NITROSAMINES
Ambient Water Quality Criteria
Criteria and Standards Division
Office of Water Planning and Standards
U.S. Environmental Protection Agency
Washington, D.C.
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C22
CRITERIA DOCUMENT
NITROSAMINES
Criteria
Aquatic Life
N-nitrosadiphenylamine
[For freshwater aquatic Mfe, no criterion for N-nitro-
sodiphenylamine can be derived using the Guidelines^ and
there are insufficient data to estimate a criterion using
other procedures.
[~For saltwater aquatic life, no criterion for N-nitro-
sodiphenylamine can be derived using the Guidelines^ and
there are insufficient data to estimate a criterion using
other procedures.
Human Health
N-nitrosodimethylamine
1 For the maximum protection of human health from the
potential carcinogenic effects of exposure to N-nitrosodi-
methylamine through ingestion of water and contaminated
aquatic organisms, the ambient water concentration is zeroT^
Concentrations of N-nitrosodimethylamine estimated to result
in additional lifetime cancer risks ranging from no additional
risk to an additional risk of 1 in 100,000 are presented
in the Criterion Formulation section of this document.
The Agency is considering setting criteria at an interim
— 5 * _ c _ n
target risk level in the range of 10 , 10~ , or 10 with
corresponding criteria of 0.026 jig/1, 0.0026 jug/1, and 0.00026
jig/1, respectively.
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N-nitrosidiethylamine
For the maximum protection of human health from the
potential carcinogenic effects of exposure to N-nitrosodiethy-
1amine through ingestion of water and contaminated aquatic
organisms, the ambient water concentration is zero. Con-
centrations of N-nitrosodiethylamine estimated to result
in additional lifetime cancer risks ranging from no additional
risk to an additional risk of 1 in 100,000 are presented
in the Criterion Formulation section of this document.
The Agency is considering setting criteria at an interim
target risk level in the range aof 10~5, 10~6, or 10~7 with
corresponding criteria of 0.0092 fig/1, 0.00092 pg/1, and
0.000092 jug/1, respectively.
N-nitrosodi-n-butylamine
For the maximum protection of human health from the
potential carcinogenic effects of exposure to N-nitrosodi-
n-butylamine through ingestion of water and contaminated
aquatic organisms, the ambient water concentration is zero.
Concentrations of N-nitrosodi-n-butylamine estimated to
result in additional lifetime cancer risks ranging from
no additional risk to an additional risk of 1 in 100,000
are presented in the Criterion Formulation section of this
document. The Agency is considering setting criteria at
an interim target risk level in the range of 10~^, 10~®,
or 10~7 with corresponding criteria of 0.013 ^jg/1, 0.0013
jug/1, and 0.00013 pg/1, respectively.
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N-nitrosopyrrolidine
For the maximum protection of human health from the
potential carcinogenic effects of exposure to N-nitrosopyr-
rolidine through ingestion of water and contaminated aquatic
organisms, the ambient water concentration is zero. Con-
centrations of N-nitrosopyrrolidine estimated to result
in additional lifetime cancer risks ranging from no additional
risk to an additional risk of 1 in 100,000 are presented
in the Criterion Formulation section of this document.
The Agency is considering setting criteria at an interim
— 5 - 6 — 7
target risk level in the range of 10 ,10 , or 10 with
corresponding criteria of 0.11 fiq/1, 0.011 /ig/1, and 0.0011
/jg/1, respectively.
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Introduction
The nitrosamines belong to a large group of chemicals
generally called N-nitroso compounds. Also included in
this group are the structurally-related nitrosamides. Because
they frequently coexist with N-nitrosamines in the environment,
nitrosamides are addressed also in this document.
Synthetic production of N-nitrosamines is limited to
small quantities, and the only nitrosamine produced in quantities
greater than 450 kg per year is N-nitrosodiphenylamine.
It is used as a vulcanizing retarder in rubber processing
and in the manufacture of pesticides. Other N-nitroso com-
pounds are produced primarily as research chemicals and
not for commerical purposes (U.S. EPA, 1976).
Nitrosamines are characterized by the functional group
)
-N-N=0 and nitrosamides are characterized by the functional
Q-
group -C-N-N=0. Depending on the nature of the radical
group, nitrosamines exist in several forms, including symmetrical
dialkyl-nitrosamines, asymmetrical dialkyl-nitrosamines,
nitrosamines with functional groups, cyclic nitrosamines
and acyalkylnitrosamines with functional groups, cyclic
nitrosamines and acylalkylnitrosamines or nitrosamides (Searle,
1973).
The nitrosamines vary widely in their physical properties
and may exist as solids, liquids, or gases. They are soluble
in water and organic solvents. Nitrosamines of low molecular
weight are volatile at room temperature, and high molecular
weight nitrosamines are steam volatile (U.S. EPA, 1976).
N-nitrosamines are widespread in the environment, and anthro-
pogenic sources contribute negligibly to these levels.
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The most significant source of N-nitrosamines and N-
nitrosamides in the environment is probably nitrosation
of amine and amide precursors (Bogovski, et al. 1972).
These reactions may occur in air, soil, water, food, and
animal systems, when the precursors occur simultaneously
(Mysliwy, et al. 1974; Fine, et al. 1977b; Rounbehler, et
al. 1977; Mills, 1976). Concentrations in the nanogram
to microgram per unit volume or mass range have been recorded
in air, water, soil, plants, and foodstuffs (Fine, et al.
1977a). Laboratory tests show that N-nitroso-diphenylamine
bioconcentrates in the bluegill sunfish by a factor of 217
(U.S. EPA, 1975). A survey of U.S. waters and industrial
effluents, conducted by U.S. EPA (1977), recorded levels
of various nitrosamines ranging from less than 0.1 jug/1
in industrial pipe sources to less than 10 ;ig/l in ambient
streams. The extent of exposure of the general population
of N-nitrosamines and N-nitrosamides is unknown. The most
significant exposures, resulting from anthropogenic sources,
are probably restricted to limited industrial areas (Fine,
et al. 1977a, 1977b, 1977c).
Nearly 70 percent of all N-nitrosamines studied have
been found to be carcinogenic in a wide range of laboratory
animals including various aquatic organisms (U.S. EPA, 1976).
The carcinogenic and toxic properties are well established;
and both N-nitrosamines and N-nitrosamides are considered
to be among the most potent of all mutagenic, teratogenic,
and carcinogenic agents known (Montesano and Bartsch, 1976:
Czygan et al. 1973) . They have been demonstrated to induce
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tumors in essentially all vital organs via all routes of
administration (Druckrey, 1967). Since tumor production
can occur after long-term exposure to small doses, there
is concern about human exposure to these agents in water
(Druckrey, 1973a, 1973b; Magee, et al. 1976; Lijinsky and
Taylor, 1977).
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REFERENCES
Bogovski, P., et al. 1972. N-nitroso compounds, analysis
and formation. IARC Sci. Pub. NO. 3. Int. Agency Res.
Cancer, Lyon, France.
Czygan, P.H., et al. 1973. Cytochrome P-450 content and
the ability of liver microsomes from patients undergoing
abdominal surgery to alter the mutagenicity of a primary
and a secondary carcinogen. Jour. Natl. Cancer Inst. 51:
1761.
Druckrey, H., et al. 1967. Organotropric carcinogenic action
of 65 different N-nitroso compounds, in BD rats. Z. Krebsforsch.
69: 103.
Druckrey, H. 1973a. Specific carcinogneic and teratogenic
effects of "indirect" alkylating methyl and ethyl compounds,
and their dependency on stages of oncogenic development.
Xenobiotica 3: 271.
Druckrey. H. 1973b. Mechanisms of transplacental carcinogenesis.
Iji Tomatis, L. and U. Mohr, eds. Transplacental carcinogenesis.
IARC Sci. Pub. No. 6 Int. Agency Res. Cancer, Lyon, France.
Fine, D.H., et al. 1977a. Human exposure to N-nitroso compounds
in the environment. I_n H.H. Hiatt, et al. eds. Origins
of human cancer. Cold Spring Harbor Lab., Cold Spring Harbor,
New York.
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Fine, D.H. et al. 1977b. Formation jm vivo of volatile
N-nitrosamines in man after ingestion of cooked bacon and
spinach. Nature 265: 753.
Fine, D.H., et al. 1977c. Determination of dimethylnitrosamine
in air, water and soil by thermal energy analysis: measurements
in Baltimore, Md. Environ. Sci. Technol. 11: 581.
Lijinsky, W., and H.W. Taylor. 1977. Nitrosamines and
their precursors in food. In H.H. Hiatt, et al. eds. Origins
of human cancer. Cold Spring Harbor Lab., Cold Spring Harbor,
New York.
Magee, P.N., et al. 1976. N-nitroso compounds and related
carcinogens. JHi C.S. Searle, ed. Chemical carcinogens.
ACS Monograph No. 1973. Am. Chem. Soc. Washington,D.C.
Mills, A.L. 1976. Nitrosation of secondary amines by axenic
cultures of microorganisms and in samples of natural ecosystems.
Ph.D. thesis. Cornell Universtiy, Ithaca, New York.
Montesano, R., and H. Bartsch, 1976. Mutagenic and carcinogenic
N-nitroso compounds; possible environmental hazards. Mutat.
Res. 32: 179.
Mysliwy, T.S., et al. 1974. Formation of N-nitrosopyrrolidine
in a dog's stomach. Br. Jour. Cancer 30: 279.
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Roundbehler, D.P., et al. 1977. Quantitation of dimethyl-
nitrosamine in the whole mouse after biosynthesis un vivo
from trace levels of precursors. Science 197: 917.
Searle, C.S. 1973. Chemical carcinogens; ACS monograph,
Am. Chem. Soc., Washington, D.C.
U.S. EPA. 1976. Environmental assessment of atmospheric
nitrosamines. MTR-7512. Mitre Corp., McLean, Va. Contract
No. 68-02-1495.
U.S. EPA. 1977. Scientific and assessment report on nitro-
samiens. EPA 600/6-77-001. Off. Res. Dev. U.S. Environ.
Prot. Agency, Washington, D.C.
U.S. EPA. 1978. In-depth studies on health and environmental
impacts of selected water pollutants. Contract No. 68-01-
4646. U.S. Environ. Prot. Agency.
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AQUATIC LIFE TOXICOLOGY*
FRESHWATER ORGANISMS
Introduction
The data base is limited to three fish and invertebrate
species; acute tests with N-nitrosodiphenylamine were con-
ducted using static and unmeasured procedures. Feeding
studies with dimethylnitrosamaine (N-nitrosodimethylamine)
and rainbow trout demonstrated a dose-related carcinogenic
response. This response is similar to dose-related effects
with mammals and numerous nitrosamines, including dimethyl-
nitrosamaine. Details of these later studies are available
in the human health effects portion of this document.
Acute Toxicity
The adjusted 96-hour LC50 for the bluegill is 3,200 jag/1.
This value results in a Final Fish Acute Value of 820 jug/1
(Table 1). This result is significantly different from
that for the mummichog, a saltwater species, for which the
adjusted 96-hour LC50 is 1,804,100 pg/1 (Table 6). No explanation
for this difference can be offered without conjecture.
*The reader is referred to the Guidelines for Deriving Water
Quality Criteria for the Protection of Aquatic Life C43
FR 21506 (May 18, 1978) and 43 FR 29028 (July 5, 1978)J
and the Methodology Document in order to better understand
the following discussion and recommendation. The following
tables contain the appropriate data that were found in the
literature, and at the bottom of each table are the calcu-
lations for deriving various measures of toxicity as described
in the Guidelines.
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The 48-hour EC50 for Daphnia magna after adjustment
for test methods is 6,570 jiq/1. Since the Guidelines sensi-
tivity factor for invertebrate species is much larger than
that for fish species, the Final Acute Value is based on
Daphnia magna and is 310 jig/1 (Table 2).
Chronic Toxicity
The chronic effects of N-nitrosodiphenylamine on Daphnia
magna have been studied (U.S. EPA, 1978) but no adverse
effects were observed at any test concentration, even the
lowest at 48 jig/1 (Table 3) . This result divided by the
Guidelines species sensitivity factor of 5.1 results in
a Final Invertebrate Chronic Value of less than 9.4 pg/1,
which also becomes the Final Chronic Value.
Residues
Bioconcentration of N-Nitrosodiphenylamine by the blue-
gill (U.S. EPA, 1978) reached equilibrium within 14 days
and the bioconcentration factor was 217 (Table 4). The
depuration rate was rapid so that the half-life of this
compound in the tissues was less than 1 day and for this
reason N-nitrosodiphenylamine is less likely to be a potential
residue hazard for wildlife and consumers of aquatic life.
