Organic Chemicals in Drinking Water
Summary of the National Organics Monitoring Survey
The United States Environmental Protection Agency (EPA)
has conducted the National Organics Monitoring .Survey (NOMS)
since March 1976, to determine the frequency of occurrence
of specific contaminants in drinking water supplies and to
provide data for the possible establishment of additional
maximum contaminant levels for organic compounds or for a
treatment requirement for the control of organic compounds
in drinking water.
Included in the NOMS were 113 community water supplies,
representing various types of sources and treatment proces-
ses. These were monitored three times (phases) during a
twelve month period. A fourth phase is currently underway.
The source of these compounds may be: (1) naturally
occurring organic matter (e.g. humus); (2) contaminants
introduced as a result of treatment (e.g. trihalomethanes);
(3) synthetic chemicals from point sources; and (4)
chemicals from non-point sources. The naturally occurring
substances constitute by far the major portions of the
organic chemicals found in drinking water.
Compounds selected for the NOMS study include:
chloroform, 1,2-dichloroethane, carbon tetrachloride,
bromodichloromethane, trichloroethylene, dibromochloro-
methane, bromoform, benzene, vinyl chloride, bis (2-chloro-
ethyl) ether, p-dichlorobenzene , 1 , 2,4-trichlorobenzen«',
2,4-dichlorophenol, pentachlorophenol, polychlorinated

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2
biphenyls, fluoranthene, 1,12-benzoperylene, 3,4-benzopyrene
and indeno(1,2,3-cd)pyrene. These compounds were chosen on
the basis of possible occurrence, available toxicological
data, and the existence of analytical methodology for their
identification.and quantification. In addition, several
general organic class parameters, such as total organic
carbon (non-purgeable) , carbon chloroform extract,
ultraviolet absorbance and emission fluorescence scan were
studied in an attempt to determine a possible relationship
between one or more of them and specific compound
occurrences. Certain sampling and analytical modifications
were instituted in Phase III to take into consideration the
findings of the earlier phases. NOMS data for
trihaloraethanes (THMs) are summarized below. (Table I).

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3
TABLE I - Analytical results of chloroform, bromoform,
bromodichloromethane, and dibromochloromethane and
total trihalomethane in water supplies from NOMS
(Concentrations in milligrams per liter)
Phase I Phase II Phase III
Chloroform:	Dechlorinated terminal
Median	

0.
,027

0.059
0.022

0.
.044
Mean	

0.
.043

0.083
0.035

0.
.069
Range	

-0.
.271
NF
-0.47
NF-0.20
NF-
-0.
,540
Bromoform:









Median	


LD

LD
LD


LD
Me a n	

0.
,003

0.004
0.002

0.
.004
Range.............
. NF-
-0.
.039
NF-
0.280
NF-0.137
NF-
-0.
. 1 90
Dibromochloromethane:









Median............
•

LD

0.004
0.002

0.
.003
Mean	

0.
.008

0.012
0.006

0.
,01 1
Range	

-0,
.190
NF-
•0.290
NF-0.114
NF-
-0,
.250
Bromodichloromethane:









Median	

0,
.010

0.014
0.006

0,
.011
Mean	

0.
.018

0.018
0.009

0.
.017
Range.............
. NF-
-0,
.183
NF-
• 0.180
NF-0.072
NF-
-0,
.125
Total Trihalomethane:









Median	

0,
.045

0.087
0.037

0.
.074
Mean	

0.
.068

0.1 17
0.053

0.
.100
Range	
. NF-
-0,
.457
NF-
¦=1"
OO
t—
•
o
NF-0.295
NF-
-0,
.695
NF=not found
LD=less than detection limit
In Phase I, samples were collected and analyzed in a
fashion similar to that employed in the National Organics
Reconnaissance Survey (NORS). Samples were shipped from the
utility and stored at 2-8°C for 1-2 weeks prior to
analyses. In Phase II samples were allowed to stand at
20-25°C for 3-6 weeks prior to analyses. Under these
conditions THM formation was permitted to proceed to
reaction end points (terminal values) generally correspond-
ing to the consumption of free chlorine residual in the

