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Metro Phoenix, Arizona:
As a result of extensive regulations,
guidelines and water quality testing,
drinking water supplies in the United State
are among the cleanest and safest in the
world. Yet despite efforts to standardize
the cleanliness and quality of drinking
water nationwide, the quality of water
served by individual systems varies over
time due to changes in the water source from
which it is drawn and the treatment it
undergoes.
Drinking water comes from two major sources:
surface water such as lakes, rivers, and
reservoirs; and groundwater, which is pumped
from wells. Sometimes these sources are
close to a community, but water can also be
transported long distances by canals or
pipelines.
In
Arizona, many communities get their drinking
water from sources managed by
Salt River Project
or the
Central Arizona
Project
.
These companies do not supply drinking water
directly to consumers, but they provide most
of the water used by public water systems in
the Phoenix metropolitan area.
Because
of its exposure to the environment and the
potential for contamination, surface water
typically requires both filtration and
disinfection to reach drinking water quality
standards.
Normally groundwater is considered to be the
most pure source of water because it is
naturally filtered as it passes through the
layers of rock and sediment in an aquifer.
However, the geology of the rocks in the
aquifer may have a major impact on the
quality of the groundwater. Many times the
technology required to remove these
contaminants can be more complicated and
expensive than surface water treatments.
Regardless of the water treatment technology
employed to clean drinking water, most water
systems add chlorine or another disinfectant
to ensure the water remains clean within the
water distribution system. Disinfection of
drinking water supplies was an important
advance in public health and a major
accomplishment of the 20th century.
Community water suppliers throughout the
country are required to provide an annual
water quality report (also know as a
consumer confidence report) to their
customers. These reports are prepared by the
water systems and are usually made available
to consumers in July. They provide
information on your local drinking water,
including the water's source, the
contaminants found in the water, and how
consumers can get involved in protecting
drinking water.
The
goal of consumer confidence reports is to
help consumers make health-based decisions
regarding their drinking water. Many
municipal water systems place these reports
online at the city or town Web site.
Consumers with questions should contact
their water company to request a copy of the
report.
Drinking Water Contaminants
Almost all drinking water contains some
impurities, whether natural such as minerals
or man-made such as chlorine or other
disinfectant additives. These impurities,
while referred to as contaminants, are often
beneficial to human health in trace amounts.
The EPA
has set standards for more than 80 primary
contaminants that may occur in drinking
water and pose a risk to human health. These
standards, called maximum contaminant
levels, are the safety limits established
for safe drinking water.
The
taste and smell of drinking water may also
be affected by secondary contaminants,
sometimes referred to as aesthetic
contaminants. While these contaminants may
make tap water less desirable, they do not
pose a health risk and are not regulated to
the same degree as primary contaminants.
ADEQ
has adopted
maximum contaminant
levels
that EPA established for two different
categories of harmful contaminants based on
the exposure required to cause health
effects. Acute contaminants are those that
have health effects that occur within hours
or days of exposure. In other words, they
can make people sick very quickly. These
include microbial contaminants, nitrates and
nitrites.
Chronic
contaminants, by contrast, generally require
exposure above the maximum contaminant level
for many years to cause harm. The levels for
chronic contaminants are based on a lifetime
exposure, defined by EPA as an average adult
consuming 2 liters of water everyday for 70
years. They include many man-made chemicals,
some naturally occurring minerals and
radionuclides.
People
with HIV/AIDS or for another reason have a
weakened immune systems may be more
susceptible to microbial contaminants,
including Cryptosporidium, in drinking
water. Those in such situations should
contact their health care providers to find
out if additional precautions are warranted.
Young
children are particularly susceptible to the
effects of high levels of certain
contaminants, including nitrate and lead. To
minimize the risks of exposure to lead, use
water from the cold tap for making baby
formula, drinking, and cooking, and let the
water run for a minute or more if the water
hasn't been turned on for six or more hours.
If your water supplier alerts you that your
water does not meet EPA's standard for
nitrates and you have children less than six
months old, consult your health care
provider. You may want to find an alternate
source of water that contains lower levels
of nitrates for your child until your
drinking water system corrects this problem.
For
more information on drinking water and your
health see:
source : Arizona Department of Environmental
Quality
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