United States
Environmental Protection
1=1 m m Agency
EPA/690/R-06/022F
Final
8-22-2006
Provisional Peer Reviewed Toxicity Values for
Nitroglycerin
(CASRN 55-63-0)
Derivation of Subchronic and Chronic Oral RfDs
Superfund Health Risk Technical Support Center
National Center for Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268

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Acronyms and Abbreviations
bw	body weight
cc	cubic centimeters
CD	Caesarean Delivered
CERCLA	Comprehensive Environmental Response, Compensation and
Liability Act of 1980
CNS	central nervous system
cu.m	cubic meter
DWEL	Drinking Water Equivalent Level
FEL	frank-effect level
FIFRA	Federal Insecticide, Fungicide, and Rodenticide Act
g	grams
GI	gastrointestinal
HEC	human equivalent concentration
Hgb	hemoglobin
i.m.	intramuscular
i.p.	intraperitoneal
IRIS	Integrated Risk Information System
IUR	inhalation unit risk
i.v.	intravenous
kg	kilogram
L	liter
LEL	lowest-effect level
LOAEL	lowest-observed-adverse-effect level
LOAEL(ADJ)	LOAEL adjusted to continuous exposure duration
LOAEL(HEC)	LOAEL adjusted for dosimetric differences across species to a human
m	meter
MCL	maximum contaminant level
MCLG	maximum contaminant level goal
MF	modifying factor
mg	milligram
mg/kg	milligrams per kilogram
mg/L	milligrams per liter
MRL	minimal risk level
MTD	maximum tolerated dose
MTL	median threshold limit
NAAQS	National Ambient Air Quality Standards
NOAEL	no-ob served-adverse-effect level
NOAEL(ADJ)	NOAEL adjusted to continuous exposure duration
NOAEL(HEC)	NOAEL adjusted for dosimetric differences across species to a human
NOEL	no-ob served-effect level
OSF	oral slope factor
p-IUR	provisional inhalation unit risk
p-OSF	provisional oral slope factor
p-RfC	provisional inhalation reference concentration
p-RfD	provisional oral reference dose
PBPK	physiologically based pharmacokinetic
ppb	parts per billion
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ppm
parts per million
PPRTV
Provisional Peer Reviewed Toxicity Value
RBC
red blood cell(s)
RCRA
Resource Conservation and Recovery Act
RDDR
Regional deposited dose ratio (for the indicated lung region)
REL
relative exposure level
RfC
inhalation reference concentration
RfD
oral reference dose
RGDR
Regional gas dose ratio (for the indicated lung region)
s.c.
subcutaneous
SCE
sister chromatid exchange
SDWA
Safe Drinking Water Act
sq.cm.
square centimeters
TSCA
Toxic Substances Control Act
UF
uncertainty factor
Hg
microgram
|imol
micromoles
voc
volatile organic compound
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8-22-2006
PROVISIONAL PEER REVIEWED TOXICITY VALUES FOR
NITROGLYCERIN (CASRN 55-63-0)
Derivation of Subchronic and Chronic Oral RfDs
Background
On December 5, 2003, the U.S. Environmental Protection Agency's (EPA's) Office of
Superfund Remediation and Technology Innovation (OSRTI) revised its hierarchy of human
health toxicity values for Superfund risk assessments, establishing the following three tiers as the
new hierarchy:
1.	EPA's Integrated Risk Information System (IRIS).
2.	Provisional Peer-Reviewed Toxicity Values (PPRTV) used in EPA's Superfund
Program.
3.	Other (peer-reviewed) toxicity values, including:
~	Minimal Risk Levels produced by the Agency for Toxic Substances and Disease
Registry (ATSDR),
~	California Environmental Protection Agency (CalEPA) values, and
~	EPA Health Effects Assessment Summary Table (HEAST) values.
A PPRTV is defined as a toxicity value derived for use in the Superfund Program when
such a value is not available in EPA's Integrated Risk Information System (IRIS). PPRTVs are
developed according to a Standard Operating Procedure (SOP) and are derived after a review of
the relevant scientific literature using the same methods, sources of data, and Agency guidance
for value derivation generally used by the EPA IRIS Program. All provisional toxicity values
receive internal review by two EPA scientists and external peer review by three independently
selected scientific experts. PPRTVs differ from IRIS values in that PPRTVs do not receive the
multi-program consensus review provided for IRIS values. This is because IRIS values are
generally intended to be used in all EPA programs, while PPRTVs are developed specifically for
the Superfund Program.
Because science and available information evolve, PPRTVs are initially derived with a
three-year life-cycle. However, EPA Regions or the EPA Headquarters Superfund Program
sometimes request that a frequently used PPRTV be reassessed. Once an IRIS value for a
specific chemical becomes available for Agency review, the analogous PPRTV for that same
chemical is retired. It should also be noted that some PPRTV manuscripts conclude that a
PPRTV cannot be derived based on inadequate data.
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Disclaimers
Users of this document should first check to see if any IRIS values exist for the chemical
of concern before proceeding to use a PPRTV. If no IRIS value is available, staff in the regional
Superfund and RCRA program offices are advised to carefully review the information provided
in this document to ensure that the PPRTVs used are appropriate for the types of exposures and
circumstances at the Superfund site or RCRA facility in question. PPRTVs are periodically
updated; therefore, users should ensure that the values contained in the PPRTV are current at the
time of use.
It is important to remember that a provisional value alone tells very little about the
adverse effects of a chemical or the quality of evidence on which the value is based. Therefore,
users are strongly encouraged to read the entire PPRTV manuscript and understand the strengths
and limitations of the derived provisional values. PPRTVs are developed by the EPA Office of
Research and Development's National Center for Environmental Assessment, Superfund Health
Risk Technical Support Center for OSRTI. Other EPA programs or external parties who may
choose of their own initiative to use these PPRTVs are advised that Superfund resources will not
generally be used to respond to challenges of PPRTVs used in a context outside of the Superfund
Program.
Questions Regarding PPRTVs
Questions regarding the contents of the PPRTVs and their appropriate use (e.g., on
chemicals not covered, or whether chemicals have pending IRIS toxicity values) may be directed
to the EPA Office of Research and Development's National Center for Environmental
Assessment, Superfund Health Risk Technical Support Center (513-569-7300), or OSRTI.
INTRODUCTION
A reference dose (RfD) for nitroglycerin (also known as trinitroglycerol) is not available
on the Integrated Risk Information System (IRIS) (U.S. EPA, 2006) or in the Health Effects
Assessment Summary Tables (HEAST) (U.S. EPA, 1997). The Drinking Water Standards and
Health Advisories list (U.S. EPA, 2004) does not include an RfD for nitroglycerin, but does
include 1-day, 10-day, and lifetime drinking water health advisories of 0.005 mg/L based on a
mean therapeutic dose of 0.005 mg/kg-day used for treatment of acute angina (U.S. EPA, 1987).
The Chemical Assessments and Related Activities (CARA) list (U.S. EPA, 1991, 1994) does not
include any other review documents for nitroglycerin. Neither the Agency for Toxic Substances
Disease and Registry (ATSDR) (2005), National Toxicology Program (NTP) (2005),
International Agency for Research on Cancer (IARC) (2005) nor the World Health Organization
(WHO) (2005) has produced any documents regarding nitroglycerin. Literature searches were
conducted from 1965 to July 2003 in TOXLINE (including NTIS and BIOSIS updates),
CANCERLIT, MEDLINE, CCRIS, GENETOX, HSDB, EMIC/EMICBACK,
DART/ETICBACK, RTECS and TSCATS. Update literature searches were performed in
August 2005 in MEDLINE, TOXLINE (NTIS subfile), TOXCENTER, TSCATS, CCRIS,
DART/ETIC, GENETOX, HSDB, RTECS and Current Contents.
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REVIEW OF PERTINENT LITERATURE
Human Studies
Contact with nitroglycerin can occur through occupational exposure in the explosives
industry or through its medical use as a vasodilator in the relief of angina pectoris. Adverse
effects caused by vasodilation include hypotension, reflex tachycardia, cardiac arrhythmias,
headache, dizziness and nausea. Key issues that must be considered in deriving toxicity values
for nitroglycerin are (1) acute vasodilation in persons exposed to nitroglycerin therapeutically as
discussed below or in combination with other compounds in the workplace, (2) the rapid
development of tolerance to the vasodilatory effects of nitroglycerin with repeated exposures
(therapeutic dosage regimens are designed to avoid continuous exposure to nitroglycerin and
include daily nitrate-free periods), (3) the lack of accumulation of nitroglycerin in the body due
to its short half-life, (4) the association of chronic exposure to the compound with organic nitrate
dependence, in which withdrawal from the treatment can cause severe rebound hypertension
leading to (occasionally fatal) heart attack and stroke in subjects who may have adapted to the
continuous presence of the compound to maintain optimum cardiovascular function and (5) the
potential for the compound to be associated with systemic toxicity as indicated by long-term
exposure studies in laboratory animals.
Therapeutic Use of Nitroglycerin
Aliphatic nitrates, such as nitroglycerin, have been used therapeutically for over 100
years in the treatment of myocardial ischemia (angina pectoris), providing an extensive clinical
experience (Kerins et al., 2001). Aliphatic nitrates are used to control angina pectoris because
exposure to them causes vasodilation, thereby, lowering blood pressure and reducing the cardiac
workload. The mechanism of vascular smooth muscle relaxation is brought about by the
generation of nitric oxide, a potent vasodilator (Katzung and Chatterjee, 2001; Kerins et al.,
2001; NIOSH, 1978). In developing treatment regimens, nitroglycerin and other aliphatic
nitrates are prescribed for intermittent use with dose levels established by the degree of relief
from symptoms afforded to the patient as the nitroglycerin amount is raised. This approach
reflects the rapid onset of the compound's pharmacological effects, rapid development of
tolerance and the marked individuality of response to treatment among different patients
(Abrams, 1980a).
Aliphatic nitrate compounds are administrated by the oral, sublingual, buccal, dermal and
intravenous routes. Sublingual administration is the preferred route for treatment of acute
anginal attacks, due to the rapid onset of action and avoidance of extraction of orally
administered nitroglycerin through hepatic metabolism. In clinical medicine, oral nitroglycerin
is used for long-term control of angina pectoris and is only administered as sustained- or
extended-release preparations designed to provide stable blood levels and therapeutic efficacy
for 6-8 hours (Katzung and Chatterjee, 2001). Based on data available in the clinical literature,
there is no information to determine the minimum effective dose of nitroglycerin. The lowest
available (i.e., marketed) single oral dose of sustained-release nitroglycerin is 2.5 mg (equivalent
to 0.036 mg/kg-day, assuming a typical body weight of 70 kg) with a recommended maximum
total daily oral dose of 38 mg/day (Katzung and Chatterjee, 2001; Kerins et al., 2001). Doses
administered by non-oral routes are generally lower than those used for oral administration since
non-oral routes avoid first pass metabolism. Due to the high first-pass hepatic extraction of
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orally administered nitroglycerin, extrapolation of dose-response relationships observed for
intravenous, sublingual, buccal or dermal routes cannot be readily extrapolated to the oral route.
Thus, only information pertaining to the oral route of administration is considered quantitatively
applicable to the development of an oral RfD.
Estimates of the oral bioavailability of nitroglycerin range from <1% (Kerins et al., 2001)
to <10-20% (Katzung and Chatterjee, 2001). Active metabolites of nitroglycerin (1,2- and 1,3-
dinitroglycerol) are responsible for some, if not all, of the vasodilatory effects following oral
administration since first-pass metabolism eliminates nearly all absorbed nitroglycerin before it
can be detected in the systemic blood (Kerins et al., 2001; Kwon et al., 1992). Compared to
nitroglycerin, the nitroglycerol metabolites appear to be less potent and longer-lived in the
plasma (Katzung and Chatterjee, 2001; Kerins et al., 2001). Plasma half-life estimates for the
dinitroglycerols range from 40 minutes (Kerins et al., 2001) to up to 3 hours (Katzung and
Chatterjee, 2001), compared to 2-9 minutes for nitroglycerin (Katzung and Chatterjee, 2001;
Kerins et al., 2001).
The extent of clearance of nitroglycerin administered orally was examined by Laufen and
Leitold (1988), who administered 20 mg of oral "sustained-release" nitroglycerin (Nitro Mack:
Retard) to six human volunteers. Nitroglycerin and its metabolites were measured in serial blood
samples taken between 10 minutes and 28 hours after dosing. No unchanged nitroglycerin was
observed in plasma, indicating the importance of first-pass metabolism in the clearance of this
compound from the circulation. Plasma concentrations of the mono- and dinitrate metabolites
peaked at about 5 hours. Kwon et al. (1992) used a similar experimental protocol to compare the
efficacy of sustained-release nitroglycerin versus oral solution or sublingual doses of
nitroglycerin. There were eight healthy volunteers who participated in a crossover study in
which the various dosings were separated by a 3-day "washout" phase. Serial blood samples
were collected at 10 minute intervals for the first 40 minutes then hourly to 12 hours and at 14,
16, 20 and 24 hours after dosing. Periodic measurements of blood pressure were also made
within the same time frame. Unchanged nitroglycerin was detected in blood after sublingual
dosing, but not after the oral dosing, confirming the rapid and near-total clearance of
nitroglycerin from the circulation after oral dosing. Kwon et al. (1992) found higher levels of
1,2-glyceryl dinitrate in the blood compared with the 1,3-isomer. The absence of unchanged
nitroglycerin in the systemic circulation after oral dosing with nitroglycerin reported by Laufen
and Leitold (1988) and Kwon et al. (1992) has been interpreted as evidence that the metabolites
of nitroglycerin contribute to, and possibly account for, all the pharmacological activity of
orally-administered nitroglycerin.
At therapeutic doses, regardless of the route of administration, adverse effects of
nitroglycerin result from non-specific vasodilation, and include hypotension, reflex tachycardia,
cardiac arrhythmias, headache, dizziness and nausea. Headache is commonly reported by
patients treated with aliphatic nitrates and can be severe (Kerins et al. 2001). Effects can range
in intensity from mild to severe, depending upon dose and individual susceptibility (Kerins et al.,
2001). When nitroglycerin is administrated repeatedly, tolerance develops to the vasodilatory
effect, leading to reduced therapeutic efficacy and a lessening of adverse effects (Abrams,
1980a). Due to the rapid development of tolerance, therapeutic dosage regimens are designed to
avoid continuous daily exposure by providing a daily nitrate-free period of 8-12 hours (Kerins et
al., 2001; Abrams, 2002). With an elimination half-time estimated to be approximately 2-9
minutes (Kerins et al., 2001), the nitrate-free interval is sufficiently long for essentially all
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nitroglycerin to be eliminated from the body. Since tolerance reverses rapidly following a
nitrate-free period, adverse effects associated with vasodilation redevelop upon subsequent
exposures. The phenomenon of repeated redevelopment of acute adverse effects following short
nitrate-free periods has been described for therapeutic (Katzung and Chatteijee, 2001; Kerins et
al., 2001) and occupational (Daum, 1983) exposures to nitroglycerin. Attempts to overcome
tolerance by dose escalation have consistently failed, with therapeutic efficacy restored only after
nitrates are absent from the body for several hours (Kerins et al., 2001).
Nitroglycerin also has the capacity to cause dependence, whereby cessation of repeated
exposure can cause rebound vasoconstriction that may be severe, leading to the development of
hypertension, angina, weakness, palpitations, coronary artery vasospasm, difficulty in breathing
and, in some cases, death (Abrams, 1980b; Daum, 1983; Kerins et al., 2001). For therapeutic use
of nitroglycerin, rebound vasoconstriction is most commonly associated with continuous
intravenous infusion over several days (Kerins et al., 2001).
The clinical experience with nitroglycerin is that methemoglobinemia can occur, but only
at doses higher than those used in the treatment of cardiovascular diseases (Katzung and
Chatteijee, 2001). Therapeutic doses of nitroglycerin were not associated with the development
of methemoglobinemia following sublingual administration to healthy volunteers (Paris et al.,
1986) or intravenous infusion to patients (Kaplan et al., 1985). Intravenous infusion of
nitroglycerin to patients at rates approximately 10-fold higher than the recommended infusion
rate of 5 |ig/hr (Kerins et al., 2001) resulted in development of slight methemoglobinemia
