United States
Environmental Protection
hI	Agency
The Fourth Unregulated Contaminant Monitoring Rule
(UCMR 4): Data Summary, October 2018
Background
EPA uses the Unregulated Contaminant Monitoring Rule (UCMR) program to collect nationally representative
data for contaminants suspected to be present in drinking water, but that do not have regulatory standards.
UCMR 4 requires monitoring for 30 chemicals between 2018 and 2020. This monitoring is used by EPA to
understand the frequency and level of occurrence of unregulated contaminants in the nation's public water
systems (PWSs). Every five years EPA develops a new list of UCMR contaminants, largely based on the
Contaminant Candidate List (CCL). The Safe Drinking Water Act (SDWA) calls for EPA to:
	Require monitoring for no more than 30 contaminants per 5-year cycle
	Collect data from large PWSs (i.e., those that serve more than 10,000 people)
	Collect data from a representative sample of small PWSs (i.e., those serving less than or equal to 10,000
people)
	Store analytical results in the National Contaminant Occurrence Database (NCOD)
State and local officials may also use UCMR data to assess the need for actions to protect public health. When
evaluating UCMR data, State and local officials should consider the following limitations:
	UCMR monitoring generates a robust national data set that is representative of occurrence at a national
level; it is not designed to be representative of occurrence at a State or local level.
	UCMR results are not available immediately after sample collection. UCMR 4 allows PWSs and the
laboratories that support their monitoring up to six months to report results to EPA.
	There is limited information about health effects and treatment techniques to address some of these
unregulated contaminants.
This dataset represents the first NCOD release of UCMR 4 analytical results received to-date. This dataset is not
complete. Updates will occur approximately quarterly. Data are added and possibly removed or updated over the
course of this reporting cycle. These results are subject to change following further review by analytical
laboratories, PWSs, States and EPA. Before conducting your own assessment of the data, please review the "Data
Considerations" section.
Office of Water (MS-140)
EPA 815-S-18-002
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Contaminants and Methods
Contaminant
CAS Registry
Number
EPA Method
Contaminant Classification
germanium
7440-56-4
200.8
Metal
manganese
7439-96-5
200.8
Metal
alpha-hexachlorocyclohexane
319-84-6
525.3
Pesticide
chlorpyrifos
2921-88-2
525.3
Pesticide
dimethipin
55290-64-7
525.3
Pesticide
ethoprop
13194-48-4
525.3
Pesticide
oxyfluorfen
42874-03-3
525.3
Pesticide
profenofos
41198-08-7
525.3
Pesticide
tebuconazole
107534-96-3
525.3
Pesticide
total permethrin (cis- & trans-)
52645-53-1
525.3
Pesticide
tribufos
78-48-8
525.3
Pesticide
butylated hydroxyanisole
25013-16-5
530
Semivolatile organic compound
o-toluidine
95-53-4
530
Semivolatile organic compound
quinoline
91-22-5
530
Semivolatile organic compound
1-butanol
71-36-3
541
Alcohol
2-methoxyethanol
109-86-4
541
Alcohol
2-propen-l-ol
107-18-6
541
Alcohol
"total microcystins"
NA
546
Cyanotoxins
microcystin-LA
96180-79-9
544
Cyanotoxin
microcystin-LF
154037-70-4
544
Cyanotoxin
microcystin-LR
101043-37-2
544
Cyanotoxin
microcystin-LY
123304-10-9
544
Cyanotoxin
microcystin-RR
111755-37-4
544
Cyanotoxin
microcystin-YR
101064-48-6
544
Cyanotoxin
nodularin-R
118399-22-7
544
Cyanotoxin
anatoxin-a
64285-06-9
545
Cyanotoxin
cylindrospermopsin
143545-90-8
545
Cyanotoxin
HAA5 (five regulated haloacetic acids)
NA
552.3/557
Disinfection Byproducts
HAA6Br (six brominated haloacetic acids)
NA
552.3/557
Disinfection Byproducts
HAA9 (nine haloacetic acids)
NA
552.3/557
Disinfection Byproducts
Office of Water (MS-140)
EPA 815-S-18-002
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Reference Concentrations
EPA has established UCMR 4 Minimum Reporting Levels (MRLs) based on the capability of laboratories to
perform the analytical method, not based on a level established as "significant" or "harmful." UCMR 4 results
reported at or above those MRLs should be interpreted accordingly. The detection of a UCMR 4 contaminant
does not represent cause for concern, in and of itself.
Reference concentrations are health-based and provide context for the detection of a UCMR contaminant. They
do not represent regulatory limits or action levels and should not be interpreted as an indication that the Agency
intends to establish a future drinking water regulation. UCMR occurrence data will be used to inform the
Agency's Regulatory Determination process. Visit EPA's Regulatory Determination website for more information.
