STATEMENT OF BASIS AND PURPOSE
FOR AN AMENDMENT TO THE
NATIONAL INTERIM PRIMARY DRINKING WATER REGULATIONS
ON TRIHALOMETHANES
JANUARY 1978
OFFICE OF WATER SUPPLY
CRITERIA AND STANDARDS DIVISION
ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D. C. 20460
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TABLE OF CONTENTS
PAGE
I. INTRODUCTION ................... ............ 1
H. THE ROLE OF CHLORINATION
AND ALTERNATE DISINFECTANTS ........ ..... 6
SOURCES OF TR3HALOMETHANE EXPOSURE ____ 10
IV. METABOLISM ................................. 14
V. ACUTE AND CHRONIC HEALTH EFFECTS IN
ANIMALS ................. ........ . .......... 19
A . Hepatotoxicity
B. Nephrotoxicity
C. Teratogenicity
D. Mutagenicity
E. Carcinogenicity
VI. HUMAN HEALTH EFFECTS ...................... 28
A . NAS Principles of Toxicological Evaluation
B. Epidemiologic Studies
VII. RISK ASSESSMENT .............................. 46
VIE. SUMMARY ................................... 53
IX. MAXIMUM CONTAMINANT LEVELS .............. 57
X. REFERENCES ........................ ..... ...... 61
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I. Introduction
The extent and significance of organic chemical contamination of
drinking water or drinking water sources first came to public
attention in 1972, when a report, "Industrial Pollution of the Lower
Mississippi River in Louisiana" was published (EPA, 1972). While this
report did not include quantification of the pollutants found, and was
directed toward locating industrial discharges responsible for the pol-
lution, the report did include analyses of finished (treated) drinking
water and provided evidence of the presence of trihalomethanes (THM)
in such water. Subsequently, a. more thorough examination of finished
drinking water in the New Orleans area was carried out, using the
most sophisticated analytical methods available (EPA, 1974). This latter
study confirmed the presence of trihalomethanes and many other organic
chemicals in finished drinking water, and furthermore demonstrated
that one of them, chloroform, was present in extremely high relative
concentrations.
The findings in New Orleans promoted other studies, primarily for the
purpose of determining how widespread and serious the organic chemical
contamination of drinking water was. Impetus was added by the passage
of the Safe Drinking Water Act (?. L. 93-523), which directed the
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Environmental Protection Agency to conduct a comprehensive
study of public water supplies and drinking water sources to
determine the nature, extent, sources of, and means of control
of contamination by chemicals or other substances suspected of
being carcinogenic. The National Organics Reconnaissance
Survey of Halogenated Qrganics (NORS) (Symons, et.al 1975),
or "80 City Study", was aimed primarily at determining the
extent of the presence of four trihalomethanes, chloroform.
bromodichloromethane. dibromochloromethane and bromoform,
along with carbon tetrachloride and 1, 2-dichloroethane, and at
determining what effect raw water source and water treatment
practices had on ths formation of these compounds (refer to
Table 1). The presence of trihalomethanes in finished drinking
water was confirmed, and some trend relating non-volatile
total organic carbon (NVTOC) of the raw water and the
total trihalomethane concentration (TTHM) was postulated.
Chloroform occurred invariably in water which had been
chlorinated, while it was absent or present at lower concentra-
tions in the raw water. Water samples were collected at the
treatment plant in winter and iced for shipment but not
dechiorinated. Thus, these values might approximate minima
for human exposure in the areas selected. Of the various
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Table 1. Analytical Results of Chloroform, Bromoform, Bromo-
dichloromethane, and Dibroraochloromethane and
Trihalomethane in Water Supplies from NOBS and NOMS
Concentrations in mg/liter
Median
Mean
Range
Median
Mean
Range
NORS
Chloroform
0.021
NF-0. 311
Bromoform
0.005
NF-0. 092
NOMS
Phase I
0.027
0.043
NF-0. 271
ID
0.003
NF-0. 039
Phase II
0.059
0.083
NF-0. 47
LD
0.004
NF-0. 280
Phase m
Dechlorinated
0.022
0.035
NF-0. 20
LD
0.002
NF-0. 137
Terminal
0.044
0.069
NF-0. 540
LD
0.004
NF-0. 190
Dibromochloromethane
Median
Mean
Range
0.001
NF-0. 100
LD
0.008
NF-0. 19
0.004
0.012
NF-0. 290
0.002
0.006
NF-0. 114
0.003
0.011
NF-0. 250
Bromodichloromethane
Median
Mean
Range
Total
Median
Mean
Range
0.006
NF-0. 116
0.010
0.018
NF-0. 183
0.014
0.018
NF-0. 180
0.006
0.009
NF-0. 072
0.011
0.017
NF-0. 125
Trihalomethane (TTHM)
0.027
0.067
NF-0. 482
0.045
0.068
NF-0. 457
0.087
0.117
NF-0. 784
0.037
0.053
NF-0. 295
0.074
0.100
NF-0, 695
NF = not found
LD = less than detection limit
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trihalomethanes, chloroform was found at the highest concen-
trations (averaging approximately 75 percent of the total THM),
with progressively less bromodichloromethane, dibromo-
chloromethane and bromoform being detected. In some cases
chloroform was found at concentrations greater than 0.300 mg/1;
(the highest value found was 0.540 mg/1). Carbon tetrachloride
and 1, 2-dichloroethane were found at very low concentrations.
The concentration of these two components did not increase after
the chlorination process, therefore, it can be assumed that the
presence of these compounds is not related to the disinfection
process.
A Joint Federal/State Survey of Qrganics and Inorganics in 83
Selected Drinking Water Supplies, carried out by EPA's Region V
(Chicago) provided additional evidence of the ubiquitous nature of
chloroform and other trihalomethanes in chlorinated drinking water
(EPA, 1975). Two conclusions reached in that study were that raw
water relatively free of organic matter results in finished water
that is relatively free of chloroform and related halogenated com-
pounds, and that there is a correlation in some instances between
the concentrations of chloroform, bromodichloromethane, dibromo-
chloromethane and bromoform in finished water and the amount of
organic matter found in raw water. It appeared that these compounds
resulted from the chlorination of precursors in the raw water.
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A more recent study, the National Qrganics Monitoring Study
(NOMS), directed by Section 141.40 of the National Interim
Primary Drinking Water Regulations (40 F.R. 59574, December
24, 1975), was aimed not only at determining the presence of
trihalomethanes in additional water supplies, but also at determining
the seasonal variations in concentration of these substances.
The NOMS sample size was 113 public water systems designated
by the Administrator. The study also included analyses for approxi-
mately 20 specific synthetic organic chemicals deemed to be candidates
of particular concern and analyses of several surrogate group chemical
parameters which are indicators of the total amount of organic con-
tamination. Three phases of this study have been completed and the
mean, minimum, and maximum values of chloroform and trihalomethanes
in drinking water are reported in Table 1. Phase I analyses in the NOMS
were conducted similarly to the NORS. Phase II analyses were performed
after the THM-producing reactions were allowed to run to completion.
Phase IE analyses were conducted on both dechlorinated samples and
on samples that were allowed to run to completion (terminal). Again
chloroform was found at the highest concentrations in most cases,
however, in a few cases bromoform was found to be the highest
concentration of the THM's (0.280 mg/1). The mean concentrations
of chloroform were 0.043 mg/1, 0.083 mg/1, 0.035 mg/1, and 0.069
mg/1 for Phase I, n, III (dechlorinated) and El (terminal), respectively;
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the mean concentrations for total tribalornethanes were 0.068 mg/1,
0.117 mg/1, 0.053 mg/1 and 0.100 mg/1 for Phase I, H, m
(dechlorinated) and III (terminal), respectively.
H. The Role of Chlorination
All evidence indicates that chlorination of drinking water
containing organic chemicals is the major factor in the formation
of halogenated organic chemicals, particularly the trihalome.thanes
in finished drinking water. Chlorinated organic compounds, however,
can also be introduced into our drinking water from industrial outfalls,
urban and rural runoff, rainfall, through polluted air or from the
chlorination of sewage and industrial wastewater.
Several studies in addition to those mentioned above, have
demonstrated increased trihalomethane concentrations in drinking
>
water. Work by J. J. Rook (1974) in the Netherlands, and the studies
by Bellar, Lichtenberg and Kroner (1974). showed that chloroform
and other halogenated methanes are formed during the water chlorina-
tion process. It should be noted that these findings came as a
result of the development of more sensitive and refined analytical
techniques. Recent work by Rook (1974, 1977) has provided some
insight as to the organic precursors which might be responsible for
the formation of the trihalomethanes. Studies by Sontheimer and Kuhn
(1977) indicate that the THM's may represent only a portion of the total
halogenated products of chlorination of water. Bunn et al. (1975)
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have demonstrated that hypochlorite in the presence of bromide
and iodide ions but not fluoride will react with natural organic
matter to produce ail ten possible trihalogenated methanes.
It can be concluded from the above studies and others that the
trihalomethanes occur in chlorinated drinking waters, and that the
concentrations of rhe various trihalomethanes are dependent on the
type and Quantity of organic precursor substances, the amount of
chlorine used, s.nd the presence of other halogen ions as well as
contact time, temperature and pH.
There are a number of methods available for reducing levels
of THM's in drinking water. These options include modifications
of current treatmen practices, such as moving the point of.
chlorination, the use of alternative disinfectants such as chlorine
dioxide or ozone, and various methods that will reduce organic
precursor concentrations such as use of adsorbents like granular
activated carbon (GAG).
The two chemicals most often mentioned as alternative disinfec-
tants, chlorine dioxide and ozone, are both well known as effective
disinfectants and chemical oxidants, and some history of their practical
use in water treatment has been accumulated particularly in Europe.