(Gibson et al., 1982; Husum et al., 1982). Although studies specifically investigating the ability
of oral nitroglycerin to induce methemoglobinemia were not identified from the published
literature, clinical studies using the sublingual and intravenous routes suggest that
methemoglobinemia is only observed at nitroglycerin doses greater than those used
therapeutically.
Occupational Exposure
Additional information on human exposure to nitroglycerin via the inhalation route is
available from studies on occupationally exposed workers in the explosives industry (Abrams,
1980a; Craig et al., 1985; Daum, 1983; Kristensen, 1989). The findings of these studies
demonstrate the importance of the development of rebound vasoconstriction in workers whose
normally elevated organic nitrate body burden becomes depleted during a brief period of absence
(1-2 days) from the workplace. The well-documented phenomenon of "Monday Morning
Death" has been described for munitions workers in whom cardiovascular events can be
triggered by unrestrained compensatory vasoconstriction as the organic nitrate in the body
becomes reduced (Abrams, 1980a). Incidence of sudden death in such persons is up to 15 times
the expected rate (Daum, 1983). Kristensen (1989) discussed an apparent double effect of
nitroglycerin in cardiovascular disease, where the incidence of "Monday Morning Death" was
compounded by an apparently increased risk of heart attack and stroke that continued in
chronically exposed subjects long after the cessation of exposure.
Craig et al. (1985) carried out a death certificate study of persons who had been
employed at an explosives factory in Scotland. The investigation covered the time period 1965
to 1980 and compared the causes of death of potentially exposed workers with internal controls
(unexposed workers at the same factory) and members of the general male population. Blasting
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workers (exposed to nitroglycerin and ethylene glycol dinitrate) and propellant workers (exposed
to nitroglycerin alone) were stratified by age and then by high- and low-exposure subcategories,
depending on the position of their work station or the nature of their duties. Causes of death for
each target group included acute myocardial infarction (MI), ischemic heart disease (IHD),
cerebrovascular disease, lung cancer, cancer of the colon or rectum and all cancers. Among the
non-cancer related responses, there was an increased risk of MI and IHD in the 15-49 age-group
of high-exposure blasting workers compared with internal controls or with members of the
general population, with six deaths observed in the high-exposure blasting group compared to
three expected deaths. However, these findings do not necessarily implicate nitroglycerin as no
effect was reported among propellant workers exposed to nitroglycerin alone.
Animal Studies
Ellis et al. (1984) conducted a chronic toxicity study with nitroglycerin in dogs, rats and
mice. In this study, beagle dogs (6/sex/group) were administered daily capsules that provided
doses of 0, 1, 5 or 25 mg nitroglycerin/kg-day for 12 months. Groups of CD rats (38/sex/group)
and CD-I mice (58/sex/group) were fed diets containing 0, 0.01, 0.1 or 1% nitroglycerin for up
to 24 months. The intakes of nitroglycerin estimated by the investigators for male and female
rats, respectively, in the treated groups were 3.04 and 3.99 mg/kg-day, 31.5 and 38.1 mg/kg-day
and 363 and 434 mg/kg-day. For mice, the nitroglycerin intakes for male and females,
respectively, in the treated groups were 11.1 and 9.72 mg/kg-day, 114.6 and 96.4 mg/kg-day and
1022 and 1058 mg/kg-day. During the first several weeks of exposure all animals were observed
daily for clinical signs of toxicity, with none observed. Animals were not assessed for
vasodilatory effects. Since all animals were sacrificed at the end of the exposure period, the
potential for the development of cardiovascular dependence and associated morbidity and
mortality could not be evaluated.
The only effect observed in dogs during the 12 months of treatment (Ellis et al., 1984)
was occasional minimal methemoglobinemia, usually less than 3% (values for control dogs were
not provided). The incidence of methemoglobinemia was reported to be dose-related and was
apparently present to some extent in all treated groups (data not shown). No adverse effects
were observed in dogs regarding body weights, clinical chemistry parameters and gross or
microscopic appearance of organs and tissues. The dose level of 25 mg nitroglycerin/kg-day can
be considered a minimal effective level for methemoglobineamia for dogs in a long-term oral
study.
In rats, body weight gain and final body weight were significantly reduced in the high-
dose groups (Ellis et al., 1984). Significantly reduced food consumption in high-dose rats of
both sexes was apparent during the first 3 weeks of the study and in females throughout the
study. Unscheduled deaths occurred in all groups and were mainly due to pituitary adenomas,
ulcerated subcutaneous tumors and other causes not specified. High-dose females survived
significantly longer than control females, which could possibly be attributed to reduced
incidence of mammary and pituitary tumors in the high dose group compared to other exposure
groups. Changes in clinical chemistry and hematology parameters, monitored throughout the
study, were restricted to the high-dose groups and included methemoglobinemia (10-30%,
normal is <1%) and compensatory reticulocytosis, increased erythrocyte count, hematocrit and
hemoglobin indicated hemoconcentration. In addition, high-dose males had elevated serum
ALT, AST and alkaline phosphatase levels, suggesting hepatocellular damage and cholestasis.
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Histopathologic effects were evident after 12 months of feeding in high-dose rats and consisted
of increased absolute and relative liver weight, cholangiofibrosis, proliferation of the bile ducts
and increased pigmentation of the spleen and kidney epithelium. Lesions observed in rats killed
after 24 months of treatment were similar to those seen at 12 months, but with higher incidence
and severity. Further details regarding other tissues were not provided. For rats, the high dose of
363 mg/kg-day is considered a LOAEL for hematological and hepatic effects and 31.5 mg/kg-
day a NOAEL in this chronic study.
In mice, food consumption in the high-dose groups was reduced during the first week, but
subsequently recovered (Ellis et al., 1984). Nevertheless, body weight in the high-dose groups
was reduced throughout the study. Mortality did not differ significantly between control and
treated groups of mice. After 12 months, high-dose mice had a compensated anemia (normal
erythrocyte count, elevated reticulocyte count and Heinz bodies); high-dose males also had
methemoglobinemia. The only nitroglycerin-related alteration seen in organs and tissues was
hyperpigmentation in the liver, spleen and kidney in most high-dose mice and in some mid-dose
mice. Lesions observed after 24 months of treatment were similar to those observed after 12
months; further details were not provided. The dose of 1022 mg/kg-day is considered a LOAEL
for hematological effects in mice and the dose of 96.4 mg/kg-day is a NOAEL.
Ellis et al. (1984) also conducted a 13-week subchronic toxicity study in dogs, rats and
mice. Beagle dogs (6/sex/dose level) were administered nitroglycerin in capsules to provide time
weighted average (TWA) doses of 0, 0.04, 0.4 or 4 mg nitroglycerin/kg-day over a period of 13
weeks. Male CD rats (6/dose level) received TWA dietary doses of 0, 1.6, 17.3 or 164 mg
nitroglycerin/kg-day, whereas females (6/dose level) were given 0, 1.9, 18.7 or 167 mg
nitroglycerin/kg-day. Male CD-I mice (6/dose level) were treated with 0, 5.2, 49 or 476 mg
nitroglycerin/kg-day TWA, and females with 0, 5.6, 47.6 or 453 mg nitroglycerin/kg-day. Blood
samples were taken from the dogs at several intervals during the study and from rats and mice at
termination. All major organs and tissues of the three species were examined for gross lesions
and processed for light microscopy. No adverse effects were observed in dogs. The only
treatment-related effect observed in rats was reduced body weight gain (statistical significance
not provided), and this was observed only in high-dose groups. No adverse effects were
observed in mice other than mild to moderate extramedullary hematopoiesis in the liver and/or
spleen; however, the incidence and severity of the lesion was not dose-related.
As part of the same study, Ellis et al. (1984) fed CD rats (3/sex/group) a diet containing 0
or 2.5% nitroglycerin for 13 weeks. This diet provided doses (estimated by the investigators) of
1406 mg nitroglycerin/kg-day for males and 1416 mg nitroglycerin/kg-day for females. A
significant reduction in food consumption and body weight was observed in treated rats during
the first 8 weeks; this resulted in a significant reduction in final body weight. Treatment with
nitroglycerin induced significant increases in erythrocytes, reticulocytes, hematocrit, hemoglobin
concentration and alkaline phosphatase and a decrease in fasting blood glucose; no
methemoglobin was detected. Histopathological observations revealed the presence of pigment
deposits in the liver and spleen and moderate to severe testicular degeneration and/or atrophy
with severe-to-complete aspermatogenesis. No other effects were reported.
In 4-week short-term studies (Ellis et al., 1984), five consecutive doses of 25, 50, 100 or
200 mg nitroglycerin/kg-day, given to dogs (6/sex/dose), produced transient dose-related
increases in methemoglobin. Serial determinations of methemoglobin for 24 hours after each
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dose showed that the duration of methemoglobinemia was also dose-related. No other endpoints
were examined.
Earlier studies in rats and mice found no effects of chronic exposure to nitroglycerin.
Groups of 50 male and 48 female 8-week-old Sprague Dawley rats were given drinking water
containing 0.03% nitroglycerin (31 mg/kg-day, as estimated by the researchers) for 10 months,
followed by plain tap water for an additional 8 months, at which time survivors were sacrificed
for necropsy, hematology and serum chemistry (5/sex), organ weight measurements and
histopathological examination of a wide range of tissues (Takayama, 1975). A control group of
53 male and 49 female rats provided with plain tap water for the entire 18-month experimental
period was similarly examined at termination. Mortality due to pneumonia claimed 38 male and
23 female rats in the treated group and 36 male and 32 female control rats during the experiment.
Treatment had no effect on survival, behavior, general physical appearance or body weight.
There were no treatment-related effects on hematological parameters or on several serum
chemistry tests to detect impaired function of, or damage to, the liver and kidney;
methemoglobinemia was not evaluated. There were no effects on organ weights in the treated or
control rats surviving to 18 months. Treatment with nitroglycerin had no effect on incidence of
non-neoplastic lesions or tumors. The tested dose of 31 mg/kg-day is a NOAEL in this study,
but interpretation of the study is limited by high mortality in all groups, failure to include
additional dose levels and the long recovery period between the end of treatment and toxicology
evaluation. Although the treatment-free recovery period would allow for observations regarding
the potential for nitroglycerin-induced dependence and rebound vasoconstriction, this was not
evaluated.
Suzuki et al. (1975) provided 4-week-old C57BL/6Jms mice with drinking water in
which was dissolved 0, 10, 40 or 330 mg/L nitroglycerin in saline (doses of 0, 1.5, 6.2 and 58.1
mg/kg-day estimated by the researchers). The high-dose mice (49 males and 45 females)
received nitroglycerin for 52 weeks followed by control drinking water for an additional 28
weeks. The mid-dose (66 males and 49 females), low-dose (54 males and 50 females) and
control (60 male and 63 females) groups received appropriate concentrations of nitroglycerin for
the entire 80-week experimental period. The mice were subjected to necropsy and
histopathological examination of heart, liver, kidney, spleen, bone marrow and all gross lesions.
There were no clearly treatment-related effects on behavior or general appearance. The body
weights of high-dose mice of both sexes were below their respective controls starting at about
13-14 months, but statistical analyses were not performed and the difference from controls was
less than 10%. The investigators noted that a higher incidence of early mortality (30-40 weeks
of treatment) occurred in the high-dose females compared with controls, but the effect appeared
to be slight and statistical analysis was not performed. Histopathologic examination revealed no
treatment related noncarcinogenic effects. The high dose of 58.1 mg/kg-day is a NOAEL in this
study. The study was limited by the long recovery period between the end of treatment and
toxicology evaluation in the high-dose group and failure to find an effect level. Although the
treatment-free recovery period would allow for observations regarding the potential for
nitroglycerin-induced dependence and rebound vasoconstriction, this was not evaluated.
Wang and Fung (2002) measured arterial pressure in exposed obese and normal SD rats
(1 and 10 |ig/min) challenged hourly with 30 |ig nitroglycerin via intravenous route. They
neither observed any development of nitroglycerin tolerance or changes in hemodynamic effects.
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Information on the developmental and reproductive toxicity of nitroglycerin is limited to
an oral 3-generation reproduction study in animals (Ellis et al., 1978, as discussed in U.S. EPA,
1987) and several studies involving parenteral administration of nitroglycerin (Oketani et al.,
1981a,b,c,d; Yallampalli and Garfield, 1993). In the 3-generation reproduction study (Ellis et al.,
1978), groups of male and female rats were fed diets containing 0, 0.01, 0.1 or 1.0%
nitroglycerin (the authors estimated the doses to be 0, 3.04, 31.5 and 363 mg/kg-day for males
and 0, 3.99, 31.5 and 434 mg/kg-day for females). For the parental generation, groups of 10
male and 20 female rats were exposed to nitroglycerin for 6 months prior to mating and during
gestation and lactation of two litters. Groups of Fib rats (10-12 pairs) were fed the nitroglycerin
diet during growth, mating, gestation and lactation. Groups of F2b rats were similarly treated.
No effects on fertility were observed in the F0 rats. Severely impaired fertility was observed in
the high-dose Fi groups, attributed to aspermatogenesis with increased interstitial tissue in the
testes and significantly smaller testicular size in the high-dose males. Litter size, live-born
index, birth weight, viability and lactation indices were decreased in the Fia, Fib and F2a offspring
of the high-dose group. The authors attributed these effects to a marked decrease in food intake
(65% lower than controls for the F0 females) and body weight (81% lower than controls for the
F0 females) in the dams. The marked reduction in food consumption may be attributed to taste
aversion; thus contributing to smaller testicular size and impaired fertility.
Oketani et al. (1981a,b) observed no adverse developmental effects (fetal and postnatal
development, fertility of offspring, incidences of external, visceral or skeletal abnormalities) in
the offspring of rats treated intraperitoneally with doses of 1, 10 or 20 mg/kg-day nitroglycerin
on gestation days 7-17 (Oketani et al., 1981a) or on gestation day 17 through lactation day 21
(Oketani et al., 1981b). The authors noted that a transient convulsion or sedation was
occasionally observed in the dams treated with 20 mg/kg-day nitroglycerin. No developmental
effects (pup mortality or pup size) were reported in rats administered 240 or 480 |ig/day
nitroglycerin via an osmotic pump (0.8 or 1.5 mg/kg-day using the initial body weight of 0.312
kg) on gestation days 17-22 (Yallampalli and Garfield, 1993). No developmental effects were
observed in rabbits intravenously administered 0.5, 1 or 4 mg/kg-day nitroglycerin on gestation
days 6-18. Transient convulsions were observed in the does treated with 4 mg/kg-day (Oketani
et al., 1981c).
In a reproduction study conducted by Oketani et al. (1981d), groups of male and female
rats received intraperitoneal doses of 1, 10 or 20 mg/kg-day nitroglycerin. The male rats were
dosed for 63 days prior to mating and the female rats were dosed for 14 days prior to mating and
during gestation days 0-7. A transient convulsion or sedation was occasionally observed in rats
administered 20 mg/kg-day. No adverse effects on mating, fertility or reproductive indices (no
details provided) were observed. In addition, no developmental effects were observed in the
offspring.
DERIVATION OF A PROVISIONAL RfD FOR NITROGLYCERIN
It is generally accepted that the adverse effects associated with therapeutic and
occupational exposure to nitroglycerin are secondary to actions on the cardiovascular system,
with vasodilation as the initiating event (Kerins et al., 2001). Therefore, vasodilation is
considered as the critical effect upon which to base the RfD. Adverse effects of concern from
nitroglycerin for all routes of exposure include hypotension, reflex tachycardia, cardiac
9