Community water systems must inform their consumers of UCMR monitoring results (including the average and
range of detections). See 40 CFR 141.153(d)(7) for Consumer Confidence Report (CCR) regulatory requirements
and Section IV of EPA's guidance, "Preparing Your Drinking Water Consumer Confidence Report" for details on the
contents of the report.
Non-transient, non-community water systems required to monitor for UCMR must inform their consumers of the
availability of monitoring results. See 40 CFR 141.207 for Tier 3 Public Notice (PN) regulatory requirements and
EPA's web page for PN guidance.
Some UCMR 4 contaminants have reference concentrations associated with short-term exposure. Therefore,
large PWSs may want to request results for these contaminants early (i.e., before their laboratory posts the
results to the UCMR web-based reporting system) so that these PWSs can inform their consumers in a timely
manner. EPA manages the laboratory analysis for small PWSs and will work to communicate results in a timely
manner.
States may establish requirements for drinking water contaminants not yet regulated by EPA, and those
requirements may be based on State-established levels that differ from EPA's reference concentrations. PWSs
are responsible for being aware of, and complying with their State's requirements, if any.
Reference Concentration Table
The table below provides MRL and reference concentration information for each contaminant monitored under
UCMR 4. When developing the table, EPA followed these principles:
(1)	EPA based the reference concentrations on publicly-available health information found in the following
EPA resources:
a.	2018 Edition of the Drinking Water Standards and Health Advisories Tables.
b.	CCL 4 Contaminant Information Sheets, and
c.	Human Health Benchmarks for Pesticides (HHBPs).
The primary sources of the health information used to derive the reference concentrations in the
resources referenced above are the products of peer-reviewed assessments from EPA or other
governmental agencies. The reference concentrations are subject to change as new health assessments
are completed. They are not legally enforceable federal standards.
(2)	If health information was available from more than one of the EPA resources listed above, the most
recent health information was used for the reference concentrations.
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(3)	If both (chronic) cancer and non-cancer health endpoints were available from the most recent EPA source,
the lower (more conservative) of the two concentrations was used except for oxyfluorfen, a "Group C"
possible human carcinogen (per 1986 Cancer Guidelines). As noted in the Regulatory Determination
protocol, regulatory decision making for Group C chemicals typically considers the non-cancer health
value. Please review the "EPA References" in the table below for additional health effects information.
(4)	If non-cancer health effects were the basis for the reference concentration, and both chronic and short-
term exposure values were available from the most recent EPA source, the lower concentration
(associated with the chronic exposure) was used. In those cases where the chronic and short-term
exposure values were the same, both are noted in the table. Please review the "EPA References" in the
table below for health effects information (e.g., additional short-term or chronic values).
(5)	For chemicals with reference concentrations based on a cancer endpoint, the table presents a range of
concentrations associated with risks of 10"6 (1 in 1,000,000) to 10"4 (1 in 10,000) over a lifetime.
(6)	For chemicals with reference concentrations based on a non-cancer endpoint, the exposure duration
(short-term, intermediate/long-term, chronic) associated with the toxic effect is shown.
EPA will periodically update the following table as new information becomes available. For more health effects
information visit: EPA's Drinking Water Contaminant Human Health Effects Information.
Office of Water (MS-140)
EPA 815-S-18-002
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Reference Concentrations
Contaminant
MRL
(M/L)
Reference Concentration
(M/L)
Reference Concentration
based on a Cancer Endpoint
(Y/N)
EPA Reference(s)
germanium1
0.3
NA
-
-
manganese2
0.4
300
N
[chronic and short -term
exposure (10-day infants)]
Health Advisory for Manganese
alpha-
hexachlorocyclohexane3,4
0.01
0.006 to 0.6
Y
CCL 4 Contaminant Information Sheets
chlorpyrifos5
0.03
2
N
(chronic exposure)
2018 Edition of the Drinking Water Standards and
Health Advisories Tables
dimethipin6
0.2
140
N
(chronic exposure)
Human Health Benchmarks for Pesticides (HHBPs)
ethoprop4,7
0.03
1.14 to 114
Y
Human Health Benchmarks for Pesticides (HHBPs)
oxyfluorfen8
0.05
200
N
(chronic exposure)
Human Health Benchmarks for Pesticides (HHBPs)
1	The CCL 4 Contaminant Information Sheet provides a concentration for this contaminant, but it is based on a single study. Therefore, no reference concentration is provided for
UCMR4.
2	Mn also has a non-mandatory secondary drinking water standard based on aesthetic factors (taste and color) and staining (plumbing fixtures and laundry).
310"6 cancer risk < MRL< 10"4 cancer risk. The MRL was established based on the capability of the analytical method.