EPA is currt-^f-Iy involved in studying the health effects of
chlorine dioxide in water, utilizing several animal species. Studies
of the toxicology of chlorine dioxide and chlorite ion in drinking water
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8
reveal considerable variations. These compounds have been reported to
affect the hematopotetic systems such as oxidative changes in hemoglobins
and hemolysis of red blood cells. Other bioeffects observed include
gastrointestinal disturbances. The preliminary results indicate species
variability in biological manifestations. Cats and African green
monkeys appear to lie at the extreme ends of the spectrum from amor.g
the species studied; cats are very sensitive to the hematopoietic
effects whereas monkeys were apparently insensitive even at levels as
high as 200 mg/1. An upper limit for chlorine dioxide usage has
been set primarily because of the lack of data concerning the safety of
this material, and particularly its decomposition products, at higher
concentrations (Musil et al., 1963 and Fridlyand and Kagan, 1971).
Studies with cats have shown that chlorite, which is an oxidant and
can cause anemias, has a deleterious effect on red blood cell survival
rate at chlorine dioxide concentrations above 10 mg/1. Therefore a
limit of 1.0 mg/1 is necessary to prevent potential adverse effects
on sensitive individuals, particularly children.
A preliminary study concerning ozonation of 29 organic compounds
potentially present in water supply sources indicated the formation of
a number of products (Cotruvo, Simmon, Spanggord, 1976, 1977). These
reaction mixtures were assayed for mutagenic activity employing 1) five
strains of Salmonella typhimurlum (Ames Salmonella/microsome assay)
and 2) mitotic recombination in the yeast Saccharoroyces cerevisiae D3.
After very extensive ozonation in water some of the organic compounds
exhibited mutagenic activity in these systems. Similar studies under
extreme conditions with chlorine dioxide byproducts thus far have
exhibited minimal mutagenic activity.
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Combining ammonia with chlorine to form chloramines has been called
the chloramine process, chloramination, and combined residual chlorination.
The products of this process are monochloramines, dichloramines or tri-
chloramines (nitrogen trichloride) depending on the pH and the chlorine
to ammonia ratio. The production of the latter species is referred to
as "breakpoint" chlorination and may contribute to taste and odor problems
in the finished water.
Based on the results of numerous investigations, the comparative
disinfectant efficiency of chloramines ranks last when compared to ozone,
chlorine dioxide, hypochlorous acid (HOCL), and hypochlorite ion (OC1~)
(NAS, 1977). Early studies by Butterfield and Waties (1944, 1956, 1948)
demonstrated that chloraraines required approximately a 100 fold increase
in contact time to inactivate coliform bacteria and enteric pathogens as
compared to free available chlorine at pH 9.5. This work was later
confirmed in 1953 by Kabler (1953) and by Clarke et al., (1962).
Results with cysts of Entamoeba histolytica and viruses also
confirm the decreased effectiveness of chloramines as a disinfectant.
Studies by Fair et al., (1947) showed that additional dichloramine is
about 60 percent and monochloramine about 22 percent as effective as
hypochlorous acid at pH 4.5 cysts of E^ histolytica. Kelly and Sanderson
(1960) found that chloramines in the concentration of 1 mg/1 at 25°C
required 3 hours at pH 6, or 6 to 8 hours at pH 10 to achieve a 99.7
percent inactivation of polio virus. With 0.5 mg/1 free chlorine at
pH 7.8, by comparison, inactivation of 99.99 percent of polio virus
can be achieved in approximately 15 minutes (Liu and McGrovan, 1973).
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9a
Chloramine treatment finds its widest application in maintenance of chlorine
residuals in the distributing systems. The health effects of water
treatment with chloramine have not been studied in detail.
Although these disinfectants do not produce trihalomethanes,
questions have also been raised on both their toxicology and the toxicology
of their by-products. Studies are underway to clarify this matter and
could result in the designation of maximum permissible levels for certain
disinfectants when applied to drinking water. In the meantime, EPA has
determined- that chlorine dioxide applications should be limited to no
more than one milligram per liter which is not uncommon in today's usage
and that chloramines should not be used as primary disinfectants.
The use of adsorbents for trihalomethane removal has also introduced
some unknown factors. Assuming that the adsorption process is effective
for its intended purpose, there is always the possibility that a break-
through of adsorbed chemicals will occur, that these substances will be
adsorbed and subsequently slough off to produce contaminant concentrations
intermittently, or that bacteria and/or toxins will be added to the water
from growth on the adsorbent. All of these potential effects are controllable
in practice, and EPA encourages the use of GAC to purify contaminated
waters and to control THM precursors.
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1C
Thus, it is essential tnat the THM concentrations be reduced
bat without compromising public health from either infectious
disease transmission or from the technology that is used. Out-
breaks of infectious waterbozae disease have been noted when there
have been breakdowns in colorination. The alternative control methods
outlined previously are effective and are also being studied for their
possible side effects. As soon as data becomes available EPA
will rnftkft specific recommendations regarding their use. At the
present time the best approach to reduce the organic precursors
is to use adsorbents such as GAG. This approach has the benefit
of reducing the concentrations of many of the organic chemicals
in the water in addition to the precursors to THM and other cholor-
inated organics. Thus, once :he organic chemical concentrations
in the water have been reduced, the chemical demand for applied
disinfectant will also be reduced, thus human exposure to all disin-
fectant chemicals, and their degradation products and by-products
will be minimized.
m. Sources of Trihalomethane Exposure
McConnell et al. (1975) have reported that chloroform occurs
in many common foods and that while some halogenated compounds
in food may result from manufacturing and pest control practices,
chloroform may be introduced as the result of geochemical
processes. Chlorinated compounds are the halogenated species
most prevalent in food, but at least one food, Limn Kohu, a sea-
weed or alga eaten in Hawaii, contains an essential oil which
is composed largely of bromoform (Burreson, et al. 1976).
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Chloroform has been widely used as an anesthetic, and until
recently *as a common ingredient In dentifrices and cough
preparations. The Food and Drug Administration has taken
action to halt the use of chloroform in drug products, cosmetic
products, and food-contact articles (41F.R. 145026, April 9,
1976). The Environmental Protection Agency has issued a
notice of "rebuttable presumption" against continued registra-
tion of chloroform-containing pesticides (41 F.R. 14588, April 6,
1976). Thus, in addition to drinking water, exposure to some
or all of the trihalomethanes is complicated by other environmen-
tal sources, however, exposure from some of those sources is
being reduced.
The relative contribution and uptake of chloroform can be
estimated Tor three major sources of human exposure: atmos-
phere, drinking water, and the food supply. The calculations of
human uptake were based on the fluid intake, respiratory volume,
and food consumption data for reference man as compiled by
the International Commission on Radiological Protection. The
combined uptake for human adults from all three sources was
estimated by multiplying estimated exposure levels times estimated
intakes.
Human uptake of chloroform from air, food and drinking water
is given in Table 2. Chloroform and trihalomethane uptake from
drinking water was estimated by multiplying the chloroform and
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trihalomethane concentrations found in drinking water supplies.
from NCMS data (Table 1) and the average consumption of 2 liters
of water per day. Qie hundred per cent absorption of the
amount of chloroform in drinking water was assumed for these
calculations. The total chloroform uptake from water was
estimated as a mean value of 64 rug per year and a maximum
uptake value of 343 mg per year.
In order to determine human uptake of chloroform from
foods, the concentrations of chloroform in various foods was
multiplied by the average consumption of each food item in
North American diets which was multiplied by the average
consumption of each food item by human adults in the United
States, and one hundred per cent absorption of ingested chloroform
was assumed. A calculated maximum value of about 16 mg of
chloroform uptake per year and a mean value of 9 mg per year
from total food consumed was obtained.
The calculation for the uptake of chloroform by humans from
air was based upon the assumption that an average of 63 per cent
of chloroform present in ambient air was absorbed after
inhalation; the volume of air inhaled by an average adult was
6
taken as 8.1 X 10 liters per year; 0.02 and 10 ppb (by volume)
chloroform concentrations in urban air as minimum and maximum
values, respectively. The minimum and maximum values for the
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Table 2. Human Uptake of Chloroform and Trihalomethanes from
Drinking Water, Food and Air
Exposure Levels mg/year
Chemical Drinking Water Food Air41
Mean (Range) Mean (Range) Mean (Range)
Chloroform 64 (0.001-0.540) 9(2-15.97) 20(0.41-204)
Trihalomethanes 85 (0.001-0.784)
* Calculated from data supplied by Strategies and Air Standards
Division, Office of Air Quality Planning and Standards. Environmental
Protection Agency, Research Triangle Park. The air samples were
collected both from the rural and industrial areas during the years
1974 - 76. The mean value was derived from the concentrations
obtained from urban industrialized areas, the minimum value from
the rural area and the maximum value from an urban industrialized
area.
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uptake of chloroform by an adult were estimated as 0.41 and
204 mg per year respectively. At minimum conditions from
all sources of exposure the atmosphere contributes 13 percent
of the total chloroform while the drinking water contributes 23
percent and food is most significant. At maximum conditions from
all sources water is the major contributor at 61 percent, with air
at 36 percent. Under conditions of maximum exposure from
the water and minimum exposure from the air, the major
contribution by far is drinking water as a source of chloroform
uptake, which is estimated to be as much as 97 per cent.
Thus, relative contributions of drinking water as a source of
chloroform to the total body burden may change from a
moderate to a maximum contributor as the annual exposure
from water ranges from nil to 343 nig/year and from 204 to 0.41
mg/year in ambient air.
IV. Metabolism
Several reports (Brown, et al., 1974: Labigne & Marchand,
1974; Fry et al., 1972 Paul and Rubinstein, 1963' Taylor ot al.,
1974) have indicated that chloroform is rapidly absoroed on
oral and intraperitoneal administration and subsequently metabo-
lized to carbon dixoide and unidentified metabolites in urine.