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arrhythmias, headache, dizziness, nausea and vomiting. Effects can range in intensity from mild
to severe, depending upon dose and individual susceptibility (Kerins et al., 2001). An additional
concern associated with nitroglycerin-induced vasodilation is the development of organic nitrate
dependence, whereby constant exposure is required to maintain optimum cardiovascular
function. Upon rapid withdrawal from exposure in adapted individuals, severe rebound
hypertension leading to heart attack and stroke can result, as reported in munitions workers
(Daum, 1983). Dependence to organic nitrates can develop within days of exposure (Katzung
and Chatterjee, 2001; Kerins et al., 2001) but may also develop following a more prolonged
exposure duration (Daum, 1983). At exposure levels below those causing acute vasodilation,
acute adverse effects (e.g., headache, hypotension) and dependence are not expected to develop.
Furthermore, due to rapid elimination of nitroglycerin and the active dinitroglycerol metabolites,
bioaccumulation is not expected in long-term/chronic exposure, thus eliminating the possibility
of cumulative damage to the target organ(s).
Due to their rapid elimination (2-9 minutes for nitroglycerin and 40 minutes to 3 hours
for the dinitroglycerol metabolites), nitroglycerin and the dinitroglycerol metabolites do not
accumulate in the body. In practical terms, this means that the adverse effect level (for
vasodilatory-related effects) for subchronic and chronic exposure will be no lower than the
adverse effect level for acute exposure. For this reason, a subchronic and chronic p-RfD can be
derived based on the acute dose-response information. Therefore, a p-RfD based on acute
vasodilation is applicable to subchronic and chronic exposures.
A substantial amount of information exists regarding the effects of nitroglycerin in
humans due to its therapeutic use and in the manufacturing of explosives. Since nitroglycerin
has a short half-life (3-9 minutes) and quantitative data for continuous occupational exposure in
epidemiological studies are inadequate, these studies were not used as a basis for the derivation
of toxicity values. In general, these studies lack data regarding exposure levels and duration of
exposure as well as information on confounding factors such as health history and life style of
the subjects. Simultaneous exposure to other chemicals, as in the case of workers in the
manufacturing of dynamite, is an additional confounding factor.
In clinical medicine, oral nitroglycerin is used for long-term control of angina pectoris
and is only administered as sustained- or extended-release preparations designed to provide
stable blood levels and therapeutic efficacy for 6-8 hours (Katzung and Chatterjee, 2001). The
lowest prescribed single oral dose of sustained-release nitroglycerin is 2.5 mg (equivalent to
0.036 mg/kg-day, assuming a typical body weight of 70 kg) with a recommended maximum total
daily oral dose of 38 mg/day (Katzung and Chatterjee, 2001; Kerins et al., 2001). Therapeutic
exposure to oral sustained-release nitroglycerin is similar to the conditions of occupational
exposure, in which daily exposure occurs over the course of the workday. When administered
by the sublingual route, lower doses of nitroglycerin (0.15-1.2 mg) are effective in controlling
acute angina (Katzung and Chatterjee, 2001). However, due to differences in the
pharmacokinetics of nitroglycerin administered by the oral and sublingual routes (e.g., no first
pass metabolism following sublingual administration), sublingual exposure is not considered
relevant to the quantitative development of an RfD for oral exposure.
The lowest prescribed therapeutic oral dose of 0.036 mg/kg-day is associated with
adverse effects caused by vasodilation (Katzung and Chatterjee, 2001; Kerins et al., 2001).
Since no information on the dose-response relationship for oral nitroglycerin was identified in
10