4	Reference concentration range based on cancer risk of 10"6 to 10"4.
5	The Office of Pesticide Programs (OPP) Reregistration Eligibility Decision, 2006 is the basis for the health advisory. Additional OPP health effects information and information on
subsequent regulatory actions by the pesticides program is available for chlorpyrifos.
6	Dimethipin does not currently have any actively registered pesticide products and is not scheduled for review under the registration review program, per the Agency's October
2015 Notice; dimethipin is no longer a registered pesticide under EPA's program.
7	Additional OPP health effects information is available for ethoprop.
8	Since oxyfluorfen is classified as Group C (possible human carcinogen), and not as Group A (human carcinogen) or Group B (probable human carcinogen), the reference
concentration is based on the non-cancer value.
Office of Water (MS-140)
EPA 815-S-18-002
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Contaminant
MRL
(M/L)
Reference Concentration
(M/L)
Reference Concentration
based on a Cancer Endpoint
(Y/N)
EPA Reference(s)
profenofos9
0.3
0.3
N
(chronic exposure)
Human Health Benchmarks for Pesticides (HHBPs)
tebuconazole
0.2
190
N
[chronic and short-term
exposure (1-day children)]
Human Health Benchmarks for Pesticides (HHBPs)
total permethrin4,10
0.04
3.344 to 334.4
Y
Human Health Benchmarks for Pesticides (HHBPs)
tribufos11
0.07
0.6
N
(chronic exposure)
Human Health Benchmarks for Pesticides (HHBPs)
butylated hydroxyanisole1
0.03
NA
-
-
o-toluidine112
0.007
NA
-
-
quinoline3,4
0.02
0.01 to 1
Y
CCL 4 Contaminant Information Sheets
1-butanol
2.0
700
N
(chronic exposure)
CCL 4 Contaminant Information Sheets
2-methoxyethanol112
0.4
NA
-
-
2-propen-l-ol12
(allyl alcohol)
0.5
35
N
(chronic exposure)
CCL 4 Contaminant Information Sheets
"total microcystins" 1314
0.3
0.3 (bottle-fed infants and
young children); 1.6 (school-
age children and adults)
N
[Short-term exposure (10-day)]
Drinking Water Health Advisory Documents for
Cvanobacterial Toxins
microcystin-LA14
0.008
0.3 (bottle-fed infants and
young children); 1.6 (school-
age children and adults)
N
[Short-term exposure (10-day)]
Drinking Water Health Advisory Documents for
Cvanobacterial Toxins
9	Profenofos is undergoing voluntary cancellation; see the Agency's April 2017 Notice for the cancellation order and see the Agency's April 2017 final decision/case closure.
Additional OPP health effects information is available for profenofos.
10	Additional OPP health effects information is available for total permethrin.
11	Additional OPP health effects information is available for tribufos.
12	The support document for EPA's Provisional Peer-Reviewed Toxicity Values (PPRTV) for superfund includes health effects information for this contaminant that is more recent
than that used in the development of the CCL4 Contaminant Information Sheets.
13	The term 'Total microcystes" is used in UCMR 4 to represent the results of EPA Method 546. The method uses ELISA to detect the Adda amino acid side chain, which is
common to microcystin and nodularin congeners.
14	EPA's Cvanotoxins in Drinking Water website includes "Recommendations for Public Water Systems to Manage Cyanotoxins in Drinking Water," additional tools and resources.
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Contaminant
MRL
(M/L)
Reference Concentration
(M/L)
Reference Concentration
based on a Cancer Endpoint
(Y/N)
EPA Reference(s)
microcystin-LF14
0.006
0.3 (bottle-fed infants and
young children); 1.6 (school-
age children and adults)
N
[Short-term exposure (10-day)]
Drinking Water Health Advisory Documents for
Cvanobacterial Toxins
microcystin-LR14
0.02
0.3 (bottle-fed infants and
young children); 1.6 (school-
age children and adults)
N
[Short-term exposure (10-day)]
Drinking Water Health Advisory Documents for
Cvanobacterial Toxins
microcystin-LY14
0.009
0.3 (bottle-fed infants and
young children); 1.6 (school-
age children and adults)
N
[Short-term exposure (10-day)]
Drinking Water Health Advisory Documents for
Cvanobacterial Toxins
microcystin-RR14
0.006
0.3 (bottle-fed infants and
young children); 1.6 (school-
age children and adults)
N
[Short-term exposure (10-day)]
Drinking Water Health Advisory Documents for
Cvanobacterial Toxins
microcystin-YR14
0.02
0.3 (bottle-fed infants and
young children); 1.6 (school-
age children and adults)
N
[Short-term exposure (10-day)]
Drinking Water Health Advisory Documents for
Cvanobacterial Toxins
nodularin-R14
0.005
NA
-
-
anatoxin-a14 15
0.03
NA
-
-
cylindrospermopsin14
0.09
0.7 (bottle-fed infants and
young children); 3 (school-age
children and adults)
N
[Short-term exposure (10-day)]
Drinking Water Health Advisory Documents for
Cvanobacterial Toxins
H AA516
-
60
Y/N
(chronic exposure)
The MCL for the National Primary Drinking Water
Regulation
HAA6Br17
-
NA
-
-
H AA918
-
NA
-
-
15	The Health Effects Support Document for the Cvanobacterial Toxin Anatoxin-a concluded that the data from the oral toxicity studies evaluated contained too few dose levels
and study endpoints to derive a reference dose (RfD).