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sampling vial. All supplies were sampled in Phase III both
with and without a chlorine reducing agent present at the
time of sampling (quenched and terminal). In addition,
samples with a reducing agent added were collected at five
points in the distribution system in each of ten cities. A
site at a distant point in most systems was sampled. These
experiments were incorporated in Phase III in order to more
fully understand the distribution of total trihalomethanes
(TTHM) concentrations that can reach the consumer, since it
is recognized that the extent of THM formation depends on
the type and chemical composition of raw water, pH, water
temperature, chlorine contact time, treatment method, and in
certain cases, season.
The NOMS demonstrated that considerable amounts of THMs
could form in the water after it had entered the distribu-
tion systems on the way to the consumer's tap. It also
showed that THMs far exceeded the concentrations of other
synthetic organic contaminants in finished drinking water,
and that brominated THMs could also exceed the chloroform
concentrations in some situations. Part of the THM
concentration variation between Phases I, II and III might
also be attributable to seasonal effects.
Other than trihalomethanes, compounds studied in the
NOMS are generally present in finished drinking water due to
raw water contamination (Table 2). An exception is

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5
2,4-dichlorophenol which is produced on treatment by
chlorination of phenol, or related precursors.

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at

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prior to unalyses ,
a	vcrc ihJppcd «t ambUnt air t*nperatiir«, noted at 20"-2S*C for 3-6 wcaka prior to analyses.

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6
In general, the data shows that the trihalomethanes
(chloroform, bromodichloromethane, dibromochloromethane,
bromoform and dichloroiodomethane) are by far the most
ubiquitous synthetic organic contaminants in drinking water,
and they also occur at the highest concentrations (up to 784
ppb were detected). They are produced by chlorination
during treatment of their naturally occurring precursors,
probably humus, but algae and other chemicals may also be
precursors. Pentachlorophenol was also commonly found in
parts per trillion levels.
Although a large number of other synthetic products were
also detected in various waters, the concentrations were
generally very low (usually sub parts per billion) and the
number of occurrances was generally small. The common
volatile halogenated solvents and chemical intermediates
(i.e. chlorinated ethanes, ethylenes and benzenes) were
typical. Carbon tetrachloride when found in finished water
was probably a result of contamination of the chlorine.
Chemical oxygen demand (COD) and Non-purgeable Total Organic
Carbon (NPTOC) correlated reasonably well with the THM
formation potential.
Besides the above mentioned organic contaminants, Table
3 lists additional organic compounds that have been detected
at least once in the NOMS study.
The EPA has published in the Federal Register on
February 9, 1978, proposed regulations to establish a

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7
maximum contamination level of 100 parts per billion for
THMs and to require the installation of granular activated
carbon treatment to control general synthetic organic
contaminants.
Environmental Protection Agency
Criteria and Standards Division
Office of Drinking Water (WH-550)

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TABLE
Additional Organic
Acetone
Aniline
Benzaldehyce
Bromotrichloroethylene
n-3utyl acetate
Di-£-butyl ether
Chlorobenzene
Chioros tyr ene
Chlorctoluene
Chioroxylene
Dibroaodicr.loroeth ylene
Ethyl benzene
Isobutyl acetate
1, 2-Dichloropropane
Isopropyl ether
Methylene brorside
Me thycyclohexane
Methylraethacrylate
4	-Methyl -2-pen t a none
Naphthalene (or Azulene)
Phenol
cis-beta-Terpineol
Terpineol isomer
1,1,2,2-Tetrachloroethane
c t r a h yd r o f u r a n
Toluene
Tribroraochloroethylene
Trichlorobenzene isomer
X yl e n e s
rleptadecane
N-Methylaniline
Benzyl cyanide
Atr azine
Alpha-Berganotir.e and
3 related compounds
Tr i3e thyl isocyanurate
t_ris-Chloroe th yl
phosphate
hexachloroethane
1,1,2-Trichloroethane
Trichlorofluoronethane
5	t yr e n e
Tetralin
1,1 and 1,2-Dibrccoethane
I'ethylstyrene
Chlorocicrin
Compounds Detected in NCMS
Iodone thane
Eroraochloroir.e thane
1-naphthyl-N-me	thyl carbamate
Fluorobe nzene
cronoethane
Methyl bromide
Dimethyl disulfide
Phenol
Te rpinenes
Nitrotoluene
Trichlorobutane
Acetonitrile
cis and trans-Dichloroethylene
Diethyl adipate
Dioctyl adipate
Trichlorophenol
2-Chioropropane
Et h yl e t he r
1,1 Dichloroethene

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