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the published literature, the RfD is based on the lowest prescribed oral dose of 0.036 mg/kg-day,
which is considered the LOAEL for vasodilation. No evidence is available from the clinical
literature to suggest that chronic exposure to therapeutic doses of nitroglycerin by any route of
administration results in toxicity to the liver or other organs, as shown in subchronic and chronic
exposure studies in laboratory animals (Ellis et al., 1984). It is possible that toxicity to other
organs (liver) in humans may occur at higher doses than those which produce vasodilation,
which is consistent with the relatively high NOAELs and LOAELs for hepatic toxicity in
animals. However, due to the severity of acute adverse effects associated with vasodilation,
clinical studies in humans have not explored the potential adverse effects of high-dose
nitroglycerin in humans. Dosages necessary to cause methemoglobinemia observed in
occupational studies are much greater than those causing vasodilation (Katzung and Chatteijee,
2001). Furthermore, tolerance dosage, which could trigger angina or a myocardial infarction in a
sensitive individual with cardiovascular disease, appears to be higher. Thus, an RfD based on
the lowest prescribed oral therapeutic dose would be considered protective for the development
of methemoglobinemia.
The NOAEL of 31.5 mg nitroglycerin/kg-day for methemoglobinemia and liver effects
from the chronic oral study conducted by Ellis et al. (1984) in rats was not considered as a basis
for the RfD since vasodilatory-related adverse effects in humans occur at doses approximately
1000 times lower than the rat NOAEL. The available animal studies did not examine
vasodilation as an endpoint, so it is possible that vasodilation-related adverse effects occurred at
lower exposure levels than methemoglobinemia and liver effects.
The subchronic and chronic p-RfD for nitroglycerin was derived from the LOAEL of
0.036 mg/kg-day for acute adverse effects related to vasodilation as follows:
p-RfD = LOAEL -h UF
= 0.036 mg/kg-day -^300
= 1E-4 mg/kg-day (0.12 |ig/kg-day)
Dividing the LOAEL of 0.036 mg/kg-day by an uncertainty factor of 300 yields a p-RfD
of 1E-4 mg/kg-day (0.12 |ig/kg-day). The uncertainty factor of 300 is composed of factors of
10 for use of a LOAEL for potentially serious adverse effects, 3 for incomplete database
(absence of dose-response data) and 10 to account for human variability, including sensitive
subgroups (individuals with cardiovascular diseases such as hypertension, angina, congestive
heart failure, children with inadequate MFO or metabolic activity and cardiac arrhythmias).
Although this p-RfD is based on the acute vasodilatory effects of nitroglycerin, adverse effects
related to vasodilation will not occur over the course of subchronic and chronic exposures. Thus,
the p-RfD based on acute effects is considered protective for subchronic and chronic exposures
to nitroglycerin.
Confidence in the LOAEL value for vasodilation is low-to-medium. The LOAEL value
for vasodilation in humans is based on the lowest prescribed oral dose used for the therapeutic
control of angina pectoris in patients. Dose-response data for oral nitroglycerin were not
available. It is possible that vasodilation leading to adverse effects in patients and healthy
individuals may occur at lower oral exposure levels. Although organic nitrates have been used
for over 100 years in the treatment of cardiovascular diseases and clinical experience does not
suggest that significant adverse effects other than those related to vasodilation will results from
11

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chronic exposure, controlled studies evaluating the effects of chronic exposure in humans have
not been published. Low-to-medium confidence in the provisional RfD results.
REFERENCES
Abrams, J. 1980a. Nitrate tolerance and dependence. Am. Heart J. 99:113-123.
Abrams, J. 1980b. Nitroglycerin and long-acting nitrates. N. Eng. J. Med. 203:1234-1237.
Abrams, J. 2002. How to use nitrates. Cardiovasc. Drugs Ther. 16:511-514.
ATSDR (Agency for Toxic Substances and Disease Registry). 2005. Toxicological Profile
Information Sheet. Available at http://www.atsdr.cdc.gov/toxpro2.html.
Craig, R., C.R. Gillis, C.D. Hole and G.M. Paddle. 1985. Sixteen year follow up of workers in
an explosives factory. J. Soc. Occup. Med. 35:107-110.
Daum, S. 1983. Nitroglycerin and alkyl nitrates. In: Environmental and Occupational
Medicine. W.M. Rom, Ed. Little, Brown and Co., Boston, p. 639-648.
Ellis III, H.V. et al. 1978. Mammalian toxicity of munitions compounds. Phase III: Effects of
life-time exposure Part II: Trinitroglycerin. Progress Report No. 8. Midwest Research Institute,
Kansas City, MO, Contract No. DAMD-17-74-C-4073. AD A078746. (Cited in U.S. EPA,
1987)
Ellis III, H.V., C.B. Hong, C.C. Lee et al. 1984. Subacute and chronic toxicity studies of
trinitroglycerin in dogs, rats and mice. Fund. Appl. Toxicol. 4: 248-260.
Gibson, G.R., J. B. Hunter, D.S. Raabe, D.L. Manjoney and F.P. Ittleman. 1982.
Methemoglobinemia produced by high-dose intravenous nitroglycerin. Ann.Int. Med.
96(5):615-616.
Husum, B., T. Lindenburg and E. Jaconsen. 1982. Methemoglobinemia formation after
nitroglycerin infusion. Br. J. Aneasth. 54:571.
IARC (International Agency for Research on Cancer). 2005. IARC Agents and Summary
Evaluations. Available at http://www-cie.iarc.fr/htdig/search.html.
Kaplan, K.J., M. Taber, J.R. Teagarden, M. Parker and R. Davison. 1985. Association of
methemoglobinemia and intravenous nitroglycerin administration. A, J. Cardiol. 55:181-183.
Katzung, B.G. and K. Chatterjee. 2001. Vasodilators and the treatment of angina pectoris. In:
Basic & Clinical Pharmacology. B.G. Katzung, Ed. Lange Medical Blooks/McGraw-Hill
Companies, Inc., Medical Publishing Division, New York.
Kerins, D.M., R.M. Robertson and D. Robertson. 2001. Drugs used for the treatment of
myocardial ischemia. In: Goodman and Gilman's The Pharmacological Basis of Therpeutics.
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J.G. Hardman, L.E. Limbird, and A.G. Gilman Eds. McGraw-Hill Companies, Inc., Medical
Publishing Division, New York.
Kristensen, T.S. 1989. Cardiovascular diseases and the work environment. Scand. J. Work
Environ. Health. 15: 245-264.
Kwon, H-R., P. Green and S.H. Curry. 1992. Pharmacokinetics of nitroglycerin and its
metabolites after administration of sustained-release tablets. Biopharm. Drug Dispos.
13: 141-152.
Laufen, H. and M. Leitold. 1988. The pattern of glyceryl nitrates after oral administration of
glyceryl trinitrate. Arzneim.-Forsh./Drug Res. 38:103-105.
NIOSH (National Institute for Occupational Safety and Health). 1978. Criteria for a
Recommended Standard. Occupational Exposure to Nitroglycerin and Ethylene Glycol
Dinitrate. DHEW (NIOSH) Publication No. 78-167. U.S. Department of Health, Education and
Welfare, Washington, DC.
NTP (National Toxicology Program). 2005. Management Status Report. Available at
http://ntp-server.niehs.nih.gov/cgi/iH Indexes/ALL SRCH/iH ALL SRCH Frames.html.
Oketani, Y., T. Mitsuzono, K. Ichikawa et al. 1981a. Toxicological studies on nitroglycerin
(NK-843). 8. Teratological study in rats. Oyo. Yakuri. 22: 737-751. [Chem. Abstr. 96: 210627t
(1982)]
Oketani, Y., T. Mitsuzono, K. Ichikawa et al. 1981b. Toxicological studies on nitroglycerin
(NK-843). 9. Perinatal and postnatal study in rats. Oyo. Yakuri. 22: 753-763. [Chem. Abstr.
96: 210628u (1982)]
Oketani, Y., T. Mitsuzono, K. Ichikawa et al. 1981c. Toxicological studies on nitroglycerin
(NK-843). 6. Teratological study in rabbits. Oyo. Yakuri. 22: 633-638. [Chem. Abstr.
96:115735t (1982)]
Oketani, Y., T. Mitsuzono, Y. Itono et al. 198Id. Toxicological studies on nitroglycerin (NK-
843). 7. Fertility studies in rats. Oyo. Yakuri. 22:639-648. [Chem. Abstr. 96: 115736u (1982)]
Paris, P.M., R.M. Kaplan, R.D. Stewart and L.D. Weiss. 1986. Methemoglobinemia levels
following sublingual nitroglycerin in human volunteers. Ann. Em erg. Med. 15:171-173.
Suzuki, K, K. Sudo, T. Yamamoto and K. Hashimoto. 1975. The carcinogenicity of N-
ethyoxycarbonyl-3-morpholinosydnonimine (Molsidomine) in comparison with nitroglycerin in
C57BL/6Jms mice. Pharmacometrics. 9(2): 229-242.
Takayama, S. 1975. Carcinogenicity of molsidomine and nitroglycerin in rats.
Pharmacometrics. 9(2): 217-228.
U.S. EPA. 1987. Health Advisory for Trinitroglycerol. Office of Drinking Water, Washington,
DC. NTIS PB90-273558.
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U.S. EPA. 1991. Chemical Assessments and Related Activities (CARA). Office of Health and
Environmental Assessment, Washington, DC. April.
U.S. EPA. 1994. Chemical Assessments and Related Activities (CARA). Office of Health and
Environmental Assessment, Washington, DC. December.
U.S. EPA. 1997. Health Effects Assessment Summary Tables. FY-1997 Update. Prepared by
the Office of Research and Development, National Center for Environmental Assessment,
Cincinnati, OH, for the Office of Emergency and Remedial Response, Washington, DC. July.
EPA/540/R-97/036. NTIS PB 97-921199.
U.S. EPA. 2004. 2004 Edition of the Drinking Water Standards and Health Advisories. Office
of Water, Washington, DC. EPA 822-R-02-038. Available at
http://www.epa.gov/waterscience/drinking/standards/dwstandards.pdf.
U.S. EPA. 2006. Integrated Risk Information System (IRIS). Office of Research and
Development, National Center for Environmental Assessment, Washington, DC. Available at
http://www.epa.gov/iris/.
Wang, E.O. and H.L. Fung. 2002. Effects of obesity on the pharmacodynamics of nitroglycerin
in conscious rats. AAPS Pharmsci. 4:1208-1219.
WHO (World Health Organization). 2005. Online Catalogs for the Environmental Criteria
Series. Available at http://www.who.int/dsa/cat98/zehc.htm.
Yallampalli, C. and R.E. Garfield. 1993. Inhibition of nitric oxide synthesis in rats during
pregnancy produces signs similar to those of preeclampsia. Am. J. Obstet. Gynecol. 169:1316-
1320.
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Provisional Peer Reviewed Toxicity Values for
Nitroglycerin
(CASRN 55-63-0)
Derivation of Subchronic and Chronic Inhalation RfCs
Superfund Health Risk Technical Support Center
National Center for Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268

