United States
kS^laMIjk Environmental Protection
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EPA/690/R-06/005F
Final
9-22-2006
Provisional Peer Reviewed Toxicity Values for
Bis(2-chloroethoxy)methane
(CASRN 111-91-1)
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
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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 TOXICITY VALUES FOR
BIS(2-CHLOROETHOXY)METHANE (CASRN 111-91-1)
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
Neither subchronic nor chronic RfDs or RfCs for bis(2-chloroethoxy)methane (BCM) are
available on IRIS (U.S. EPA, 2006a), the HEAST (U.S. EPA, 1997) or the Drinking Water
Standards and Health Advisories list (U.S. EPA, 2004). A carcinogenicity assessment for bis(2-
chloroethoxy)methane is available on IRIS (U.S. EPA, 2006a) that includes a classification of
Group D, not classifiable as to human carcinogenicity, based on no human or animal data. The
CARA list (U.S. EPA, 1991a, 1994) includes no documents for this chemical. The toxicity of
bis(2-chloroethoxy)methane has not been reviewed by ATSDR (2006), IARC (2006), or WHO
(2006). ACGIH (2006), NIOSH (2006) and OSHA (2006) have not established occupational
exposure limits for this compound. The NTP (2006) Management Status Report provided no
relevant information. A technical report on haloethers prepared for EPA in 1975 (Durkin et al.,
1975) and the Ambient Water Quality Criteria Document for Chloroalkyl Ethers (U.S. EPA,
1980) were reviewed for pertinent information. Literature searches were conducted from 1965 to
September 2002 in TOXLINE, CANCERLIT, MEDLINE, GENETOX, HSDB,
EMIC/EMICBACK, DART/ETICBACK, RTECS and TSCATS for relevant studies. During
April 2004, these databases were again searched for relevant studies; none were identified that
would change the conclusions of the risk estimate.
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REVIEW OF PERTINENT DATA
Bis (2-chloroethoxy)methane is a synthetic organic chemical used as a solvent and as a
reactant in the manufacture of polysulfide elastomers. More than 95% of polysulfide elastomers
are made from bis (2-chloroethoxy) methane starting material and sodium polysulfide. The
resulting products are used as heat- and solvent resistant sealants. The U.S. Food and Drug
Administration has approved bis(2-chloroethoxy)methane for use in the manufacture of resins
approved for direct contact with food packaging materials. Bis (2-chloroethoxy)methane is on
the U.S. EPA's 1990 High Production Volume chemical list (U.S. EPA, 2006b); in 1977, 10 to
50 million pounds of bis(2-chloroethoxy)methane were produced in the U.S. (HSDB, 2005).
Human Studies
Oral Exposure. No reports were located regarding the subchronic or chronic toxicity or
carcinogenicity of bis(2-chloroethoxy)methane in humans by oral exposure.
Inhalation Exposure. No reports were located regarding the subchronic or chronic toxicity or
carcinogenicity of bis(2-chloroethoxy)methane in humans by inhalation exposure.
Animal Studies
Oral Exposure. Non-fasted Sprague-Dawley rats (10/sex/dose group) were treated with oral
doses of 0, 10, 20, 40, 80, or 120 mg/kg-day of bis(2-chloroethoxy)methane by daily gavage in
corn oil for 90 days (Bio/Dynamics, 1990a). Physical observations, body weight and food
consumption measurements were recorded weekly. Hematology and clinical chemistry
evaluations were performed after one month of treatment and at termination. Ophthalmoscopic
examinations took place at termination. Complete gross post-mortem examination was
conducted on all animals. The control and high-dose groups received comprehensive
histopathological examinations, while only the kidneys, liver, lungs and gross lesions were
examined in the intermediate dose groups.