Miscellaneous
Grieco, et al. (1978) fed Shasta strain rainbow trout
dimethylnitrosamine (N-nitrosodimethylamine) in the diet
for 52 weeks (Table 5). After this time the fish were placed
on a control diet for an additional 26 weeks. No hepatocellu-
lar carcinomas were detected at 26 weeks after feeding
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began. At 52 weeks, however, a direct dose-related response
of hepatocellular carcinoma occurred in trout fed 200, 400,
and 800 mg dimethylnitrosamine/kg. A greater incidence
of carcinoma was observed at 78 weeks, even though feeding
was discontinued after 52 weeks. For further information
and details on mammalian carcinogenesis of nitrosamines,
the reader is referred to the human health effects portion
of this document.
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CRITERION FORMULATION
Freshwater - Aquatic Life
Summary of Available Data
The concentrations below have been rounded to two signi-
ficant figures.
N-nitrosodiphenylamine
^ Final Fish Acute Value = 820 jjg/1
Final Invertebrate Acute Value = 310 pg/1
Final Acute Value = 310 pq/l
Final Fish Chronic Value = not available
Final Invertebrate Chronic Value = less than 9.4 fig/1
Final Plant Value = not available
Residue Limited Toxicant Concentration = not available
Final Chronic Value = less than 9.4 pq/1
0.44 x Final Acute Value = 140 ^jg/1
No freshwater criterion can be derived for N-nitrosodi-
phenylamine using the Guidelines because no Final Chronic
Value for either fish or invertebrate species or a good
substitute for either value is available, and there are
insufficient data to estimate a criterion. However, the
results of the incomplete chronic test with Daphnia magna
indicate that the Final Chronic Value would be lower than
9.4 ^ig/1.
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fable 1, Freshwater flah acute values for nltroaamlnea (U.8. EPA, 1978)
Adjusted
BiOAfisay Test Chemical, Time LCSli LC&O
prgflQlaw flfcthod* pone.** pescyiptton Iftrg)
Blueglll, S U M-Mltroao- 96 5.850 3,200
Lapom!a macrochlrue dlphenylamine
* S - atatie
** U ¦ unmeasured
Geometric mean of adjusted valuesi
N-Nltrosodlphenylamlne ¦ 3,200 Mg/l ¦ 820 pg/l
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Table 2, Freshwater Invertebrate acuta values for nltrosamlnea (U.S. EPA, 1978)
Adjusted .
Bloaaaay Teat Chemical Tina lcmi LCbu
PEflflniaa He Mi 94*, pons.** Pspcrmisn inta) mafH—
Cladoceran, S U N-Nltroao- 48 7,760 6,570
Daphnla magna dlphenylamlna
*
**
S - atatlc
U - unmeaaured
Geometric mean of adjusted valuesi
N-Nltroaodlphanylanlne - 6,370 |ig/l -jp- - 310 |ig/l
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Table 3. Freshwater Invertebrate chronic values for nltrosamlnea (U.8. EPA, 1978)
Citron ic
Limits Value
organism lilt*
M-Hltroaodlphanylamlne j
Cladoceran, LC <48 <48
Daphnla magna
* LC - life cycle or partial life cycle
Geometric mean of chronic valuea * *48 |ig/l 49.4. mb/1
Lowest; chronic value " <48 |ig/l
0)
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Table 4. Freshwater residues for nicroasmines (U.S. EPA, 1978)
Time
Organism pjoconcentration Factog (days)
M-Nltroflodlphenylamina
Bluegili, 217 14
Lepotnia roacrochlrus
03
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Table 5, Other freshwater data for nltrooamlnea (Grleco, et al. 1978)*
Teat Result
organ! aw fittiatifitt Eff£&fc .|U9^»
Rainbow trout, 26-78 vk« Dose related Feeding In
Salmo galrdnert hepatocellular diet at 200-
carclnomas 800 tog/kg
* Data are for dinethylnltroaamlna (N-nltroaodimathylamlne).
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SALTWATER ORGANISMS
Introduction
The only datum for nitrosamines and saltwater aquatic
life is the acute effect of N-nitrosodiphenylamine on the
mummichog.
Acute Toxicity
When the 96-hour LC50 for the mummichog is adjusted
by the Guidelines factors to account for testing methods
and species sensitivity, the resultant Final Fish Acute
Value for N-nitrosodiphenylamine is 490,000 jag/1. This
concentration also becomes the Final Acute Value.
As discussed in the Freshwater Organisms section, this
result is significantly different from that derived from
data for the bluegill (Final Fish Acute Value = 820 jiq/1) .
No explanation for this difference can be offered without
conjecture.
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CRITERION FORMULATION
Saltwater - Aquatic Life
Summary of Available Data
The concentrations below have been rounded to two signi-
ficant figures.
N-nitrosodiphenylamine
Final Fish Acute Value = 490,000 pg/1
Final Invertebrate Acute Value = not available
Final Acute Value = 490,000 /ag/1
Final Fish Chronic Value = not available
Final Invertebrate Chronic Value = not available
Final Plant Value = not available
Residue Limited Toxicant Concentration = not available
Final Chronic Value = not available
0.44 x Final Acute Value = 220,000 /jg/1
No saltwater criterion can be derived for N-nitrosodi-
phenylamine using the Guidelines because no Final Chronic
Value for either fish or invertebrate species or a good
substitute for either value is available, and there are
insufficient data to estimate a criterion using other pro-
cedures.
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Table 6. Marine fish acute values for nltrosamlnea (Ferraro, et al. 1977)
Biaaeeay Teat Chemical Time LC&u
staanliB Mfrtnad*_ concx** p^c^p^on mta) iiiam. ina^u—
Huomtchog, S U N-nitroao- 96 3,300,000 1,804,100
Fundulua heteroclltus dimethylamina '
* S - static
** U - unmeasured
Geometric mean of adjusted'values• " 1,804,100 »g/l ¦ 490,000 ng/1
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REFERENCES
Ferraro, A.F., et al. 1977. Acute toxicity of water-borne
dimethylnitrosamine (DMN) to Fundulus heteroclitus (L).
Jour. Fish Biol. 10: 203.
Grieco, M.P., et al. 1978. Carcinogenicity and acute toxicity
of dimethylnitrosamine in rainbow trout (Salmo gairdneri).
Jour. Natl. Cancer Inst. 60: 1127.
U.S. EPA. 1978. In-depth studies on health and environmental
impacts of selected water pollutants. Contract No. 68-01-
4646. U.S. Environ. Prot. Agency.
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NITR0SAMINE3
Human Health Effects
INTRODUCTION
The N-nitrosamines represent one group of chose organic compounds
characterized by containing a nitroso group (-N=0) attached to a nitrogen
(N-nitroso compounds). Closely related to the N-nitrosamines are the N-
nitrosamides. The formation of both groups of compounds from precursors
in the environment, and in the animal or human body, occurs through a
common mechanism (nitxosacion). Both groups of compounds are typically
highly toxic, again probably through common mechanisms. It is extremely
unlikely that the human population would be exposed only to nitrosanines
or only to nitrosamides since the precursors of both generally occur to-
gether. Thus, although this document is Intended to refer specifically
to N-nitrosamines, it has been considered prudent to follow the prece-
dent of earlier literature (in tfiich the term "nitrosamines" is 'frequently
used synonymously with N-nitroso compounds) and to include some discussion
of the N-nitrosamides.
It has also not proven possible to treat the health effects of N-
nitrosamines without considering sources or both preformed N-nicrosamines
and their precursors.
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SOURCES OF AND ROUTES OF EXPOSURE TO N-NITROSO COMPOUNDS
Exogenous Sources. N-nitrosamines are widespread in the environment.
Concentrations in the nanogram to microgram per unit volume or mass range
have been recorded in air, water, soil, plants and foodstuffs (Fine, et
al. 1977a). Synthetic production is limited to small quantities? N-
oitrosodiphenylamine is the only nitrosamine produced in quantities
greater than 450 kg per year. Other M-nitroso compounds are produced
primarily as research chemicals and not for commercial purposes (Walker,
et al. 1976). The most probable source of environmental N'-nitrosamiaes
and N-nitrosamides is nitrosation of amine and amide precursors
(Bogovski, et al. 1972).
Both nitrosating agents and nicrosatable compounds are ubiquitous in
the environment from natural and aan-made sources. The form of inorganic
nitrogen most widespread is nitrate. Nitrate is a common constituent of
plants and is the primary form which plants absorb from the soil. Nitrite
is found only in low concentrations because of its greater reactivity.
However, nitrate is readily converted to nitrite by microbial reduction^
and, according to some evidence (Kiubes and Jonsdorf, 1971), bacteria are
capable of promoting the synthesis of nitrosamines from a secondary amine
and nitrate without conversion of the latter to nitrite. Oxides of nitro-
gen may also act as nitrosating agents. It has been estimated that 20.7
9
x 10 kg of nitrogen oxides were emitted from industrial, commercial, and
domestic sources in the United States during 1970 (U.S.EPA., 1977).
Nitrosatable compounds occur in great variety. Some are ubiquitous in
nature either as components of living organisms (for example, amino acids
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such as proline, tryptophan and arginine; cyclic amines such as purines and
pyrimidines) or as products of the anaerobic decay of protein-rich organic
matter (amines, ureas, etc.)* Many agricultural chemicals are nitrosatable
amino compounds (for example, the antisuckering agent, dimethyldodecylamine;
the methylcarbamate insecticides). Amines are emitted froa coking plants
and petroleum refineries andr together with other forms of combined nitro-
gen, including nitrates, from sewage treatment plants, etc. Industrial
amine production has been reviewed and summarized by Walker, et al (1976).
Nitrosation of amide or amine precursors may occur in the air, soil,
water and in some stored or preserved foods. The major requirement is
probably the simultaneous presence of precursors (Mills, 1976).
Endogenous Sources. There is now conclusive evidence that nitrosa-
tion of amines and amides even in trace concentrations occurs in the
gastrointestinal tract of both animals and man (Mysliwy, et al. 1974; Fine,
et al. 1977b, Rounbehler, et al. 1977).
Nitrite may be ingested in the food, mainly as a preservative in cured
meats. It can originate in the body from reduction of nitrate by bacteria
containing the enzyme nitrate reductase. The major site is the oral cavity
by bacterial reduction of nitrate in ductal saliva (Tannenbaum, et al.
1974), although other sites have been demonstrated or proposed, including
the stomach,, in human subjects with gastric hypoacidity (Sander and Schweins-
berg, 1972), and the infected urinary bladder (Hawksvorth and Sill, 1974).
Recent studies (Tannenbaum, et al. 1978a) indicate that nitrite is also
formed de novo in the upper portion of the human intestine, probably iron
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ammonia or organic nitrogen compounds. As material passes through the
intestine, some nitrite is converted to nitrate. Absorbed nitrate is
recycled into saliva via the salivary glands, the stomach via the parietal
glands, and the bladder via the urine. Absorbed nitrite is rapidly des-
troyed in the blood.
The amount of nitrosaaine formed at any site is affected by many fac-
tors such as nucleophilicity of the amine, substrate concentration and pti.
A detailed discussion is provided by Mirvish (1973). Conditions in the
stomach of monogastric animals following a meal (pH range 1 to 5) particu-
larly favor nitrosation. Tannenbaum, et al. (1978a) suggest that nitrite
originating in the intestine may react to form N-nitroso compounds in the
cecum and colon, which are relatively more aci'dic than the small intestine.
Nitrosamine formation has also been shown to be possible in saliva even at
neutral pH(although the amount formed is small (Tannenbaum/ et al. 1973b).
Some substances, such as thiocyanate, Increase the rate of nitrosamine
formation (Boyland, et al. 1971). Thiocyanate occurs in saliva, especially
that of smokers, and in gastric juice. Others, such as ascorbic acid inhib-
it the reaction (Mirvish, et al.-1972).
The situation with regard to inhaled potential nitrosamine precur-
sors is considerably more speculative. Nitrous acid is rapidly formed when
a mixture of nitric oxide (NO), nitrogen dioxide (NO^) and water Interact
in systems of high surface to volume ratio (Wayne, et al. 1951; Graham, et
al. 1972; Chan, et al. 1976). It therefore seems reasonable to expect that
if these gases are inhaled as pollutants of ambient air,they will rapidly
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equilibrate in Che lung Co form nitrous acid. The neutral, buffered pH of
the lung is not normally regarded as favorable to formation'of N-nitroso
compounds (although, as indicated above, nitrosamine formation in saliva has
been observed at neutral pH). However, it has been suggested (U.S.EPA,
1976) that, if nitric* acid, sulfuric acid, or other common atmospheric
acidic pollutants were inhaled in sufficient amount to produce local acid-
ity within the respiratory tract, nitrosation could occur by interaction
between inhaled nitrogen oxides and tissue amines and amides. It is also
said (U.S.EPA, 1976) to be theoretically possible for all the precursors
necessary for nitrosamine formation to be generated in acid aerosol drop-
lets in an atmosphere containing significant amounts of nitrogen oxides,
sulfur oxides and anmonim ion.