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Acronyms and Abbreviations
bw	body weight
cc	cubic centimeters
CD	Caesarean Delivered
CERCLA	Comprehensive Environmental Response, Compensation and Liability Act
of 1980
CNS	central nervous system
cu.m	cubic meter
DWEL	Drinking Water Equivalent Level
FEL	frank-effect level
FIFRA	Federal Insecticide, Fungicide, and Rodenticide Act
g	grams
GI	gastrointestinal
HEC	human equivalent concentration
Hgb	hemoglobin
i.m.	intramuscular
i.p.	intraperitoneal
i.v.	intravenous
IRIS	Integrated Risk Information System
IUR	inhalation unit risk
kg	kilogram
L	liter
LEL	lowest-effect level
LOAEL	lowest-observed-adverse-effect level
LOAEL(ADJ)	LOAEL adjusted to continuous exposure duration
LOAEL(HEC)	LOAEL adjusted for dosimetric differences across species to a human
m	meter
MCL	maximum contaminant level
MCLG	maximum contaminant level goal
MF	modifying factor
mg	milligram
mg/kg	milligrams per kilogram
mg/L	milligrams per liter
MRL	minimal risk level
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MTD
maximum tolerated dose
MTL
median threshold limit
NAAQS
National Ambient Air Quality Standards
NOAEL
no-observed-adverse-effect level
NOAEL(ADJ)
NOAEL adjusted to continuous exposure duration
NOAEL(HEC)
NOAEL adjusted for dosimetric differences across species to a human
NOEL
no-observed-effect level
OSF
oral slope factor
p-IUR
provisional inhalation unit risk
p-OSF
provisional oral slope factor
p-RfC
provisional inhalation reference concentration
p-RfD
provisional oral reference dose
PBPK
physiologically based pharmacokinetic
PPb
parts per billion
ppm
parts per million
PPRTV
Provisional Peer Reviewed Toxicity Value
RBC
red blood cell(s)
RCRA
Resource Conservation and Recovery Act
RDDR
Regional deposited dose ratio (for the indicated lung region)
REL
relative exposure level
RfC
inhalation reference concentration
RfD
oral reference dose
RGDR
Regional gas dose ratio (for the indicated lung region)
s.c.
subcutaneous
SCE
sister chromatid exchange
SDWA
Safe Drinking Water Act
sq.cm.
square centimeters
TSCA
Toxic Substances Control Act
UF
uncertainty factor
Hg
microgram
|j,mol
micromoles
voc
volatile organic compound
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PROVISIONAL PEER REVIEWED TOXICITY VALUES FOR
NITROGLYCERIN (CASRN 55-63-0)
Derivation of Subchronic and Chronic Inhalation RfCs
Background
On December 5, 2003, the U.S. Environmental Protection Agency's (EPA's) Office of
Superfund Remediation and Technology Innovation (OSRTI) revised its hierarchy of human
health toxicity values for Superfund risk assessments, establishing the following three tiers as the
new hierarchy:
1.	EPA's Integrated Risk Information System (IRIS).
2.	Provisional Peer-Reviewed Toxicity Values (PPRTV) used in EPA's Superfund
Program.
3.	Other (peer-reviewed) toxicity values, including:
~	Minimal Risk Levels produced by the Agency for Toxic Substances and Disease
Registry (ATSDR),
~	California Environmental Protection Agency (CalEPA) values, and
~	EPA Health Effects Assessment Summary Table (HEAST) values.
A PPRTV is defined as a toxicity value derived for use in the Superfund Program when
such a value is not available in EPA's Integrated Risk Information System (IRIS). PPRTVs are
developed according to a Standard Operating Procedure (SOP) and are derived after a review of
the relevant scientific literature using the same methods, sources of data, and Agency guidance
for value derivation generally used by the EPA IRIS Program. All provisional toxicity values
receive internal review by two EPA scientists and external peer review by three independently
selected scientific experts. PPRTVs differ from IRIS values in that PPRTVs do not receive the
multi-program consensus review provided for IRIS values. This is because IRIS values are
generally intended to be used in all EPA programs, while PPRTVs are developed specifically for
the Superfund Program.
Because science and available information evolve, PPRTVs are initially derived with a
three-year life-cycle. However, EPA Regions (or the EPA HQ Superfund Program) sometimes
request that a frequently used PPRTV be reassessed. Once an IRIS value for a specific chemical
becomes available for Agency review, the analogous PPRTV for that same chemical is retired. It
should also be noted that some PPRTV manuscripts conclude that a PPRTV cannot be derived
based on inadequate data.
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Disclaimers
Users of this document should first check to see if any IRIS values exist for the chemical
of concern before proceeding to use a PPRTV. If no IRIS value is available, staff in the regional
Superfund and RCRA program offices are advised to carefully review the information provided
in this document to ensure that the PPRTVs used are appropriate for the types of exposures and
circumstances at the Superfund site or RCRA facility in question. PPRTVs are periodically
updated; therefore, users should ensure that the values contained in the PPRTV are current at the
time of use.
It is important to remember that a provisional value alone tells very little about the
adverse effects of a chemical or the quality of evidence on which the value is based. Therefore,
users are strongly encouraged to read the entire PPRTV manuscript and understand the strengths
and limitations of the derived provisional values. PPRTVs are developed by the EPA Office of
Research and Development's National Center for Environmental Assessment, Superfund Health
Risk Technical Support Center for OSRTI. Other EPA programs or external parties who may
choose of their own initiative to use these PPRTVs are advised that Superfund resources will not
generally be used to respond to challenges of PPRTVs used in a context outside of the Superfund
Program.
Questions Regarding PPRTVs
Questions regarding the contents of the PPRTVs and their appropriate use (e.g., on
chemicals not covered, or whether chemicals have pending IRIS toxicity values) may be directed
to the EPA Office of Research and Development's National Center for Environmental
Assessment, Superfund Health Risk Technical Support Center (513-569-7300), or OSRTI.
INTRODUCTION
An RfC for nitroglycerin (also known as trinitroglycerol) is not available on IRIS (U.S.
EPA, 2003) or in the HEAST (U.S. EPA, 1997). The CARA list (U.S. EPA, 1991, 1994) does
not include any other review documents for nitroglycerin, but a Drinking Water Health Advisory
document is available (U.S. EPA, 1987). Lee et al. (1977), on a contract with the U.S. Army
Medical Bioengineering Research Laboratory (U.S. AMBRDL), developed a report on a
mammalian toxicity study on Trinitroglycerin. The U.S. Army Center for Health Promotion and
Preventative Medicine (U.S. ACHPPM) completed a wildlife toxicity assessment for
Nitroglycerin (U.S. ACHPPM, 2000). Neither ATSDR (2003), NTP (2003), IARC (2003), nor
WHO (2003) have produced documents regarding nitroglycerin. ACGIH (2001, 2003) has
adopted a threshold limit value - time weighted average (TLV-TWA) of 0.05 ppm (0.46 mg/m3)
for nitroglycerin to minimize the potential for vasodilation expressed by headache and decreases
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in blood pressure. The TLV-TWA is based on human data and by analogy to propylene glycol
dinitrate. NIOSH (2003) recommends a short-term exposure level (STEL) of 0.1 mg/m3 and an
immediately dangerous to life and health (IDLH) of 75 mg/m3. The OSHA (2003) permissible
exposure limit (PEL) is 0.2 ppm as a ceiling limit. Literature searches were conducted for the
period from 1965 to July 2003 in the following databases: TOXLINE (including NTIS and
BIOSIS updates), CANCERLIT, MEDLINE, CCRIS, GENETOX, HSDB, EMIC/EMICBACK,
DART/ETICBACK, RTECS, and TSCATS. Additional literature searches from July 2003
through September 2004 were conducted by NCEA-Cincinnati using MEDLINE, TOXLINE,
Chemical and Biological Abstracts databases.
REVIEW OF PERTINENT LITERATURE
Human Studies
Contact with nitroglycerin can occur through occupational exposure of persons employed
in the explosives industry, or through its medical use in the relief of angina pectoris. Among the
key issues to be weighed in considering the extent of nitroglycerin's toxicity in exposed
individuals are (1) the development of adverse symptoms such as headache, dizziness,
palpitations, and nausea in persons exposed to nitroglycerin therapeutically or (along with other
compounds) in the workplace; (2) the development of tolerance to the pharmacological effects of
nitroglycerin, whereby the severity of side-effects of the compound can become reduced, or
where an increase in the administered dose becomes necessary to maintain stability; (3) the
association of chronic exposure to the compound with organic nitrate dependence, in which
withdrawal from the treatment can cause (occasionally fatal) heart attack and stroke in subjects
who may have adapted to the continuous presence of the compound to maintain an optimum
level of coronary flow; (4) the consequent desirability of maintaining stable levels of organic
nitrates and their derivatives in patients to guard against debilitating fluctuations in body burden;
and (5) the potential for the compound to be associated with systemic toxicity, as indicated by
long-term exposure studies in laboratory animals.
The capacity of aliphatic nitrates such as nitroglycerin to lower blood pressure forms the
basis for the compound's use in medicine; for example, in the control of angina pectoris (NIOSH,
1978). As a drug, nitroglycerin is prescribed for intermittent use, with dose levels established by
the degree of relief from symptoms afforded to the patient as the nitroglycerin amount is raised.
This approach reflects the rapid onset of the compound's pharmacological effects and the marked
individuality of response to treatment among different patients (Abrams, 1980). Where the
requirement for organic nitrate therapy becomes repeated, well-recognized side-effects of
nitroglycerin treatment such as headache, palpitations, nausea, and vomiting may become
reduced as the compound becomes tolerated by the host (Abrams, 1980). Unfortunately,
nitroglycerin has the capacity to cause dependence, whereby cessation of repeated exposure to
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the compound may itself become associated with sometimes severe reactions, such as angina,
weakness, palpitations, difficulty in breathing, and, in some cases, death (Daum, 1983). This is
an especially important issue in occupationally exposed workers, such as those in the explosives
industry, whose normally elevated organic nitrate body burden becomes depleted during a period
of absence from the workplace, such as the weekend. The well-documented phenomenon of
"Monday Morning Death" has been described for munitions workers in whom cardiovascular
events can be triggered by unrestrained compensatory vasoconstriction, as the organic nitrate in
the body becomes reduced (Abrams, 1980). Incidence of sudden death in such persons is up to
15 times the expected rate (Daum, 1983). Kristensen (1989) discussed an apparent double effect
of nitroglycerin in cardiovascular disease, where the incidence of "Monday Morning Death" was
compounded by an apparently increased risk of heart attack and stroke that continued in
chronically exposed subjects long after the cessation of exposure.
Craig et al. (1985) carried out a death certificate study of persons who had been employed
at an explosives factory in Scotland on January 1, 1965. The investigation covered the time
period 1965 to 1980, and compared the causes of death of potentially exposed workers with
internal controls (unexposed workers at the same factory) and members of the general male
population. Blasting workers (exposed to nitroglycerin and ethylene glycol dinitrate) and
propellant workers (exposed to nitroglycerin alone) were subdivided by age and then by high-
and low-exposure subcategories, depending on the position of their work station or the nature of
their duties. Causes of death for each target group included acute myocardial infarction (MI),
ischemic heart disease (IHD), cerebrovascular disease, lung cancer, cancer of the colon or
rectum, and all cancers. Among the non-cancer related responses, there was an apparent
increased incidence of MI and IHD in the 15-49 age group of high-exposure blasting workers
compared with internal controls or with members of the general population. However, these
findings do not necessarily implicate nitroglycerin, as no effect was reported among propellant
workers exposed to nitroglycerin alone.
Animal Studies
No studies were located regarding inhalation exposure of animals to nitroglycerin.
FEASIBILITY OF DERIVING PROVISIONAL SUBCHRONIC AND CHRONIC RfCs
FOR NITROGLYCERIN
As previously indicated, a substantial amount of information exists regarding the effects
of nitroglycerin in humans, mainly due to its use as a pharmaceutical and in the manufacturing of
explosives. However, lack of quantitative data in epidemiological studies preclude their use as
basis for derivation of risk assessment values. In general, these studies lack data regarding
exposure levels and duration of exposure, as well as information on confounding factors such as
4