Of the 20 rats that received the highest dose (120 mg/kg-day), all ten males and seven of
ten females died or were killed in moribund condition prior to completion of the study
(Bio/Dynamics, 1990a). One death occurred after a single dose and seven more occurred during
the first week. Subsequent deaths occurred as late as day 76 of the study. These deaths were
considered by the researchers to be chemical-related; myocardial degeneration seen by
microscopic examination in all 120 mg/kg-day rats that died after day 14 of the study was
considered by the researchers to be a possible cause of death. One female in the 80 mg/kg-day
dose group died on day 78; a death that was also considered to be chemical-related by the
investigators in part because microscopic examination revealed myocardial degeneration similar
to that seen in the 120 mg/kg-day animals that died. One female in the 40 mg/kg-day group died
due to gavage error, but no chemical-related deaths were observed in the 10, 20 or 40 mg/kg-day
dose groups. Rats killed in moribund condition and some of those that died exhibited
emaciation, poor food consumption, hypothermia, lethargy/prostration, dyspnea, gasping, moist
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rales, ataxia, abnormal posture, slight tremors, salivation, and brown-yellow stains on the snout,
paws, ventral surface and anogenital area. Clinical signs were unremarkable in rats that survived
the experiment. In male rats treated with the highest dose of bis(2-chloroethoxy)methane, body
weight was significantly reduced by 17-18 % after weeks 1 (n=6 survivors) and 2 (n=4
survivors), and 7 to 21% thereafter (n=l or 2 survivors). Mean body weights of males receiving
80 mg/kg-day were slightly lower than control during the second two months of the study: 6%
deficit at week 5 and 10% deficit at week 12 (differences from control not statistically
significant). Mean body weights for males in the lower dose groups were similar to controls, and
no effect on body weight was evident in females at any dose level. Food consumption was
reduced in the high-dose male group during the first 2 weeks of the study, but was similar to
controls subsequently in the 2 survivors of this group. Food consumption was similar to or
higher than controls in all other test groups. Ophthalmological examinations were unremarkable.
No statistically significant changes in hematological parameters were observed
(Bio/Dynamics, 1990a). Exposure to 120 mg/kg-day induced statistically significant alterations
in several clinical chemistry parameters in both males and females. The alterations that were
considered to be indications of an effect of exposure to 120 mg/kg-day of bis(2-
chloroethoxy)methane were: 1) slight elevations in serum aspartate aminotransferase (AST) at
one month in both males and females, with a marked, statistically significant elevation in AST
among high-dose females at study termination (no high-dose males survived to study
termination), 2) a statistically significant elevation in serum alkaline phosphatase in males at one
month and nonsignificant elevations in females at both one and three months, and 3) increased
blood urea nitrogen (BUN) in females at 1 month (nonsignificant) and 3 months (statistically
significant). In the 80 mg/kg-day group, there was a slight, statistically significant increase in
serum alanine aminotransferase (ALT) among male rats at 3 months. No changes in clinical
chemistry parameters were observed among male or female rats receiving 10, 20, or 40 mg/kg-
day of bis(2-chloroethoxy)methane compared to controls.
Absolute and relative liver weights were statistically significantly increased in a dose-
related fashion in female rats treated with 80 or 120 mg/kg-day (Bio/Dynamics, 1990a). Liver
weight measurements were not available for males in the 120 mg/kg-day dose group due to early
mortality; the only statistically significant change in males was a small increase in relative liver
weight at 40 mg/kg-day. Histopathologic examination of the liver revealed a dose-related
increased incidence of minimal-to-slight hypertrophy of the centrilobular hepatocytes in males
treated with 20, 40, or 80 mg/kg-day (0/10, 0/10, 3/10, 4/10, 6/10, and 0/10 in the 0, 10, 20, 40,
80, and 120 mg/kg-day groups, respectively). The difference from controls was statistically
significant in the 40 and 80 mg/kg-day groups (Fisher exact test conducted for this assessment).
The lesion was not observed in males of the 120 mg/kg-day group, but rats in this group all died
early. Liver lesions were not found in female rats. Mean adrenal weights (absolute and relative)
were reduced relative to control among male rats receiving 20, 40, or 80 mg/kg-day. This effect
on adrenal weight, however, was not observed among females and adrenal morphology was
normal; thus, the toxicological significance of this effect on the adrenal gland is uncertain.
Significant increases in relative kidney and testes weights in male rats at 80 mg/kg-day were
considered by the researchers to be secondary to reduced body weight in this group. Kidney
lesions, seen only in male rats, were increased incidences of minimal to moderate tubular
nephrosis, accompanied in some cases by birefringent intracytoplasmic inclusions in the
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convoluted tubular epithelium, and hyaline droplets in the epithelial cytoplasm of the proximal
convoluted tubules. The incidence and severity of the renal lesions increased with dose, with the
10 mg/kg-day group being similar to controls and the 80 mg/kg-day group showing the most
pronounced effects.