It is evident that the human population is exposed to both preformed
N-nitroso compounds in the environment and to similar compounds formed
endogenously from precursors in the environment. Assessment of the rela-
tive significance of various exposure pathways is clearly invalid unless
both "nitrosamines" and their precursors are considered.
Exposure through Drinking Water. Precursor chemicals of nitrosamines
are ubiquitous in soils and water. The concentration of simple aliphatic
amines is normally low (nanogram-to-milligram per kilogram amounts) since
they are rapidly metabolized by microorganisms (National Academy of Sci-
ences, 1978). Many pesticides have been shown to be nitrosatabie.and some,
such as atrazine, are only slowly degraded and persist in soil ana water.
Nitrite concentrations in soil and water are normally low (_< 1 mg/kg ni-
trite N). However, the concentrations of nitrite (and its precursors,
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.imtnonia and nitrate) and nitrosatable compounds can be auch greater in
soils heavily fertilized with organic waste matter or in waters receiving
runoff from agricultural areas or discharges of industrial or municipal
wastewater containing substantial amounts of amines. Levels of nitrate in,
municipal drinking waters in the United States seldom exceed 10 mg/1 ni-
ctate N although some smaller water supplies and private wells contain much
.aore nitrate. Concentrations as high as 100 to 500 mg/1 of nitrate N have
>een reported in polluted wells (National Academy of Sciences, 1977).
It has been amply demonstrated that nitrosamines are formed in soils,
water and sewage after addition of relatively large amounts of secondary or
tertiary amines and nitrite or nitrate (Ayanaba^et al. 1973' Ayanaba and
Alexander, 1974). N-nitrosodimethylamine has been found in a number of
soil samples (Fine, et al. 1977c) at the 1 to 8 jjg/kg (dry basis) level.
:ine, et al. speculate that this may have arisen from absorption of pre-
formed nitrosodimethylamine from the air or absorption of dimethylacine
with subsequent nitrosation. Another possible source is pesticide appli-
cation. Several pesticides (carbamates and N", N-disubstitutad amides) have
been shown to yield nitrosodimethylamine upon nitrosation (Mirvish, 1975).
Others, such as the phenoxyacetic acid derivatives, are formulated as amine
salts} some commercial preparations have been found to contain as much as
r>.06 percent nitrosodimethylamine as a contaminant (Fine, et al. 1977a).
I trosamines are readily leached through the soil profile by percolating
-•iter and thus may eventually contaminate stir face ana ground waters if
formed in the soil (Dean-Raymond and Alexander, 1976). These authors
ii.-ive also found N-nitroso diemthylamine to be taken up from soil by spin-
ach and lettuce, the percentage taken up from the soil varying from 0.02
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Co 5.1 with che experimental conditions. However, under natural condi-
tions, nitrosamines are not commonly found in plants (see below).
Significant concentrations of nitrosamines have been reported for a
limited number of samples of ocean water, river water, and waste treatment
plant effluent adjacent to or receiving wastewater from industries using
oicrosamines or secondary amines in production operations. Thus nitroso-
dimethylamine has been reported at the 3 to 4 jig/1 level in waste water
samples (Fine, et al. 1977c). To whac extent the nicrosamine arose from
impurities in the aaune process or from nitrosation in che waste treataent
plant is not known. In water samples from wells characterized by both high
nitrate levels and coliform counts, the concentration of volatile and non-
volatile nonionic nitrosamines was less than 0.015 jig/1 (U.S. EPA, 1977).
Volatile nitrosamines have not been detected in drinking water (Fine, et
al. 1975). However^non-volatile nitrosamines (including N-nitrosatrazine)
have been tentatively found in Mew Orleans water at levels of 0.1 to 0.5
jig/1 (Fine, et al. 1976).
Nitrosamines are rapidly decomposed by photolysis and do not persist
for a significant time in water illuminated in sunlight. Thus, it is un-
likely that they will be present in high (greater than 1 mg/1) concentra-
tions in surface waters. However, In the absence of light they can be
expected to persist (Tate and Alexander, 1976). No degradation of N-
nitrosodimethylamine, N-nltrosodiethylamine or N-nitrosodipropylaaine was
observed in lake water during a 3.5 month period (Tate and Alexander,
1975). Fine, et al. (1977a) have shown that nitrosodimethylamines can
exist for extended periods of time in the aquatic environment.
C-7
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Exposure through Food. Many food constituents are either directly
capable of conversion to N-nitroso compounds or give rise through chemical
action or metabolic processes to nitrosatable products. Walters (1977)
has listed some of these compounds. Amino acids such as proline, hydroxy-
proline, tryptophan, arginine, etc., are nitrosatable. The action of heat
on other amino acids can give rise to degradation products such as pipe-
colic acid containing secondary amino groups. There is no evidence that
proteins are nitrosated directly, but they release nitrosatable amino acids
during food processing or digestion. Walters suggests that prolyl pep-
tides may be more readily nitrosated than proline itself. A number of
other tissue components, such as choline and phospholipids, contain terti-
ary amines and quaternary ammonium which can be dealkylated to secondary
amines. Many of the purine and pyriaidlne bases of the nucleic acids
contain amino groups capable of forming N-nitroso derivatives, as do some
vitamins, for example folic acid. Other nitrosatable compounds include
caffeine in coffee, theanine in tea, and orotic acid in milk. Some pesti-
cides (for example, atrazine, carbaryl, farbam, siaazin) are nitrosatable
and hence residues in or on food represent another source of precursors
of N-nitroso compounds (Elsperu and Lijinsky, 1973).
Nitrate and nitrite are also well supplied in the diet. The mean
Intake in food of nitrate plus nitrite in the United States has been cal-
culated to be approximately 120 mg per day (White, 1975), although there
must be considerable individual variability. According to these estimates
86 percent of the nitrate comes from vegetables such as celery, potatoes,
lettuce, melons, cabbage, spinach and root vegetables; some, such as
spinach and beets, contain 2000-3000 ppm of nitrate. Cured meac supplies
C- 8
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9 percent of Che oitrace. Only 2 percenc of the nitrite is supplied by
vegetables; 21 percenc comes from cured meac.
Nitrace is secreced in Che saliva, che mean amount being approxi-
mately 40 mg per day. Of chis, abouc 10 mg per day is reduced co oi trite
in che mouch by che oral flora (Tannenbaun, et al. 1974). These quanti-
ties, alchough internally derived, also represenc inputs to che gastro-
intestinal trace. Ingestion of vegetables containing high levels of
nicrace has been shown Co lead Co extremely high concentracions ox nicrice
in saliva,and Chese j.evels may persisc for several hours (Tannenbaum, ec
al. 1976).
Preformed nitrosamines have been found in food, particularly in aeacs
such as sausages, ham and bacon which have been cured with nicrice. To
date, analyses have been confined largely to the volatile N-nitroso com-
pounds. N-nitrosodimethylamine has been found Co be present in a variety
of foods (including smoked, dried or salced fish, cheese, salami, frank-
furters and cured meats) in the 1 to 100 /ig/kg range,but more usually in
the 1 to 10 /ig/kg range (Montesano and 3artsch, 1976). Other nitrosamines
tentatively identified in meat products are Ji-aitrosodiethylamine, N-aitro-
sopiperidine and N-nitrosopyrrolidine (Montesano and Bartsch, 1976). N-
nitrosopyrrolidine has been consistently found to be present in cooked
bacon at the 10 to 50 jig/kg concentration level but not in rav bacon (Fine,
et al. 1977a). It apparently arises from N-nitrosoproline by decarboxy-
lation during the cooking process (Lijinsky, et al. 1970). The source of
nitrosamines in meat products is undoubtedly nitrosacion; a report from a
USDA Expert Panel on Nitrites and Nitrosamines (U.S. Dep. Agric., 1973)
C-9
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therefore recommends substantial reductions in the amounts of nitrate and
nitrite used in cured meats.
Nitrosamines are not commonly found in planes. N-nitrosodimethyla-
mine is said to have been isolated froa the fruit Solanum Incan'jg, used by
the Transkeian Bantu to sour milk (OuPlessis, et al. 1969). Nitrosamines
have also been reported in mushrooms in concentrations of 0.4 to 30 pg/kg
(Snder and Ceh, 1968) and In wheat plants, grain and flour (Kedler and
Marauardt, 1968). However, Thewlis (1968) was unable to find N-nitrosodi-
ethylamine in wheat flour and Kroller (1967) also was unable to- detect
N-nitrosodiethylsmine at levels greater than 10 j.ig/kg in only one of 30
samples of wheat flour examined.
It is necessary to note that studies prior to 1970 reporting the
presence of nitrosamines in foods are open to question since the analyti-
cal methodology employed is new known ta have been non-specific.
C-10
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A bioconcentration factor (BCF) relates the concentration of a
chemical in water to the concentration in aquatic organisms, but
BCF's are not available for the edible portions of all four major
groups of aquatic organisms consumed in the United States. Since
data indicate that the BCF for lipid-soluble compounds is
proportional to percent lipids, BCF's can be adjusted to edible
portions using data on percent lipids and the amounts of various
species consumed by Americans. A recent survey on fish and
shellfish consumption in the United States (Cordle, et al. 1978)
found that the per capita consumption is 18 .7 g/day. From the data
on the nineteen major species identified in the survey and data on
the fat content of the edible portion of these species (Sidwell, et
al. 1974), the relative consumption of the four major groups and
the weighted average percent lipids for each group can be
calculated:
Consumption Weighted Average
Group (Percent) Percent Lipids
Freshwater fishes 12 4.8
Saltwater fishes 61 2.3
Saltwater molluscs 9 1.2
Saltwater decapods 18 1.2
Using the percentages for consumption and lipids for each of these
groups, the weighted average percent lipids is 2.3 for consumed
fish and shellfish.
C-ll
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A measured steady-state bioconcentration factor of 217 was
obtained for N-Nitrosodiphenylaraine using bluegills containing
about one percent lipids (U.S. EPA, 1978). An adjustment factor
of 2.3/1.0 s 2.3 can be used to adjust the measured BCF from the
1.0 percent lipids of the bluegill to the 2.3 percent lipids that
is the weighted average for consumed fish and shellfish» Thus,
the weighted average bioconcentration factor for N-Hitrosodi—
phenylamine and the edible portion of all aquatic organisms
consumed by Americans is calculated to be 217 x 2.3 = 500.
Exposure through Aabient Air. Ia theory there are saverai possible
routes to the formation of nitrosaaines ia the acaosphere. These have been
discussed in soae detail (U.S.EPA, 1976, 1977). Due to the photolabile
nature of ait^osamiaes it seess unlikely that concentrations ia aabient air
would exceed a few ppb except very near sources of direct eaissions of
nitrosamines. This has since been confirmed by recent observations of Fine,
et al. (1977a). N-aitrosodiaethylaoine was identified as an air pollutant
near two chesical plants, one using the anine as a raw material and the
other discharging it as an unwanted byproduct. Typical levels at the
first factory were 6 .to 36 jug/a^ on site, 1 fig/a"* in the residential neigh-
C-12
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3
borhood adjacent Co Che iaccory, and 0.1 pg/m 2 miles away. Typical daily
human exposures were calculated Co be 39 pg on site, 10 ^ig in the adjacent
residential neighborhood, and 0.3 jUg 2 ailas away. Typical levels adjacent
3
to the second site were 0.001 to 0.04 jig/m . However, nitrosaaines were
detected only twice at 40 collection points in New Jersey and New York
3
City, and then only below che 0.01 pg/m level. Fine, ec al. (1977a) con-
clude chat airborne N-aitroso compounds may not represent a daily wide-
spread air pollution problem, but rather a localized problem associated with
a particular segment of a specialized industry or with a particularly
severe pollution level.
Other Sources and Routes of Exposure. Many drugs and medicines con-
tain secondary or tertiary amine groups. Model and animal experiments
have demonstrated that these compounds can be readily nitrosated and thus
suggest that they are precursors of N-nitroso compounds in vivo (Lijin-
sky and Taylor, 1977).
Tobacco and tobacco smoke contain both secondary amines and nitro-
samines. Mitrosamines are not present in fresh tobacco,but are found
during curing (Hoffman, et al. 1974). In relatively high concentrations
3
(in the order of 100 mg/m ) secondary amines and nitrogen dioxide can react
rapidly to form nitrosamines; this reaction apparently occurs In tobacco
smoke (U.S.EPA, 1977). The mainstream smoke from an 85 mm U.S. blended
cigarette without a filter tip has been found to contain 0.084 jig N-
nitrosodimethylamine, 0.030 ug N-nitrosomethylethylamine, 0-137 jig N-
nitrosonomicotine, and traces of N-nitrosodiethylamine (Hoffman, et al.
