This is a fact sheet about a chemical that may be found in some public or
private drinking water supplies. It may cause health problems if found
in amounts greater than the health standard set by the United States
Environmental Protection Agency (EPA).
What is Arsenic and where does it come from?
Arsenic (As) is a naturally occurring contaminant found in many ground waters. It generally occurs in
two forms (valences or oxidation states): pentavalent arsenic (also known as As(V), As(+5), or arsenate)
and trivalent arsenic (also known as As(III), As(+3), or arsenite). In natural ground water, arsenic may
exist as trivalent arsenic, pentavalent arsenic, or a combination of both. Although both forms of arsenic
are potentially harmful to human health, trivalent arsenic is considered more harmful than pentavalent
Can I remove Arsenic from my water?
Yes, and here are the details. Trivalent arsenic is generally more difficult to remove from drinking water than pentavalent arsenic. Trivalent arsenic must first be converted to pentavalent arsenic in the presence of an effective oxidant such as free chlorine. The arsenic in water containing detectable free chlorine or that has been treated with another effective oxidant will be converted to the pentavalent arsenic form. Treatment with chloramine (combined chlorine) is not sufficient to ensure complete conversion of trivalent arsenic to pentavalent arsenic. Once trivalent arsenic is converted to pentavalent arsenic, it can be captured with KDF/GAC filters. KDF is kinetic degredation fluxion, and GAC is granular activated carbon. KDF/GAC filters are common and easy to find. If you wish to avoid the complications associated with oxidizing the trivalent arsenic, reverse osmosis systems utilizing a TFC (thin film composite) membrane can effectively reduce trivalent arsenic by 70-80% and pentavalent arsenic by 93-99%. CTA (cellulose triacetate) membranes are less effective with 60-70% and 85-90% reduction for trivalent and pentavalent arsenic respectively.
How do I know if my water is contaminated with Arsenic?
Consumers using public water supplies can contact their utility to verify whether free chlorine treatment chemicals
are being used. Private water supplies and waters that do not have detectable free chlorine residuals should be
analyzed to determine the form(s) of arsenic present and the potential need for oxidation of trivalent arsenic to
Arsenic does not generally impart color, taste, or smell to water, therefore, it can only be detected by a chemical
analytical test. Public water supplies are required to monitor treated water for total arsenic (trivalent arsenic plus
pentavalent arsenic) and the results are available to the public from the utility. Consumers using private water sources
will need to make arrangements for testing. A total arsenic test usually costs about $15-$30 and it is recommended a
certified laboratory conduct the test. Local health departments or environmental protection agencies can help provide
consumers with a list of certified laboratories. Some laboratories may also be able to analyze specifically for (speciate)
the two forms of arsenic present in a water sample if requested.
Water treatment systems are tested under laboratory conditions and found to reduce either 0.30 mg/L or 0.050 mg/L
(refer to the product listing for influent tested levels) in the test water to less than 0.010 mg/L, under standard
testing conditions. Actual performance of the system may vary depending on specific water quality conditions at the
consumer's installation. Following installation of this system, the consumer should have the treated water tested for
total arsenic to verify arsenic reduction is being achieved and the system is functioning properly.
The pentavalent arsenic removal component of this system must be replaced at the end of its useful life. Replacement
component(s), can be purchased from the original source of this system (retailer or distributor), from other sources
of this treatment system, or directly from the manufacturer. Refer to the installation and operation manual of your
water treatment device to obtain replacement frequency and ordering information.
Note: The above fact sheet is part of a larger
publication adapted from NSF publication: National Sanitation Foundation Contaminant Guide.
What are we announcing?
EPA is proposing a new drinking water standard of 5 g/L for arsenic and taking comment on
regulatory options of 3 g/L (the feasible level), 10 g/L and 20 g/L. EPA is proposing a
Maximum Contaminant Level Goal (MCLG) of zero for arsenic. This proposal also clarifies how
compliance is demonstrated for many inorganic and organic contaminants in drinking water.
What are the requirements of this proposed rule?
Community water systems (CWSs), which are public water systems that serve at least 15 locations
or 25 residents regularly year round, will be required to reduce the arsenic concentration from
the current standard of 50 g/L to 5 g/L.
At the same time, EPA is proposing that non-transient, non-community water systems (NTNCWSs) be
required to notify people served by these systems when arsenic exceeds the drinking water standard.
NTNCWSs are public water systems that are not a CWS and serve at least 25 of the same people more
than 6 months per year (e.g. schools and nursing homes).
The proposal will also reduce the ambiguities in some existing regulations. Compliance averages will
be based on actual number of samples collected. New systems and new sources must demonstrate compliance
within the State-specified time and sampling frequencies.
How soon after publishing the final rule will the changes take effect?
For CWSs serving > 10,000 people - compliance 3 years after the final rule.