Other organs affected by the 120 mg/kg-day dose were the heart (myocardial
degeneration), brain and spinal cord (vacuolization, gliosis), spleen, bone marrow, and thymus
(atrophy, hypocellularity), and epididymides (oligospermia, degenerated seminal product);
however, these organs were not systematically examined in rats receiving lower doses
(Bio/Dynamics, 1990a). Of particular interest is the heart. Postmortem examination revealed
slight-to-moderate degeneration of the myocardium in all high-dose animals that died after 2
weeks of exposure to bis(2-chloroethoxy)methane. The overall incidence of myocardial
degeneration was 6/10 males and 6/10 females at 120 mg/kg-day (versus 0/10 for controls of
each sex). The authors speculated that myocardial degeneration was a possible cause of death.
Despite the prevalence of this effect among high-dose rats of both sexes, and absence among
controls, the authors did not conduct histopathological examinations of the hearts of rats
receiving lower doses, aside from one female from the 80 mg/kg-day group (the female that was
found dead on day 78) and one female from the 40 mg/kg-day group that died accidentally in
week 5. Histological examination revealed myocardial degeneration in the 80 mg/kg-day
female, but not the 40 mg/kg-day female.
The renal effects seen in male rats are consistent with the pattern of early stages of alpha-
2u globulin-associated rat nephrotoxicity, as established by the Risk Assessment Forum (U.S.
EPA, 1991b), wherein the Agency concluded these renal effects are not appropriate as a critical
effect for human health risk assessment. This study identified a LOAEL of 20 mg/kg-day based
on liver lesions (hypertrophy of the centrilobular hepatocytes) in males rats and a NOAEL of 10
mg/kg-day following subchronic oral administration of bis(2-chloroethoxy)methane.
More recently, the general toxicity of BCM was evaluated in mice (Battelle, 2002a) and
rats (Battelle, 2002b) exposed to BCM (in 95% ethanol) dermally for 5 days per week for 90
days. Applied doses for rats and mice were 0, 50, 100, 200, 400 and 600 mg/kg. Duration
adjusted doses were 0, 36, 71, 143, 286 and 429 mg/kg. Available reports do not indicate
whether the dose site was occluded. For all rats, the 600 mg/kg dose was lethal, and
observations consistent with heart failure were noted in some rats in the 400 and 600 mg/kg dose
groups. BCM was lethal in two of 10 female rats receiving 400 mg/kg. Selected organs were
histologically examined at sacrifice. Hematology and clinical chemistries were not altered.
Histopathic cardiomyopathy was considered the most toxicologically significant finding, and a
dose-dependent increase in severity was noted in the 400 and 600 mg/kg dose groups. In male
rats, histologic alterations were noted in the glandular stomach, mesenteric lymph nodes, spleen,
thymus, Harderian gland and olfactory epithelium, but only in high dose animals. Findings in
female rats differed only in that spleen, Harderian gland and olfactory epithelium were affected
at 400 mg/kg and renal tubular (cortex) damage was noted in high dose females.
In mice, Battelle (2002b) reported no findings of lethality in males, but BCM was lethal
to 3/10 female mice receiving 600 mg/kg. Erythrocyte-related parameters (RBC, hemoglobin,
hematocrit) were significantly reduced in male mice at and above 200 mg/kg and both absolute
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and relative kidney weights were increased at 400 and 600 mg/kg. In female mice, absolute liver
weight was increased and myocardial vacuolization were observed at 400 mg/kg. At 600 mg/kg,
additional findings included histopathic alterations in heart and liver, erosion and inflammation
of the stomach and duodenum, and reductions in erythrocyte parameters. Dunnick et al (2004a)
also reported the results from this study and noted an increased (2/10) incidence of myocyte
cytoplasmic vacuolization in female rats exposed to 200 mg/kg, with incidences of 5/10 and 8/10
in the two higher doses, respectively.
From these studies, a dermally applied, duration adjusted LOAEL of 71 mg/kg-day is
indicated for decreased hemoglobin content in male mice and increased incidence of myocyte
cytoplasmic vacuolization in female rats. Correspondingly, the NOAEL values would be 36
mg/kg-day. Special considerations and information must be available to translate this dermally
applied dose to a corresponding internal dose. Some pertinent information describe the
distribution and elimination of 14C from a 14C-labelled BCM dermal administration study
(Mathews and Jeffcoat, 2002). In those studies, BCM was dermally applied. Ex vivo studies
with excised skin demonstrated a loss of 85% of the applied dose within one hour of application.