Species variation in the metabolism of chloroform has been
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Table 3. Uptake of Chloroform for the Adult Human from Air,
Water, and Food
Source
Atmosphere
Water
Food Suoclv
Total
Atmosphere
Water
Food Supply
Total
Atmosphere
Water
Food Supply
Total
Adult
msr/yr
Maximum Conditions
204
343
16
563
Minimum Conditions
0.41
0.73
2.00
3.14 . ,
Max-Water Mtn-Air
0.41
343.00
9.00
352.41
Percent
uptake
36
61
3
100.00
13
23
64
100.00
1
97
2
100.00
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summarized in Table 4. It is noteworthy that the mouse, a
species which shows greater sensitivity to the oncogenic
effect of (Brown et al. 1974) chloroform (Eschenbrenner & Miller
1945), metabolized chloroform extensively to carbon dioxide (80%)
metabolites (3%) from an oral dose of 60 mg/kg.
Hats also metabolize chloroform to carbon dioxide but to a
lesser extent (66%). In another report, Paul and Rubinstein
(1963) recovered 4 percent carbon dioxide after administering
T41K ffig?lEg~T!hlarcfonn intraduodenally to rats. The discrepancy
in these two results may be dose related.
Dose related differences in the metabolism of compounds
are known and hare recently been reported for the carcinogen
vinyl chloride. Non-human primate squirrel monkeys, when
given 60 nag/kg of chloroform orally excreted 97 per cent of
the dose with i7 par cent as carbon dioxide and 78 per cent as
chloroform. Fry et al. , (1972) recovered unmetabolized
chloroform rangi'ig from 17. 8-66. 6 percent of a 500 mg dose
of chloroform given to human volunteers during an 8 hour time
period (eouivalent to about 7 mg/kg). Since the metabolism
of xenobiotics is also dependent on age and sex, the widespread
variation in the quantitative disposition of chloroform in human
subjects may be due to the experimental protocols wherein
subjects ranging from 18-50 years of age were used.
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IdEpor-i'vlc:M of Chliircfnri* •• Epeulea Var
ANIMAL
SPECIES SEX
MOUSE M
^9Sf ^u
Mff
ma M
MONKEY M
STRMN
CBft.
CP/tP
C57
Spragua
Dawley
Spragua
Dawley
Squirrel
•Includes radioactivity in
Po - Orally
id - intradeudenallv
DOSE
60 po
.60 po
14M id
471fl ip
60 po
carcaa*
_ _ MtTAaOLISM (PERCENT)
UK&B TC/IM.
atci3 cx>2 races BOCTICN
6 80 3 93*
20 66 7 93
70
0.39
78 17 2 97
MRFERENCES
Brcwn et al (1974)
Brown et al 1974
Pml fi P*4^Atein (19413)
Brown et al (1974)
ip - intrapazitoneal
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13
A related halogenated hydrocarbon, carbon tetrachloride
(CC1 ) has been shown (NCI, 1976) to be carcinogenic in
4
GBborne-Mendel rats and in B6C3F1 mice at dosages ranging
from 57-160 mg/kg and 1250-2500 mg/kg respectively.
Dosages for oncogenic effects of chloroform were 90-200
mg/kg for rats and 138-477 mg/kg for mice. Metabolic
similarities between those compounds include the appearance
of nalide ions in urine and carbon dioxide in breath. Carbon
dioxide is one of the major metabolites of chloroform in mice
and rats whereas it is a minor one in carbon tetrachloride
metabolism. Carbon tetrachloride also is metabolized to
chloroform in trace amounts, which may in turn, be biotrjns-
formed to carbon dioxide. Carcinogenicity of carbon
tetrachloride, however, has been attributed to a free radical
(CC1 ) which is postulated as an intermediate in the metabolic
3
processes.
Many carcinogens have been reported to form complexes
with proteins, DNA and RNA (Miller & Miller, 1966). In some
instances the first stage in chemical carcinogenesis may involve
metabolism of the carcinogen to a secondary and moire active
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19
compound. In the case of chloroform, Heft et al., (1973)
reported covalent bonding of chloroform metabolite(s) to
tissue macromolecules of mice. The covalent bonding
increased or decreased when the animals were pretreated
with phenobarbital or piperonyl butoxide, agents which
stimulate or inhibit the metabolism of foreign compounds by
drug metabolizing enzymes. This is suggestive of the
involvement of chloroform metabolism in these processes.
Information regarding the metabolism of bromoform and
other haloforms is not available. However, the structural
similarities of these haloforms with chloroform indicate that
these compounds should also be absorbed by the oral and inhalation
routes of exposure and then biotransformed into carbon dioxide
and halide ions. Belated halogenated hydrocarbons of the
dihalomethane series, i.e. dichloromethane, dibromomethane
and bromochloromethane have been reported (Kubic et al. 19T4)
to be metabolized to carbon monoxide; the rate of metabolism of
dibromomethane was higher than that of the chloro isomer.
V. Acute and Chronic Health Effects
Biologic responses on exposure of chloroform to mammals
include its effect on the central nervous system resulting in
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20
narcosis, hepatotoxicity, nephrotoxicity, teratogenicity, and
carcingenicity. Reported LD are as follows: for rats
50fs
300 mgAg administered orally (DHEW, 1C70} and for mice
705 mgAg (Plaa, et al. 1958).
Acute studies involving single dosage level in animals have been
reported by several researchers. Jones et al. (1958) studied the
effect of various doses of chloroform fed to mice and made the
following observations after 72 hours of exposure:
35 mgAg — threshold hepatotoxic effect - minimal midzonal
fatty changes
70 mgAg — minimal central fatty Infiltration
140 mgAg " massive fatty infiltration
350 mg/kg — centrilobular necrosis
1100 mgAg — minimum lethal dose
In regard to acute effects on exposure to chloroform and bromoform,
species variation has been observed. Reported lethal doses for chloro-
form and bromoform axe:
Species Subcutaneous Lethal Doss Values in mgAg
M?use LD 704 (Chloroform)
50 1820 (Bromoform)
Rabbit LD 800 (Chloroform)
LO 410 (Bromoform)
Data on the acute toxicity of dibromochloromethane and
dichloromethane are not available.
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21
A. Hepatotoxicity
Plaa et al. (1958) established a dose-response relationship
In mice, measuring parameters indicative of hepatotoxicity.
ED values of 1.4 mM/k$ {168 mgAg) were found in mice
50
which received chloroform subcutaneously. The inhalation
exposure of chloroform by mice for 4 hours at concentrations
ranging from 100-800 ppm resulted in fatty infiltration of the
liver at all dose levels. These changes were observed at
necropsy after 1-3 days of exposure.
Like chloroform, brotr.oform exposure leads to fatty degenera-
tion and centrilobular necrosis of the liver (von Oettingen, 1953).
Dibromochloromethane and dichlorobromomethane may bring about
similar responses.
B. Nephrotoxicity
Nephrotoxic effectiof chloroform wu-tstudied by Plaa and Larson
(1965). Median effective doses (ED ) of chloroform in mice were 178
50
mg/kg as measured by phenolsulfophthalein excretion. Increases in
urinary protein and glucose, indices of kidney damage, had an ED
50
104 mg/kg for chloroform. Data concerning the nephrotoxLc effect of
other tribalomethanes are not available.
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22
C. Teratogenicity
Teratogenic response on oral dosing of animals to chloroform
were investigated by Thompson et al. (1973). Rats and rabbits
were administered chloroform at 126 and 50 mg/kg respectively.
No significant fetal deformities were observed. Inhalation
of chloroform by Sprague Dawley rats at 30, 100 and 300 ppm for
7 hours a day on days 6 through 15 of gestation revealed significant
fetal abnormalities including: acaudia, imperforate anus,
sitlxrutaneous edema, missing ribs and delayed skull ossification
(Scirretz etal. 1974).
In an attempt to explain reproductive failure in laboratory animals
i.e. mice and rabbits, McKlnney et al. (1976) conducted a study
using CD-I mice wherein groups of mice were given tap water and
purified tap water (passed through a Corning 3508 QRC and a Corning
3?C8 3 deminerallzer). The analysis of the water indicated reduced
amounts of chlorinated compounds in the purified water. The study
was inconclusive in relating chloroform and other chlorinated organics
in tap water to reproductive failures in laboratory animals, since
tie concentration of chlorinated organics in water was lowest in months
when reproductive failure was highest, although there did appear to
be small differences in these parameters between the highly purified
and tap water. In another study involving the effect of Durham tap
water and purified tap water as in the above study, Chernoff (1977)
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23
did not find striking differences in the reproductive parameters
of CD-I mice. No teratogenic studies on the haloforms other
than chloroform were available.
D. Mutagenicity
The trihalomethanes (chloroform, bromodichloromethane,
dibromochloromethane and bromoform) were assayed for in
vitro mutagenic activity using strains of Salmonella tvphimurium
(TA100 & TA1535). The assays were conducted in desiccators such
that each compound was allowed to volatilize and only the vapor
phase came in contact with bacteria on the petri plates. The activation
system was tested and found not to be required for the bromo-
halomethanes since they were positive in the absence of activa-
tion. The results obtained were as follows: (a) chloroform
was not mutagenic in TA100 neither with or without activation nor
•in TA 1535 without activation; (b) bromodichloromethane was
mutagenic in TA100 without activation, with a doubling dose of
approximately 25 microliters; (c) dibromochloromethane was
mutagenic in TA100 without metabolic activation, with a doubling
dose of approximately 3.5 microliters; (d) bromoform was
mutagenic in TA100 without metabolic activation, with a doubling
dose of approximately 25 microliters, and was also mutagenic
in TA1535 with metabolic activation, with a doubling dose of
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24
approximately 100 microliters (Tardiff, 1976). All three compounds
demonstrating mutagenic activity did so in a dose-response mode.
For certain classes of compounds the Ames test which utilizes
Salmonella typhimurium bacteria correlates highly ( 90 percent)
with the in vivo carcinogenicity btoassay. However, for certain
chlorinated hydrocarbons the test has been shown to have limita-
tions in detecting gene mutations (Ames et al., 1973), which can
be demonstrated in other test systems.
E. Carcinogenicity
Prolonged administration of chloroform at relatively high dose
levels to animals, specifically mice and rats, manifested oncogenic
effects. The investigation conducted by Eschenbrenner and Miller
(1945) revealed hepatomas in female mice (strain A) given repeated
dosages ranging from 0.145 to 2.32 mg of chloroform for a period
of four months. Minimum doses of 593 mg/kg chloroform par day
(total of 30 doses) produced tumors in all of the surviving animals.
