Janice Woodard, Blake Ross, Kathleen Parrott
University Cooperative Extension
Table
of Contents
People
are exposed to lead from a variety of sources. In Virginia there
are negligible amounts of lead in surface water and groundwater,
but the water in household plumbing systems can contain high
levels of lead. Because lead is a serious health hazard, it
is very important to reduce lead contamination of drinking water.
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If
your plumbing was installed before 1930, it probably contains
lead pipes. Since then copper pipes have largely replaced lead
pipes, but lead solder is still commonly used.
In many
cases, lead levels decrease as a building ages because mineral
deposits from the water coat the inside walls of pipes, providing
a barrier between the lead and the water. However, water with
very low pH is too corrosive to deposit this protective coating,
or scale. Instead, corrosive water will dissolve the metal
pipe and fittings, depending on the extent of the water's
corrosivity, its temperature, and the length of time it is
in contact with the lead source.
Shallow
groundwater sources are generally more corrosive than deep
wells. Soft water enhances dissolving of lead from plumbing
because the absence of minerals in soft water tends to make
the water more reactive.
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Lead
reacts with enzymes in the body to slow or stop essential physiological
reactions. Since lead is accumulated and stored in the bones,
continued exposure to it will severely affect our health. When
lead levels become so high that they saturate the bones, blood
lead levels begin to affect nerve tissue.
Fetuses,
infants, and young children are particularly vulnerable to
lead poisoning. Doses of lead that might have little effect
on adults can severely affect small bodies. Also growing children
rapidly absorb any lead they consume. A child's mental and
physical development can be irreversibly stunted by over-exposure
to lead.
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The
current drinking water standard for lead is 0.05 milligrams
per liter (or 50 parts per billion in water). The only sure
way to determine if your water contains too much lead is to
have it tested. You should be particularly suspicious and pursue
testing if your home has lead pipes (lead is a dull-gray metal
that is so soft you can easily scratch it with a house key),
and/or there are signs of corrosion in the plumbing system (frequent
leaks, rust colored water, or stained dishes or laundry).
Water
samples can be analyzed for lead content at a certified water
testing laboratory. For more information about the location
of these laboratories, contact the local Cooperative Extension
office or county health department. To evaluate the highest
levels of lead present, you should take a sample from the
tap after water has been held in the pipes for several hours
or overnight. A second sample, taken after the water has flowed
from the tap for four or five minutes, will show if flushing
the line substantially decreases lead content. For reliable
results, carefully follow the laboratory's instructions when
you collect each water sample.
The
water should also be tested for pH and corrosivity. A pH below
the recommended standard of 6.5 indicates the water is acidic
enough to corrode plumbing systems.
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If
tests confirm that drinking water contains too much lead, avoid
consuming water that has been in contact with the plumbing for
more than six hours. Let the cold tap water run for four or
five minutes before you drink it or use it for cooking. Use
only cold water for preparing baby formula and cooking. Hot
water dissolves more lead from pipes. Bottled water is an alternative
to tap water.
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The
first step in limiting lead in drinking water may be to neutralize
acidic water by using a soda or phosphate feeder or a tank that
contains lime. High or persistent lead levels in drinking water
can be reduced by reverse osmosis (RO) or distillation treatment.
These methods also will remove a high percentage of other impurities
from drinking water.
Ordinary
carbon and mechanical filters are not designed to remove lead.
If lead is a problem in your plumbing system, do not connect
water softeners to pipes leading to drinking water taps. All
water treatment devices must have proper maintenance to achieve
effective lead removal.
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The
June 1986 amendments to the federal Safe Drinking Water Act
banned the use of any pipe or pipe fitting with more than 8%
lead and any solder or flux with more than 0.2% lead in public
drinking water supply systems, residences, and other buildings
connected to a public drinking water system. Furthermore, the
Virginia uniform building code prohibits the use of lead pipe
and solder in plumbing in all new home construction.
Such
alternative products as tin/antimony (95/5%) or tin/ silver
(96/4%) can be used for solder in home plumbing systems. Both
materials have been shown to be more resistant than lead solder
to the dissolving action of corrosive water. Plastic piping,
if allowed by local building codes, should also be considered
as an alternative.
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
Janice Woodard,
Retired Extension Specialist, Home Management and Equipment
Blake Ross, Extension Specialist, Agricultural Engineering
Kathleen Parrott, Extension Specialist, Housing
Adapted
with permission from a publication by Faye T. Plowman, University
of New Hampshire Cooperative Extension.
Publication
Number
356-483
,
September 1996
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