16	Since HAA5 is regulated, EPA is using a different authority (Section 1445(a)(1)(A) of SDWA) as the basis for UCMR 4 monitoring. The MCL was based on a consideration of
cancer and non-cancer effects. HAA5 = Dibromoacetic Acid, Dichloroacetic Acid, Monobromoacetic Acid, Monochloroacetic Acid, and Trichloroacetic Acid.
17	HAA6Br= Bromochloroacetic Acid, Bromodichloroacetic Acid, Dibromoacetic Acid, Dibromochloroacetic Acid, Monobromoacetic Acid, and Tribromoacetic Acid.
18	HAA9 = Bromochloroacetic Acid, Bromodichloroacetic Acid, Chlorodibromoacetic Acid, Dibromoacetic Acid, Dichloroacetic Acid, Monobromoacetic Acid, Monochloroacetic
Acid, Tribromoacetic Acid, and Trichloroacetic Acid.
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Terms
a)	UCMR Reference Concentration = The reference concentrations are based on publicly-available health information found in the
following EPA resources: 2018 Edition of the Drinking Water Standards and Health Advisories Tables [i.e., Health advisories
(HA)], the CCL 4 Contaminant Information Sheets [i.e., Health Reference Levels (HRLs)], and the Human Health Benchmark for
Pesticides (i.e., HHBPs). The primary sources of the health information used to derive the guideline values in the resources
referenced above are peer-reviewed assessments from EPA or other governmental agencies. The reference concentrations are
subject to change as new health assessments are completed. Reference Concentrations are not legally enforceable federal
standards.
b)	MRL = UCMR Minimum Reporting Level. The minimum concentration that may be reported by a laboratory as a quantified
value for a method analyte following analysis. The MRLs were established based on the capability of the analytical method, not
based on a level established as "significant" or "harmful." [Note that the Agency for Toxic Substances & Disease Registry
(ATSDR) uses the term "MRL" for a different purpose (i.e., to describe "Minimal Risk Levels"). The UCMR term and the ATSDR
term have no relationship to each other.]
c)	HRL = Health Reference Levels. The CCL process derives HRLs for screening purposes using available data. The CCL HRLs derived
from health assessments can be used in the Regulatory Determination process as risk-derived concentrations against which to
evaluate the occurrence data to determine if contaminants may occur at levels of public health concern. HRLs are not final
determinations about the level of a contaminant in drinking water that is necessary to protect any particular population and, in
some cases, are derived prior to development of a complete exposure assessment using the best available data. HRLs are not
legally enforceable federal standards.
d)	HA = Health Advisories. HAs provide information on contaminants that can cause human health effects and are known or
anticipated to occur in drinking water. EPA's health advisories are non-enforceable and non-regulatory and provide technical
information to State agencies and other public health officials on health effects, analytical methodologies, and treatment
technologies to assist with risk management decisions.
e)	HHBP = Human Health Benchmarks for Pesticides. EPA has developed HHBPs for informational purposes for use by States,
water systems and the public to assist with risk management decisions and to prioritize monitoring efforts for pesticides that
have no drinking water standards or health advisories. All benchmarks for the contaminants on UCMR 4 were calculated with
updated exposure assumptions [body weight (80 kg) and drinking water intake (2.5 L/day)]. The HHBPs are not legally
enforceable federal standards.
f)	MCL = Maximum Contaminant Level. The highest level of a contaminant allowed in drinking water. MCLs are enforceable
standards.
g)	Cancer Risk of 10"6 to 10"4 (chronic exposure) = The concentration of a contaminant in drinking water corresponding to an
excess estimated lifetime cancer risk of one-in-a-million (lx 10"6) to one-in-ten-thousand (1 x 10"4). The 2018 Edition of the
Drinking Water Standards and Health Advisories Tables provide the cancer risk at 1 x 10"4. The CCL 4 Contaminant Information
Sheets provide the cancer risk at lx 10"6. The Human Health Benchmarks for Pesticides provide a risk range (10 6 to 10"4).