C-13
-------
1974). Ic can be estimated that Che intake from smoking 20 cigarettes per
day would therefore be approximately 2 pg N-nitrosodimethylamine, 1 jig
N-nittosomethylethylamine, and 3 jig N-nitrosonornicotine. Walker, et al.
(1976) have attempted to evaluate the exposure to nitrosaaines of a non-
smoker exposed to tobacco smoke. Assuming exposure to the smoke of five
simultaneously burning cigarettes under crowded conditions with no ventil-
ation, levels in air were calculated to be approximately 0.013 fig/aP K-
3
nitrosodimethylamine, 0.004 jig/m N-nitrosomethylethylamine and 0.015
3
/ug/a N-nitrosonornicotine, with traces of N-nitrosodiethylamine.
N-nitroso-bis(2-hydroxyethyl)amine (N-nitrosodiethanolamine) has
been reported to occur in cosmetic preparations, including facial creams,
hand lotions and hair shampoos, in concentrations ranging from 20 to
48,000 jug/kg (Fan, et al. 1977). The extent to which this compound is
absorbed from the skin is unknown.
Commercial pesticide formulations available for home use have been
found to contain as much as 0.06 percent N-nitrosodinethylsmine as a con-
taminant (Fine, et al. 1977a). The contamination could have arisen during
the manufacturing process or from nitrosation of dimethylamine by nitrite
rust inhibitors added to prevent corrosion of the can. The main routes of
exposure from home use of pesticides can be expected to be inhalation and
absorption through the skin during spraying operations. Severn (1977),
using data from three studies on inhalation and deraai exposure to pesti-
cides during spraying of orchards, estimated that the intake from skin
deposition, assuming 50 percent absorption, averaged about 325 times more
C-14
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Chan che Intake via inhalation and concluded that the same ratio would hold
for individuals performing hand spot-spraying. Inhalation, dermal, and/or
oral exposure could also occur from careless use of these pesticides.
Relative Significance of Routes of Exposure. Fine, et al. (1977a)
have calculated the daily exposure to preformed N-nicrosamines under worst
case conditions (Table 1). The intake from nitrite preserved foods assumes
100 g cooked bacon to be consumed daily. Air exposure is based on the
highest concenrations measured on a factory site. For che general popula-
tion, however, exposure information is very limited. Ic has been escimacea
Table 1. Calculated daily hiznan exposure to N-nieroso compounds
(Fine, et al. 1977a)
Daily intake
(PS)
Nitrite preserved foods, 100 g.
1
5
Tobacco smoke, 20 cigarettes
2
3
4
Drinking water, New Orleans
8*
Air, factory site
40
10*
Herbicide formulation, 1 ml spill
640
* Tentative, unconfirmed identification as N-nitroso compound.
C-15'
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chat air, diet and smoking all play a roughly equivalent role in direct
human exposure, contributing a few micrograms per day, with direct intake
from drinking water probably much less than 1 jig per day (U.S.ZPA, 1976).
There is even greater uncertainty with regard to the significance of
exposure to precursors. The chief source of the nitrate body burden,
except in the newborn, is ingested vegetables, unless rural well water
high in nitrate is consumed. Food and water normally contribute a few
hundred milligrams per day. Inhalation may also contribute several
Table 2. Calculated average daily exposure to
nitrate and nitrite of U.S. residents
(White, 1975)
Nitrate Nitrite
Source mg % mg S
Vegetables
86.1
86.3
0.20
1.8
Fruits, juices
1.4
1.4
0.00
0.0
Milk and products
0.2
0.2
0.00
0.0
Bread
2.0
2.0
0.02
0.2
Water
0.7
0.7
0.00
0.0
Cured me&ts
9.4
9.4
2.38
21.2
Saliva
(30.0)
*
8.62
76.8
Total
99.8
100
11.22
100
*Not included in total.
C-16
-------
hundred micrograms per day (U.S.EPA, 1977). On a daily basis, the major
source of nitrite is saliva (Table 2). However, salivary nitrite is pre-
sented to the body as a continuous, low-level input, in comparison with the
relatively high concentrations over short periods resulting frcm ingestion
of cured meats. This may be significant since the rate of nitrosation is a
function of the square of the nitrite concentration (U.S.EPA, 1977).
Estimates of the contribution to the daily intake of N-nitroso compounds
(as nitrosodimethylamine) have been attempted (Natl. Acad. Sci., 1973).
Using blood levels of nitrosamines measured in one human subject before and
after consuming a lunch consisting of spinach, cooked bacon, tomato, bread
and beer (Fine, 1977b), it was calculated that in vivo formation contrib-
uted 2.8 jig per day nitrosodinethylamine. For various reasons it is
believed that the total amount of nitrosamine formed may have beer, con-
siderably more than this. A second approach assumed that the rate of
formation of nitrosamines is equal to 5 percent of the amount of nitrite
present. This yielded an estimated daily production from precursors of 962
pg nitrosodimethylamine. However, this approach is likely to give a sub-
stantial overestimate. The conclusion appears inescapable that in vivo
nitrosation provides a major contribution to the total body burden of N-
nitroso compounds.
It must also be concluded that water supplies are a relatively minor
source when compared with other potential sources of either preformed N-
nitroso compounds or their precursors.
C-17
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PHARMACOKINETICS
Following intravenous injection into rats, nltrosamides (e.g., N-
nitrosomethylurea, N-nitrosoethylurea) and nitrosamines (e.g., N-nitroso-
dimethyiamine, N-nitrosomorpholine) are rapidly and apparently fairly
uniformly distributed in the body (Magee, 1972; Stewart, et al. 1974).
Orally administered nitrosodiethylaoiine is found in the milk of lactating
rats (Schoental, et al. 1974). Both nltrosamides (e.g., nitrosodiechyl-
amine) and nitrosamines (e.g., N-nitrosoethylurea) can presumably cross the
placenta since they are capable of inducing neoplasms in the offspring if
administered to rats in late pregnancy (Magee, et al. 1976).
The nltrosamides are rapidly metabolized in the animal body. The
half-lives of intravenously administered N-nitrosomethylurea and N-nitro-
soethylurea in rats are about 2 min. and 5-6 min. respectively. The
14
metabolism of C-labeled N-methyl-N'-nitro-N-nitroso-guanidine has been
studied in some detail. Following an oral dose, most of the radioactivity
was excreted in the urine within 24 hours and less than 3% in the feces.
Less than 3% of the radioactivity remained in the body as acid-insoluble
materials at 24-43 hours (Magee, et al. 1976).
The nitrosamines are metabolized less rapidly and persist in the body
unchanged for a longer period. The rate of metabolism depends upon the
14
chemical structure. In the rat or souse, administration of C-labeled
14
nitrosodimethylamine leads to about 60% of the isotope appearing as CO.,
within 12 hours. Corresponding figures for labeled nitrosodiechylamine and
C-18
-------
nitrosomorpholine are about 45 percent and 3 percent respectively. For the
three compounds, corresponding urinary excretions are 4, 14' and 80 percent^
respectively. Metabolic products of dialkylnitrosamines found in the urine
include other nitroso compounds, formed by w-oxidation of the alkyl groups
to give the corresponding alcohols and carboxylic acids (Magee, et al.
1976).
In vitro studies have demonstrated that the organs in the rat with the
major capacity for metabolism of nitrosodiaethylamine are the liver and
kidney and that this compound is metabolized to a ONA-methylating agent
by human liver slices at a rate slightly slower than but comparable with
that of rat liver slices (Montesano and Magee, 1974). (It is the pro-
duces) of metabolism of N-nitrosamines which are thought to be responsi-
ble for the mutagenicity and/or carcinogenicity of many of them. One
hypothesis is that these .active intermediates alkylate DMA at specific
sites). Although the liver appears to be the major site of decomposition,
other organs, such as kidney and lung, possess varying capacity to metabo-
lize nitrosamines. The relative metabolic activity of different organs
toward the same compound varies between species (Magee, et al. 1976).
Evidence' to support the various proposed metabolic pathways of N-
nitroso compounds is inconclusive. However, the in vitro studies of
Montesano and Magee (1974) indicate that nitrosamines are metabolized
similarly by human, guinea pig, and rat tissue.
C-19
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EFFICTS
General Toxicity. N-nitroso compounds are acutely toxic to every
animal species tested and are also poisonous to humans.
The dialkyl and cyclic JT-nitrosamines are characteristically hepa-
toxins, producing hemorrhagic centrilobular necrosis. In experimental
animals acute exposure to nitrosodiaethylamine or nitrosodiethylamine
produces liver lesions in 24 to 43 hours; death occurs in 3 to 4 days or
the animals survive and apparently recover completely in about 3 weeks.
Other organs than the liver are less severely affected; the main features
are peritoneal and sometimes pleural exudates^which may contain a high pro-
portion of blood, and a tendency to hemorrhage into the lungs and other
organs. Kidney lesions, limited to the convoluted renal tubules, and
testicular necrosis have been described in protein-deficient rats follow-
ing treatment with nltrosodimethylamine (Magee, et al. 1976).
The livers of rats and other species chronically exposed to nitrosa-
mines exhibit various pathological changes, including biliary hyperplasia,
fibrosis, modular parenchymal hyperplasia, and the formation of enlarged
hepatic parenchmal cells with large nuclei (Magee, et al. 1976). Chronic
administration of uiany nitrosamines induces tumors of the liver and other
organs (see below).
The N-nitrosamides also induce a liver necrosis, but it is not as
pronounced as that seen with the N-nitrosamines and is localized in the
C-20
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periportal areas. Unlike Che nicrosamines, che nicrosamides cause severe
tissue injury at the sice of concacc. The degree of local damage may be
related to the rate at which the compound decomposes ac che site since che
damage is probably caused by a breakdown product rather than by the com-
pound Itself. The systemic cargecs of che aicrosamides are mainly che
organs of rapid cell turnover, including che bone marrow, crypt cells of
the small intestine, and lymphoid tissues (Magee, et al. 1976).
The effects of human exposure to nitrosodimethyl amine were first
reported by Freund in 1937. The following description is from Weisburger
and Raineri (1975). "Freund recorded the case of a young chemist engaged
in che synthesis of dimethylnicrosamiae, who presented with a number of
syndromes eventually traced to occupational exposure. The patienc had ill-
defined pains in che abdomen, exhaustion, headaches, and distended abdomen.
A. second case, which involved an accidental single severe exposure due to a
spill of nitrosaaine, again led to abdominal fluid accumulation. During an
exploratory laparotomy, ascitic fluid was found and the liver was enlarged.
This patient failed to survive. Microscopic findings at autopsy revealed
liver necrosis and areas of intense regenerative proliferation of the liver
cell."
Further cases are now on record. Of two men accidentally exposed to
nitrosodimechylamine used as a solvent in an aucomobile factory, one recov-
ered after exhlbicing signs of liver damage, while che ocher died in a
clinical accidenC and a necropsy revealed a cirrhocic liver wich regener-
acing nodules. Two of Chree men in an lnduscrial research la'ooracory,
C- 21
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working with nitrosodiaethylanine over a period of 10 months, showed signs
of liver injury. One died of bronchopneumonia and a necropsy found liver
cirrhosis. The other developed a hard liver with an irregular surface,but
recovered after exposure was terminated (Shank, 1975). The two individuals
surviving this 1953 episode were still alive in 1976 (Weisburger and
Raineri, 1975).
The acute toxicity of the N-nitroso compounds varies considerably.
Single dose oral LDjq values in adult rats, range from 18 mg/kg body weight
for N-nitrosomethylbenzylamine to more than 7,500 mg/kg for N-nitrosoethyl-
2-hydroxy-ethyl amine (Table 3). The acute oral in cixe ra£ ^or ^itroso-
diphenylamine, the only nitrosamine now produced in the U.S. in amounts
greater than 450 kg per year, is given as 1,650 ng/kg (Natl. Inst. Occ.
Safety Hlth. 1976) or 3,000 mg/kg (Druckrey, et al. 1967). The rela-
tionship between structure and acute toxicity is not fully understood;
however, for the dialkylnitrosamines acute toxicity appears to decrease
with chain length (Shank, 1975). The predominant hepatoxic effect of these
compounds is consistent with the hypothesis that the biologically active
species is a metabolite and not the parent compound since the liver,
metabolically, is generally the most active organ. It is unlikely that
under environmental conditions N-nitroso compounds would be present in
sufficient quantity to provide an acutely toxic dose.