In a more recent study (NCI, 1976) linking chloroform with
oncogenicity, rats and mice of both sexes were fed doses of
chloroform ranging from 90 to 477 mg/kg. In this study, the
lowest dose for observed carcinogenic effect (kidney epithelial
tumors) in male rats was 100 mg/kg and for mice 138 mg/kg
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25
administered to the animals for a total period of 73 weeks. A
related halogenated hydrocarbon, carbon tetrachloride, has
been shown as carcinogenic in Qsborne Mendel rats and in
B6C3F1 mice at dosages ranging from 47 to 160 nag/kg and 1250
to 2500 mg/kg, respectively. The incidence of hepatocellular tumors
formed in these animals at both dose levels almost approached one
hundred percent (Table 5). The percent survival in mice treated
with chloroform and carbon tetrachloride is depicted in Table 6.
Almost all the animals on treatment with carbon tetrachloride
died between 91 - 92 weeks whereas with chloroform treatment
at both dose levels, 73 and 46 percent of the animals survived.
Miklashevskii et al. (1966) fed chloroform to rats at 0.4 mg/kg
apparently for 5 months and detected no histopafhlogical abnormali-
ties after this treatment. A recent study on the carcinogenic
effect of chloroform at dose levels of 17 mg/kg/day and 60 mg/
kg/day was conducted by Roe (1976), utilizing the rat (Sprague-
Dawley), the beagle dog and four strains of mico (ICC Swiss,
C57B1, CVA and CF/1). Comparison with the NCI study (1976)
indicates that the number of animals and the duration of the
experiment were essentially similar: the major differences
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26
Table 5. Comparison of Hepatocellular Carcinoma Incidence in
Chloroform and Carbon Tetrachloride-Treated Mice
Animal Group Chloroform Carbon Tetrachloride
Males Controls 5/77 5/77
Low Dose 18/50 49/49
High Dose 44/45 47/48
Females Controls
Low Dose
High Dose
1/80
36/45
39/41
1/80
40/40
43/45
Table 6. Comparison of Survive! of Chloroform and Carbon
Tetrachloride - Treated Mice
Chloroform
TniHal
Animal
Males
-
Grouo
Controls
Low Dose
High Dose
Females Controls
Low Dose
High Dose
No.
77
50
50
80
50
50
78
W<*eto
53
43
41
71
43
36
90
Weeks
38
37
35
65
36
11
Carbon Tetrachloride
Initial
No.
77
50
50
80
50
50
78
Weeks
53
11
2
71
10
4
91-92
Weeks
38
0
0
65
0
1
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27
were the dosages, which were lower than in the NCI study,
and the vehicle, which was toothpaste. The only finding of
neoplasia. was an excess of tumors of the renal cortex in the
male 1C I -Swiss mice at a dose level of 60 mg /kg/day. However,
fed 17 mgAg/day of chloroform showed no incidence of
renal carcinoma.
Some renal tumors were also seen in control animals
in a later study. The negative results observed in the dog
experiment may be explained on the basis that either the
antipais were not exposed for a suitable length of time (i.e.
duration of life span) or that an insufficient number of animals
were tested, or that this species may not hare been responsive
to the oncogenic effect of chloroform. The negative results of
the rat study may be explained on the basis of lack of strain
sensitivky.
Much less information is available on the carcinogenicity of
bromohaiomsthanes . Preliminary results from the strain
A mouse pulmonary tumor induction technique (Theiss et
al. , 1977) indicated that bromoform produced a positive
pulmonary adenoma response while chloroform did not. Other
studies (Poirier, et. al. , 1975) indicated that in several
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28
instances brominated compounds exhibited more carcino-
genic activity than their chlorinated analogs in the pulmonary
adenoma bioassay.
VI. Human Health Effects
A. NAS Principles of Toxicological Evaluation.
The NAS (1977) in a recent report entitled "Drinking Water
and Health'* identified several principles that are the basis of
assessing the irreversible effects of long and continued ex-
posure to carcinogenic substances on humans at low dose rates.
Principle 1: Effects in animals, properly qualified, are
applicable to man.
Principle 2: Methods do not now exist to establish a thres-
hold for long-term effects of toxic agents.
Principle 3: The exposure of experimental animals to
toxic, agents in high doses is a necessary and valid method
of discovering possible carcinogenic hazards in man*
Principle 4: Material should be assessed in terms of human
risk, rather than as "safe" or "unsafe".
On the basis of chloroform studies in animals and human toxi-
cological data the NAS (1977) has recommended that strict criteria
should be applied for establishing exposure limits.
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29
The National Institute for Occupational Safety and Health
has recommended that the occupational exposure to chloro-
form should not exceed 2 ppm determined as time-weighted
average exposure for up to a 10 hour work day.
The human health effects as observed in accidental,
habitual, and occupational exposures appear to* indicate that
the bioeffects on exposure to chloroform are similar to that
found in experimental animals. These include the effects on
the central nervous system, liver and kidney.
The symptoms observed (Storms, 1973) in a 14 year old
patient following an accidental exposure to an unknown amount
of chloroform included cyanosis, difficulty in breathing and
unconsiousness. Liver function tests measured by serum
enzyme levels after four days of ingestion indicated very high
levels of SCOT, SGFT, and LDH. The authors also noted
cerebellar damage characterized by an instability of gait and
a slight tremor on finger-to-nose testing. The symptoms
disappeared in two weeks.
Several cases of habitual chloroform use have also been
recorded by Heilbrunn et al. (1965). A case study of
interest was a 33 year old male who had habitually inhaled
chloroform for 12 years. The subject showed psychiatric and
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30
neurological symptoms including restlessness, hallucinations,
convulsions, dysarthria, ataxia and tremor of tongue and
fingers.
Lunt (1953) reported on the delayed chloroform poisoning
in obstetric patients. Laboratory findings indicated renal
dysfunction including: albumin, red blood cells, and pus in
the urine. Chloroform exposure to humans by inhalation
was studied by Lehman and Schmidt-Kehl (1936). Ten
different concentrations of chloroform were used and the
chloroform concentrations were determined by the alkaline
hydrolysis method. Exposure at concentrations of 7 ppm for
7 minutes and at all higher levels up to 3000 ppm caused
symptoms of central nervous system depression.
Limited information is available on the controlled bio-
effect studies in humans exposed to chloroform. Desalva et
al. (1975) studied the effects of chloroform in humans; th«
subjects were given dentifrice containing 3.4% chloroform
and mouthwash with 0.43% chloroform for 1 to 5 years. No
hepatotoxic effects were observed at estimated daily ingesticn
of 0.3 to 0.96 nag/kg chloroform. Reversible hepatotoxic
effects were manifested at 23 to 37 mg/kg/day chloroform
ingested for 10 years in a study conducted by Wallace (1959).
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31
B. Epidemiologic Studies.
M ot July 1977 there tad been U different epidemiological
studies with additional unpublished reporcs that investigated
the relationship between cancer mortality and morbidity and
coBSituente in drinking water. Two of the studies have been pub-
lishedjthree others were submitted for publication as of July
1977, and the remaining studies were unpublished. All of the
studies were retrospective in design; nins were correlations
using an indirect design, two used a case-control or direct
design approach. Two studies utilized cancer morbidity
or incidence rather than mortality as a measure of disease
frequency. The studies vary in sample size, cancer sites
considered, confounding factors selected as variables,
parameters selected as indicators of water quality, and
statistical analysis.
There are several problems peculiar to these studies which
make it difficult to interpret their results: 1) there is a limited
amount of water quality data on organics, and the data which exists
covers less than a five year time period; and 2) the water quality
data is often from geographic areas not conterminous with areas
(usually counties) reporting cancer mortality data.
The water quality data on organics is of recent origin and
it is not known the extent to which current levels may reflect
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32
past exposures. This Is important, since the latent period
for most types of cancer induction is measured in decades,
not months or years. Comparison of the various study
results is difficult because of the different approaches used.
In general, indirect, retrospective epidemiological
studies are a useful methodological tool in hypothesis genera-
tion. A positive correlation cannot establish causal
relationship. However, the results from these studies,
when viewed collectively can provide some insight into associa-
tions of potential causal relationships which need to be tested
further by more highly focused direct methods, such as case-
control or cohort studies.
The studies do provide evidence that there is reason for
concern. When the evidence from all studies is weighed, the
emphasis should he placed not only on the statistical signifi-
cance of single correlation coefficients but on their consistency
and patterns. When more than one independent study shows
positive associations for site-specific cancers, then the
association may not be due to chance alone. When the associa-
tion is verified by consistent results across all four sex race
groups, the association may be due to the variable con-
sidered and the evidence should be viewed more seriously.
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33
A large body of data, provides evidence (both epidemio-
logical and experimental) that the majority of human cancers
result from multifactorial causes .(Weisburger, 1977).,
particularly for cancers of the gastrointestinal and urinary
tract. Ettologic factors, such as smoking and its association
with lung cancer, that result in increased relative risk
greater than 5, were the first to be discovered. The etiologic
factors associated with cancers of the gastrointestinal and
urinary tract are more difficult to evaluate from epidemiological
studies because of the lower incidence and mortality rates
and because of the mutifactorial interaction of environmental
causes. The increased relative risk of most potential factors
associated with gastrointestinal and urinary cancers are probably
less than 3. Thus, any correlation in a sound, indirect, retrospec-
tive study between drinking water and cancer mortality would most
probably be weak as is shown in the studies completed.
A number of epidemiologic studies that have been conducted
did not define the water quality parameter by chemical constituents
and therefore compared various sources of water supply. One
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34
investigation was performed by Page and Harris (1974).
The study involved Louisiana county (parish) cancer mortality
rates, 1950-69, for total cancer and selected sites in white
males. The parishes were categorized by the percentage of the
county population drinking Mississippi River water. The
variables controlled were rural-urban characteristics,
median income, population density, and proportion of employed
population in the; pstroleum, chemical, and mining industries.