Cancer risk is derived using drinking water exposure assumptions, risk level and a cancer slope factor (CSF), a toxicity value for
evaluating the probability of an individual developing cancer from exposure to a certain level of a contaminant over a lifetime.
Generally, when evaluating risk for health endpoints associated with chronic exposures, averages from multiple measurements
(potentially spanning a period of time) are more representative of a lifetime risk than results from a single measurement.
h)	Non-cancer (short-term exposure) = Based on a dose, "an estimate (with uncertainty spanning perhaps an order of magnitude)
of a daily oral exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk
of non-cancer effects after short-term exposure." Short-term exposure typically refers to animal toxicological studies with an
exposure duration of days to weeks. One-day is protective for up to 1 day of exposure, and is typically based on an animal
study with a duration of 7 days or less. Ten-day is protective for up to 10 days of exposure, and is typically based on an animal
study with a duration of 7 to 30 days. Generally, when communicating risk for health endpoints associated with short-term
exposures, a single detection is more relevant.
i)	Non-cancer (chronic exposure) = Based on a reference dose (RfD), "an estimate (with uncertainty spanning perhaps an order of
magnitude) of a daily oral exposure to the human population (including sensitive subgroups) that is likely to be without an
appreciable risk of non-cancer effects following long-term exposure." Chronic exposure typically refers to animal toxicological
studies with an exposure duration of months to years; representing a lifetime exposure in humans. Generally, when evaluating
risk for health endpoints associated with chronic exposures, averages from multiple measurements (potentially spanning a
period of time) are more representative of a lifetime risk than results from a single measurement.
j) PPRTV = Provisional Peer-Reviewed Toxicity Value. A toxicity value (expressed as mg/kg-day) derived for use in the Superfund
Program when a value is not available in EPA's Integrated Risk Information System (IRIS, the first tier in the Superfund hierarchy
of human health toxicity values). PPRTVs are derived after a review of the relevant scientific literature using the methods,
sources of data and guidance for value derivation used by the EPA IRIS Program. All provisional peer-reviewed toxicity values
receive internal review by EPA scientists and external peer review by independent scientific experts.
k) NA = Not Available
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October 2018 Data Summary
Contaminant
MRL
(Hg/L)
Reference
Concentration
(Hg/L)
Total
number
of
results
Number
of
results
>MRL
Number of
results
>Reference
Concentration
% of total
results
>Reference
Concentration
Total
number
of PWSs
with
results
Number
of PWSs
with
results
>MRL
Number of
PWSs with
results
>Reference
Concentration
% of PWSs
with results
>Reference
Concentration
germanium
0.3
NA
2,509
155
--
--
787
84
--
--
manganese
0.4
300
2,470
1,737
10
0.4%
776
636
8
1%
alpha-hexachlorocyclohexane
0.01
0.006/0.61
2,042
1
I/O2
0.05% / 0%2
652
1
I/O2
0.2% / 0%2
chlorpyrifos
0.03
2
2,041
0
0
0%
652
0
0
0%
dimethipin
0.2
140
2,023
1
0
0%
641
1
0
0%
ethoprop
0.03
1.14/ 1141
2,040
0
0/02
0% / 0%2
651
0
0/02
0% / 0%2
oxyfluorfen
0.05
200
2,012
0
0
0%
645
0
0
0%
profenofos
0.3
0.3
2,021
0
0
0%
640
0
0
0%
tebuconazole
0.2
190
2,019
1
0
0%
638
1
0
0%
total permethrin
0.04
3.344 / 334A1
2,023
5
0/02
0% / 0%2
648
3
0/02
0% / 0%2
tribufos
0.07
0.6
2,004
1
0
0%
639
1
0
0%
butylated hydroxyanisole
0.03
NA
2,107
0
--
--
678
0
--
--
o-toluidine
0.007
NA
2,096
7
--
--
676
4
--
--
quinoline
0.02
0.01/l1
2,107
9
9 / 02
0.4% / 0%2
678
5
5/0
0.7% / 0%2
1-butanol
2.0
700
2,057
22
0
0%
678
15
0
0%
2-methoxyethanol
0.4
NA
2,058
8
--
--
679
7
--
--
2-propen-l-ol
0.5
35
2,057
4
0
0%
679
1
0
0%
"total microcystins"
0.3
0.3/ 1.63
2,340
4
4 / 02
0.2% / 0%2
495
4
4 / 02
0.8% / 0%2
microcystin-LA
0.008
0.3/ 1.63
I4
0
0/02
0% / 0%2
I4
0
0/02
0% / 0%2
microcystin-LF
0.006
0.3/ 1.63
I4
0
0/02
0% / 0%2
I4
0
0/02
0% / 0%2
microcystin-LR
0.02
0.3/ 1.63
I4
0
0/02
0% / 0%2
I4
0
0/02
0% / 0%2
microcystin-LY
0.009
0.3/ 1.63
I4
0
0/02
0% / 0%2
I4
0
0/02
0% / 0%2
microcystin-RR
0.006
0.3/ 1.63
I4
0
0/02
0% / 0%2
I4
0
0/02
0% / 0%2
microcystin-YR
0.02
0.3/ 1.63
I4
0
0/02
0% / 0%2
I4
0
0/02
0% / 0%2
nodularin-R
0.005
NA
I4
0
--
--
I4
0
--
--
anatoxin-a
0.03
NA
3,000
5
--
--
563
5
--
--
cylindrospermopsin
0.09
0.7 /33
3,018
1
0/02
0% / 0%2
562
1
0/02
0% / 0%2
HAA5 (regulated)
NA
60
3,434
3,3795
676
2.0%6
710
6985
386
5.4%6
HAA6Br
NA
NA
3,429
3,3305
--
--
713
6925
--
--
HAA9
NA
NA
3,406
3,3535
--
--
708
6975
--
--
'The first number is the reference concentration for 10"6 cancer risk; the second number is the reference concentration for 10"4 cancer risk.
