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List of Contaminants & their Maximum Contaminant Level (MCLs)
From:
U.S Environmental Protective Agency
Website:
http://www.epa.gov/safewater/mcl.html
Disinfection Byproducts
| Contaminant |
MCLG1
(mg/L)2 |
MCL or TT1
(mg/L)2 |
Potential Health
Effects from Ingestion of Water |
Sources of
Contaminant in Drinking Water |
|
Bromate |
zero
|
0.010
|
Increased risk of cancer |
Byproduct of drinking water disinfection |
|
Chlorite |
0.8
|
1.0
|
Anemia; infants & young children: nervous
system effects |
Byproduct of drinking water disinfection |
|
Haloacetic acids (HAA5) |
|
0.060
|
Increased risk of cancer |
Byproduct of drinking water disinfection |
|
Total Trihalomethanes (TTHMs) |
|
0.10
----------
0.080
|
Liver, kidney or central nervous system
problems; increased risk of cancer |
Byproduct of drinking water disinfection |
Disinfectants
| Contaminant |
MRDL1
(mg/L)2 |
MRDL1
(mg/L)2 |
Potential Health
Effects from Ingestion of Water |
Sources of
Contaminant in Drinking Water |
|
Chloramines (as Cl2) |
MRDLG=41
|
MRDL=4.01
|
Eye/nose irritation; stomach discomfort,
anemia |
Water additive used to control microbes |
|
Chlorine (as Cl2) |
MRDLG=41
|
MRDL=4.01
|
Eye/nose irritation; stomach discomfort |
Water additive used to control microbes |
|
Chlorine dioxide (as ClO2) |
MRDLG=0.81
|
MRDL=0.81
|
Anemia; infants & young children: nervous
system effects |
Water additive used to control microbes |
Notes
1 Definitions:
Maximum Contaminant Level (MCL) - The highest level of a
contaminant that is allowed in drinking water. MCLs are set as close to
MCLGs as feasible using the best available treatment technology and taking
cost into consideration. MCLs are enforceable standards.
Maximum Contaminant Level Goal (MCLG) - The level of a contaminant
in drinking water below which there is no known or expected risk to
health. MCLGs allow for a margin of safety and are non-enforceable public
health goals.
Maximum Residual Disinfectant Level (MRDL) - The highest level of a
disinfectant allowed in drinking water. There is convincing evidence that
addition of a disinfectant is necessary for control of microbial
contaminants.
Maximum Residual Disinfectant Level Goal (MRDLG) - The level of a
drinking water disinfectant below which there is no known or expected risk
to health. MRDLGs do not reflect the benefits of the use of disinfectants
to control microbial contaminants.
Treatment Technique - A required process intended to reduce the
level of a contaminant in drinking water.
2 Units are in milligrams per liter
(mg/L) unless otherwise noted. Milligrams per liter are equivalent to
parts per million.
3 EPA's surface water treatment rules
require systems using surface water or ground water under the direct
influence of surface water to (1) disinfect their water, and (2) filter
their water or meet criteria for avoiding filtration so that the following
contaminants are controlled at the following levels:
-
Cryptosporidium (as of1/1/02 for systems serving >10,000 and 1/14/05
for systems serving <10,000) 99% removal.
- Giardia lamblia: 99.9% removal/inactivation
- Viruses: 99.99% removal/inactivation
-
Legionella: No limit, but EPA believes that if Giardia
and viruses are removed/inactivated, Legionella will also be
controlled.
-
Turbidity: At no time can turbidity (cloudiness of water) go above 5
nephelolometric turbidity units (NTU); systems that filter must ensure
that the turbidity go no higher than 1 NTU (0.5 NTU for conventional or
direct filtration) in at least 95% of the daily samples in any month. As
of January 1, 2002, turbidity may never exceed 1 NTU, and must not
exceed 0.3 NTU in 95% of daily samples in any month.
-
HPC: No more than 500 bacterial colonies per milliliter.
-
Long Term 1 Enhanced Surface Water Treatment (Effective Date:
January 14, 2005); Surface water systems or (GWUDI) systems serving
fewer than 10,000 people must comply with the applicable Long Term 1
Enhanced Surface Water Treatment Rule provisions (e.g. turbidity
standards, individual filter monitoring, Cryptosporidium removal
requirements, updated watershed control requirements for unfiltered
systems).
-
Filter Backwash Recycling; The Filter Backwash Recycling Rule
requires systems that recycle to return specific recycle flows through
all processes of the system's existing conventional or direct filtration
system or at an alternate location approved by the state.
4 more than 5.0% samples total
coliform-positive in a month. (For water systems that collect fewer than
40 routine samples per month, no more than one sample can be total
coliform-positive per month.) Every sample that has total coliform must be
analyzed for either fecal coliforms or E. coli if two consecutive
TC-positive samples, and one is also positive for E.coli fecal
coliforms, system has an acute MCL violation.
5 Fecal coliform and E. coli
are bacteria whose presence indicates that the water may be contaminated
with human or animal wastes. Disease-causing microbes (pathogens) in these
wastes can cause diarrhea, cramps, nausea, headaches, or other symptoms.
These pathogens may pose a special health risk for infants, young
children, and people with severely compromised immune systems.
6 Although there is no collective
MCLG for this contaminant group, there are individual MCLGs for some of
the individual contaminants:
-
Trihalomethanes: bromodichloromethane (zero); bromoform (zero);
dibromochloromethane (0.06 mg/L). Chloroform is regulated with this
group but has no MCLG.
-
Haloacetic acids: dichloroacetic acid (zero); trichloroacetic acid
(0.3 mg/L). Monochloroacetic acid, bromoacetic acid, and dibromoacetic
acid are regulated with this group but have no MCLGs.
7 MCLGs were not established before
the 1986 Amendments to the Safe Drinking Water Act. Therefore, there is no
MCLG for this contaminant.
8 Lead and copper are regulated by a
Treatment Technique that requires systems to control the corrosiveness of
their water. If more than 10% of tap water samples exceed the action
level, water systems must take additional steps. For copper, the action
level is 1.3 mg/L, and for lead is 0.015 mg/L.
9 Each water system must certify, in
writing, to the state (using third-party or manufacturer's certification)
that when acrylamide and epichlorohydrin are used in drinking water
systems, the combination (or product) of dose and monomer level does not
exceed the levels specified, as follows:
- Acrylamide = 0.05% dosed at 1 mg/L (or equivalent)
- Epichlorohydrin = 0.01% dosed at 20 mg/L (or equivalent)
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