For CWSs serving 25 to 10,000 people - compliance 5 years after the final rule.
For NTNCWSs - required to monitor and notify within 3 years after the final rule.
Before the effective date, all CWSs will begin providing health information and arsenic
concentrations in their annual consumer confidence report for water that exceeds the new standard.
Why is this rule significant?
In the 1996 amendments to the Safe Drinking Water Act, Congress directed EPA to propose a new
arsenic regulation by January 1, 2000 and to issue the final rule by January 1, 2001. The 1996
amendments also added discretionary authority to adjust the maximum contaminant level (MCL) if
the benefits would not justify the costs (1412(b)(6)). This is the first drinking water regulation
which will set a standard higher than technically feasible (3 g/L) because EPA determined that
costs would not justify the benefits. This rule would also only require NTNCWS to monitor and report
(as opposed to treating) because of cost-benefit considerations and because of the relatively low
occurrence for these water systems.
The implementation clarifications will more consistently identify exceedances of many drinking water
standards and codify existing State requirements for new system and new source compliance.
What health effects are associated with exposure to arsenic from drinking water?
In most drinking water sources, the inorganic form of arsenic tends to be more predominant than
organic forms. Inorganic arsenic in drinking water can exert toxic effects after acute (short-term)
or chronic (long-term) exposure. Although acute exposures to high doses of inorganic arsenic can
cause adverse effects, such exposures do not occur from public water supplies in the U.S. at the
current MCL of 50 g/L. EPA's proposed drinking water regulation addresses the long-term, chronic
effects of exposure to low concentrations of inorganic arsenic in drinking water. Chronic effects
at low concentrations include:
Cancer Effects: skin, bladder, lung, and prostate cancer.
Non-cancer effects: skin pigmentation and keratosis (callus-like skin growths seen earliest and most
often), gastrointestinal, cardiovascular, hormonal (e.g., diabetes), hematological (e.g., anemia),
pulmonary, neurological, immunological, reproductive/developmental functions.
What are the sources of arsenic contamination in water?
The contamination of a drinking water source by arsenic can result from either natural or human
activities. Arsenic is an element that occurs naturally in rocks and soil, water, air, plants,
and animals. Volcanic activity, the erosion of rocks and minerals, and forest fires are natural
sources that can release arsenic into the environment. Although about 90 percent of the arsenic
used by industry in the United States is used for wood preservative purposes, arsenic is also
used in paints, drugs, dyes, soaps, metals and semi-conductors. Burning fossil fuels and wastes,
paper production, glass manufacturing, cement manufacturing, mining and smelting can also release
arsenic. While arsenic can no longer be used in making pesticides, weed killers and embalming fluids,
the Agency is aware that prior to this ban these substances have contributed to drinking water contamination.
How many people and how many systems will be affected by this rule?
Higher levels of arsenic tend to be found more in ground water sources than in surface water sources
(i.e., lakes and rivers). Compared to the rest of the United States, the Western states have more
systems with arsenic levels greater than 10 g/L. Parts of the Midwest and New England have systems
with 2-10 g/L of arsenic. While many systems may not have any detected arsenic in their drinking
water, there may be "hot spots" with systems higher than the predicted occurrence for an area. About
12 percent of the nation's 54,000 CWSs will need to take measures to lower arsenic in their drinking
water. Of the affected systems, 94 percent serve less than 10,000 people. Tables 1 and 2 below show
the estimated number of CWSs and NTNCWSs that would be affected by this rule and the estimated population
served by these public water systems.
Table 1. Estimates of the
Community Water Systems That Would Need to Treat
and the Population Served by These CWSs
Number of CWSs Affected
Total Population Served
|Option of 3
|Option of 10
|Option of 20
Table 2. Estimates of the
Non-Transient, Non-Community Water Systems That
Would Need to Notify and the Population Served by These
Number of NTNCWSs Affected
Population to Notify
|Option of 3
|Option of 10
|Option of 20
Soon after the final rule is published, EPA will release a health advisory with suggestions on how the
public can reduce infant exposure to arsenic before the effective date of the final rule. Infant formula
can be reconstituted using water containing low levels of arsenic.
What are the benefits of this rule?
Reducing arsenic from 50 g/L to 5 g/L - protects an additional 22.5 million Americans and will prevent
about 20 cases of bladder cancer per year and approximately 5 bladder cancer deaths per year.
At a regulatory option of 3 g/L, reducing arsenic from 50 g/L to 3 g/L - protects an additional 35.7 million
Americans and will prevent about 25 cases of bladder cancer and approximately 7 bladder cancer deaths per year.
At a regulatory option of 10 g/L, reducing arsenic from 50 g/L to 10 g/L - protects an additional 10.7 million
Americans and will prevent about 13 cases of bladder and approximately 3 bladder cancer deaths per year.