Absent a capacity of absorption and removal from the site, these results indicate that up to 85%
of the administered dose may be lost to volatilization within the first hour of application. Results
from dermal studies in rats exposed to 10 and 0.1 mg/kg with and without dose site appliances
(covers) demonstrated that dermal absorption resulted in a total absorbed dose of approximately
15%) of the administered dose with appliances and approximately 40 to 44% of applied dose
without appliance, seemingly indicative of additional ingestion via grooming (Mathews and
Jeffcoat, 2002). In mice with the dermal appliance, these samples accounted for approximately 9
and 18%) of a dermally applied dose of 0.1 or 10 mg/kg, with dose site accounting for
approximately 1% of the administered dose. Mice administered BCM without the site-protective
appliance absorbed 13 and 21% of applied doses of 0.1 and 10 mg/kg, respectively. The pattern
of tissue distribution, extent of urinary elimination and other pharmacokinetic information,
demonstrated for total radiolabel derived from 14C-labelled BCM, demonstrate appreciable
similarity between dermal and oral exposures. While these data indicate dermal absorption,
potential and undescribed differences in the metabolism of orally and dermally exposed animals
exist and complicate the development of a dermal correction factor, especially so in light of
studies that seem to indicate thiodiglycolic acid as the potentially bioactive (toxic) metabolite
(Mathews and Jeffcoat, 2002). This metabolite is common to other cardiotoxic compounds, as
well. Without further adjustment, the dermally applied, duration adjusted NOAEL values
indicated by Battelle (2002a,b) and quantified by Dunnick et al (2004a) are higher than NOAEL
value (10 mg/kg-day) for liver lesions developed from orally administration studies
(Bio/Dynamics, 1990a).
In a range-finding study for the oral subchronic study (Bio/Dynamics, 1990a), non-fasted
Sprague-Dawley rats (5/sex/dose group) were treated with 0, 20, 40, 50, 60, 80, or 100 mg/kg-
day of bis(2-chloroethoxy)methane by daily gavage in corn oil for two weeks (Bio/Dynamics,
1990b). When no signs of toxicity were noted after one week of dosing, the 20 and 40 mg/kg-
day doses were increased to 150 and 200 mg/kg-day, respectively, for the second week of
treatment and satellite groups of 5 rats/sex/group were started on doses of 120 or 160 mg/kg-day.
Animals were observed twice daily for mortality and gross toxicity. Physical examinations and
body weight and food consumption measurements were performed weekly. Blood was collected
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from all rats surviving to study termination for hematology and clinical chemistry evaluations.
Complete gross postmortem examinations were performed on all animals. The brain, heart,
liver, kidneys, adrenals, and gonads were weighed for animals killed at terminal sacrifice.
Histopathology was not performed.
Doses of 120 mg/kg-day and above clearly produced treatment-related mortality (7/10-
10/10 dead after 1-9 doses) (Bio/Dynamics, 1990b). The only deaths in the lower dose groups
were single deaths in the 60 and 80 mg/kg-day groups (1/5 females and 0/5 males died in each
group after 16 doses) that may also have been due to treatment. Findings in rats that died or
were sacrificed moribund included clinical signs (lethargy, tremor, dyspnea, irregular gait,
yellow or brown staining of the anogenital area, salivation, moist rales, hypothermia, and general
poor condition in some rats just prior to death), antemortem weight loss, hematological changes
(increased hemoglobin, hematocrit, and red blood cell count in males, but not females), and
serum chemistry changes (increases in serum markers for hepatotoxicity and nephrotoxicity,
including ALT, AST, alkaline phosphatase, BUN, and glucose). Due to the high mortality in the
> 120 mg/kg-day dose groups, meaningful comparisons based on group means were not possible
for these groups. Among the 20-100 mg/kg-day groups, there were no significant differences
from controls for food intake or body weight, and no clinical signs were observed. The only
significant hematology finding was an increase in red blood cell count in females, but not males,
at 100 mg/kg-day. Blood urea nitrogen was significantly increased in the 50, 80, and 100 mg/kg-
day female groups, and non-significantly increased in the 60 mg/kg-day female group. The
magnitude of the change from controls was small for this parameter (-20%) and did not increase
with dose. No other serum chemistry changes were seen in females or males. Absolute and
relative liver weights were significantly increased in females in the 80 and 100 mg/kg-day
groups (by 21-27%, a moderate change for this parameter). No other significant organ weight
changes were found. Gross postmortem examination revealed no abnormalities attributable to
bis(2-chloroethoxy)methane. The results of this study support the finding of the subchronic
study that the liver is an important target for bis(2-chloroethoxy)methane.