Mutagenicity. The N-nitroso compounds include some of che most power-
ful chemical mutagens known. Montesano and Bartsch (1976) reported on the
mutagenicity of 90 N-nitroso compounds from direct mutagenicity assays and
C- 22
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Table 3. - Acute oral LD^q values (Druckrey, at al. 1967) and
relative carcinogenic potency expressed as log (l/D^g)
(Wishnok and Archer, 1976) in 3D rats. Classification of
of N-nitroso compounds follows that of Druckrey, et al. (1967)
ldTT
COMPOUND (nig/Kg) Log(l/D-0)
Symmetrical dialkyl( aryl)nitrosamines:
N-nitrosodimethylamine
40
2.27
N-nitrosodiethylamine
280
3.20
N-nitrosodi-n-propylamine
480
2.05
N-nitrosoai-iso-propylamine
850
0.97
N-nitrosodiallylamine*
800
-
N-nitrosodi-tr-butylamine
1,200
1.61
N-nitrosodi-n-amylamine
3,000
0.59
N-nitrosodicyclohexylamine*
5,000
-
N-nitrosodiphenylamine*
3,000
-
N-nitrosodibenzylamine*
900
Asymmetrical alkyl(aryl)nitrosamines:
N-nitrosomethylethylanine
90
2.32
N-nitrosomethylvinylamine
24
2.89
N-nitrosoaethylallylamine
340
2.10
N-nitrosonethyl-n-amylamine
120
2.60
N-nitrosomethylcyclohexylamine
30
2.98
N-nitrosomethyl-n-heptylamine
-
1.53
N-nitrosomethylphenylamine
280
1.60
N-nitrosooethylbenzylamine
18
3.10
N-nitrosooethyl-(2-phenylechyl)amine
48
3.01
N,N'-dime thyl-N,N'-dinicrosoethylenediamine
150
2.40
N-citrosoethylvinyl amine
88
2.64
N-nitrosoechyl-iso-propylamine
1,100
1.49
N-ni troso ethyl-n-butylamine
380
2.11
N-nitrosoethyl-tert-butylamine*
1,600
-
N-nitrcso-n-butyl-n-amylamine
2,500
1.00
Cyclic nitrosamines:
N-nitrosopyrrolidine
900
1.41
N-nitrosoproline (ethyl ester)*
5,000
-
N-nitrosopiperidine
200
1.91
N,N'-dinitrosopiperazine
160
1.95
N-uitroso-N'-aethylpiperazine
1,000
0.95
N-nitroso-N'-carbethoxypiperazine
400
1.91
C- 23
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Table 3. (Continued)
^50
COMPOUND (mg/xg) Log(l/D-0)
Cyclic nitrosanines: (Continued)
N-nitrosoindoline 320 0.88
N-nitrosoaorpholine 320 1.95
N-nitrosohexamethyleneiaine 340 -
N-nitrosoheptamethyleneimine 280
N-nitrosoctamethyleneimine 370 -
N—nitroso compounds with functional substituent groups:
3-(N-nitroso-N-methylamino)-sulfolane 750 1.82
N-nitroso-N-phe:.ylhydrcxylanine 2,000 1.15
N-nitrosotriaethylhydrazine 95 2.24
N-nitrosoethyl-2-hydroxyethylaaine 7,500 0.18
N-nitroso-bis(2-hydroxyethyl) amine 7,500
N-nitroso-bis(acetoxyethyl)anir.e 5,000 0.74
N-nitroso-n-butyl-(4-hydroxy-nrbutyl)amine 1,800 1.51
N-nitrosoaethyl-2-chloroethylanine 22 3.21
N-nitrosomethylcyanomethylsmine 45 2.18
N-nitroso-bis(cyanomethyl)amine 163 1.92
N-nitrososarcosine 5,000 0.60
N-nitrosoethylsarcosinate 4,000 1.18
2-methyl-2(N-nitroso-N-me thylamine)
-pentan-4-one 2,100 1.04
Nitrosamides:
N,n'-dinitroso-N,N'-diaethyloxanide 96 2.40
N-methyl-N-nitrosoacetaaide 20 2.31
N-methyl-N-nitrosourethane 240 2.01
N-ethyl-N-nitrosouretnane - 1.96
N-methyl-N-nitrosourea 110 2.18
N,N'-dimethyl-N-nitr050urea 280 1.95
N-nitroso&rimechylurea 240 2.00
N-ethyl-N-nitrosourea 240 2.67
N-n-butyl-N-nitrosurea 1,200 2.10
Eydrazodicarboxylic acid bis(methyl
-nitrosamide) 200 2.38
N-methyl-n'-nitro-N-nitrosoguanidine 420 2.51
N-nitrosoinidazolidone 250 2.26
*Nott-carcinogenic in 3D rats (Druckrey, et al 1967),
C-24
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dominant lethal tests. Data on chromosome observations and tests in
Drosoohila aelanogaster are also listed. As with other biological effects,
there, is a clear distinction between the mutagenic actions of N-nitrosa-
mides and N~aitrosamines. N-aitrosamides are mutagenic in almost all test
systems, due to non-enzymic formation of degradation products. N-nitrosa-
mines, on the other hand, are not mutagenic in microbial test systems
without metabolic activation.
Liver microsomal preparations from mouse, rat, hamster and man are
capable of activating nitrosamihes. Czygan, et al. (1973), using human
liver microsomes obtained from patients undergoing abdominal surgery,
found considerable variations in the capacity of the microsomes to acti-
vate the mutagenicity of N-nitrosodiaethylamine. The cytochrome P-450
content showed proportional variations. (Cytochrome P-450 is the term-
inal enzyme in the microsomal system responsible for metabolism of foreign
compounds). Czygan, et al. attributed the variations in cytochrome P-450
content to "diseases, therapy, or environmental pollutants." Czygan, et al.
(1974) later demonstrated a positive correlation betveen the protein and
choline content of the diet and the microsomal P-450 content, and con-
cluded that activation of nitrosamines can be influenced by nutritional
factors. Extracts from organs other than liver are either ineffective or
much less effective in activating nitrosamines to bacterial mutagens. Yet
these organs may be the target for tumor induction in vivo by the same
compounds. Thus, both nitrosodimethylamine and nitrosodiethylamine induce
tumors in mouse lung and rat kidney; yet rat, mouse and hamster lung
microsomal preparations and mouse kidney preparations are ineffective In
C- 25
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activating those compounds to mutagens In Salaonella typhiaurium and
Escherichia respectively (Montesano and Bartsch, 1976).
Nitrosodimethylamine and nitrosodiethylamine have been reported to
induce forward and reverse nutations in typhiaurium, E. coli,
Neurospora crassa, etc., gene recombination and conversion in Saccharo-
myces cerevislae, "recessive lethal mutation" in Dropsoohlla, and chromo-
some aberrations in mammalian cells (Montesano and Bartsch, 1976). They
gave a negative response in the mouse dominant lethal test, probably due
to the inability of the germ cells in the male to metabolize these com-
pounds.
Not all N-nitroso compounds have been found to be mutagenic, although
many have been tested only in microbial systems. Of the 23 N-nitrosamines
listed by Montesano and Bartsch as having been tested in systems which
included metabolic activation, six show no mutagenic activity. These
include N-nitrosodiphenylamine, which is reported as yielding a negative
response in both S. tyohimurium and E. coli after activation with a rat
liver microsomal preparation (Bartsch, et al. 1976; Nokajima, et al. 1974).
Teratogenicity. N-nitrosa compounds can also be potent teratogens.
The effects of experimental administration to pregnant animals have been
studied systematically by Druckrey (1973a). In summary, whereas the
N-nitrosamides were found to be teratogenic over an extended period of
gestation, the N-nitrosamines were active only when administered late in
pregnancy. Thus, near-LD.^ levels of N-nitrosoalkylureas and N-nitroso-
C- 26
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ikylanilines given Co pregnane rats on day 9 or 13 o£ gestation produced
uuilformations of the eye and brain in the offspring: similar levels of
N-nitrosodimethylamine or N—nitrosodiethylamine did not (Napalkov and
Alcxandrov, 1968). Given at other periods of development, both N-nitrosa-
uiines and N-nitrosaoides have been shown to be embryo toxic or carcinogenic
(.Uruckrey, 1973b).
The two principal factors determining the response appear to be the
state of differentiation of the various embryonic tissues and the meta-
bolic competence of these tissues. Magee (1973) has adduced evidence
suggesting that the lack of teratogenic and carcinogenic response to
N'-nitrosamines in early and mid-pregnancy is because the tissues have not
yet acquired the competence for metabolic activation.
In Druckrey's studies (1973a), it was observed that some malforma-
tions, mainly those of the central and peripheral nervous systems, were
associated with good survival times and that no tumors appeared at the
sites of malformation. This led Druckrey to suggest that teratogenesis and
carcinogenesis are two independent processes and that the molecular mechan-
isms of induction may be different.
Carcinogenicity
Animal Data: Magee, et al.(1976) summarized data from studies
through about 1975 on the carcinogenic activity of N-nitroso and related
compounds. Of the 107 N-nitroso compounds (including S3 N-nitrosanines)
C- 27
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listed, 87 (including 67 N-nitrosamines) are reported as having carcino-
genic activity. Since that time more compounds have been tested and, to
date, approximately 100 N-nitroso compounds are known to be carcinogenic in
one or more species of experimental animal (Lijinsky and Taylor, 1977).
All animal species tested are vulnerable. These include mice, rats,
Chinese, Syrian and European hamsters, gerbils, guinea pigs, rabbits, mink,
dogs, pigs and monkeys. Sensitivity varies with species. The African
white-tailed rat, Mystromys albicaudatus, apparently remarkably free from
spontaneous tumors, developed liver tumors after treatment with nitroso-
diethylamine,although only after' about 40 weeks exposure to 30 to 100 mg/1
in the drinking water as compared with rats in which extensive hepato-
cellular carcinomas were seen 10 weeks after a 10-week exposure at 40 ag/1
(Yamamoto, et al. 1972). Not all carcinogenic N-nitroso compounds have
induced tumors in all species. The cyclic nitrosamine N-nitrosoazetidine
(N-nitrosotrimethyleneimine) is reported as inducing lung, liver and kidney
tumors in the rat, and lung and liver tumors in the mouse but induced no
tumors under the test conditions used in the Syrian golden hamster; toluene-
p-sulfonylmethylnitrosamide is said to have failed to induce tumors in the
rac but to produce lung tumors in the mouse (Magee, et al. 1976).
t
Not all N-nitrosamines have been found to induce tumors, although in
most cases only one test species has been used, usually the rat. Those
compounds observed by Druckrey, et al. (1967) to give a negative response
in rats are indicated in Table 3. Others include N-nitrosoethyl-
(3-hydroxypropyl)amine, N-nitroso-n-butylcarboxymethylamine, N-nitroso-n-
C-28
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butyl-(3-hydroxypropyl)amine, N-nittroso-jn-butyl-(3-hydroxybutyl) amine, N-
nittroso-
-------
compounds by subcutaneous or intravenous injection or inhalation. The mean
time to tusior varied, with dose rate and compound, between 160 and 840
days.- Druckrey, et al. (1967) made Che following general observations
(paraphrased from the English summary to their paper).
All symmetrically substituted dialkylnitrosaaines produced carcinomas
of the liver. The only exception was N-nitrosodi-n-butylamine, which
also lead to carcinomas of the urinary bladder. Subcutaneous injection of
this compound produced only bladder tumors. N-nitrosodiamylamine given
subcutaneously selectively produced lung cancer.
Asymmetrical dialkylnitrosanines, especially those possessing a methyl
group and with the second substituent group amyl-, cyclohexyl-, phenyl-,
benzyl- or phenylethyl-, and also N,M'-dimethyl-N,N'-dinitrosoethylene
/
diamine, N-nitrosethylvinylamine, and N-nitrosoethyl-n-butylamine, selec-
tively produced carcinomas of the esophagus following both oral and paren-
teral administration. N-nitrosomethylalkylamines induced aaglinant tumors
of the kidney, particularly after intravenous injection.
The cyclic nitrosamlnes, N-nitrosopyrrolidine, N-nitrosoaorpholine,
and N-nitroso^-N'-carbethoxypiperazine induced cancer of the liver.
N-nitrosopiperidine and N,N'-dinitrosopiperazine produced carcinomas of
the esophagus after both oral and intravenous administration but tumors
of the *nasal cavity, mostly esthesioneuroepitheliomas, after subcutaneous
injection.
C- 30
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Nitrosamines with functional substituent groups also produced malig-
nant tumors in different organs. 3-(N-nitroso-N-methylamine)-sulfolane
and N-hitrososarcosine and its ethyl ester induced esophageal cancer.
N-aitroso-rt-butyl-(4-hydroxy-n-butyl) amine selectively induced carcinomas
of the urinary bladder. N-nitrosoethyl-2-hydroxyethylamine and N-nitroso-
bis(2-hydroxyethyl)amine regularly produced liver tumors following chronic
exposure but exhibited minimal toxicity in acute experiments 7,500
mg/kg).