An unweighted, regression analysis resulted in a positive
correlation oetv/een drinking water and total cancer (minus
cancer of the ling, urinary tract, GI tract, and liver),
gastrointestinal organs, and lung cancer mortality. These
investigations suggested the possibility that there was
an association oetween the cancer mortality rates and
drinking Mississippi River water. As a result serious ques-
tions were raised as to the safety of drinking water contaminated
by suspected carcinogens, particularly various organic
chemicals in the water.
Tar one and Gart (1975) reviewed "The Implications of
Cancer-Causing Substances in Mississippi River Water" by
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Page and Harris and included an additional variable, the
elevation above sea level. By using a weighted regression
analysis for four race-sex groups, weak but, statistically
significant, positive correlations were found between the
water variable and total cancer and lung cancer mortality
for white males (WM), non-white males (NWM), and non-
white females (NWF). The correlations were not statisti-
cally significant for white females (WF) for the same sites.
Thus, there was a lack of consistency across the four
sex-race groups for the aforementioned cancer sites.
Another report by Meinhardt et al. (1975) commenting on
the Page and Harris report, looked at the cancer mortality
gradient and concluded that there was a random distribution
of high and low cancer mortality rates among the river water
consumers along the lengths of the Missouri and Mississippi
River systems. From this study it was pointed out that
the controls used might not be representative.
A second report by Page and Harris (1975, 1976) on the
"Relation Between Cancer Mortality and Drinking Water in
Louisiana" utilized independent variables and cancer sites
similar to those in the first study, however, relationships
for all four sex-race groups were added. Positive regression .
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36
coefficients for the water variable that were statistically
significant are as follows:
Total cancer sites: WM, NWM, NWF
All other than lung: WM
Urinary Tract: WM, NWF
Gastrointestinal: WM, NWM, WF, NWF
DeRouen and Diem (1975) did another analysis of the relation-
ship of cancer mortality in Louisiana and the Mississippi
River as the drinking water source. An additional variable,
latitude, was included, which divided Louisiana into a northern
and southern section. This variable effectively resulted in an
ethnic division of the population. The variables urban-rural
characterisitcs, median income, employment characteristics,
and elevation above sea level included in previous studies
(Page and Harris, 1974; Tarone and Gart, 1975; Page and Harris,
1975; Page et al., 1976) were omitted. Tha water variable was
handled differently by the investigators, i.e. population groups
studied either obtained none of their water from the Mississippi River,
or obtained some or all or from the river. The results are in agree-
ment with the Page and Harris results that show a positive relationship
between cancer mortality and drinking water for gastrointestinal
cancer. The cancer mortality rates for southern parishes of
Louisiana whose source of drinking water is the Mississippi
River tend to be higher than the southern parishes whose source
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37
of drinking water is not the Mississippi River water for the
following:
Stomach: NWF Cervix: NWF
Rectum: WM Lung: NWF
Large Intestine: WF, NWF Total Cancer: NWF
The cancer mortality rates tend to be slightly higher for the
southern parishes with river water than northern parishes for
cancer of the urinary tract, gastrointestinal tact, and the lung.
In another set of analyses and comments, DeRouen and
Diem (1975) discuss the problems associated with interpreta-
tion of regression coefficients as they relate to the Page and
Harris Report, particularly the problem of making inferences
from indirect studies. They concluded that the inconsistencies
in the data and failure to see the same relationships for other
sex-race groups damages the credibility of the hypothesis.
An analysis was done by McCabe (1975) of EPA using
50 of the 80 cities from the NOBS data. Only those cities with
a 1950 population greater than 25,000 and 70 percent or
more of the city's population receiving water comparable
to that sampled by EPA were included in the study. The
results showed a statistically significant correlation between
the chloroform concentrations in the drinking water and the
cancer mortality rate by city for total cancer combined.
In a second analysis done by McCabe (1977) using Region V
data, correlations between CHC1 and THM's and total cancer
3
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38
mortality were not positive. When the same correla-
tions were done using Region V plus NORS riata for
CHC1 and THM concentration levels, a positive statistically
3
significant result was obtained.
Several epidemiological studies have been conducted in
the Ohio River area. Buncher (1975) conducted a study of 88
counties bordering the Ohio River in which 14 of the counties
used the Ohio River as a drinking water sovrce. The results da
not show a significant relationship with drinking water from the
Olio River and the higher cancer mortality rates. There
was a weak positive correlation between the chloroform
concentration in 23 cities and the cancer mortality rate for
all cancer sites in white males. Similar results were found
in 77 cities (59 surface water suppliers) between chloroform
concentrations and pancreas cancer mortality in white males.
For cities that accounted for more than 70 percent of the
county population, there was a significant; correlation between
chloroform concentration and bladder cancer mortality rates
for both white males and white females.
Another study by Kuzma et al. (1977) considered the 88
counties of Ohio, which were classified ;us either ground water
or surface water counties based on the source of the drinking
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39
water used by a majority of the county residents. A two-
stage analysis was performed and no statistically significant
results were shown between the drinking water from the
Qiio River and cancer mortality rates. Mortality
rates for stomach, bladder, and total cancers were slightly
higher for white males and for stomach cancer for white
females in counties served by surface water supplies than
in counties served b\ ground water supplies.
Reiches et al. (i976> treated the 88 counties of .Ohio
by using a different methodology. Correlations between the
surface drinking water variable and cancer mortality rates
of stomach cancer and total cancers for both white males
and females were statistically significant. The correlations
between the drinking water variable and cancer mortality
rates of the pancreas, bladder, esophagus, gastrointestinal
tract, and urinary organs was significant for white males
only.
Although several studies defined the water quality para-
meter by the chlorination or levels of chloroform, only one
study has done an analysis of all trihalomethanes, both
collectively and separately. Cantor et al. (1976) studied
the correlation of cancer mortality at sixteen anatomical sites
with the presence of THM concentration levels in drinking
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40
water for whites. Counties were grouped according to the
percent of the county population served by the sampled water
supply. In both sexes, there was a gradient of increasing
correlation between halomethane concentration and
bladder cancer in going from the low to intermediate to
high percent served county groups or strata. The correla-
tion was stronger for the brominated THM's than with
chloroform. There was a negative correlation in white
females of stomach cancer with total THM levels. Kidney
caucer in white males showed a weakly positive correlation
with chloroform levels. Lung cancer in white females showed
a positive correlation with THM levels. Among white males
non-Hodgkins' lymphoma showed a positive correlation with
the brominated trihalomethanes. A gradient of increasing
association was observed between brain cancer mortality in
both sexes and chloroform, but the associations were not
strong.
Alavanja et al. (1976) conducted a retrospective, case-
control study of female cancer mortality and its relationship
to drinking water chlorination in seven selected New York
counties. A statistically significant association was found
between drinking from a chlorinated drinking water supply
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41
and combined gastrointestinal and urinary tract cancer
mortality rates. Further, there was a higher mortality
for the summed gastrointestinal and urinary cancer in urban
areas served by chlorinated surface or ground drinking
water supplies than in urban areas served by nonchlorinated
supplies.
Kruse (1977) conducted a retrospective, case control
study of white males and females in Washington County,
Maryland. The relationship between mortality and morbidity
from liver (including biliary passages) and kidney cancer in
areas supplied by chlorinated public water supplies was
analyzed. While there was a slightly higher incidence of
liver cancer among the exposed ^roup. i.e. the group which
consumed chlorinated drinking water, the correlations were
not statistically significant. It should be noted that ths
sample size was relatively small.
Salg (1977) also conducted a retrospective study of various
cancer mortality rates and drinking water as defined by source
of supply and type of treatment in 346 counties in seven states
bordering the Ohio River Valley Basin. She looked at mortality
rates for white and nonwhite males and females. With weighted
regression analyses, surface water usage showed weak but
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42
statistically significant associations with the following:
for white males -esophagus, lung, larynx, trachea, large
intestine, rectum, bladder, othar urinary organs and
lymphosarcoma aid reticulosarcoma; for white females - breast
and rectum, and for non-white females - esophagus and
larynx. Only rectal cancer showed positive correlations across
all race-sex groups. It should be noted that the test of signifi-
cance utilized for this study was p >0.10 or less stringent than
all other studies, except for Cantor's study, which used even less
stringent criteria for some correlations.
Man et al. (1977) conducted a retrospective study in the
Los Angeles County area. The relationship between cancer
mortality and morbidity and the chlorinated drinking water
supply was analyzed for white populations only. Results did not
reveal any trends and were not significant both for mortality
and morbidity cancer rates. The authors point out several
methodological problems, including the diluting effect of migra-
tion in the highly mobile area covered by this study.
Hogan et al. (1977) also utilized the chemical analysis
of the NORS and Region V data sets and applied various
statistical procedures to the data in order to determine the
appropriateness of the statistical model. Thus, it is not surprising
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43
that results were similar to previous studies showing a positive
correlation between rectal-intestinal and bladder cancer
mortality rates and chloroform levels in drinking uater when
a weighted regression analysis were applied.
In summary, many but not all of the studies have found
positive correlations between drinking water and various
cancer mortality/morbidity rates. It is bayond tht scope of
this document to evaluate each study in depth, however, it is
partinent to consider tha interpretations and conclusions
that can be drawn from these retrospective epidoiriological
studies collectively.
It is also extremely important in the evaluation process to
consider th3 results from other epidemiolo^ica! sti-dies as they
develop hypotheses of potential causal associations between
cancer mortality and other agents. For example, the
confounding factors of diet, occupation, and smoking all have
been suggested as potential causative agents of bladder cancer,
Cole (1977). Therefore, any epidemiological study that investi-
gates the possible association between bladder cancer and
drinking water should either control for the aforementioned
variables or analyze to avoid tha problems that result in
confounding of the data. None of the studies completed thus
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far have obtained data on or controlled for diet; several studies
have attempted to control for occupational exposure: Page
and Harris, (1974 and 1975), Cantor, et al. (1976); only one
study by Kruse (1977) attained smoking history data.