In a short term study to characterize and examine the short-term time course of BCM-
induced cardiotoxicity, rats were exposed dermally for up to 12 days to 400 and 600 mg/kg BCM
in 95% ethanol (Dunnick et al, 2004b). Within two days of exposure to 600 mg/kg, most but not
all cardiac myocytes examined showed toxic effects. Mitochondrial alterations were the most
prominent, but other alterations included distention of the sarcoplasmic reticulum, myofibrillary
degeneration and occasional Z-banding misalignments. Severe disintegration of mitochondria
and the presence of megamitochondria were observed. Swelling of the sarcoplasmic reticulum
was presented as a sign of cellular injury due to loss of membrane function in maintaining water
balance. The authors noted in animals surviving to day 16 a "resolvement of the manifestations
of the lesions".
Inhalation Exposure. No reports were located regarding the subchronic or chronic toxicity of
bis(2-chloroethoxy)methane in animals by inhalation exposure.
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Other Studies
Toxicokinetics. The disposition of BCM was investigated in rats and mice by Research Triangle
Institute (RTI) under contract to NIEHS (Mathews and Jeffcoat, 2002). In that study, male and
female F-344 rats and male and female B6C3F1 mice received 14-C-labeled BCM via the oral,
intravenous (i.v.) and dermal routes. BCM appeared poorly absorbed via dermal application,
potentially due to volatility, and so will not be further presented here. Initial 72-hr studies
characterized the tissue distribution and elimination of a 10 mg/kg gavage (water vehicle) dose
of BCM. Parent BCM and 14C-C02 were quantified in expired air, and total 14C was quantified
in urine, feces and tissues from male and female mice and male rats. The routes, rates and extent
of elimination appeared similar in male and female mice, with combined urinary and fecal
elimination accounting for 60-74% of the dose at 14 hours and with urine accounting for 50-60%
and approximately 25% of the dose excreted in urine and feces, respectively, at 72 hours.
Approximately 10-12% was excreted as 14C-C02 in breath, cumulative to 72 hours; less than
0.12%) was excreted as BCM in breath of male mice. Cumulative elimination via all routes
accounted for greater than 90% of dose in each sex.
Tissue distribution in male and female mice was similar, and body burdens approximated
less than 1% of the administered dose. After 24 hours, 14C in blood was unextractable. At 72
hours, blood concentrations of 14C (in BCM equivalents) were 162 ng/gram, and 118 ng/gram
for male and female mice, respectively. For males, tissues with 14C concentrations higher
(ratios of tissue:blood concentrations in parentheses) than blood included liver (2.88), kidney
(2.48), thymus (1.72), skin (1.33), lung (1.31), spleen (1.29), and adipose (1.18). For female
mice, tissues with 14C concentrations higher than blood included liver (3.10), thymus (2.72),
kidney (2.61), adipose (1.86), ovaries (1.82), lung (1.56), spleen (1.41), and skin (1.05). Heart
tissue contained concentrations of 14C approximating 85% that of blood for both sexes.
As in mice, BCM was rapidly eliminated from orally-exposed male rats, but higher rates
and extent of elimination occurred via the urine; this route accounted for more than 50% of the
dose at 8 hours, and for 90% of the dose at 72 hours. Feces accounted for approximately 0.4% of
the dose at 72 hours. Exhalation of 14C-C02 accounted for approximately 7% of the dose, and
exhaled BCM accounted for less than 0.2% of the administered dose. Less than 2.5% of the
dose's 14C equivalent was retained in the body at 72 hours. Blood concentrations of 14C (in
BCM equivalents) were 390 ng/gram. For male rats, tissues with 14C concentrations higher
(ratios of tissue:blood concentrations in parentheses) than blood included liver (1.74) and thymus
(1.69). While higher blood concentrations in the rat may lead to speculation that species
differences in the apparent concentrations of BCM in blood may shift the pattern of blood:tissue
distribution, most rat solid tissues also contained higher concentrations of BCM equivalents than
their mouse counterparts.