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health history and life style of the subjects. Simultaneous exposure to other chemicals, as in the
case of workers in the manufacturing of dynamite, is an additional problem.
The lack of adequate epidemiological studies in humans, or subchronic or chronic
inhalation toxicity data in animals precludes derivation of a subchronic or chronic p-RfC for
nitroglycerin.
REFERENCES
Abrams, J. 1980. Nitrate tolerance and dependence. Am. Heart J. 99:113-123.
ACGIH (American Conference of Governmental Industrial Hygienists). 2001. Nitroglycerin.
Documentation for the Threshold Limit Values for Chemical Substances and Physical Agents
and Biological Exposure Indices. 7th edition. Cincinnati, OH.
ACGIH (American Conference of Governmental Industrial Hygienists). 2003. 2003 Threshold
Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices.
Cincinnati, OH.
ATSDR (Agency for Toxic Substances and Disease Registry). 2003. Toxicological Profile
Information Sheet. Online, http://www.atsdr.cdc.gov/toxpro2.html
Craig, R., C.R. Gillis, C.D. Hole and G.M. Paddle. 1985. Sixteen year follow up of workers in
an explosives factory. J. Soc. Occup. Med. 35: 107-110.
Daum, S. 1983. Nitroglycerin and alkyl nitrates. In: Environmental and Occupational Medicine.
W.M. Rom, Ed. Little, Brown and Co., Boston, p. 639-648.
I ARC (International Agency for Research on Cancer). 2003. IARC Agents and Summary
Evaluations. Online, http://www-cie.iarc.fr/htdig/search.html
Kristensen, T.S. 1989. Cardiovascular diseases and the work environment. Scand. J. Work
Environ. Health. 15: 245-264.
Lee, C.C., H.V. Ellis, III, J.J. Kowalski et al. 1977. Mammalian toxicity of munition
compounds Phase II: Effects of multiple doses Part I: Trinitroglycerin. Report No. 2. Midwest
Research Institute, Kansas City, Mo, Contract No. DAMD-17-74-C-4073, AD AO47067. (Cited
in U.S. EPA, 1987)
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NIOSH (National Institute for Occupational Safety and Health). 1978. Criteria for a
Recommended Standard. Occupational Exposure to Nitroglycerin and Ethylene Glycol Dinitrate.
DHEW (NIOSH) Publication No. 78-167. U.S. Department of Health, Education and Welfare,
Washington, DC.
NIOSH (National Institute for Occupational Safety and Health). 2003. NIOSH Pocket Guide to
Chemical Hazards. Online. http://www.cdc.gOv/niosh/npg/npgd0000.html#F
NTP (National Toxicology Program). 2003. Management Status Report. Online.
http://ntp-server.niehs.nih.gov/cgi/iH Indexes/ATI, SRCH/iH ATI, SRCH Frames.html
OSHA (Occupational Safety and Health Administration). 2003. OSHA Standard 1910.1000
Table Z-l. Part Z, Toxic and Hazardous Substances. Online.
http://www.osha-slc.gov/OshStd data/1910 1000 TABLE Z-l.html
U.S. Army Center for Health Promotion and Preventative Medicine (U.S. ACHPPM). 2000.
Wildlife Toxicity Assessment for Nitroglycerin. U.S. ACHPPM Doc. No: 37-EJ-l 138-01F.
U.S. EPA. 1987. Health Advisory for Trinitroglycerol. Office of Drinking Water, Washington,
DC. NTIS PB90-273558.
U.S. EPA. 1991. Chemical Assessments and Related Activities (CARA). Office of Health and
Environmental Assessment, Washington, DC. April.
U.S. EPA. 1994. Chemical Assessments and Related Activities (CARA). Office of Health and
Environmental Assessment, Washington, DC. December.
U.S. EPA. 1997. Health Effects Assessment Summary Tables (HEAST). FY-1997 Update.
Prepared by the Office of Research and Development, National Center for Environmental
Assessment, Cincinnati, OH for the Office of Emergency and Remedial Response, Washington,
DC. July. NTIS# PB97-921199.
U.S. EPA. 2003. Integrated Risk Information System (IRIS). Office of Research and
Development, National Center for Environmental Assessment, Washington, DC. Online.
http://www.epa.gov/iris/
WHO (World Health Organization). 2003. Online Catalogs for the Environmental Criteria
Series. Online, http://www.who.int/dsa/cat98/zehc.htm
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Provisional Peer Reviewed Toxicity Values for
Nitroglycerin
(CASRN 55-63-0)
Derivation of a Carcinogenicity Assessment
Superfund Health Risk Technical Support Center
National Center for Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268