Several N-nitrosamiaes produced carcinomas of the fore-stomach after
oral administration or local sarcomas at the site of injection. Intra-
venous N-methy1-N-nitrosourethane selectively produced lung cancer.
Methylnitrosoureas induced malignant tumors in the brain, spinal cord,
and/or peripheral nervous system.
Lijinsky and his co-workers have systematically studied the effects
of modification of chemical structure on the biological activity and organ
specificity of the nitrosamines. They have found that minor changes can
have a profound effect on the target organ. For example, chronic adminis-
tration in the drinking water of N-nitrosohexamethyleneimine induces
liver tumors in rats; of N-nitrosoheptamethyleneimine, lung tumors.
Lijinsky (1977) has discussed his findings in relation to what is known
of the mechanism of action of nitrosamines (see below). His conclusion
is that the major factor responsible for variations in biological activity
is the reactivity of hydrogen atoms on carbon atoms adjacent to the nitroso
group (alpha hydrogen atoms).
C- 31
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The response Co a particular compound also varies between species.
The following attempt to illustrate the diversity of responses is derived
froo Magee, ec al. (1976). In most species, as in the rat, the predominant
tumors following prolonged oral administration of dialkyl cyclic and many
other N-nitrosamines are in the liver. Tumors in rats have been described
as hepatomas and hepatocellular carcinomas, chloangiamas and c'nolangio-
carcinomas, fibrosarcomas, and angiosarcomas. The tumor type(s) observed
in mice depend upon both the strain and the compound. Nitrosodimethylsnine
produced mainly hemangiomatous tumors, with few parenchymal ceil tumors.
Nitrosodiethylamine induced mainly parenchymal tumors in seven strains of
mice but predominantly hemangiosarcomas and hemangioendotheliomas in two
strains. Nitrosodiethylamine given to Syrian golden hamsters by the intra-
gastric, intraperitoneal or intradermal routes produced hepatocellular
carcinomas which metastasized and were transplantable; continuous oral
administration induced cholangiocarcinomas. However, following single or
multiple subcutaneous injections both adult and newborn hamsters developed
mainly respiratory tumors and very few liver tumors. In the Syrian golden
hamster respiratory tract tumors induced by nitrosodiethylamine are con-
fined mainly to the nasal cavities, larynx, and trachea irrespective of the
route of administration. In the mouse, guinea pig and rabbit liver tumors
following prolonged oral administration of nitrosodiethylamine are accom-
panied by adenocarcinomas of the lung.
In their first studies demonstrating the carcinogenicity of nitroso-
dimethy1amine, Magee and Barnes (1956) reported that 19 of 20 rats fed 50
mg/kg in the diet continuously developed primary hepatic tumors within 40
C- 32
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weeks. However, Chey later (Magee and 3arnes, 1959) found chat, in rats
exposed for 1 week, at 100 or 200 mg/kg in Che diet, kidney tumors predom-
inated over liver tumors. A single, near-LD.g dose (30 mg/kg body weight)
of nitrosodimethylamine produced no progressive liver lesions nor liver
tumors but a 20 percent incidence of kidney tumors. A single intraperi-
toneal injection given to newborn mice Induced hepatocellular carcinomas
(Toth, et al. 1964). A single dose to partially hepatectomized adult rats
(Craddock, 1973) or to rats previously treated with a single dose of carbon
tetrachloride (Pound, et al. 1973) induced liver tumors. 3oth treatments
induce liver cells to divide and these observations prompted Craddock
(1973) to speculate that both injury to the genetic material and the
occurrence of cell replication before the damage has been repaired are
required for carcinogenesis. However, the incidence of liver tumors
following chronic administration of either nitrosodimethylamine or nitroso-
diethylamine was the same in both intact and partially hepatectomized rats
(Hajewski, et al. 1966). There seems to be no simple explanation as to
why a single oral dose of nitrosodimethylamine, while ineffective in the
adult mouse or rat, is capable of Inducing liver tumors in the adult Syrian
golden hamster (Tomatls and Cefis, 1967).
Some N-nltroso compounds administered during pregnancy induce cancer
not only in the mother but also in the offspring. A single administration
of N-nitrosoethylurea to pregnant rats resulted in malignant tumors of the
vagina, uterus or ovaries. Given on days 15 through 18 of gestation (but
not before day 11) the compound produced brain and spinal cord tumors in
the offspring. Ethylurea and nitrite given orally to pregnant rats also
C- 33
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produced nervous system tumors. The sensitivity of the nervous system
during prenatal development was estimated to be about 50 times that of
adults (Druckrey, et al. 1969). Exposure during days 10 through 21 of
gestation led to renal tumors in the offspring several months after treat-
ment (Shank, 1975). The N-nitrosoamines, including nitrosodimethylamine,
nitrosodiethylamine, nitrosomethylbutylamine, nitrosoethylvinylamine and
nitrosopiperidine have Induced tumors in the. offspring of mice, rats and
Syrian golden hamsters only when administered during the last days of
pregnancy. Subcutaneous, intraperitoneal, intravenous, and o.ral adminis-
tration and inhalation were equally effective (Tomatis, 1973). In rats the
tumors observed were mainly neurogenic. However, Mohr, et al.(1966)
observed tracheal papillomas in almost half the offspring of pregnant
Syrian golden hamsters within 25 weeks of subcutaneous administration of N-
nitrosodiethylamine on days 9 through 15 of gestation; In mice, treatment
with nitrosodiethylamine on day 16, 17 or 18 of gestation Induced mainly
lung tumors. It has been suggested that the inefficacy of the nitrosaair.es
in early pregnancy is due to the lack in the fetus of enzyme systems neces-
sary for metabolic activation (Druckrey, 1973b). Presumably, although
active products are produced in the maternal tissues, they are generally
too unstable to survive crossing the placenta and hence do not affect the
fetus.
Exposure to N-nitrosamides during pregnancy may result in a risk not
only to the Immediate offspring but for at least two more generations of
animals. An increased incidence of tumors has been reported in the F^,
?2 and F^ descendants of rats treated with N-nitrosomethylurethane or
C- 34
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tt-nitrosomethylurea during pregnancy (Montesano and 3artsch, 1976). There
is no experimental evidence Co indicate that N-nitrosaaines pose a sinilar
threat.
Nitrosodiethylamine has been found in the stomach contents of suckling
rats following oral administration to the dam. The young rats subsequently
developed multiple tuaors (Schoental and Appleby, 1973).
The carcinogenic action of the N-nitroso compounds can be modified by
appropriate treatment. The effect of partial hepatectomy or prior admin-
istration of carbon tetrachloride has already been mentioned. Other
interactions have also been demonstrated. The Intragastric administration
of aethylcholanthrene to mice (which would be expected to increase the
activity of liver nitrosanine-metabolizing enzymes) together with intra-
peritoneal injection of nitrosodiaethylamine resulted in increased inci-
dence and decreased latency period to tumors as compared with mice treated
with either compound alone (Cardesa, et al. 1973). Intratracheal instilla-
tion of ferric oxide and subcutaneous injection of nitrosodiaethylamine in
Syrian golden hamsters induced esthesioneuroepitheliomas of the nasal
cavity, a type of tumor not induced in hamsters by nitrosodimechylamine
alone (Stenback, et al. 1973). Ferric oxide is frequently used as a
carrier for introducing carcinogenic chemicals into the lung by intra-
tracheal instillation. It is believed to facilitate the penetration and
retention of the carcinogen in the lung tissue. However, in the present
instance, ferric oxide can be considered a cocarcinogen. Other studies
have shown enhanced bronchial metaplasia and tracheal papilloma formation
C- 35
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in hamsters Created with nitrosodiethyl amine by subsequent exposure to ciga-
rette smoke, volatile acids, aldehydes, and methyl nitrite and increased
incidence of lung tumors by subsequent intratracheal instillation of
benzo(a)pyrene and/or ferric oxide particles (Magee, ec al. 1976). The
toxicity and carcinogenicity of various alkylnitrosoureas ar*e said to be
increased '^en administered with copper, nickel or cobalt ions (Magee, et
al. 1976). Magee, et al. (1976) cite examples of agents known to depress
the activity of drug metabolizing enzymes which have been reported to
modify the action of N-nitrosamines. A protein-deficient diet protected
against acute liver damage in rats and resulted in an almost two-fold
increase in the LD^O' however the incidence of kidney tumors in survivors
was 100 percent. Aminoacetonitrile, which inhibits the metabolism of
nitrosodisethylamine both in vivo and _in vitro, prevented its toxic and
carcinogenic effect in rat liver. At the present time, these interactions
appear to be of academic rather than practical interest.
Although there is a wealth of reported studies on the carcinogenicity
of N-nitroso compounds, these tend to address structure-activity relation-
ships or mechanisms of action: information on dose-response characteristics
is sparse. Table 4 includes experimental data culled from studies in the
published literature in which nitrosamines were administered over the
lifetime of experimental animals at two or more daily dose levels which
induced tumors in some but not all animals exposed. Although only tumors
(benign and malignant) occurring in the principal target organ are listed,
in all cases other organs were also affected. Some comments are necessary.
The data of Druckrey, et al. (1963) are difficult to interpret since many
C-36
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Table 4. - Dose-response daca frcm studies involving lifeciae
exposure to four N-aitrosamines
Daily Dose Aniaals with tuaors
(ag/kg (Anlaals exposed)
Body vt.) Male Female
Compound: N-Nltrosodinethylanine
Vehicle: Diet
0
0(12)
0(29)
Species: Rat
0.067
1(19)
Target organ: Liver
0.12
0(18)
(Terracini, et al. 1967)
0.17
1(6)
0.30
4(62)
0.60
2(5)
1.2
15(23)
6.0
10(12)
Compound: N-Nitrosodiethylamine
Vehicle: Drinking water
0.075
5(60)
Species: Rat
0.15
¦ 22(45)
Target organ: Liver
0.30
63(80)
(Druckrey, et al. 1963)
0.60
51(60)
1.2
36(40)
Compound: N-Nitrosodi-nrbutylamine
Vehicle: Drinking Water
7.6
17(47)
Species: Mouse
8.2
2(42)
Target organ: 31adder
29.1
36(45)
(Bertram and Craig, 1970)
30.9
8(45)
Compound: N-Nitrosopyrrolidine
«
Vehicle: Drinking Water
0
0(61)
Species: Rat
0.30
3(60)
Target organ: Liver
1.0
17(62)
(Preussaann, et al. 1977)
3.0
31(38)
C- 37
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animals were lose through intercurrent infections. Thus, of the 60 animals
orglnally exposed to nitrosodiethylamine at the 0.075 mg/kg body weight
level, 40 succumbed to a "pneumonia-infection" curing the first 600 days of
the experiment and, by the time the first (and only) hepatic carcinoma had
been identified in this group, there were only three survivors. The sex of
the animals used in this study is not specified. However, it is probable
that they were male 3D II (albino) rats. In addition to tumors of the
urinary bladder, Bertram and Craig (1970) report a very high incidence of
esophageal tumors unrelated to dose following administration of N-nitrosodi-
n- butyl amine. The incidence of bladder ttsaors in females was relatively
low but these tumors developed significantly later than in males. The
authors speculate that, had not death from esophageal tumors intervened,
both sexes would have had a uniformly high bladder tumor incidence.
Preussman, et al. (1977) report that other dose response studies (initially
with N-nitrosopiperidine). are under way or planned. In other studies with
nitrosodimethylamine, mink, apparently the most sensitive species, devel-
oped tumors when fed 0.03 mg/kg body weight 2 days per week (Natl. Acad.
Sci., 1978). An increase in the Incidence of malignant liver and kidney
tumors was found in male but not female rats, and not in mice of either
2
sex, when the animals continuously inhaled air containing 200 jig/m of
dinitrosomethylamine for 17 months (mice) or 25 months (rats). A con-
centration of 5 jig/m"1 produced no increase in tumors (Natl. Acad. Sci.,
1978). Preussman, et al. (1977) have attempted to derive "no-effect-levels"
for rats for nitrosodimethylamine and other carcinogenic aitrosamines
(although they themselves question the validity of such levels). Expressed
as dietary levels, the estimates are: nitrosodimethylamine, 1 to 2 mg/kg;
C- 38
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nitrosodiethylamine, < 1 mg/kg; N-nitrosopyrrolidine, 3 to 5 mg/kg (corres-
ponding Co a daily intake of approximately 0.1, < 0.1, and 0.3 mg/kg body
weight, respectively).