Only a few studies considered four sex-race groups (the
number of non-whites is too small in some of the geographic
areas) and of those studies only a few showed consistent
patterns of association of specific cancer sites, i.e.
Salg-rectum. Several studies which considsred only white
populations found positive correlation coefficients for
both sexes: Buncher (1975) - bladder; Reiches (1976) -
stomach; and Cantor (197o) - bladder.
A decreasing level of association from high to low
levels of ths water quality variable, i.e. chloroform or
THM, with :ancer mortality rates is an important criteria
in evaluating the evidence. This pattern of association should
be observed if the difference in mortality rates is due to
the water variable. Only a fe\v studies defined the water
quality variable by the chloroform concentrations (McCabe,
1975; Buncher, 1975; Canter et al., 1976; Hogan et al.,
1977), and by the THM concentrations (Cantor et al., 1976).
Of particular interest are the correlations of liver and
kidney cancer mortality rates with drinking water, since
the animal exposure data indicate that hepatocellular
carcinomas and hepatic modular hypsrplasias have been
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45
observed in B6C3F1 strains of mice after life time exposure.
Several 01 the preliminary studies grouped the cancer sites
for the anatomical systems, i.e. gastrointestinal and urinary
organs, in order to increase the sample size. Only one of
the studies (Cantor, 1976) which considered site-specific
cancer mortality showed a positive association between
drinking water and cancer of the kidney in white males. The
absence of any positive association between drinking water
and liver cancer mortality may be due in part to small
sample sizes, very low incidsnce of the disease, or because the
exposure levels of contaminants in trace amounts over a
lifetime :nay be below the no-effect level (Weisburger, 1977)..
Thus, the evidence is incomplete and tha trends and
patterns cf association have not been fully developed. As
stated previously, a causal relationship cannot be established,
nor can it be disproven. When viewed collectively, the
epidsmiological studies completed thus far provide sufficient
evidence for maintaining a hypothesis that there may be a
health risk and that the positive correlations may be
due to some association between drinking water and cancer
morteitiy. Only when viewed in conjunction with animal
studies, both acute and chronic toxicity studies, is the
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46
evidence evaluated in the appropriate context for policy decision making.
Additional direct epidemiological studies may provide evidence regarding
the strength of the associations and the possibility of a casual relationship
between drinking water and cancer mortality.
VII. Bisk Assessment
The establishment of chloroform as an animal carcinogen, plus
the epidemiological data and mutagenesis data on TBM's, show that
a potential human risk exists from the consumption of trihalomethanes.
but these data do not Quantify the risk. Methods have been developed to
estimate quantitatively the size of the risk under the assumption that there
is no threshold level for a carcinogen. The state-of-the-art at the present
time is such that no experimental tools can accurately define, with any degree
of certainty, the absolute numbers of excess cancer deaths attributable
to chloroform in drinking water. Due to the biological variability and
a number of assumptions reouired, each of the risk estimates reports
different absolute numbers with a wide degree of variability.
It is generally agreed that it is not possible to project with accuracy
risk estimates to absolute numbers of cancers in human population from
exposure to a given agent, using statistical extrapolation models with
animal data. Given that caveat, it may be useful to apply one or more
risk estimation procedures in an attempt to estimate a possible range of
impact to affected populations both in the absence of the interim proposed
standard and at some alternate standard levels.
The EPA Science Advisory Board (SAB) (1975), using the highest levels
of chloroform then reported in drinking water bythe NORS data (0.300 mg/1)
-------
and assuming a maximum daily intake of 4 liters of water for a 70
kg man, attempted to compute an estimated risk. The estimates were
based on the Eschenbrenner and Miller (1945) animal data, which
are highly speculative since the experimental protocol involved only
5 animals per sex per dose. Using a linear extrapolation of the animal
data over more than 2 orders of magnitude of dose from mice to
humans at the 0.300 mg/1 concentration level, the lifetime incidence
of liver tumors in man were estimated in the range of 0 to
-5
. 001 (95% of confidence limits) or 0 to 100 X 10 in a lifetime.
This rate may be compared with the lifetime incidence of
-5
260 X 10 for malignancy of liver derived from data of the
Third National Cancer Survey (1976). This estimate would range
from zero to approximately 40% of the observed incidence of liver
cancer in the United States that may be attributable to exposure to
chloroform in drinking water at the 0.300 mg/1 level. It
should be noted that this value is at the upper limit of the
confidence interval and the linear non-threshold dose-effect
model allows an estimate of maximal risk where a risk has
actually been observed. Other models would all yield lower
estimates. The SAB, however, also stated that a more
reasonable assumption would yield lower estimates of the risk.
Tardiff (1976) using four different models, calculated the maxi
mum risk from chloroform ingestion via tap water. Using a
margin of safety of 5000 applied to the minimum effect animal
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48
dose, the "safe" level was calculated to be 0.02 mg/kg/day.
Using th« log problt model and the slope recommended
by Mantel and Bryan, the conclusion reached was that at a
maximum daily dose of 0.01 mg/kg the risk would be between
0.016 and 0.683 cancers per million exposed population per year.
Using the identical data, but -with the actual slope of the dose res-
ponse curre as opposed to the slope of the one in the previous
calculation, the conclusion reached was that a maximum daily dose
of 0.01 mg/kg would produce less than one tumor per billion popu-
lation per lifetime. Using the linear or one hit model, usually
considered to be the most conservative, a risk estimate of
between 0.42 and 0.84 cancers per million population per year
was calculated to result from a maximum dosage level of 0.01
mg/kg/day. The two step model produced an estimated maximum
risk of between 0.267 and 0.283 cancers par million population
per year at a maximum dose level of 0.01 mg/kg/day.
In the National Academy of Sciences (1977) report on
"Drinking Water and Health," life-time risks were estimated from
the NCI animal data. For concentrations of 10 ppb exposure the
number of excess cases of cancers computed to one for every 50,000
-5
exposed persons assuming a risk of 2 X 10 and 2 liters per day
of water consumed. If the U.S. population using chlorinated water
is assumed to be approximately 160 million people this translates
into 3,200 excess lifetime deaths from cancer or 45.7 cases per
year.
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49
For a concentration of chloroform at 1 ug/liter the estimated
-7
lifetime cancer risk would fall at approximately 3.7 X 10 at the
upper 95% confidence limits.
In evaluating the risk estimates, it is important to compare
the calculated maximum risk with the current cancer mortality
data. Both liver and kidney cancer ara rare diseases in the
U.S. The standardized mortality rates in the U.S. for white males
and females combined are 52.5 per million per year for liver car-
cinoma and 29.2 per million per year for kidney carcinoma.
Based on his risk estimates, Tardiff (1976) calculated that the per-
cent of the cancer mortality rates attributable to chloroform in drinking
water would be 1.60% and 1.44% for liver and kidney cancer incidence
per year respectively assuming the maximum exposure levels. Applying
these percentages to the actual cancer mortality rates, the number
of cancer deaths per year would be 168 from liver carcinoma or 84
from kidney carcinoma; an estimated maximum of 252 cancer deaths
per year attributable to chloroform in drinking water.
EPA's Carcinogen Assessment Group's (CAG) risk estimations
for chloroform exposure are shown in Table 7. The risks were
computed for several exposure levels and were extrapolated from
data from the National Cancer Institute (NCI 1976) bioassay with
the male rat and female mouse. Human exposure from drinking
water was computed using a weighted average of chloroform con-
centrations in drinking water for 160 million people whose drinking
water supplies are chlorinated.
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TOTAL TUMORS TOTAL TUMORS
ACTION PER YEAR PER YEAR REDUCED BY ACTIONS
NONE 23.1*-207.0**
CITIES GREATER THAN
50,OCO REDUCE TO:
100 ugm/1
50 ugm/1
10 ugm/1
18.6-166.6
15.6-140.1
9.6-85.6
4.5-40.4
7.5-66.9
13.5-121.4
LT
O
CITIES GREATER THAN
75,000 REDUCE TO:
100 ug/1
50 ug/1
10 ug/1
19.6-175.3
17.3-155.4
12.1-108.5
3.5-31.7
5.8-51.6
11.0-98.5
Risks extrapolated from NCI bioassay data *male rate and **female mouse.
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51
In the absence of a THM standard the CAG statistical risk model
would predict from 23 to 207 total tumors per year in the exposed
human population, depending which animal data (rat or mouse) is
utilized as the base.
Computations of estimated human risk and risk reduction at
various levels of control were made for the total population in
cities larger than 75,000 which are affected by this regulation.
A standard of 100 ug/1 would reduce the annual risk accord-
ing to the statistical model to 19 to 175 total tumors; a standard
of 50 ug/1 would reduce the risk to 17 to 155 total tumors; a
standard of 10 ug/1 would reduce the risk to 12 to 108 tumors.
Given that it is not possible to project with certainty or
accuracy from risk estimates based on animal data to absolute
numbers of cancers in a human population, such extrapolations
are useful in attempting to quantify a range of possible impacts
of alternate standards.
It should be noted, however, that these average exposure
levels which refer to chloroform alone and do not consider the
risk from other contaminants in the impacted population are
overestimates of the risk in light of the facts that: 1) the compu-
tations are based upon lifetime exposure, while in actuality the
proposed interim standard is a temporary, phased standard which
will be reduced in the future and therefore, the lifetime exposure
values would be less, 2) the interim standard clearly calls for
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52
maximum reductions obtainable using available technology thus
indicating a lower arerage exposure. They may be underestimated
since the risk estimates are based upon toxicity exposure data
from chloroform, which is only a portion of the total THM's and
other contaminants found in drinking water. Therefore the
magnitude of the contribution to the risk of the other THM's
(bromohalomethanes), which in some cases consists of a substan-
tial portion of the THM's, and the many other possible contaminants
is unknown.