Under a regulatory option of 20 g/L, reducing arsenic from 50 g/L to 20 g/L - protects an additional 4.4 million
Americans and will prevent about 7 cases of bladder cancer and approximately 2 bladder cancer deaths per year.
EPA expects that arsenic-related lung cancers (that could number as many as two to five times the number of bladder
cancers) and cardiovascular diseases will be reduced with a lower standard as well.
The estimated values of the benefits of this rule range from as high as $90 million for bladder cancer to $384
million for lung cancer.
Where can the public get more information about this proposed rule?
For general information on arsenic in drinking water, contact the Safe Drinking Water Hotline, at (800) 426-4791, or visit
the EPA Safewater website
In addition to this technical fact sheet, the following documents and fact sheet is available to the public at EPA's
web site on arsenic in drinking water.
Studies have linked long-term exposure to arsenic in drinking water to cancer of the bladder, lungs,
skin, kidney, nasal passages, liver, and prostate. Non-cancer effects of ingesting arsenic include
cardiovascular, pulmonary, immunological, neurological, and endocrine (e.g., diabetes) effects.
Short-term exposure to high doses of arsenic can cause other adverse health effects, but such effects
are unlikely to occur from U.S. public water supplies that are in compliance with the existing arsenic
standard of 50 ppb.
The current standard of 50 ppb was set by EPA in 1975, based on a Public Health Service standard originally
established in 1942. A March 1999 report by the National Academy of Sciences concluded that the current standard
does not achieve EPA's goal of protecting public health and should be lowered as soon as possible.
On June 22, 2000, EPA proposed a new drinking water standard of 5 ppb for arsenic and requested comment on options
of 3 ppb, 10 ppb and 20 ppb. EPA evaluated over 6,500 pages of comments from 1,100 commenters. Under the Safe Drinking
Water Act Amendments of 1996, EPA is required to issue a final rule by January 1, 2001 and Congress subsequently
extended this date to June 22, 2001.
EPA is setting the new arsenic standard for drinking water at 10 ppb to protect consumers against the effects of
long-term, chronic exposure to arsenic in drinking water. EPA is using its discretionary authority under the 1996
Amendments to the Safe Drinking Water Act to set the standard at a level that "maximizes health risk reduction
benefits at a cost that is justified by the benefits."
The new standard will apply to all 54,000 community water systems. A community water system is a system that
serves 15 locations or 25 residents year-round, including most cities and towns, apartments, and mobile home
parks with their own water supplies. EPA estimates that roughly five percent, or 3,000, of community water
systems, serving 11 million people, will have to take corrective action to lower the current levels of arsenic
in their drinking water.
The new standard will also apply to 20,000 water systems that serve at least 25 of the same people more than
six months of the year, such as schools, churches, nursing homes, and factories. EPA estimates that five percent,
or 1,100, of these water systems, serving approximately 2 million people, will need to take measures to meet the
new arsenic standard. Of all of the affected systems, 97 percent are small systems that serve fewer than 10,000
Arsenic occurs naturally in rocks and soil, water, air, and plants and animals. It can be further released into
the environment through natural activities such as volcanic action, erosion of rocks, and forest fires, or
through human actions. Approximately 90 percent of industrial arsenic in the U.S. is currently used as a wood
preservative, but arsenic is also used in paints, dyes, metals, drugs, soaps, and semi-conductors. Agricultural
applications, mining, and smelting also contribute to arsenic releases in the environment.
Higher levels of arsenic tend to be found more in ground water sources than in surface water sources
(i.e., lakes and rivers) of drinking water. Compared to the rest of the United States, western states have
more systems with arsenic levels greater than 10 ppb. Parts of the Midwest and New England have some systems
whose current arsenic levels are greater than 10 ppb, but more systems with arsenic levels that range from 2-10
ppb. While many systems may not have detected arsenic in their drinking water above 10 ppb, there may be geographic
"hot spots" with systems that may have higher levels of arsenic than the predicted occurrence for that area.
The average increase in household cost for water that meets the new arsenic standards depends on the size
of the water system and how many people are served by that system. For small community water systems (those
serving fewer than 10,000 people), the increase in cost is expected to range between $38 and $327. For community
water systems that serve greater than 10,000 people, annual household costs for water are expected to increase
from $0.86 to $32.
Systems may apply for financial assistance through EPA's drinking water state revolving fund. Since 1996, EPA's
drinking water state revolving fund program has made available $3.6 billion to assist drinking water systems with
projects to improve their infrastructure. EPA has funded over 1000 loans for projects around the country.
In addition to financial assistance, compliance period extensions of up to 9 years (resulting in a total compliance
period of 14 years) are available to small systems through an exemption process.
Note: This fact sheet is part of a larger
publication adapted from U.S. EPA publication: EPA National Primary
Drinking Water Regulations.