Attempts have been made to derive some measure of the relative car-
cinogenic potency of N-nitroso compounds in the absence of complete dose-
response information. The favored data base is the review of Druckrey, et
al. (1967) of studies in which adult.BD rats received small daily doses
(usually orally) of 51 M-nitrosamines and 13 N-nitrosamides. Druckrey, et
al. calculated the mean total carcinogenic dose required for production of
tumors in 50 percent of the animals (D^q) • Wishnok and Archer (1976) have
used only those D^q values corresponding to a daily dose that was approxi-
mately a constant fraction (1 to 3 percent) of the acute oral LD-q
(a dose which gave a mean induction time for appearance of tumors of about
300 to 600 days), and, in order to have increasing carcinogenicity reprer-
sented by increasing (and manageably small) numbers, have expressed car-
cinogenic potency as log (1/D^q) . Table 6 lists the values given by
Wishnok and Archer (1976) for most of the carcinogenic H-nitroso compounds
examined by Druckrey, et al. (1967). For the four N-nitrosanines for which
dose-response are available the order of increasing potency as measured by
log (1/D-q) i's: JT-nitrosopyrrolidine (1.41); N-nitroso-n-butylamine (1.61)
N-nitrosodiaethylamine (2.27); N-nitrosodiethylamine (3.20). Analysis of
the experimental dose-response data places these compounds in the same
order (Table 5). Despite this (possibly fortuitous) agreement, log
(1/D^q) values can be regarded only as providing general guidance.
Wishnok and Archer (1976) and Wishnok, et al. (1973), using the log
C- 39
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(I/D^q) value as a measure of carcinogenicity have attempted to relate
carcinogenicity to the chemical and physical properties of N-nitroso con-
pounds. Wishnok, et al. (1973) have derived an equation which takes into
account, not only cheaical structure but also the partition coefficient of
the N-nitroso compounds, and their electronic factors as expressed by Taft
a* values of substituencs on the a-carbon atoms. With certain explainable
exceptions, which are discussed by Wishnok, et al., the equation appears to
serve as a reasonably reliable method for assessing carcinogenicity.
Hunan Data: Tiere is no instance known of occupational exposure to
specific nitrosamines having resulted in a cancer in man. The epidemio-
logic evidence for the association of N-nitroso compounds with human cancer
is also very limited. These data have been reviewed by a panel convened by
Che National Academy of Sciences (1978) and the following is taken in its
entirety from this report.
A few epidemiological studies have attempted to associate
environmental nitrates, nitrites, and nitroso compounds with
human cancer. A problem common to all the early studies was the
inability to measure with high specificity N-oitroso compounds in
biological samples. For example, African studies associating
esophageal cancer with a nitrosamine in a local alcoholic bever-
age (McGlashan, 1969) and a study relating carcinoma of the
cervix with nitrosamine formation in the vagina of South African
women (Harington, et al. 1973) were done without the advantage of
mass spectroscopic confirmation that is needed to identify the
nitrosamines.
The International Agency for Research on Cancer has investi-
gated the possible association between N-nitroso compounds in the
diet and esophageal cancer in specific areas of Iran and France,
where these tumors occur at a high rate, and in nearby areas
where the tumor rates are not elevated (Sogovski 1974). Complete
studies of possible sources of exposure to the carcinogens have
C-40
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not been made, but 15 of 29 samples of cider contained 1 co 10
/ig/kg DMN (nitrosodimethylamine) and two samples also contained
OCN (nitrosodiethylamine) (less Chan 1 /ig/kg) . Correlations
between dietary intake of N-nitroso compounds and incidence of
esophageal cancer have not yet been made.
The Chinese conducted a similar study in the Anyang region,
where it is claimed chat approximately 20 percent of all deaths
(not just cancer deaths) result from esophageal cancer (Coordin-
ation Group, 1975). Twenty-three percent of the food samples
from areas with the highest cancer rates were reported to con-
tain DMN, DEN, and methylbenzyl nitrosamine. However, confirma-
tion of this analysis by gas chromatography and mass spectroscopy
is required before the finding can be accepced. Dietary nitrice
levels were higher in areas of- high cancer incidence Chan in
low Incidence areas. Chickens in areas where there were high,
rates of esophageal cancer in huaans also had a high incidence
of similar tumors, suggesting an environmental etiology for the
disease.
Zaldivar and Wetterstand (1975) demonstrated a linear regres-
sion between death rates from stomach cancer and the use of NaNO^
as fertilizer in various Chilean provinces. Fertilizer use was
presumed equitable co human exposure Co nitrates and nitrosamines,
but no actual exposure data were reported. Araijo and Coulson
(1975) have shown similar correlations. These reports suggest
that nitrate frcm fertilizer enters the diet in neat, vegetables,
and drinking water, is reduced to nitrite by microbial action,
and thus is available for in vivo nitrosacion of secondary
amines in the diet, to form carcinogenic nitrosamines, which
induce stomach cancer. As yet, no scientific data have been
gathered that support chis hypothesized etiology, and the sug-
gested causal relationship remains highly speculative.
Hilly et al. (1973) correlated differences in rates of stomach
cancer with the nitrate content of drinking water in two English
towns; but again, che evidence required co demonscrace a causa-
tive role for nitrate is not available. Gelperin, et al. (1976)
compared death rates ascribed to cancer of the gastrointestinal
tract and liver wich nitrate levels of drinking water in three
unmatched population groups in Illinois used in an infant mor-
tality sCudy. No significant differences in cancer races were
found among che chree groups (che level of significance was
noc stated). It is doubtful, however, whether the available
mortality data permitted an analysis that could have detected
an effect in the high nitrate population.
Increased rates of stomach cancer have been observed in
Japan in occupational groups and other populations characterized
by an unusually high consumption of salt-preserved foods (Saco,
et al. 1959); presumably, these foods are high in nitrate and
perhaps in nitrite.
C-41
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A statistical correlation is presented of the incidence of cancer mor-
tality with estimated exposures of urban populations in che United States
to various environmental and diecary factors. Again to quote the report
(Natl. Acad. Science, 1978): "Strong positive correlations were shown
between the aggregate rate of cancer mortality and components of the diet,
particularly nitrite and protein; however, insufficient biological evidence
is available to confirm the hypothesized causal' pathway (involving forma-
tion of JT-nitroso compounds from nitrite and amines, reacting in the
stomach)." There is, in fact, direct evidence for formation of nitrosamines
from precursors in the human stomach (see, for example, Fine, et al. 1977b):
still in contention is the extent to which nitrosation occurs.
Mechanism of action: Although N-nitrosamines such as N'-nitrosodi-
methylamine and 51-uitrosomorpholine are rapidly and fairly evenly dis-
tributed throughout the bodies^of rats after injection (Magee, 1972;
Stewart, et al. 1974), the acute toxic damage they produce is more severe
in the liver than elsewhere, and tumors following chronic exposure are con-
fined mainly to the liver and kidney (Druckrey, et al. 1967). In vitro
studies have shown that the liver and kidney possess che greatest capacity
for metabolism of N-nitrosodimethylamine (Montesano and Magee, 1974).
These observations are most readily explained on che assumption that car-
cinogenesis and other biological actions of nitrosamines are mediated by
metabolic products. The lack of mutagenic activicy exhibited by nicrosa-
mines in bacterial test systems in the absence of a metabolic activating
system (Montesano and Bartsch, 1976) supports this hypothesis, which is now
generally accepted.
C- 42
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The N-nitrosanides differ from Che N-nitrosamines in that Chey are
chemically unstable ac physiological pH, and decompose norc-enzymically,
again inco active metabolic produces, upon contact wich che tissues. They
therefore tend to produce damage or tumors at the site of administration.
The nature of the metabolite(s) responsible for the carcinogenic
activity of N-oitroso compounds is -still in debate. Magee (1977) has
adduced considerable evidence in support of the commonly accepted hypothe-
sis that the active agents are electrophilic alkylating agents which bind
to DNA. The major product formed in rat liver after administration of
nitrosodisiethylamine or nitrosodiethylanine is the corresponding 7-alkyl-
guanine. However, little correlation has been found between the occurrence
of 7-alkylguanine in DNA and the tumor-producing activity of the nitrosa-
mines. A much better correlation has been demonstrated between the forma-
tion and persistence of Q^-alkylguanines and tumor incidence (?egg ana
Nicoll, 1976). These authors postulate that che formation ana persistence
5
until cell division of certain promutagenic produces such as 0 -methyl-
guanine mighc be responsible for che initiation of cmors and that che
differing abilities of various cissues co catalyze DNA repair might account
for part of che differing susceptibilities cf chese cissues to che carcino-
genic action of the N-nitroso compounds (Pegg and Nicoll, 1976). However
Lijinsky and coworkers found chat a series of cyclic nicrosamines, while
equally carcinogenic wich the aliphatic nitrosamines, gave rise to much
less alkylated guanines: in some cases none could be dececced (Lijinsky, 1977).
For this and other reasons, Lijinsky concludes chac che inicial seep cannot
be a simple alkylation of DNA.
C-43
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Summary. Many N-nitrosamines (and N-nitrosamides) are teratogenic,
mutagenic, and/or carcinogenic. Evidence from experimental animals sug-
gests that, as carcinogens, they are most effective by the oral route and
when given as multiple small doses. However, some are capable of inducing
tumors after a single dose and they are also capable of inducing tumors in
certain organs and tissues regardless of the route of administration, i.e.,
they are systemic carcinogens. In the rat, at least, every organ is proba-
bly susceptible to tumor induction by some nitrosamine. There is a strong
relation between chemical structure and type of tumor induced. There are
large differences in tumor response among species, both in type of tumor
produced and in susceptibility.
The late fetus and neonate appear to be highly susceptible to the car-
cinogenic action of both N-nitrosamines and N-nitrosaaides. The sensi-
tivity of the nervous system to some N-oitrosamides during prenatal
development is about 50 times that in the adult. A single exposure to some
nltrosamldes during pregnancy may result in development of tumors not only
in the immediate descendants but in ac least two succeeding generations.
Although prolonged exposure to some nitrosamines is needed to elicit tumors
in adult animals, a single dose of the compound will Induce tumors in the
newborn.
The epidemiological studies to date have been inadequate to establish
any correlation between exposure to N-nitroso compounds or their precursors
and human cancer as valid causal relationships. Nevertheless, the ability
of N-nitrosaaines to Induce tumors in a wide range of species other than
C- 44
-------
man, together with the fact that huaan liver tissue is capable of foraing
alkylating and mutagenic aetabolites, suggest strongly that it is inproba-
ble that hunans are refractory to the carcinogenic action of these com-
pounds .
C-45
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CRITERION FORMULATION
Existing Guidelines and Standards
Current Levels of Exposure
For the general population exposure information is
very limited. It has been estimated that air, diet and
smoking all play a roughly equivalent role in direct human
exposure, contributing a few micrograms per day, with direct
intake from ingested water probably much less than 1 pg
per day (U.S. EPA, 1976).
There is even greater uncertainty with regard to the
significance of exposure to precursors. The chief source
of the nitrate body burden, except in the newborn, is ingested
vegetables, unless rural well water high in nitrate is con-
sumed. Food and water normally contribute a few hundered
milligrams per day. Inhalation may also contribute several
hunder micrograms per day (U.S. EPA, 1977). On a daily
basis, the major source of nitrite is saliva. However,
salivary nitrite is presented to the body as a continuous,
low-level input, in comparison with the relatively high
concentrations over short periods resulting from ingestion
of cured meats. This may be significant since the rate
of nitrosation is a function of the square of the nitrite
concentration (U.S. EPA, 1977).
The concentrations of nitrite (and its precursors,
ammonia and nitrate) and nitrosatable compounds can be much
greater in soils heavily fertilized with organic waste matter
C-46
-------
or in waters receiving runoff from agricultural areas or
discharges of industrial or municipal waste waters containing
substantial amounts of amines. Levels of nitrate or municipal
drinking water in the U.S. seldom exceed 10 mg/1 nitrate
N,although some private supplies contain much more.
Significant concentrations of nitrosamines have been
reported for a limited number of samples of ocean water,
river water and waste treatment plant effluent adjacent
to or receiving wastewater from industries using nitrosamines
or secondary amines in production operations. Nitrosodi-
methylamine has been reported at the 3-4 ng/1 level in these
samples. Nitrosamines, however, are rapidly decomposed
by photolysis and do not persist for a significant time
in water exposed to sunlight.
Although it is difficult to analyze this wide spectrum
of exposure potential, it must be concluded that ingested
water is a relatively minor source of exposure when compared
with other potential sources of either preformed N-nitroso
compounds or their precursors.
Special Groups at Risk
Because of the ubiquitous nature of nitrosatable com-
pounds and nitrosating agents in the environment (food,
air, drugs, tobacco, water, soil) special risk groups would
have to include those individuals who are exposed to multiple
exposure situations. To quantify this, however, is almost
impossible at this point because of the need to create expo-
sure scenarios for which the bounding factors are unknown
or relatively wide ranging.