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VIII. Summary
The occurrence of trihalomethanes in drinking water supplies
of various communities across the United States has been
documented. Chloroform was found at concentrations ranging
from 0.001-0.540 mg/1 and trihalomethane potential concentra-
tions as high as 0.784 mg/1 have been detected. The concentra-
tion of THM increased on treatment of raw water supplies with
chlorine in the process of disinfection and subseouent prepara-
tion of water for drinking purposes. The THM concentrations
may also be indicative of the presence of other undefined chemi-
cals that are produced in water during chlorination.
Besides the presence of chloroform in drinking water
humans are exposed to chloroform from air and food. An
analysis of the relative contribution of chloroform in
drinking water as compared with air and food exposures
considered various relative levels of exposures. Depending upon
the ranges of chloroform concentrations that have been detected
in air, food and water (which is a function of location, urbaniza-
tion and industrialization), drinking water may contribute from
zero to more than 90% of the total dietary intake.
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54
Chloroform has been shown to be rapidly absorbed on
oral and intraperitoneal administration and subsequently
metabolized to carbon dioxide and unidentified metabolites
in urine. The metabolic profile of chloroform in animal
species such as mice, rats and monkeys is indicated in Table
4 and is Qualitatively similar to that in man.
Biological responses on exposure of chloroform to
mammals include its effect on the central nervous system
resulting in narcosis, hepatotoxicity, nephrotoxicity,
teratogenicity, and carcinogenicity. These responses are
discernible in mammals on exposure to high levels -of
chloroform ranging from 30-350 mg/kg; the intensity of
response was dependent upon the dose. Although less
toxicological information is available for brominated
trihalomethanes, mutagenicity and carcincgaricity have been
detected in some test systems. Physiologica1. chemical
activity should be greater for the bromiria.:ed THM's than for
chloroform.
Exposure to the low levels of trihalomethanes presently found
in drinking water supplies may not manifest detectable responses
in populations. It is the prolonged human o-xposure to trihalomethanes
that should be a matter of major concern. Prolonged administra-
tion of chloroform at relatively high dose levels (100-138 mg/kg)
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55
to animals, specifically rats and mice, manifested oncogenic
effects. The oncogenic effect was not observed at a lower
dose level (17 mg/kg). Assuming that methods do not
exist to establish a non-threshold level for long-term
effects for carcinogenesis (NAS, 1977), the preceeding data
do not imply that a safe level of exposure can be established.
Epidemiological evidence is inconclusive, although positive
correlations have been found in several studies. There have
been 11 retrospective studies that have investigated some aspect
of a relationship between cancer mortality or morbidity and use
of drinking water. Due to various limitations in the epidemio-
logical methods, in the water ouality data, and problems with
the individual studies th3 present evidence cannot lead to a
firm conclusion that there is an association between contami-
nants in drinking water and cancer mortality /morbidity.
Causal relationships can.iot be proven on the basis of results
from epidemiological studies. The evidence from these studies
thus far is incomplete and the trends and patterns of association
have not been fully developed. When viewed collectively,
however, the epidemiolcgical studies provide sufficient evidence
for maintaining the hypothesis that there may be a potential
health risk and that the positive correlations may be reflecting
a causal association between constituents of drinking water and
cancer mortality.
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56
Preliminary risk assessments made by the Science Advisory
Board (SAB), the National Academy of Sciences (NAS), Robert
Tariiff of EPA, and the Carcinogen Assessment Group (CAG)
using four different models have estimated the cancer risks
associated with the exposure from chloroform in drinking water.
The exposure to THM's from air and food have not been included
in these computations. The total cancer risk estimates associated
with the MCL at the 0.1 mg/1 level range from the NAS estimated
-5 -4
lifetime risk of 4 X 10 to the CAG's estimate of 2 X 10 using
somewhat different assumptions. These risks are similar to
the iifatime estimated risks of other known carcinogenic standards:
-5
e.g. t'or vinyl chloride emissions (about 10 ) and ionizing radia-
-5
iion exposure to the general public (about 10 ).
On the basis of the available toxicological data summarized in
tile- above report, chloroform has been shown to be a carcinogen
in rodents (mice and rats) at high dose levels. Since its meta-
bolic pattern in animals is qualitatively similar to that in man,
it may prove to be a human carcinogen. Epidemiological studies
also imply a human risk. Therefore, because a potential human
health risk does exist, levels of chloroform in drinking water
sl.ouid be reduced as much as is technologically and economi-
cally feasible using methods that will not compromise protection
from waterborne infectious disease.
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57
DC. Selected Maximum Contaminant Levels (MCL's)
Since it is evident from the foregoing that a risk to the public
exists from exposure to the trihalomethanes in drinking water,
the risk should be reduced as much as is technologically and
economically feasible without increasing the risk of microbio-
logical contamination. This can be accomplished by several
means, and the Safe Drinking Water Act (P.L. 93-523) provides
two major regulatory avenues - I) the establishment of an MCL
or. 2) the institution of a treatment requirement.
EPA has determined that the establishment of an MCL
through a phased approach, along with monitoring remiire-
ments, is the most effective and conservative approach
to regulate the levels of trihalomethanes in drinking water.
The Administrator has determined that monitoring is both
technically and economically feasible, (refer to "Economic
Impact Analysis of a Trihalomethane Regulation for Drinking
Water," EPA, 1977). Measures taken to reduce the THM
concentrations will concurrently provide the additional benefit
of reducing human exposure to the other undefined by-products
and possibly other synthetic organic contaminants.
Since it is known that chlorination of water is primarily
responsible for the relatively high levels of trihalomethanes
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58
in drinking water, modifications in the chlorination process,
the substitution of other disinfectants, and the use of adsorbents
to remove precursor chemicals are possible approaches for
control. The optimal approach would be to reduce organic
precursor concentrations by adsorbents or other means prior to
addition of the disinfectant.
Use of a chlorine residual in a less active form such as
combined chlorine or chloramine will significantly reduce
trihalomethane formation, however, chloramines are much
less potent disinfectants than free chlorine and therefore it
would not always be appropriate to adopt this approach.
The two chemicals most often mentioned as substitute disin-
fectants, ozone and chlorine dioxide, are both well known as
effective disinfectants and chemical oxidants. The issues
of the bio-effects and toxicology of these disinfectants and their
by-products are being clarified by the studies underway. In the
meantime the application of chlorine dioxide should be limited to
1 milligram per liter.
The National Organic s Monitoring Survey found that the
mean total trihalomethane (THM) concentrations in the
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59
drinking water systems evaluated were approximately 0.068,
0.117, 0.053 and 0.100 mg/1 for Phase I, n, HI (dechJorinated)
and m (terminal) respectively with the highest levels of
0.784 mg/1 in Phase n (refer to Table 1).
It is reasonable to assume that the calculated risk estimates
for chloroform from various studies do indicate a potential
risk to public health. It is possible that a percentage of the
total number of liver and/or kidney cancers are attributable
to exposure of chloroform in drinking water, although it is
most likely that drinking water interacts with a number of
other variables such as smoking and diet as effect modifiers in
a multifactorial manner. It is also likely that the other trihalo-
methanes are a potential risk.
Thus, based upon a number of risk extrapolations assuming
various levels of exposure to chloroform in drinking water,
it has been estimated that such exposures may cai'.se an
excess of cancers in the U.S. population (ranging from 0 to
several hundred). At higher levels of exposure of chloroform
(>0.300 mg/1) the risk estimates would result in larger
numbers of excess cancer cases.
The reduction of the total trihalomethanes to tho MCL
level of 0.10 mg/1 would reduce the unnecessary and excessive
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60
exposure to these potential human carcinogens, mutagens,
and chronic toxicants and may result in the reduction of excess
cases of cancer. At the same time, measures taken to re-
duce THM levels (such as the use of adsorbents) will
^concurrently result in reduction of human exposure to other
contaminants in drinking water.
Since it is economically and technologically feasible to
reduce the THM levels in drinking water and there is a
benefit achieved by reducing the health risks to exposure,
EPA has decided to set the MCL at 0.10 mg/1 as an initial step
in a phased, regulatory approach. As more data becomes
available from implementation experience standards will become
more restrictive in the future. In the meantime EPA will take
steps as necessary on a case uy case basis to provide adequate
protection for the delivery of safe drinking water to the public.
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61
Cole, P.O., Hoover, R., and Friedell, G.H., 1972. "Occupation
and Cancer of the Lower Urinary Tract," Cancer, 29:1250-60.
DeRouen. T.A. and Diem, J.E., 1975 "Ethnic, Geographical
Difference in Cancer Mortality in Louisiana.: Tulane University,
School of Public Health and Tropical Medicine, Unpublished.
DeRouen, T.A. and Diem, J.E. 1975 "The New Orleans Drinking
Water Controversy: A Statistical Perspective. "American
Journal of Public Health, 65: (No 10): 1060.
DeSalva, S., Volpe, A., Leigh, G., and Regan, T. 1975.
Long-term safety studies of a chloroform-containing dentrifice
and moutli rinse in man. Food Cosmet. Toxicol. 13: 529-532.
Envtromnental Protection Agency, April 1976. Region VI, Dallas
Texas. Industrial Pollution of the Lower Missiissippi River
in Louisiana.
Environmental Protection Agency, 1974. Region VI, Dallas,
Texas. Analytical Report, New Orleans Area Water Supply
Study.
Environmental Protection Agency, 1975. Science Advisory Board.
A Report - Assessment of Health Risk from Organics in Drinking
Water by an Ad Hoc Study Group to the Hazardous Materials
Advisory Ccmmittee. Unpublished.
Enviromn-intal Protection Agency, June 1975. Region V, Chicago,
Illinois. Region V Joint Federal/State Survey of Organics &
Inorganics in Selected Drinking Water Supplies.
Envircn.uer.tal Protection Agency, 1976. Office of Pesticides
Programs Criteria and Evaluation Division. Risk Evaluation of
Chloroform. Unpublished.
Environmental Protection Agency, 1977, Cancer Assessment Group.
Chloroiorm Risk Assessment in Drinking Water. Unpublished.
Environmental Protection Agency, August 1977. "Economic Impact
Analysis of a Trihalomethane Regulation for Drinking Water, "
prepared by Temple, Barker, and Sloan, Inc. for EPA, Office
of Water Supply.