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Acronyms and Abbreviations
bw	body weight
cc	cubic centimeters
CD	Caesarean Delivered
CERCLA	Comprehensive Environmental Response, Compensation and Liability Act
of 1980
CNS	central nervous system
cu.m	cubic meter
DWEL	Drinking Water Equivalent Level
FEL	frank-effect level
FIFRA	Federal Insecticide, Fungicide, and Rodenticide Act
g	grams
GI	gastrointestinal
HEC	human equivalent concentration
Hgb	hemoglobin
i.m.	intramuscular
i.p.	intraperitoneal
i.v.	intravenous
IRIS	Integrated Risk Information System
IUR	inhalation unit risk
kg	kilogram
L	liter
LEL	lowest-effect level
LOAEL	lowest-observed-adverse-effect level
LOAEL(ADJ)	LOAEL adjusted to continuous exposure duration
LOAEL(HEC)	LOAEL adjusted for dosimetric differences across species to a human
m	meter
MCL	maximum contaminant level
MCLG	maximum contaminant level goal
MF	modifying factor
mg	milligram
mg/kg	milligrams per kilogram
mg/L	milligrams per liter
MRL	minimal risk level
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MTD
maximum tolerated dose
MTL
median threshold limit
NAAQS
National Ambient Air Quality Standards
NOAEL
no-observed-adverse-effect level
NOAEL(ADJ)
NOAEL adjusted to continuous exposure duration
NOAEL(HEC)
NOAEL adjusted for dosimetric differences across species to a human
NOEL
no-observed-effect level
OSF
oral slope factor
p-IUR
provisional inhalation unit risk
p-OSF
provisional oral slope factor
p-RfC
provisional inhalation reference concentration
p-RfD
provisional oral reference dose
PBPK
physiologically based pharmacokinetic
PPb
parts per billion
ppm
parts per million
PPRTV
Provisional Peer Reviewed Toxicity Value
RBC
red blood cell(s)
RCRA
Resource Conservation and Recovery Act
RDDR
Regional deposited dose ratio (for the indicated lung region)
REL
relative exposure level
RfC
inhalation reference concentration
RfD
oral reference dose
RGDR
Regional gas dose ratio (for the indicated lung region)
s.c.
subcutaneous
SCE
sister chromatid exchange
SDWA
Safe Drinking Water Act
sq.cm.
square centimeters
TSCA
Toxic Substances Control Act
UF
uncertainty factor
Hg
microgram
|imol
micromoles
VOC
volatile organic compound
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PROVISIONAL PEER REVIEWED TOXICITY VALUES FOR
NITROGLYCERIN (CASRN 55-63-0)
Derivation of a Carcinogenicity Assessment
Background
On December 5, 2003, the U.S. Environmental Protection Agency's (EPA's) Office of
Superfund Remediation and Technology Innovation (OSRTI) revised its hierarchy of human
health toxicity values for Superfund risk assessments, establishing the following three tiers as the
new hierarchy:
1.	EPA's Integrated Risk Information System (IRIS).
2.	Provisional Peer-Reviewed Toxicity Values (PPRTV) used in EPA's Superfund
Program.
3.	Other (peer-reviewed) toxicity values, including:
~	Minimal Risk Levels produced by the Agency for Toxic Substances and Disease
Registry (ATSDR),
~	California Environmental Protection Agency (CalEPA) values, and
~	EPA Health Effects Assessment Summary Table (HEAST) values.
A PPRTV is defined as a toxicity value derived for use in the Superfund Program when
such a value is not available in EPA's Integrated Risk Information System (IRIS). PPRTVs are
developed according to a Standard Operating Procedure (SOP) and are derived after a review of
the relevant scientific literature using the same methods, sources of data, and Agency guidance
for value derivation generally used by the EPA IRIS Program. All provisional toxicity values
receive internal review by two EPA scientists and external peer review by three independently
selected scientific experts. PPRTVs differ from IRIS values in that PPRTVs do not receive the
multi-program consensus review provided for IRIS values. This is because IRIS values are
generally intended to be used in all EPA programs, while PPRTVs are developed specifically for
the Superfund Program.
Because science and available information evolve, PPRTVs are initially derived with a
three-year life-cycle. However, EPA Regions (or the EPA HQ Superfund Program) sometimes
request that a frequently used PPRTV be reassessed. Once an IRIS value for a specific chemical
becomes available for Agency review, the analogous PPRTV for that same chemical is retired. It
should also be noted that some PPRTV manuscripts conclude that a PPRTV cannot be derived
based on inadequate data.
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Disclaimers
Users of this document should first check to see if any IRIS values exist for the chemical
of concern before proceeding to use a PPRTV. If no IRIS value is available, staff in the regional
Superfund and RCRA program offices are advised to carefully review the information provided
in this document to ensure that the PPRTVs used are appropriate for the types of exposures and
circumstances at the Superfund site or RCRA facility in question. PPRTVs are periodically
updated; therefore, users should ensure that the values contained in the PPRTV are current at the
time of use.
It is important to remember that a provisional value alone tells very little about the
adverse effects of a chemical or the quality of evidence on which the value is based. Therefore,
users are strongly encouraged to read the entire PPRTV manuscript and understand the strengths
and limitations of the derived provisional values. PPRTVs are developed by the EPA Office of
Research and Development's National Center for Environmental Assessment, Superfund Health
Risk Technical Support Center for OSRTI. Other EPA programs or external parties who may
choose of their own initiative to use these PPRTVs are advised that Superfund resources will not
generally be used to respond to challenges of PPRTVs used in a context outside of the Superfund
Program.
Questions Regarding PPRTVs
Questions regarding the contents of the PPRTVs and their appropriate use (e.g., on
chemicals not covered, or whether chemicals have pending IRIS toxicity values) may be directed
to the EPA Office of Research and Development's National Center for Environmental
Assessment, Superfund Health Risk Technical Support Center (513-569-7300), or OSRTI.
INTRODUCTION
A cancer assessment for nitroglycerin (also known as trinitroglycerol) is not available
on IRIS (U.S. EPA, 2005a) or in the HE AST (U.S. EPA, 1997). The Drinking Water Standards
and Health Advisories list (U.S. EPA, 2002) includes a cancer risk for nitroglycerin based on
U.S. EPA (1987) analysis of liver tumors in a lifetime study in rats (Ellis et al., 1984). The
CARA list (U.S. EPA, 1991, 1994) does not include any other review documents for
nitroglycerin. Lee et al. (1977), on a contract with the U.S. Army Medical Bioengineering
Research Laboratory (U.S. AMBRDL), developed a report on a mammalian toxicity study on
Trinitroglycerin. The U.S. Army Center for Health Promotion and Preventative Medicine (U.S.
ACHPPM) completed a wildlife toxicity assessment for Nitroglycerin (U.S. ACHPPM, 2000).
Neither ATSDR (2003), NTP (2003), IARC (2003), nor WHO (2003) have produced documents
regarding nitroglycerin. Literature searches were conducted for the period from 1965 to July
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2003 in the following databases: TOXLINE (including NTIS and BIOSIS updates),
CANCERLIT, MEDLINE, CCRIS, GENETOX, HSDB, EMIC/EMICBACK,
DART/ETICBACK, RTECS, and TSCATS. Additional literature searches from July 2003
through September 2004 were conducted by NCEA-Cincinnati using MEDLINE, TOXLINE,
Chemical and Biological Abstracts databases.
REVIEW OF PERTINENT LITERATURE
Human Studies
Craig et al. (1985) investigated the cause of death, taken from death certificates, of male
workers employed in a large explosives factory in Scotland on January 1, 1965 and followed for
16 years. The workers were divided into those exposed to nitroglycerin alone (propellant
workers, n=224), to nitroglycerin and ethylene glycol dinitrate in an approximate ratio of 4:1
(blasting workers, n=659), or to neither compound (n=3159). The exposed workers were
subdivided into high- and low-exposure categories, but no attempt was made to quantify
exposures. The workers were further subdivided into those 15-49 or 50-64 years of age on
January 1, 1965. The numbers of deaths from all cancers, lung cancer, and colorectal cancer
among the exposed workers were compared to expected numbers based on the unexposed
workers (internal controls) and on the general male population of the County of Ayr in which
98% of the workers had resided. None of the categories or subcategories of exposed workers had
significantly increased occurrence of death due to all cancers, lung cancer, or colorectal cancer,
compared with either internal controls or the general male population of the County of Ayr, with
the following exception. The high-exposure category of blasting workers aged 15-49 had a
significant excess of lung cancer when compared with internal controls, but not when compared
with the general male population of the County of Ayr. Because the blasting workers were also
exposed to ethylene glycol dinitrate, and because a significant excess of lung cancer was not
observed in workers exposed to nitroglycerin alone, the observation of excess lung cancer in the
high exposure blasting workers does not support a causal relationship between exposure to
nitroglycerin and lung cancer.
Animal Studies
In a chronic toxicity study conducted by Ellis et al. (1984), groups of 6 male and 6 female
beagle dogs were administered daily capsules containing 0, 1,5, or 25 mg/kg-day nitroglycerin
for 12 months, and groups of CD rats (38/sex/group) and CD-I mice (58/sex/group) were fed
diets containing 0, 0.01, 0.1, or 1% nitroglycerin for 24 months (the authors estimated that the
dietary concentrations corresponded to doses of 0, 3.04, 31.5, and 363 mg/kg-day for male rats;
0, 3.99, 38.1, and 434 mg/kg-day for female rats; 0, 11.1, 114.6, and 1022 mg/kg-day for male
mice; and 0, 9.72, 96.4, and 1058 mg/kg-day for female mice). Groups of rats and mice
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(8/sex/species/group) were killed after 12 months of exposure. The only effect observed in the
dogs was an occasional, but dose-related, increase in blood methemoglobin concentration. There
was no mention of any tumors in the dogs, but the scope of the gross and histopathologic
examination is unclear. In addition, the duration of exposure was probably insufficient to induce
tumors with a long latency, and it is doubtful that the maximum tolerated dose was reached. This
study is considered inadequate for evaluating the carcinogenic potential of nitroglycerin in dogs.
Rats of both sexes fed the 1% diet consumed significantly less food than controls during
the first three weeks of the study; females consumed significantly less food throughout the
experiment. The body weights of the rats fed the 1% diet were notably less than the controls
throughout the experiment, and these rats had considerably less body fat (particularly abdominal
fat) than controls. Treatment with the 0.01 or 0.1% diets had no significant effect on food
consumption or body weight, although rats fed the 0.1% diet consumed slightly less and weighed
slightly less than controls, particularly after three months (males) and 12 months (females) of
exposure. Treatment had no adverse effect on survival; females fed the 1% diet had significantly
longer survival than female control rats, presumably because of a lower incidence of pituitary and
mammary tumors. Rats fed the 1% diet also had methemoglobinemia and serum biochemical
and histopathologic evidence of liver damage (Ellis et al., 1984). On the basis of the effects on
food consumption and body weight, methemoglobinemia and evidence of liver damage, it is
judged that the maximum tolerated dietary dose was reached in the rats. Evidence of
nitroglycerin-induced hepatocellular carcinogenicity in rats was apparent at the interim (12
month) sacrifice. Preneoplastic lesions occurred in the livers of 1/8, 4/6, 6/7 and 6/8 males and
of 1/8, 2/7, 3/8 and 8/8 females fed the 0, 0.01, 0.1 and 1% diets, respectively. The authors noted
a dose-related increase in both the incidence and severity of these preneoplastic lesions.
Neoplastic nodules or hepatocellular carcinomas occurred in one male fed the 0.1% diet and in
four males and one female fed the 1% diet (Ellis et al., 1984).
At the termination of the experiment, the combined incidence of neoplastic nodules and
hepatocellular carcinomas was significantly increased in rats of both sexes fed the 1% diet
(Table 1). The incidence of testicular interstitial cell tumors was significantly higher in rats fed
the 1% diet than in the controls. The incidence of pituitary chromophobe adenomas in rats of
both sexes fed the 1% diet and the incidence of mammary gland tumors in females fed the 1%
diet was notably reduced compared with the appropriate controls (Ellis et al., 1984).
Mice of both sexes fed the 1% nitroglycerin diet had sharply reduced food consumption
and frank weight loss during the first week of treatment. Thereafter, these mice began gaining
weight, but their body weights remained below the controls throughout the experiment. Mice of
both sexes fed the 1% diet evaluated at 12 months of treatment had a compensated anemia and
erythrocytes containing Heinz bodies, and the males had a significant (p<0.05), but low-grade
methemoglobinemia. Deposits of hemoglobin-derived pigments were observed at the 12-month
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Table 1. Incidence of tumors in CD rats fed diets containing nitroglycerin for 24 months*
Sex
Tumor Type
Dietary
Dose
Incidence2


level
mg/kg-day
(p value)b


(percent)


Male
Hepatocellular carcinoma
0
0
1/24 (0.001)

or neoplastic nodule
0.01
3.04
0/28 (NS)


0.1
31.5
4/26 (NS)


1
363
15/21 (0.001)
Female
Hepatocellular carcinoma
0
0
0/29 (0.001)

or neoplastic nodule
0.01
3.99
1/32 (NS)


0.1
38.1
3/28 (NS)


1
434
16/25 (0.001)
Male
Testicular interstitial cell tumor
0
0
2/24 (0.001)


0.01
3.04
1/28 (NS)


0.1
31.5
3/26 (NS)