2Where two results are presented the first number is associated with the first reference concentration; the second number is associated with the second reference concentration.
3The first number is the reference concentration for bottle-fed infants and young children, the second number is the reference concentration for school-age children and adults.
4Samples for the microcystin congeners (e.g., microcystin-LA) and nodularin-R are only analyzed if the "total microcystins" result is > 0.3 |ig/L; thus, there are very few results for the individual congeners and nodularin-R.
5The number of results or PWSs with at least one HAA in the group at or above its individual MRL.
6The HAA5 results for UCMR 4 are not reflective of the compliance status for a PWS per the Disinfectants and Disinfection Byproducts Rule (D/DBPR). HAA5 compliance for D/DBPR is based on a locational running annual average (LRAA) calculated at each monitoring
location.
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Data Considerations
Data are presented as tab delimited text files within zip files (see below for descriptions), with field names included in
the first row of each file and no text qualifier. EPA suggests importing each field into your choice of software as text.
Some of the IDs can otherwise be misinterpreted as long integer field types when they contain alpha characters.
To view results or perform additional analyses, select one of the following zip files from UCMR 4 (2018-2020)
Occurrence Data:
	"UCMR 4 Occurrence Data" to view ALL the analytical results (i.e., results for all analytes reported by all public
water systems to date). Note that we expect the "UCMR4_all.txt" file to become too large to be imported into
Excel once the majority of the UCMR 4 results are reported, in which case you can try other applications (e.g.,
Microsoft Access) or import a subset of the data as described below.
	"UCMR 4 Occurrence Data by State" to view ALL the analytical results to date, organized by tribes and states:
within that zip file, one text file ("UCMR4_AII_Tribes_AK_LA.txt") will have all results for tribal systems as well
as for the states of Alaska through Louisiana; another ("UCMR4_AII_MA_WY.txt") will have all results for the
states of Massachusetts through Wyoming. The results are organized this way to address file size limitations
and make data management easier.
	"UCMR 4 Occurrence Data by Method Classification" to view ALL analytical results to date for all systems by
analytical method. Within that ZIP file you will find individual text files with results organized by method (e.g.,
a Method 200.8 text file with results for germanium and manganese).
The following text files for the additional data elements (i.e., parameters beyond the core 30 UCMR 4 contaminants)
are also contained in the above zip files:
	UCMR4_HAA_lndicators.txt - Results for total organic carbon and bromide
	UCMR4_ZipCodes.txt - U.S. Postal Service zip code(s) for all areas served by a PWS
	UCMR4_HAA_AddtlDataElem.txt - Additional data elements for the HAAs: DisinfectantType,
DisinfectantResidual and Treatmentlnformation
	UCMR4_Cyanotoxin_AddtlDataElem.txt - Additional data elements for the cyanotoxins: DisinfectantType,
Treatmentlnformation, CyanotoxinBloomOccurrence, CyanotoxinOccurrence,
CyanotoxinPossibleBloomTreatment and CyanotoxinPossibleBloomSourceWater
Review Instructions for Using Microsoft Excel to Access UCMR 4 Results for further assistance. Additional reference
material is available at EPA's UCMR 4 website.