C- 47
-------
Basis and Derivation of Criterion
Both N-nitrosamines and N-nitrosamides exhibit acute
toxicity, teratogenicity, mutagenicity and/or carcinogenicity.
For most, it is the latter capability which demands considera-
tion in the context of human exposure since the toxicological
evidence is such that they must be treated as potential
human carcinogens. Thus, nitrosamines are included in the
American Conference of Governmental Industrial Hygienists'
(1977) List of "Industrial Substances Suspect of Carcinogenic
Potential for Man." No Threshold Limit Value is given.
The guidelines which follow are based upon the assumption
that N-nitrosamines are human carcinogens.
Adequate dose-response data to permit an assessment
of the carcinogenic risk to man are available from studies
involving lifetime exposure of rats or mice to four nitrosa-
mines (N-nitrosodimethylamine, N-nitrosodiethylamine, N-
nitrosodi-n-butylamine, and N-nitrosopyrrolidine) in their
drinking water or food (see Table 4 of the document). These
data have been used to derive estimates of the concentrations
in water which, if used as the source for man of drinking
water and edible fish and shellfish, would increase the
risk of a tumor by not more than one in 100,000 individuals
exposed for the duration of their lifespan. The method
of extrapolation and the mathematical model (a linear, non-
threshold model) used are described in the Appendix. The
water criteria numbers given in Table 5 are based upon the
tumor incidence, at the organ which is the chemical's princi-
pal site of action (see Table 4 of the document), in the
C-48
-------
most sensitive sex, at the lowest dose level which yielded
a response significantly greater than in the control animals.
The actual parameters used are given in Appendix I.
The only nitrosamine for which any data on bioaccumula-
tion in fish or shellfish are available is N-nitrosodiphenyl-
amine. One test in bluegill yielded a maximum bioconcentra-
tion factor (BCF) of 217 for the whole fish (U.S. EPA, 1978).
Using this, a weighted BCF for all species was calculated
to be 500. These values are believed not to be representa-
tive for the nitrosamines for which carcinogenicity data
are available and another approach has therefore been attempted.
A relationship has been described between the BCF and the
n-octanol/water partition coefficient, Log BCF = 0.76 Log
P - 0.23, (Veith, et al. Manuscript). The equation can
be used to estimate the BCF for aquatic organisms, that contain
about 8 percent lipids frdm the partition coefficient P.
The partition coefficients for N-nitrosodimethylamine, N-
nitrosodiethylamine, N-nitrosodi-n-butylamine and N-nitroso-
pyrrolidine are 0.27, 3, 83, and 0.65 respectively (Singer,
et al. 1977a). Values of BCF calculated using this equation
are 0.2, 1.4, 17, and 0.42 respectively, for N-nitrosodi-
methylamine, N-nitrosodiethylamine, N-nitrosodi-n-butylamine,
and N-nitrosopyrrolidine respectively. An adjustment factor
of
2.3/8.0 = 0.2875 can be used to adjust the estimated BCF
from the 8.0 percent lipids on which the equation is based
to the 2.3 percent lipids that is the weighted average for
consumed fish and shellfish.
C-49
-------
The adjusted BCF values are 0.06, 0.39, 4.9, and 0.12
respectively.
Other empirical procedures (Neely, et al. 1974) can
be used to estimate BCF's from partition coefficients.
The values obtained are of the same order of magnitude.
For purposes of calculating criteria, the estimated
BCF's for the methyl, ethyl, butyl, and pyrrolidine compounds
are judged to be rough estimates of the bioconcentration
potential. As the influence of these values ranges from
5/100 percent to 4 percent of the exposure uptake from fish
consumption, for simplicity the assumed BCF for criteria
level purposes is zero.
TABLE 5
Concentrations in water estimated to induce no more than one
excess cancer per 100,000 individuals exposed over a lifetime
Compound
Estimated
Concentration
(pg/1)
Data base
N-Nitrosodimethylamine
0.026
Rats (female)
(Druckery, et al. 1967)
N-Nitrosodiethylamine
0.0092
Rats (male?)
(Druckrey, et al. 1963)
N-Nitrosodi-n-butylamine
0.013
Mice (male)
(Bertram and Craig, 1970)
N-Nitrosopyrrolidine
0.11
Rats (mixed sexes)
(Preussman, et al. 1977)
C-50
-------
Table 3 of the document lists one measure of the rela-
tive carcinogenic potential of a number of N-nitrosamines.
The value of N-nitrosodiethylamine (3.20) is exceeded by
only that for N-nitrosomethyl-2-chloroethylamine (3.21)
and approached by only the values for N-nitroso-methylbenzyl-
amine (3.10) and N-nitrosomethyl-(2,phenylethyl)amine (3.01).
Hence, N-nitrosodiethylamine can reasonably be considered
to be one of the most carcinogenic nitrosamines. It is
therefore appropriate to base the water criterion number
for any individual nitrosamine on the number obtained for
N-nitrosodiethylamine, viz. 9.2 ng/1.
This criterion number has been derived by considering
only the excess cancer risk imposed by exposure to contami-
nated drinking water, fish, and shellfish. However, the
average daily intake of preformed nitrosamines from other
sources (air, diet, and smoking) is estimated to be in the
order of a few micrograms per day (U.S. EPA, 1976). There
is an additional and, at the present time, ill-defined contri-
bution to the body burden from the ui vivo nitrosation of
precursors. This contribution has been variously estimated
to range from a few micrograms to several hundred micrograms
daily (Natl. Acad. Sci., 1978). Thus, present evidence
suggests that control of exposure to N-nitrosamines should
take into account both preformed nitrosamines and their
precursors in the environment.
Under the Consent Decree in NRDC v.Train, criteria
are to state "recommended maximum permissible concentrations
(including where appropriate, zero) consistent with the
C-51
-------
protection of aquatic organisms, human health, and recrea-
tional activities." Nitrosamines are suspected o£ being
human carcinogens. Because there is no recognized safe
concentration for a human carcinogen, the recommended concen-
tration of nitrosamines in water for maximum protection
of human health is zero.
Because attaining a zero concentration level may be
infeasible in some cases and in order to assist the Agency
and States in the possible future development of water quality
regulations, the concentrations of nitrosamines corresponding
to several incremental lifetime cancer risk levels have
been estimated. A cancer risk level provides an estimate
of the additional incidence of cancer that may be expected
in an exposed population. A risk of 10 ^ for example, indi-
cates a probability of one additional case of cancer for
every 100,000 people exposed, a risk of 10~^ indicates one
additional case of cancer for every million people exposed,
and so forth.
In the Federal Register notice of availability of draft
ambient water quality criteria, EPA stated that it is consi-
dering setting criteria at an interim target risk level
of 10~5, 10"^ or 10"^ as shown in the table below.
C- 52
-------
Exposure Assumptions
(per day)
2 liters of drinking water
and consumption of 18.7
grams fish and shellfish. (2)
N-nitrosodimethylamine 0
N-nitrosodiethylamine 0
N-nitrosodi-n-butylamine 0
N-nitrosopyrrolidine 0
Consumption of fish and
shellfish only.
N-nitrosodimethylamine 0
N-nitrosodiethylamine 0
N-nitrosodi-n-butylamine 0
N-nitrosopyrrolidine 0
Risk Levels and Corresponding Criteria (1)
10
-7
,00026 pg/1
,000092 fig/1
,00013 jig/1
.0011 /ig/1
10
-6
.0026 ^ag/1
.00092 pg/1
.0013 ^g/1
.011 pg/1
10
-5
.026 ^ig/1
.0092 pg/1
.013 p.g/1
.11 pg/1
(1)Calculated by applying a modified "one-hit" extrapolation
model described in the Methodology Document to the animal
bioassay data presented in Appendix I and in Table 10.
Since the extrapolation model is linear at low doses, the
additional lifetime risk is directly proportional to the
water concentration. Therefore, water concentrations cor-
responding to other risk levels can be derived by multiplying
or dividing one of the risk levels and corresponding water
concentrations shown in the table by factors such as 10,
100, 1,000, and so forth.
C-53
-------
(2) Approximately zero percent of Nitrosamine exposure results
from the consumption of aquatic organisms which exhibit
an average bioconcentration potential of zero.
The remaining 100 percent of Nitrosamine exposure results
from drinking water.
Concentration levels were derived assuming a lifetime
exposure to various amounts of nitrosamines, (1) occurring
from the consumption of both drinking water and aquatic
life grown in waters containing the corresponding nitrosa-
mines concentrations and, (2) occurring solely from consump-
tion of aquatic life grown in the waters containing the
corresponding nitrosamines concentrations. Because data
indicating other sources of nitrosamines exposure and their
contributions to total body burden are inadequate for quanti-
tative use, the figures reflect in incremental risks asso-
ciated with the indicated routes only.
C-54
-------
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APPENDIX I
Derivation of Criterion for Dimethylnitrosamine
Druckery (1967) summarized a series of experiments
in which a large series of nitrosamine compounds were given
to B-D rats for a lifetime. He found that the incidence
of liver tumors increased with daily dose, d, and that the
median time when tumors were observed, was less at
higher doses and the relationship between d and fc50 was
4
d(tso)2.3 = k, where k is a constant equal to 0.81 x 10
mM/kg/day when t^Q is expressed in units of days. The extra-
polation model uses the dose units of mg/kg/day and the
time units of fractions of a lifetime. Converting k to these
units by using 728 days as the lifetime and a molecular
weight of 74 mg/mM gives the following:
k = 0.81 x 104mM/kg/day x 74 mg/mM = 0.30271
Therefore the parameters of the dose-response model are:
The result is that the water concentration should be
less than 0.026 micrograms per liter in order to keep the
(728) 2.2
^fcn = 0.30271
R = 0
L = 728 days
w = 0.35 kg
individual lifetime risk below 10"^
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Derivation of Criterion of Diethylnitrosamine
Druckery, et al. (1963) administered diethylnitrosamine
to B-D rats via drinking water in nine dose groups ranging
from .075 to 14.2 mg/kg/day.
They found that the incidence of liver tumors increased
with daily dose, d, and that the median time when tumors
were observed, t5Q, was less at higher doses and the relation-
2 3
ship between d and t5g was dtt^g) ' = k, where k is a constant.
At a dose of 0.6 mg/kg/day the incidence of tumors reached
50 percent (30 animals with liver tumors out of 60 animals
initially) at 355 days. Using a bioaccumulation factor
of zero the parameters of the extrapolation model are:
nt
= 30
d = 0.6 mg/kg/day
Nt
= 60
w = 0.28 kg
nc/N
c
= 0
L = 730 days
Le = 355 days m = 2.3 instead of 3 in the
standard model
le = 355 days dtm = 0.6 (355/730) 2,3 = 0.114
R = 0
The result is that the water concentration should be
less than 0.0092 micrograms per liter in order to keep the
individual lifetime risk below 10~5.
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Derivation of Criterion for Dibutylnitrosamine
Bertram and Crain (1970) administered dibutylnitrosamine
via drinking water to C57BL/6 mice at dose levels of about
8 and 30 mg/kg/day until the animals became moribund or
died. They found that all of the 179 animals reaching autopsy
had tumors of the bladder of espohagus except three, which
had tumor induction at either site was the males given 7.6
mg/kg/day, where the mean tumor induction time was 261 days.
Assuming a bioaccumulation factor of zero, the parameters
of the extrapolation model are:
nfc/Nfc =0.5 d = 7.6 mg/kg/day
nc/N<; = 0 L = 728 days
Le = 261 days w = .028 kg
le = 261 days R = 0
The result is that the water concentration should be
less than 0.013 micrograms per liter in order to keep the
individual lifetime risk below 10"^.
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Derivation of Criterion of N-Nitroso-pyrrolidine
Preussman, et al. (1977) found a dose-related incidence
of hepatocellular carcinomas in Sprague-Dawley rats in a
lifetime feeding study at levels of 0.3, 1.0, 3.0, and 10
mg/kg/day. The total tumor incidence was equal to controls
at the 0.3 mg/kg/day level, but was 46, 84 and 32 percent
at the successively higher doses. Animals at the highest
dose had a smaller tumor incidence because of early deaths
from pneumonia. At 3 mg/kg/day the incidence of liver tumors
was 31/38 whereas the 61 controls had no tumors. With a
negligible fish accumulation, the parameters of the dose-
response model are:
nt
=
31
le =
104 weeks
Nt
=
38
d. =
3 mg/kg/day
nc
=
0
w =
0.35 kg
Nc
=
61
L =
104 weeks
Le
104 weeks
R =
0
The result is that the water concentration
less than 0.11 micrograms per liter in order to
individual lifetime risk below 10"^.
should be
keep the
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