Male mice were dosed with 1.0 mg/kg, i.v. and female mice were dosed i.v. with BCM at
0.1 and 1.0 mg/kg. For all mice, urinary and fecal elimination was characterized for 72 hours;
tissue distribution was evaluated for male mice. Combined urinary and fecal elimination for all
dose groups approximated 85 to 95% at 72 hours, with urine accounting for 65 to 72% of the
administered dose. Sex-dependent differences in the fraction exhaled seemed evident for the 1
mg/kg mice. This route accounted for nearly 10% of the dose in males and approximately 5% of
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dose in females. Males eliminated nearly twice as much of the dose unchanged in expired air
than did females, and approximately three-fold more of the dose as C02 than did females. In
females administered an i.v. dose of 0.1 mg/kg, a slightly lower fraction of the dose was
eliminated in urine and feces, and a slightly higher fraction of the dose was eliminated as expired
C02 when compared to females administered 1.0 mg/kg via i.v.
In male mice administered 1.0 mg/kg BCM i.v., at 72 hours, approximately 4% of the
administered dose was retained in the body. Blood concentrations were approximately 19 ng
equivalents/gram, and tissues with 14C concentrations higher (ratios of tissue:blood
concentrations in parentheses) than blood included kidney (2.33), liver (1.94), adipose (1.45),
thymus (1.24), and lung (1.08). Heart contained approximately 71% the concentration of BCM
equivalents as blood.
In male and female rats administered 1.0 mg/kg BCM i.v., the time course profile
demonstrated rapid and marked decline of BCM, where levels circulating dose approximated 2%
of administered dose within 15 minutes. BCM equivalents demonstrated a biphasic decline with
the terminal slope appearing largely defined by the proportion of unextractable 14C residues.
For example, for males and females, total BCM equivalents decreased from 362 to 67 and from
283 to 45 ng equivalents/ gram blood between 15 minutes and 24 hours, respectively. During
this time the percentage of blood 14C present as unextractable fraction increased from
approximately 20% to approximately 75% for males and from approximately 22% to
approximately 95% for females. Similar results were demonstrated in male mice administered
1.0 mg/kg BCM. In addition to blood, liver and thymus tissues were analyzed for extractable
radioactivity. At 15 minutes post-dosing, less than 30% of the total radioactivity in liver was
extractable, with the majority of extracted radiolabel represented by parent compound. At 8
hours post-dosing, less that 5% of the total radioactivity present in liver tissue was extractable,
and virtually no parent BCM was demonstrated. Results in thymic tissue were qualitatively the
same: at 8 hours approximately 85% of the total radioactivity was extractable, and approximately
45% of the extractable radioactivity represented parent BCM; at 8 hours post-dosing extractable
radiolabel in thymus represented approximately 10% of total radioactivity, with parent BCM
levels approaching zero. The high level of binding early in the time profile (15 minutes) seems
inconsistent with incorporation of radiolabeled moiety into protein.
Mathews and Jeffcoat (2002) also reported the results of investigations of BCM
metabolism. The results of an experiment in which cytochrome P4502E1 was inhibited
demonstrated no change in the blood concentration-time profile in male mice administered 1.0
mg/kg BCM. Urine collected from rats administered 10 and 0.1 mg/kg BCM orally and male
rats administered 1.0 mg/kg i.v. demonstrated three distinct peaks, accounting for 80 to 88% of
urinary 14C, when analyzed by high performance liquid chromatography, and none of these
peaks was altered when urine was incubated with sulfatase, acylase and beta-glucoronidase. One
of these metabolites co-eluted with thiodiglycolic acid; subsequent gas chromatography/mass
spectrometric analysis confirmed that metabolite as thiodiglycolic acid. This metabolite
accounted for 49 to 51% of recovered 14C. The peak that co-eluted with the sulfoxide of
thiodiglycolic acid accounted for 25-31% of urinary radiolabel. Combined recoveries for these
two peaks accounted for between 74 and 82% of urinary radiolabel. With the preponderance of
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radiolabel eliminated in urine, these data support thiodiglycolic acid as the major metabolite of
BCM.