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Data Definitions for Text Files: UCMR4_ALL.txt, UCMR4_All_Tribes_AK_LA.txt, UCMR4_All_MA_WY.txt,
\JCMR4_MethodNumber.txt and UCMR4_HAA_Indicators
Field Name
Definition
PWSID
Public Water System Identification. The code used to identify each PWS. The code begins with the standard 2-character postal State
abbreviation or Region code; the remaining 7 numbers are unique to each PWS in the State
PWSName
Name of the Public Water System (PWS)
Size
Size category of the PWS for UCMR, based on retail population as indicated by the Safe Drinking Water Information System (Federal)
(SDWIS/FED) as of December 31, 2015: S (< 10,000), L (> 10,000)
FacilitylD
Public Water System Facility Identification. The 5-digit number for each applicable facility associated with water treatment or delivery
FacilityName
Name of the facility at the PWS
FacilityWaterType
Source of water at the facility: SW (surface water), GW (ground water), GU (ground water under the direct influence of surface water),
MX (Any combination of: SW, GW and GU)
SamplePointID
Identification code for each sample point location in the PWS
SamplePointName
Name of the sample point for every sample point ID at a PWS
SamplePointType
Sampling Point Type Code: EP (entry point to the distribution system), DS (distribution system), SR (source water - untreated water)
CollectionDate
Date of sample collection (month, day, year)
SamplelD
Identification code for each sample, as defined by the laboratory
Contaminant
The UCMR 4 contaminant being analyzed
MRL
Minimum Reporting Level defined by UCMR 4 in ng/L for the contaminants
MethodID
Identification code of the analytical method
AnalyticalResultsSign
Less than (<) the minimum reporting level (MRL) or equal to (=) a numeric value at or above the MRL
AnalyticalResultValue(|ag/L)
Numeric value of the analytical result in ng/L for the contaminants, null values represent less than MRL
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Field Name
Definition
SampleEventCode
Identification code for each sample event: SEC1, SEC2, SEC3, SEC4, SEC5, SEC6, SEC7 and SEC8 for cyanotoxins for SW and GU sources
only; SEA1, SEA2, SEA3 and SEA4 for the metals, pesticides, alcohols and SVOCs where "SEA1" and "SEA2" represent the first and second
sampling period for all water types and "SEA3" and "SEA4" represent the third and fourth sampling period for SW and GU sources only;
SEH1, SEH2, SEH3 and SEH4 for the HAAs where "SEH1" and "SEH2" represent the first and second sampling period for all water types
and "SEH3" and "SEH4" represent the third and fourth sampling period for SW and GU sources only
MonitoringRequirement
AM (Assessment Monitoring)
Region
EPA Region (States): 1 (CT, ME, MA, NH, Rl, VT), 2 (NJ, NY, PR (Puerto Rico), VI (Virgin Islands)), 3 (DE, DC, MD, PA, VA, WV), 4 (AL, FL, GA,
KY, MS, NC, SC, TN), 5 (IL, IN, Ml, MN, OH, Wl), 6 (AR, LA, NM, OK, TX), 7 (IA, KS, MO, NE), 8 (CO, MT, ND, SD, UT, WY), 9 (AZ, CA, HI, NV, AS
(American Samoa), GU (Guam), MP (Northern Marianas Islands), NN (Navajo Nation)), 10 (AK, ID, OR, WA)
State
State abbreviation
Additional Data Definitions for Text File: UCMR4_ZipCodes
Field Name
Definition
ZIPCODE
U.S. Postal Service zip code(s) for all areas being served water by a PWS. This data is entered by the PWS.
Additional Data Definitions for Text File: UCMR4_HAA_AddtlDataElem
Field Name:
| AdditionalDataElement
Field Name: Response
DisinfectantType
All of the disinfectants/oxidants that have been added prior to the entry point to the distribution system. Please
select all that apply.
PEMB = Permanganate, HPXB = Hydrogen peroxide, CLGA = Gaseous chlorine, CLOF = Offsite Generated
Hypochlorite (stored as a liquid form), CLON = Onsite Generated Hypochlorite, CAGC = Chloramine (formed with
gaseous chlorine), CAOF = Chloramine (formed with offsite hypochlorite), CAON = Chloramine (formed with
onsite hypochlorite), CLDB = Chlorine dioxide, OZON = Ozone, ULVL = Ultraviolet light, OTHD = Other types of
disinfectant/oxidant, NODU = No disinfectant/oxidant used
DisinfectantResidual
Disinfectant residual type in the distribution system for each HAA sample.
CL2 = Chlorine (i.e., originating from addition of free chlorine only), CL02 = Chlorine dioxide, CLM = Chloramines
(originating from the addition of chlorine and ammonia or pre-formed chloramines), CAC = Chlorine and
chloramines (if being mixed from chlorinated and chloraminated water), NOD = No disinfectant residual
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Field Name:
AdditionalDataElement
Field Name: Response
Treatmentlnformation
Treatment information associated with the sample point. Please select all that apply.