1
363
11/21 (0.001)
* Source: Ellis et al., 1984
a number of lesion-bearing rats/number of rats with readable slides
b p Values presented with the control incidence refer to the Cochran-Armitage trend test; p values presented with
the treated group incidence refer to the Fisher exact test comparing the treated and control groups; all statistical
analyses performed by SRC.
NS = not statistically significant
sacrifice and at termination in the liver, spleen and kidney of most mice fed the 1% diet and some
(not otherwise specified) mice fed the 0.1% diet (Ellis et al., 1984). On the basis of the effects
on food consumption and body weight, the compensated anemia, methemoglobinemia and the
deposits of pigments in the tissues, it is judged that the maximum tolerated dietary dose had been
reached in the mice. There was no evidence of carcinogenicity in any tissues of the mice (Ellis et
al., 1984), including the pituitary gland (Hong, 1991), which was identified as a potential site of
nitroglycerin carcinogenicity in an earlier study (Suzuki et al., 1975, described below).
A study by Tamano et al. (1996) provided corroborating evidence that nitroglycerin can
produce liver tumors in rats. Male F344/N rats received nitroglycerin, either as a single corn oil
bolus of 1200 mg/kg via gavage (n=80) at 6 weeks of age, or added to the feed at a concentration
of 1% (-500 mg/kg-day, assuming a rat consumes 5% of its body weight per day) for up to 78
weeks starting at 8 weeks of age (n=30), or both (n=80). Some animals in the bolus-only group
and those that received both treatments were subjected to 2/3 partial hepatectomy at 9 weeks of
age. An untreated control group included 10 animals. Interim sacrifices of varying numbers of
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animals among the groups were carried out at 14, 32, 52, 78 and 84 weeks of age. These animals
and others dying prematurely were subjected to necropsy, with the livers weighed and examined
for gross lesions. Pieces of liver, especially those with visible lesions, were examined
histopathologically. DNA from liver tumors was extracted and examined for mutations in the
coding regions of the K-ras (exons 1 and 2) and p53 (exons 5 to 8) genes. Body weight gain was
reduced in the rats receiving nitroglycerin in the diet compared with those animals receiving the
compound via gavage, or to controls. Marked morphological liver lesions became evident in the
diet-exposed groups from 32 weeks of age. These included tan-colored foci, with later
appearance of nodules and masses. At 78 weeks of age, both groups of rats receiving the
compound via the diet displayed >50% incidence of combined hepatocellular adenomas and
carcinomas. No liver tumors were found in control rats or those exposed only by single bolus.
DNA examination of 18 liver tumors from diet-treated rats found no mutations in the p53 gene,
but K-ras point mutations in 8 tumors (primarily those with cholangiocellular elements). All the
mutations were in codon 12 of exon 1 (4 GGT-GTT transversions, 3 GGT-GAT transitions, and
1 GGT-TGT transversion). The authors considered their data to represent only marginal
evidence of a gene modification as the initiating event in nitroglycerin-induced carcinogenicity.
An earlier study in rats found no evidence of carcinogenicity, but included only a single,
relatively low dose-level. A group of 50 male and 48 female 8-week-old Sprague Dawley rats
were given drinking water containing 0.03% nitroglycerin (31 mg/kg-day, as estimated by the
researchers) for 10 months, followed by plain tap water for an additional 8 months, at which time
survivors were sacrificed for necropsy, hematology and serum chemistry (5 rats per sex), organ
weight measurements and histopathological examination of a wide range of tissues (Takayama,
1975). A control group of 53 male and 49 female rats, provided with plain tap water for the
entire 18-month experimental period, was similarly examined at termination. Mortality due to
pneumonia claimed 38 male and 23 female rats in the treated group and 36 male and 32 female
control rats during the experiment. Treatment had no effect on survival, behavior, general
physical appearance, or body weight. There were no treatment-related effects on hematological
parameters, or on several serum chemistry tests to detect impaired function of, or damage to, the
liver and kidney. Methemoglobinemia was not evaluated. There were no effects on organ
weights in the treated or control rats surviving to 18 months. Treatment with nitroglycerin had
no effect on incidence of nonneoplastic lesions or tumors. The only tumors observed were
mammary gland tumors in 8/44 treated female rats and 5/45 female controls and a pituitary
adenoma in one control female. This study found no evidence of carcinogenicity in rats, but is
not an adequate study due to use of a single low exposure level that did not approach the
maximum tolerated dose, high non-treatment-related mortality, and short exposure duration.
Marginal evidence for carcinogenicity was found in an early study in mice. Suzuki et al.
(1975) provided 4-week-old C57BL/6Jms mice with drinking water in which was dissolved 0,
10, 40 or 330 mg/L nitroglycerin in saline (doses of 0, 1.5, 6.2, and 58.1 mg/kg-day estimated by
the researchers). The high-dose mice (49 males and 45 females) received nitroglycerin for 52
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weeks followed by control drinking water for an additional 28 weeks. The mid-dose (66 males
and 49 females), low-dose (54 males and 50 females), and control (60 male and 63 females)
groups received appropriate concentrations of nitroglycerin for the entire 80-week experimental
period. The mice were subjected to necropsy and histopathological examination of heart, liver,
kidney, spleen, bone marrow, and all gross lesions. There were no clearly treatment-related
effects on behavior or general appearance. The body weights of high-dose mice of both sexes
were below their respective controls starting at about 13-14 months, but statistical analyses were
not performed and the difference from controls was less than 10%. The investigators noted that a
higher incidence of early mortality (30-40 weeks of treatment) occurred in the high-dose females
compared with controls, but the effect appeared to be slight and statistical analysis was not
performed. Histopathologic examination revealed no treatment related noncarcinogenic effects.
It is doubtful that the maximum tolerated dose was attained in this experiment. Tumor incidence
was generally comparable to controls, except that histopathologic examination revealed pituitary
adenomas in 1/50, 1/40, 3/39 and 6/34 females in the control, low-, mid- and high-dose groups,
respectively. The incidence in the high-dose females was significantly higher than in control
females (p<0.05, Fisher exact test performed at SRC) and the Cochran-Armitage test for trend
was positive (p<0.01, performed at SRC). This study provides some evidence for carcinogenicity
of nitroglycerin in female mice, but is limited by apparent failure to attain the maximum tolerated
dose, relatively short exposure duration (especially of the high-dose group), lack of statistical
analysis, and failure of the researchers to discuss the increase in pituitary tumors.
Mode of Action
Studies of the genotoxicity of nitroglycerin have produced mixed results. Simmon et al.
(1977) found that nitroglycerin did not produce mutations in Salmonella typhimurium strains
TA1535, TA1537, TA1538, TA98, TA100 with or without metabolic activation or in
Saccharomyces cerevisiae. Other studies found mutagenic activity in S. typhimurium strains
TA1535 and/or TA1537 with or without metabolic activity (Ellis et al., 1978a; Maragos et al.,
1993). In mammalian cells, negative results were found for mutagenicity in Chinese Hamster
Ovary cells without metabolic activation (Lee et al., 1976). In vivo studies were negative. No
changes were observed in the number of tetraploids, frequency of chromatid breaks, and gaps or
translocations in bone marrow and kidney cell cultures from rats fed nitroglycerin for 13 weeks
or 24 months (Ellis et al., 1978b) or in chromosome aberrations in peripheral lymphocytes or
kidney cultures from dogs and rats fed nitroglycerin for 4-9 weeks (Lee et al., 1976). An
evaluation of the available data supports the conclusion that the data are not sufficient to
determine the mutagenicity of nitroglycerin and therefore, are not sufficient to evaluate a
mutagenic mode of action (MO A) of nitroglycerin as described in the 2005 revised Cancer
Guidelines (U.S. EPA, 2005b).
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PROVISIONAL WEIGHT-OF-EVIDENCE CLASSIFICATION
Human data are limited to the study by Craig et al. (1985) of mortality in workers in a
large explosives factory in Scotland. The high-exposure group of blasting workers experienced
an excess of death due to lung cancer; however, interpretation is confounded by simultaneous
exposure to ethylene glycol dinitrate. Although the study found no clear association between
exposure to nitroglycerin and excess deaths from all cancers, lung cancers or colorectal cancer,
the study has several limitations. The investigators did not quantify exposures other than to state
that the product handled by the blasting workers contained nitroglycerin and ethylene glycol
dinitrate in the ratio of 4:1. They also stated that ethylene glycol dinitrate is more volatile than
nitroglycerin and was more important than nitroglycerin in the exposed blasting workers.
Furthermore, it is not clear that the cancer classifications studied (all cancers, lung cancer and
colorectal cancer) were sufficient to detect all excess nitroglycerin-induced cancer deaths. The
power of the study to detect cancer is further compromised because the exposed groups
(especially the propellant workers exposed to nitroglycerin alone) were small, because the
endpoint studied was death, and because the follow-up period was limited to 16 years.
Therefore, the Craig et al. (1985) study is considered to be an inadequate cancer study.
Animal studies include the 12-month dog study and the 24-month rat and mouse studies by
Ellis et al. (1984), the 20-month rat study by Tamano et al. (1996), the 18-month rat study by
Takayama (1975) and the 80-week mouse study by Suzuki et al. (1975). As noted above, the dog
study is inadequate for evaluating the potential carcinogenicity of nitroglycerin to dogs. The rat
study by Ellis et al. (1984) administered appropriate doses by the most relevant route to
adequately sized groups of both sexes for sufficient time to induce a compound-related
carcinogenic effect (liver and testicular tumors) and provide sufficient data for quantitative risk
assessment. The study by Tamano et al. (1996) provided corroborating evidence for induction by
nitroglycerin of liver tumors in rats. Although Takayama (1975) did not observe a carcinogenic
effect in rats exposed for 10 months, the relatively short duration of exposure and the failure to
give the maximum tolerated dose render this study inadequate for evaluation of the
carcinogenicity of nitroglycerin to rats.
In mice, the situation is less straightforward. There was a statistically significant (analysis at
SRC) increase in pituitary adenomas in female mice treated with 58 mg/kg-day for 12 months
(Suzuki et al., 1975). The study, however, was limited by use of low doses and failure to attain
the maximum tolerated dose, relatively short exposure duration (especially of the high-dose
group), lack of statistical analysis, and failure of the researchers to discuss the increase in
pituitary tumors. A subsequent, adequately conducted study, in which mice were treated with
doses as high as 1000 mg/kg-day and the maximum tolerated dose was achieved, found no
evidence of a carcinogenic response in any tissue, including the pituitary gland (Ellis et al.,
1984). Therefore, there is inadequate evidence for carcinogenicity of nitroglycerin in mice.
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Genotoxicity studies provided some evidence for mutagenicity induced by nitroglycerin
(Ellis et al., 1978a; Maragos et al, 1993), although some studies produced negative results. The
Tamano et al. (1996) cancer study found marginal evidence for a gene modification (K-ras point
mutations) as the initiating event in nitroglycerin-induced liver carcinogenicity.
Collectively, the data are considered to provide sufficient evidence of the carcinogenicity of
nitroglycerin in animals, largely because of the highly significantly increased incidence of
hepatocellular carcinomas in male and female rats and interstitial cell testicular tumors in male
rats in the Ellis et al. (1984) study. This determination is supported by the early appearance (at
the 12-month interim sacrifice) of the neoplastic response in the liver in the Ellis et al. (1984)
study and the high incidence of liver tumors in the diet-exposed rats in the Tamano et al. (1996)
study. The 1998 PPRTV document for nitroglycerin is based on essentially the same literature as
the current review. The 1998 evaluation, based on the weight-of- evidence, classified
nitroglycerin as likely to be carcinogenic to humans using the proposed 1996 guidelines (U.S.
EPA, 1996), and assigned a designation of 'C' - a possible human carcinogen in accordance
with the 1986 cancer guidelines (U.S. EPA, 1986). Compared with the internal control a
significant increase in incidence of lung cancer was observed in the 15-49 age group of
explosives factory workers categorized as having high nitroglycerin exposure (Craig, et al.,
1985). However, this cancer incidence rate was not found to be significant when compared with
the general male population of the County of Ayr, Scotland, where the explosive factory was
located. A literature search revealed no cancer epidemiological studies on patients treated
medically with nitroglycerin. However, a few case reports were found on cancer in patients
using nitroglycerin. Based on these studies, no conclusion can be derived on whether or not
therapeutic use of nitroglycerin is associated with cancer. Using the 2005 Cancer Guidelines
(U.S. EPA, 2005b) nitroglycerin is classified as likely to be carcinogenic to humans because it
has tested positive in experimental animals without evidence of carcinogenicity in humans. Data
on mode of action are not conclusive.
QUANTITATIVE ESTIMATES OF CARCINOGENIC RISK
Provisional Oral Slope Factor
Three sets of data are available (see Table 1) from which it is possible to estimate a
provisional oral slope factor for the carcinogenic potency of nitroglycerin: hepatocellular tumors
in male and female rats and testicular interstitial cell tumors in male rats (Ellis et al., 1984).
Dose-response modeling was performed for only the liver tumors because the induction of liver
tumors by nitroglycerin was supported by the findings of Tamano et al. (1996).
Table 2 shows the relationship between concentrations of nitroglycerin in the feed, oral
doses to the rats, human equivalent oral doses, and tumor incidences. Mean dose estimates in
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Table 2. Data used for dose-response modeling for nitroglycerin*
Nitroglycerin
in Feed
%
Sex
Doses of Nitroglycerin
Combined
hepatocellular
adenoma and
carcinoma
tumor incidence
mg/kg-day (rat)
mg/kg-day (human)t
0
male
0
0
1/24
female
0
0
0/29
0.01
male
3.04
0.96
0/28
female
3.99
1.1
1/32
0.1
male
31.5
9.8
4/26
female
38.1
10.5
3/28
1.0
male
363
107
15/21
female
434
108
16/25
* Source: Ellis et al., 1984
f calculated using the cross-species scaling factor of body weight raised to the 3/4 power (U.S. EPA, 2003b)
rats were provided by the authors (Ellis et al, 1984). Average body weights of 0.69, 0.65 and
0.52 kg for the males, and 0.41, 0.40 and 0.27 kg for the females, were derived from data
provided in the text for the low-, middle- and high-dose groups, respectively. A default body
weight (human) of 70 kg was used in the dose transformations.
A weight of evidence evaluation supports the conclusion that a determination of a mutagenic
MOA for carcinogenicity cannot be made because there are insufficient data for determining the
mutagenicity, or for defining an MOA.
In accordance with the U.S. EPA (2005b) guidelines, the LED10 (lower bound on dose
estimated to produce a 10% increase in tumor incidence over background) was estimated from
the incidence data using the U.S. EPA (2000) benchmark dose methodology (version 1.3.2), and
a linear extrapolation to the origin was performed by dividing the LED10 into 0.1 (10%).
The LED10 value based on the male rat data (6.01 mg/kg-day) was selected as the point of
departure for calculation of the oral slope factor, since this gives a slightly more health protective
value than the LED10 based on the female rat data (Table 3). Linear extrapolation to the origin
(0.1/ 6.01 mg/kg-day) results in a human provisional oral slope factor of 1.7E-2 (mg/kg-
day)1.
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Table 3. Multi-stage modeling results for hepatocellular tumors in male and female
rats administered nitroglycerin in the diet*
Sex
BMD (ED10)a
BMDL (LED10)a
x2 p-value
AIC
Maleb
8.95
6.01
0.4549
62.134
Femaleb
10.88
7.39
0.7351
65.347
* Source: Ellis et al., 1984
a = mg nitroglycerin/kg-day
b = Restrict betas >=0, Degree of polynomial = 3
Provisional Inhalation Unit Risk
There are no human or animal inhalation data from which to derive a provisional inhalation
unit risk for nitroglycerin.
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