-------
62
Environmental Protection Agency, June 1976. "Interim Treatment
Guide for the Control of Chloroform and other Trihalomethanes".
EPA, Water Supply Research Division, MERL.
Eschenbrenner, A.B. and Miller, E., 1945. Induction of
hepatomas in mice by repeated oral administration of chloroform
with observation on sex differences. J. Natl. Cancer Inst. J5:
251-255.
Fry, F.J., Taylor, T., and Hathaway,E.D., 1972. Pulmonary
Elimination of Chloroform and its Metabolites in Man. Arch.
fat. Pharmacodyn. 196: 98-111.
Heilbrunn, G., Liebert, E., and Szanto, P.B. 1945. Chronic
Chloroform poisoning - clinical and pathological report of a
case. Arch. Neurol. Psych. 53: 68-72.
Hogan, M.D., Chi, P., Mitchell, T.J., and Hoel, D.G., 1977.
Association Between Chloroform Levels in Finished Drinking
Water Supplies and Various Site-Specific Cancer Mortality Rates,
National Institute of Environmental Health Sciences, Environmental
Biometry Branch, Research Traingle Park, North Carolina,
Draft Report.
Uett, K. F., Reid, W.P., Sipes, I.G.-and Krishna, G., 1973.
Chloroform Toxicity in Mice: Correlation of Renal and Hepatic
Necrosis with Covalent Binding of Metabilitieis to Tissue
Macromolecules. Exptl. Molec. Pathol. 19: 215-229.
Jones. W.M.. Marguis. G. and Stephen. C.P., 1958. He pa to to jri city
of Inhalation Anasthetic Drugs. Anesthesiology 19: 715-23.
Kubic, V.L., Anders, M.W., Engel, R.P., Barlow. C.H. and
Caughey, W.S. 1974. Metabolism of Dihalomethanes to Carbon
Monoxide. In Vivo Studies. Drug Metabolism and Disposition
2: 53-57.
Kruse, C.W., 1977. Chlorination of Public Water Supplies and
Cancer -Washington, County, Maryland Experience. A
Preliminary report from the John Hopkins University, School
of Hygience and Public Health to the Office of Research and
Development, Health Effects Research Laboratory, Cincinnati.
Ohio, Unpublished Draft.
Kuzma, Ronald J., Kuzma, Cecilia J., and Buncher, C. Ralph.,
1977. Ohio Drinking Water Source and Cancer Rates, American
journal of Public Health, Submitted for publication August or
September.
-------
63
National Academy of Sciences., 1977. Drinking Water and Health,
Washington, D. C.
National Academy of Sciences., 1977. Non-fluorinated Halomethanes
in the Environment, Washington, D. C.
National Cancer Institute, 1976. Report on Carcinogenesis bioassay
of Chloroform.
National Institute of Occupational Safety and Health, 1974. Criteria
for a Recommended Standard, Occupational Exposure to Chloroform.
Page. T. and Haris, R.H., 1975. Realtion Between Cancer Mortality
and drinking Water in Lousiana. Unpublished.
Page, T., Harris, R.H., and Estein, S.S., 1976. Drinking Water
and Cancer Mortality in Louisiana, Science 193: 55-57.
Page, T., Talbot E., and Harris, R.H., 1974. The Implications
of Cancer causing Substances in Mississippi River Water, A
Report by the Environmental Defense Fund.
Paul, B.B, and Rubinstein, D., 1963. Metablolism of carbon
tetrachloride and chloroform by the tat. J. Pharm. Exp. Therap.
141: 141-148.
Plaa, G.L., Evancs, E.A. and Hine, G.H., 1963. Relative
Hepatotoxicity of seven nalogenated hydrocarbons. J. Pharmacol.
Exp. Therap. 123; 224-229.
Plaa, G.L. and Larson, R.E., 1965. Relative Nephrotoxic
Properties of Chlorinated Methane, Ethane and Ethylene Derivatives
in Mice. Toxicol. Appl. Pharmacol. 7: 37-44.
Poirier, L.A., Stoner, G.D., and Shimkin, M.B,, 1975. Bioassay
of Alkgl Halides and Nucleotide Base Analogs by Pulmonary Tumor
Response in Strain A Mice. Cancer Research 35:1411-1415.
Reiches, N.A., PageT., Talbot P., and Harris, R.H., 1976.
Carcinogenic Hazards of Organic Chemicals in Drinking Water,
Unpublished.
-------
64
Foe, F. J.C. 1976. Preliminary Report of Long-Term Tests of
Chloroform in Rates, Mice and Dogs. Hazleton Laboratories,
Vienna, Virigina.
Rook, J. J. 1978. Formation of Haloforms during Chlorinaticr.
of Nattaural Waters. Water Treatment & Examination. 23:
234-243.
Rook, J. J., 1977. Chlorination Reactions of Fulvic Acids in
Natural Waters. Env. Sci. Technol. 11: 478-482.
Salg, Joyce, 1977. "Cancer Mortality Rates and Drinking Water
in 346 Counties of the Ohio River Valley Basin, " Final Report
from the University of North Carolina. Department of Epidemiology
to the Office of Research and Development, Health Effects Research
Laboratory, Cincinnati, Ohio, Unpublished.
Schwetz, B.A., Leong, B.K.J. an Gehring, P.J.. 1974. Embryo
and Fetotoxicity of Inhaled Chloroform in Rats. Toad col. Apyi.
Pharmacol. 28: 442-451.
Southheimer, H., and Kuhn, W., 1977. The Engler-Bunte Instkvite,
University of Karlsruhe, Karlsruch, Germany. Personal
Communication.
Storms, W.W. 1973. Chloroform parties. JAMA, 225: 160.
Symons. J.M., Bellar, T.A., Carswell, J.K., Demarco. J..
Kropp, K. L., Robeck, G.G., Seeger, D.R., Slocum, C.J. Smith,
B.L., and Stevens A. A., 1975. National Organics Reconnaissance
Survey for Halogenated Organics. J. Am. Waterworks ASKOC.
67: 634-646.
Tardiff, R., 1976. Personal Communication.
Tardiff, R.G., 1976. Health Effects of Organics: Risk & Hazard
Assessment of Ingested Chloroform. The 96th Annual Conference
of the American Water Works Association, New Orleans,
Louisiana.
Tarone, R.E. and Gart, J.J., 1975. The Implications of C.
causing Substances in Mississippi Rain Water, an unpublished
review of the study by R. H. Harris.
-------
65
Taylor, D.C., Brown, D.M., Keeble, R. and Langley, P.F.,
1974. Metabolism of Chloroform n. A Sex Difference in
the Metabolism of [C] Chloroform in Mice. Xenobiotica 4:
165-174.
Theiss, J.C., Stoner, G.D., Shimkin, M.B., and Weisburper,
E.K., (1977). Test fo carcinogenicity of Organic Contaminants
of United States Drinking Waters by Pulmonary Tumor Response
in strain A Mice. Cancer Research 37: 2717-2720.
United States, Department of Health, Education and Welfare,
National Institute of Occupational Safety and Health, 1973.
Toxic Substance List.
Wallace, C.J. 1959. Hepatitis and nephrosis due to cough syrup
containing chloroform. Calif. Med. 73;. 442.
Watanabe, P.O., McGowan, G.R., Madrid, E.O. and Gearing,
P. J., 1976. Fate of [C] Vinyl Chloride Following Inhalation
Exposure in Rats. Toxicol. Appl. Pharmacol. 37: 49-59.
Weisburger, John H., 1977. Social and Ethical Implications of
Claims for Cancer Hazards. Medical and Pediatric Oncology 3;
137-140.
Von Oettingen, W.F. 1955. The Halogenated Hydrocarbons: Toxicity
and Potential Dangers. Public Health Service No. 414. Warnington,
D. C.: U.S. Government Printing Office.
-------
Butterf ield, C.T. , and Wattle, E. , "Relative Resistance
of E. coli and E. typhosa to Chlorine and Chlor amines,"
.Pub. Health Rpts., 59 , 1661 (
Butterfield, C.T. , and Wattie, E. , "Influence of pH and
Temperature on the Survival of Coliforras and Enteric
Pathogens When Exposed to Chloraroine, " Pub. Health
Rpts., 61, 157U9M6).
Butterfield, C.T. , "Comparing the Relative Bactericidal
Efficiencies of Free and Combined Available Chlorine, "
J. AWWA, 40, 1305 (19^8).
Kabler, P.W. , "Relative Resistance of Coliform Organisms
and Enteric Pathogens in the Disinfection of Water with
Chlorine," J. AWWA, M3, 553 (1953).
Clarke, N.A., Berg, G. , Kabler, P.W. , and Chang, S.L. ,
"Human Enteric Viruses in Water: Source, Survival and
Removability," International Conf. Water Pollution
Research, Pergaajon Press, London (Sept., 1962).
Fair,
of
r, G.M., Morris, J.C., and Chang, S.L. "The Dynamics
Water Chlorination", S. NEWWA, 61, 285 (19^7).
Kelly, S.M., and Sanderson, W.W. , "The Effect Of
Chlorine In Water On Enteric Viruses II. , The Effect Of
Combined Chlorine On Polomyelitis And Coxackie Viruses,"
Amer. T. Pub. Health, 59, 14 (I960).
Liu, 0. C. andF. McGrowan, 1973. "Effect of
Chlorination On Human Enteric Viruses In Partially
Treated Water From the Potomac River Estuary," in Virus
In tfater, edited by G. Berg et al, APHA, Washington,
D.C. (1976).
Musil, J. et al, "Toxicological Aspects Of Chlorine
Dioxide Application For The Treatment Of Water
Containing Phenol". SF, VYS. Sk. Chem -Technol Vol 8,
PP 327-315, 1963. "
Fridlyand, S. A. and KAGAN, G. "Experimental
Validation Of Standard For Residual Chlorine Dioxide In
Drinking Water," Hygiene and Sanitation, Ho. 36, pp
18-21, 1971.
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