Oral-Dermal Dose Comparison. Data from 90-day studies conducted via the dermal route of
exposure in rats (Battelle, 2002a) and mice (Battelle, 2002b) offer additional insights on the
dose-response relationship for several toxicities. However, in order for advantage to be made
from these results, some measure of absorbed, rather than applied dose is required. The
relationship between dermally applied and absorbed dose can be developed from information
from a distribution study also recently available (Mathews and Jeffcoat, 2002). Twenty-four
hours after administration, 15.73 and 15.44% of dermally applied doses were absorbed by rats,
and urinary elimination accounted for 91.1 and 88.1% of the absorbed dose in male rats
receiving dermal doses of 0.1 and 10 mg/kg. The absorbed dose from these two exposures
corrects to 0.016 and 1.5 mg/kg. In mice, 24 hours after application, approximately 9% of a 0.1
mg/kg dose was absorbed, and urinary elimination accounted for 95.5% of the absorbed dose. In
mice dermally exposed to 10 mg/kg, approximately 18% of the dose was absorbed, and urinary
elimination accounted for 68.8% of the absorbed dose. In mice, the study authors noted the
confounding issue of cross contamination of urine and feces occurring in the metabolism cage.
Combined urinary and fecal elimination in 10 mg/kg-dosed mice accounted for 78.3% of the
absorbed dose. While the fraction of absorbed 14C eliminated in urine is similar between oral
and dermal exposures, there is no information on the comparative metabolism of 14C-labelled
BCM, and there is evidence that the thiodiglycolic acid metabolite may be responsible for the
noted cardiotoxicity.
DERIVATION OF PROVISIONAL SUBCHRONIC AND CHRONIC RfDs
FOR BIS(2-CHLOROETHOXY)ME THANE
No pertinent data regarding the oral toxicity of bis(2-chloroethoxy)methane in humans
are available. Only one subchronic study of oral administration of bis(2-chloroethoxy)methane
to rats was located: a 90-day oral gavage study conducted by Bio/Dynamics (1990a), wherein
Sprague-Dawley rats (10/sex/dose group) received oral doses of 0, 10, 20, 40, 80, or 120 mg/kg-
day of bis(2-chloroethoxy)methane in corn oil. Subchronic and chronic oral RfDs for bis(2-
chloroethoxy)methane can be derived using a NOAEL/LOAEL approach, based on liver lesions
(centrilobular hepatocellular hypertrophy) in male rats receiving 20 mg/kg-day or more of bis(2-
chloroethoxy)methane. This study identified a NOAEL of 10 mg/kg-day for the critical effect.
The finding that the liver is a sensitive target for bis(2-chloroethoxy)methane is supported by the
short-term range-finding study (Bio/Dynamics, 1990b).
To the rat NOAEL of 10 mg/kg-day for liver lesions established by Bio/Dynamics
(1990a), a combined uncertainty factor of 300 was applied. The uncertainty factors included a
10 for interspecies extrapolation, a 10 for human variability, and a 3 for database deficiencies
(including lack of reproductive and developmental toxicity tests), resulting in a combined
uncertainty factor of 300. A provisional subchronic oral RfD of 0.03 mg/kg-day was
calculated as follows:
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p-sRfD = NOAEL / UF
= 10 mg/kg-day / 300
= 0.03 mg/kg-day or 3E-2 mg/kg-day
A provisional chronic oral RfD can also be derived by dividing the NOAEL of 10 mg/kg-
day established by Bio/Dynamics (1990a) by a combined uncertainty factor of 3000. The
uncertainty factors included a 10 for extrapolation from a subchronic study, a 10 for interspecies
extrapolation, a 10 for human variability, and a 3 for database deficiencies, resulting in a
combined uncertainty factor of 3000. A provisional chronic oral RfD of 0.003 mg/kg-day was
calculated as follows:
p-RfD = NOAEL / UF
= 10 mg/kg-day / 3000
= 0.003 mg/kg-day or 3E-3 mg/kg-day
Confidence in the principal study is low. The principal study examined a number of
relevant endpoints; however, the study used only minimally adequate group sizes, failed to
conduct histopathology on all tissues at lower exposure doses, and appears to have used a dose
that was too high based on the range-finding study (Bio/Dynamics, 1990b). Confidence in the
database is also low: the database is lacking human data, supporting subchronic or chronic
animal studies, and studies of developmental, reproductive, or neurological effects of exposure to
bis(2-chloroethoxy)methane. Reflecting low confidence in the principal study and low
confidence in the database, confidence in the provisional RfD is low.
FEASIBILITY OF DERIVING PROVISIONAL SUBCHRONIC AND CHRONIC
RfCs FOR BIS(2-CHLOROETHOXY)METHANE
Derivation of a provisional subchronic or chronic RfC for bis(2-chloroethoxy)methane is
precluded by the absence of inhalation toxicity data.
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