CON = Conventional (non-softening, consisting of at least coagulation/sedimentation basins and filtration), INF =
In-line filtration, DFL = Direct filtration, SFN = Softening, SSF = Slow sand filtration, GAC = Granular activated
carbon adsorption (not part of filters in CON, SFN, INF, DFL, or SSF), POB = Pre-oxidation with chlorine (applied
before coagulation for CON or SFN plants or before filtration for other filtration plants), RBF = River bank
filtration, PSD = Pre-sedimentation, BIO = Biological filtration (operated with an intention of maintaining
biological activity within filter), UTR = Unfiltered treatment for surface water source, GWD = Groundwater
system with disinfection only, PAC = Application of powder activated carbon, AIR = Air stripping (packed towers,
diffused gas contactors), MFL = Membrane filtration, IEX = Ionic exchange, DAF = Dissolved air floatation, CWL =
Clearwell/finished water storage without aeration, CWA = Clearwell/finished water storage with aeration, ADS =
Aeration in distribution system (localized treatment), OTH = Other types of treatment, NTU = No treatment used,
DKN = Do not know
Additional Data Definitions for Text File: UCMR4_Cyanotoxins_AddtlDataElem
Field Name: AdditionalDataElement
Field Name: Response
CyanotoxinBloomOccurrence
A yes or no answer provided by the PWS for each cyanotoxin sample event.
Question: Preceding the finished water sample collection, did you observe an algal bloom in your source waters near
the intake?
YES = if yes, select ALL that apply (see CyanotoxinBloomOccurrenceDetail); NO = have never seen a bloom; DK = do
not know; NA = purchased consecutive connection (no source water)
CyanotoxinBloomOccurrenceDetail
If yes, select ALL that apply:
YD = yes, on the day the UCMR cyanotoxin sample was collected, YW = yes, between the day the sample was taken
and the past week, YM = yes, between the past week and past month, YY = yes, between the past month and past 12
months, YP = yes, more than a year ago
CyanotoxinOccurrence
A yes or no answer provided by the PWS for each cyanotoxin sample event.
Question: Preceding the finished water sample collection, were cyanotoxins ever detected in your source waters
near the intake and prior to any treatment (based on sampling by you or another party)?
YES = if yes, select ALL that apply (see CyanotoxinOccurrenceDetail); NO = have never detected cyanotoxins in
source water; NS = unaware of any source water cyanotoxin sampling
CyanotoxinOccurrenceDetail
If yes, select ALL that apply:
YD = yes, on the day the UCMR cyanotoxin sample was collected, YW = yes, between the day the sample was taken
and the past week, YM = yes, between the past week and past month, YY = yes, between the past month and past 12
months, YP = yes, more than a year ago
Select ALL that apply (i.e., all that were detected) if you answered YES to detecting cyanotoxins in source water:
MIC = Microcystins, CYL = Cylindrospermopsin, ANA = Anatoxin-A, SAX = Saxitoxins, OTH = Other (see field name
"IfOtherText" for details), DK = do not know
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Field Name: AdditionalDataElement
Field Name: Response
CyanotoxinPossibleBloomTreatment
A yes or no answer provided by the PWS for each cyanotoxin sample event.
Question: Preceding the finished water sample collection, did you notice any changes in your treatment system
operation and/or treated water quality that may indicate a bloom in the source water?
YES = if yes, select ALL that apply (see CyanotoxinPossibleBloomTreatmentDetail); NO = no changes observed; DK =
do not know
CyanotoxinPossibleBloomTreatmentDetail
If yes, select ALL that apply:
DFR = Decrease in filter runtimes, ITF = Increase in turbidity in filtered water, ICD = Need for increased coagulant
dose, TOI = Increase in taste and odor issues in finished water, IOD = Need for increase in oxidant/disinfectant dose,
IDB = Increase in TTHM/HAA5 in finished water, OTH = Describe other changes (see field name "IfOtherText" for
details)
CyanotoxinPossibleBloomSource Water
A yes or no answer provided by the PWS for each cyanotoxin sample event.
Question: Preceding the finished water sample collection, did you observe any notable changes in source water
quality parameters (if measured)?
YES = if yes, select ALL that apply to the source water (see CyanotoxinPossibleBloomSourceWaterDetail); NO = no
changes observed; DK = do not know
CyanotoxinPossibleBloomSourceWaterDetail
If yes, select ALL that apply to the source water:
UP = Increase in water temperature, ITU = Increase in turbidity, IAL = Increase in alkalinity, ITO = Increase in total
organic carbon, ICD = Increase in chlorine demand, IPH = Increase in pH and/or DPH = Decrease in pH, ICA = Increase
in chlorophyll a, IPY = Increase in phycocyanin, INU = Increase in nutrients (example: nitrogen or phosphorus), OTH =
Describe other changes (see field name "IfOtherText" for details)
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