the water
to consumers, and report on the water quality to the state. Every community water
supplier must provide an annual report to its customers on local drinking water quality.
The report also must include the water's source, the contaminants found in the water,
and how consumers can get involved in protecting drinking water. This is called a
Consumer Confidence Report.
The EPA has standards for more than 80 contaminants that may occur in drinking water
and pose a risk to human health. These are what the EPA standards cover:
Microbes (bacteria, parasites, viruses). The EPA watches disease-causing microbes.
Other microbes the EPA tests for are not harmful to people. But they show that the
water has not been properly treated.
Inorganic chemicals. These can come from natural erosion or from factories and farming.
Some chemicals that the EPA monitors are arsenic, cadmium, mercury, lead, nitrate
or nitrite, and selenium.
Organic chemicals. These can be chemicals used to treat water. They can also be chemicals
like herbicides and fungicides used in agriculture. Or they can be chemicals like
insect poisons used by homeowners, and chemicals from factories.
Radionuclides. These are naturally occurring radioactive minerals that may emit a
form of radiation. Examples include radon, radium, and uranium.
Disinfectants used in water treatment. Chlorine, chloramines, and chlorine dioxide
are used to disinfect public water supplies. Byproducts form when the disinfectants
react with naturally occurring organic matter found in the water. Over many years,
exposure to these byproducts can cause diseases or organ damage. The EPA monitors
water to find extra levels of these: trihalomethanes, haloacetic acids, bromate, and
If you need exact information about your drinking water, you can read the annual reports
issued by the EPA. The reports can be found on the EPA website.
The EPA does not regulate private water sources like wells, but some state and local
governments do set rules to protect well users. Unlike public drinking water systems
serving many people, private sources do not have experts regularly checking the water's
source and its quality. The households using this water must take special precautions
to protect and maintain their drinking water source.
How is water treated?
Public water supplies are sent through treatment plants. The treatment depends on
local conditions and impurities found in the water. Chemicals called coagulants can
be added to the water as it flows very slowly through tanks. This will make dirt and
other impurities form clumps and settle to the bottom so they can be removed. Water
can be filtered to remove the smallest impurities. Most water suppliers add chlorine
or another disinfectant to kill bacteria and other germs. If organic chemicals are
present, they can be removed with activated carbon. This soaks them up. Groundwater
from aquifers has been naturally filtered as it passes through layers of the earth.
Water pumped from wells generally contains less organic material than surface water
and may not need to go through any or all treatments.
For people who depend on wells or other private sources of water, the EPA recommends
annual testing for nitrate and coliform bacteria to detect problems early. Testing
should be more often if a problem is suspected. According to the EPA, the following
activities in your watershed may affect the water quality of your well. This is especially
possible if you live in an area without sewers:
Digestive illness that keeps coming back. Check for coliform bacteria.
The plumbing in your house contains lead. Check for lead and copper.
Radon has been found in your home, or you live in an area where radon is plentiful.
Check for radon.
The pipes in your home are corroding. Check for lead.
You live in a heavily farmed area. Check for nitrate, pesticides, and coliform bacteria.
You live near a coal mine or other mining operation. Check for metals.
You live near a gas drilling operation. Check for chloride, sodium, barium, and strontium.
You live near a dump, landfill, factory, or gas station. Check for volatile organic
compounds, sulfate, chloride, and metals.
Your water has an unpleasant taste or smell. Check for hydrogen sulfide and metals.
Your plumbing or laundry is stained. Check for iron, copper, and manganese.
For more information on safe drinking water, visit the EPA.
Bottled water is a popular way to get drinking water in the U.S. You may choose bottled
water because you prefer how it tastes. Or you may have health concerns about your
tap water. You may also choose bottled water instead of other kinds of beverages.
The FDA sets standards for bottled water in the U.S. The FDA bases its standards on
the standards set by the EPA for drinking water.
You can find out more about the bottled water you drink by looking at the label. The
label may tell you about the treatment process used. The label may also have a toll-free
number to call or a website to visit to find out more information.
This treatment information is especially important if you have a weakened immune system.
You should make sure that the bottled water you drink takes steps to protect against
the parasite Cryptosporidium. This parasite can cause serious illness. Treatments
that can block this parasite include: