U.S. Environmental Protection Agency
Supporting Documents for Risk-Based Prioritization
3/18/2008
Supporting Documents for Initial Risk-Based Prioritization of High
Production Volume Chemicals
Chemical/Category: Hexabromocyclododecane (HBCD)
CAS 3194-55-6 1,2,5,6,9,10 hexabromocyclododecane
CAS 25637-99-4 hexabromocyclododecane
Contents:
•	Page 2: Screening-Level Risk Characterization, 3/14/2008
•	Not Attached: Screening-Level Hazard Characterization, OECD SIDS Initial
Assessment Profile, 4/20/2007,
http://cs3-hq.oecd.org/scripts/hpv/ (Click on "Search" in left sidebar and enter the
CAS No.)
Note: OECD SIDS Initial Assessment Profiles (SIAP) and SIDS Initial
Assessment Reports (SIAR) are publicly available through the United Nations
Environmental Programme website. These documents are presented in an
international forum that involves review and endorsement by governmental
authorities around the world. The U.S. EPA is an active participant in these
meetings and accepts these documents as reliable screening-level hazard
assessments for the purpose of the U.S. HPV Challenge qualitative risk
characterization process.
•	Page 7: Screening-Level Exposure Characterizations, 3/14/2008
•	Page 11: Screening-Level Physical/Chemical and Environmental Fate
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QUALITATIVE SCREENING-LEVEL RISK CHARACTERIZATION FOR
Hexabromocyclododecane (CAS No. 3194-55-6)
1. Background
The High Production Volume (HPV) Challenge Program1 is a voluntary initiative aimed at developing and making
publicly available screening-level health and environmental effects information on chemicals manufactured in or
imported into the United States (U.S.) in quantities greater than one million pounds per year. In the Challenge
Program, producers and importers of HPV chemicals voluntarily sponsor chemicals; sponsorship entails the
identification and initial assessment of the adequacy of existing toxicity data/information, conducting new testing if
adequate data do not exist, and making both new and existing data and information available to the public. Each
complete data submission contains data on 18 internationally agreed to "SIDS" (Screening Information Data SetError!
Bookmark not defined.,2-j encjp0ints that are screening-level indicators of potential hazards (toxicity) for humans or the
environment and environmental fate.
The Environmental Protection Agency's Office of Pollution Prevention and Toxics (OPPT) is evaluating the data
submitted in the HPV Challenge Program on approximately 1,400 sponsored chemicals. Data submitted to the
Organisation for Economic Co-operation and Development (OECD) HPV Programme are also being evaluated.
OPPT developed a screening-level hazard characterization that consists of an objective evaluation, conducted
according to established EPA guidanceError! Bookmark not defined.'3, of the quality and completeness of the data
set provided and is based primarily on hazard data provided by sponsors. The characterization does not draw
conclusions regarding the completeness of all data generated with respect to a specific chemical substance or
mixture. The OECD SIDS documents (SIDS Initial Assessment Profile; SIAP and SIDS Initial Assessment Report;
SIAR) provide similar information. Under both the HPV Challenge and OECD HPV Programs, chemicals that have
similar chemical structures, properties and biological activities may be grouped together and their data shared across
the resulting category. Evaluation of chemical category formation and data extrapolation(s) among category
members is performed in accord with established U.S. EPA1 and OECD4 guidance.
In 2006 and 2007, EPA received data on uses of and reasonably likely exposures to chemicals on the Toxic
Substances Control Act (TSCA) Inventory of existing chemicals, submitted in accordance with the requirements of
the Inventory Update Reporting (IUR) rule5. Information is collected every five years under IUR, promulgated
under the authority of section 8(a) of TSCA. The most recent reports pertain to chemicals manufactured in
(including imported into) the U.S. during calendar year 2005 in quantities of 25,000 pounds or more at a single site.
Information is reported on the identity of the chemical manufactured or imported and the quantity, physical form,
and number of persons reasonably likely to be exposed during manufacture of the chemical. For chemicals
manufactured or imported in quantities of 300,000 pounds or more at a single site during calendar year 2005,
additional information was reported on the industrial processing and uses of the chemical, the number of industrial
processing sites and of employees reasonably likely to be exposed to the chemical at these sites, the consumer and
commercial uses of the chemical and an indication whether the chemical is used in products intended for use by
children under 14 years of age.
For these qualitative screening-level risk characterization documents, EPA has reviewed the IUR data to evaluate
exposure potential. In addition, exposure information that may have become available through prior Agency actions
has been considered, as appropriate. The resulting exposure information has been combined with the screening-
level hazard characterizations to develop this qualitative screening-level risk characterization6'7. These screening-
level risk characterizations are technical documents intended to support subsequent decisions and actions by OPPT.
Accordingly, the document is not written with the goal of informing the general public. The purpose of the
1	U.S. EPA. High Production Volume (HPV) Challenge Program; http://www.epa.gov/chemrtk/index.htm.
2	U.S. EPA. HPV Challenge Program - Information Sources; http://www.epa.gov/chemrtk/pubs/general/guidocs.htm.
3	U.S. EPA. Risk Assessment Guidelines; http://cfpub.epa.gov/ncea/raf/rafguid.cfm.
4	OECD. Guidance Document on the Development and Use of Chemical Categories;
http://www.oecd.Org/document/7/0.2340.en 2649 34379 1947463 111 1.00.html.
5	U.S. EPA - Basic IUR Information: http://www.epa.gov/opptintr/iur/pubs/guidance/basic-information.htm
6	U.S. EPA Guidelines for Exposure Assessment; http://cfpub.epa.gov/ncea/raf/recordisplav.cfm?deid=15263
7	U.S. EPA. Risk Characterization Program; http://www.epa.gov/osa/spc/2riskchr.htm.
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qualitative screening level risk characterizations is two-fold: to support initial risk-based decisions to prioritize
chemicals and inform risk management options and to identify data needs for individual chemicals or chemical
categories.
2.	Physical-Chemical Properties and Environmental Fate
This report was prepared using the best available data from a number of sources, but draws no conclusions regarding
whether additional relevant data may exist. 1,2,5,6,9,10-Hexabromocyclododecane (hexabromocyclododecane or
HBCD) is a solid at room temperature. It has low water solubility, low vapor pressure, and moderate volatility from
water. It is not expected to hydrolyze but may photolyze slowly. It is minimally mobile in soil and water systems.
Recent information (see Physical/Chemical and Environmental Fate Characterization supporting document for
details) suggests that HBCD is relatively biodegradable at environmentally relevant concentrations. Thus, HBCD is
considered bioaccumulative (B3) but not persistent (PI).
In addition, the physical-chemical properties of HBCD that allow it to exist in the atmosphere attached to small
particles in air are likely to increase its resistance to degrade in the atmosphere, and thus enhance its potential for
long-range transport. This may account for increasing levels of HBCD in biota at remote locations, as reported in
recent publications (see note at end of Exposure Characterization below).
3.	Hazard Characterization
This summary is based on information compiled both from the HPV Challenge Submission as well as the OECD
SIDS Initial Assessment Profile (SIAP) which was presented at an OECD SIDS Initial Assessment Meeting (SIAM)
in April, 2007 for HBCD. This document is presented in an international forum that involves review and
endorsement by governmental authorities around the world. The U.S. EPA is an active participant in these meetings
and accepts this process as a reliable screening-level hazard assessment for the purpose of the U.S. HPV Challenge
qualitative risk characterization process. Thus, when such documents exist there is no need to generate a separate
Hazard Characterization document. In this case, the SIDS Initial Assessment Report (SIAR) is a European Union
risk assessment which is a substantial document that is well beyond the scope of this screening level hazard/risk
characterization. The SIAP can be found at the following website: http://cs3-hq.oecd.org/scripts/hpv/ (click on
search in the left hand column).
Aquatic Organism Toxicity: The available aquatic toxicity data for the HPV Challenge endpoints (the SIDS
described above) with HBCD shows that the potential acute hazard for fish and aquatic invertebrates is low and the
acute hazard for aquatic plants is high. Chronic aquatic toxicity testing shows the hazard concern is high in aquatic
invertebrates. The overall concern for the environment is high based on acute aquatic toxicity to algae, chronic
toxicity to invertebrates, and the high potential to bioaccumulate [see above].
Human Health Toxicity: The acute toxicity of HBCD is low via the oral, dermal and inhalation routes of exposure.
HBCD has been shown to be mildly irritating to the eyes, not irritating to skin, and it is not considered a skin
sensitizer. The potential toxicity from repeated oral exposure to HBCD was assessed in a variety of studies in
laboratory animals. Liver effects were observed in several studies but based on the inconsistency of effects between
studies and sexes, and lack of dose-response, it is not clear if the observed effects are treatment-related. Effects on
the thyroid (one or both sexes) were observed at moderate to high doses in some repeated-dose studies but not
others, but could be due to the fact that the thyroid system was not thoroughly studied in the early studies. More
recent studies showed increased thyroid weights in females only. One study indicates decreased serum T4 and
increased serum TSH in both sexes, whereas another study only shows effects in females. Taken together, however,
the data are suggestive of possible treatment-related thyroid effects in adult animals. Several recent in vivo and in
vitro studies have been conducted to try and elucidate the possible mechanisms for both the observed liver and
thyroid effects, but with no clear conclusions. Functional observation battery and motor activity evaluations in adult
animals showed no evidence of neurotoxicity. The reproductive toxicity of HBCD was not specifically tested (i.e.,
there were no studies on fertility); however, repeated dose studies included an investigation of the reproductive
organs. The only reproductive organ effects observed included transient increases in prostate weights at high doses
(1,000 mg/kg/day); however, this occurred without any corresponding histopathology or functional changes in
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several measured sperm parameters. Slight inhibition of oogenesis was also observed, but only at extremely high
doses (>4 g/kg/day). Standard developmental toxicity studies with HBCD did not show any adverse effects on the
developing fetus; however, disturbances in thyroid function observed in adult animals from repeated dose studies
may have implications for the developing nervous system. The available data on genotoxicity shows that HBCD
does not affect genes or chromosomes in various tests with bacteria, cell cultures, and whole animal tests.
HBCD was considered a candidate for further work in the OECD SIDS Programme based on repeated dose toxicity
and possible developmental neurotoxicity (the latter based on a test that is beyond the SIDS). For the purposes of
the U.S. HPV Challenge Program and this qualitative risk screening process, the overall human health hazard
concern is moderate based on data suggestive of thyroid effects which could potentially affect developing fetuses in
pregnant animals.
4. Exposure Characterization
This exposure characterization was completed using available 2006 Inventory Update Rule (IUR) submissions.
Data and information that are claimed Confidential Business Information (CBI) by the submitter were reviewed and
considered by EPA in preparing this assessment but are not disclosed in this summary.
In addition, the following sources were reviewed to identify exposure and use information: the HPV Challenge
Submission, the OECD HPV Submission, the Toxics Release Inventory (TRI), OSHA PEL documentation, various
databases and public sources. See the separate Exposure Characterization for references.
HBCD was manufactured in the United States in amounts ranging from 10,000,000 to 50,000,000 pounds in 2005.
The HPV submission indicates that HBCD's reported use is as a flame retardant. Its primary application is in
extruded and expanded polystyrene foam that is used as thermal insulation in the building industry. A secondary
application is as a flame retardant for upholstery textiles. A minor application is in video or audio equipment
housing. In addition, other public sources report that HBCD is also used in crystal and high-impact polystyrene,
SAN (styrene-acrylonitrile) resins, adhesives and coatings.
Exposures to Workers
A search of the National Occupational Exposure Survey (NOES), conducted from 1981 to 1983, has no data for the
total number of workers potentially exposed to HBCD under the CAS No. 3194-55-6 but, the NOES estimated a
total of 11,921 workers potentially exposed to this chemical under CAS No. 25637-99-4. Based on IUR reporting,
which included at least one report that worker information was not readily obtainable, the maximum total number of
workers likely to be exposed to this chemical during manufacturing and industrial processing and use is between 100
and 999. There may be additional potentially exposed workers that are not included in this estimate since not all
production volume has been accounted, and there is at least one use that contains a "Not Readily Obtainable" (NRO)
response among the submissions. HBCD has a vapor pressure of 4.70E-5 torr at 21°C. OPPT has established 0.001
torr as a value above which worker exposures to vapors should be estimated for chemical assessments. Below this
value, OPPT assumes exposure to vapor is negligible. However, exposures may occur through inhalation of dusts
and dermal contact. HBCD does not have an OSHA Permissible Exposure Limit.
Based on IUR data, specifically the number of potentially exposed workers and use codes, the potential worker
exposure is high.
Exposures to the General Population and the Environment
HBCD is not on the Toxic Release Inventory. As an additive flame retardant, HBCD is not chemically bound to the
matrix of the material it protects and thus has the potential to enter the environment. Based on this use information,
EPA assumes for the purpose of this risk prioritization that there is potential for exposures to the general population
and the environment.
The IUR-based ranking for general population and the environment is high due to the assumption that there will be
exposure to this chemical.
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In addition, public sources (see Exposure Characterization) report that HBCD's production and use as an additive
flame retardant for extruded and expanded polystyrene foam, as well as uses in resins, adhesives, and coatings, may
result in releases to the environment through various waste streams.
Exposures to Commercial Workers and Consumers
The IUR information has some commercial/ consumer products listed for HBCD (fabrics, textiles, apparel, rubber
and plastics). Depending on the product, commercial workers and consumers may have potential dermal and
inhalation exposure to the chemical.
The IUR-based ranking for commercial workers/consumers is high due to the assumption that HBCD is used in
consumer/commercial products.
Exposures to Children
The IUR information suggests either that HBCD will not be used in children's consumer products or that this type of
information is not readily available. Therefore, because of this uncertainty, the IUR-based ranking for children is
moderate due to the assumption that HBCD may be present in products intended to be used by children.
NOTE: Although not discussed in the Exposure Characterization, for the purposes of this risk characterization, the
Agency acknowledges the existence of recent reports in the scientific literature regarding the detection of HBCD in
indoor air samples in homes around the world (Environmental Science and Technology, 2008, Volume 42, pp. 459-
464). Also, environmental monitoring data show the presence of HBCD in freshwater (fish, invertebrates, plants),
marine (porpoise, seal, and eel), and avian (hawks and falcons) organisms (as reported in both the OECD SIDS
SIAP and the HPV Challenge Submission). However, OPPT has not fully evaluated any of this information for this
risk characterization.
5. Risk Characterization
The statements and rationale provided below are intended solely for the purpose of this screening-level and
qualitative risk characterization and will be used for prioritizing substances for future work in the U.S. HPV
Challenge Program.
5.1. Risk Statement and Rationale
Potential Risk to Aquatic Organisms from Environmental Releases (HIGH CONCERN): EPA assumes there is
potential for exposure to aquatic organisms from environmental releases. The bioaccumulation potential and
high hazard for HBCD under acute (aquatic plants) and chronic (aquatic invertebrates) conditions suggest a
high concern for potential risk to aquatic organisms from environmental releases, although the low persistence
may mitigate this to some degree.
Potential Risk to the General Population from Environmental Releases (MEDIUM CONCERN): EPA assumes
there is potential for exposure to the general population from environmental releases. The moderate concern for
hazard to human health combined with the potential environmental exposures and low persistence suggests a
medium concern for potential risk to the general population from environmental releases.
Potential Risk to Workers (HIGH CONCERN): Data suggest that workers may be exposed to HBCD. The
moderate concern for hazard to human health combined with the likely exposures that occur in the occupational
setting suggests a high concern for potential risk to workers.
Potential Risk to Commercial Workers and Consumers from Known Uses (HIGH CONCERN): IUR
information suggests that commercial workers and consumers may be exposed to HBCD. Recent findings in
the scientific literature also suggest the potential for consumer exposures from HBCD use, although this
requires further evaluation. The moderate concern for hazard to human health combined with the likely
exposures that occur in commercial worker/consumer use settings suggests a high concern for potential risk to
commercial workers and consumers.
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Potential Risk to Children (HIGH CONCERN): Information suggests that HBCD will be used in consumer
products. It is likely that children will be exposed to consumer products containing this chemical. The moderate
concern for hazard to human health is important in the case of children's health because studies have indicated
that changes in thyroid function may lead to abnormal development, particularly for the developing nervous
system. Therefore, the overall moderate human health hazard concern (and specific concerns for developmental
effects) combined with expected exposures suggests a high concern for potential risks to children.
5.2. Uncertainties
HBCD may have minor uses that were not reported in IUR. In addition, there is uncertainty regarding the
significance of the thyroid effects and the suggested potential for possible developmental neurotoxicity effects.
Finally, although reproductive organ effects were seen only at high doses in a repeated dose study, the lack of a
reproductive toxicity introduces some additional uncertainty.
5.3. Data Needs
The potential data need concerning developmental neurotoxicity from thyroid effects in pregnant animals is
expected to be identified and addressed in the upcoming Integrated Risk Information System (IRIS) evaluation
of HBCD (initiated in 2008 see http://cfpub.epa.gov/ncea/cfm/recordisplav.cfm?deid=187215 ). IRIS
assessments address the adequacy of data and the quality of existing studies, which are factors beyond the scope
of this screening-level prioritization exercise.
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Exposure Characterization for HPV Challenge Chemical
1,2,5,6,9,10 - Hexabromocyclododecane
CAS # 3194-55-6 and 25637-99-4
March 14, 2008
Prepared by
Exposure Assessment Branch
Chemical Engineering Branch
Economics Exposure and Technology Division
Office of Pollution Prevention and Toxics
Environmental Protection Agency
1200 Pennsylvania Avenue, NW
Washington, DC 20460-0001
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Exposure Characterization for HPV Challenge Chemical
1,2,5,6,9,10 - Hexabromocyclododecane (CAS #3194-55-6 and 25637-99-4)
Non-CBI Executive Summary
Hexabromocyclododecane (HBCD) has a production volume in the range of >10 million - 50
million pounds (USEPA, 2006). Persons submitting Inventory Update Reporting (IUR)
information in 2006 asserted that some of the information was confidential and therefore cannot
be disclosed. Data and information that are CBI have been excluded from this summary.
Data provided in the HPV submission indicate that HBCD is used solely as a flame retardant. Its
primary application is in extruded (XPS) and expanded (EPS) polystyrene foam that is used as
thermal insulation in the building industry. A secondary, though important, application of
HBCD is as a flame retardant for upholstery textiles. A minor application for HBCD is in video
or audio equipment housings (BFRIP, 2005).
Recent studies show that HBCD is degraded in aquatic sediment and soil under aerobic and
anaerobic conditions by a combination of abiotic and biotic processes, with half-lives of 2 days
to 2 months. Therefore, it is rated as not persistent (i.e. PI). However, a BCF value of 18,100
indicates that 1,2,5,6,9,10-HBCD is highly bioaccumulative (B3) (USEPA, 2007b).
Exposure was characterized using both public, non-confidential sources and one or more IUR
submissions available at the time the exposure characterization was written. If additional
information warrants an update of the exposure characterization, the update will be posted on the
EPA website.
A SIDS dossier has been prepared for this chemical.
Exposures to Workers
This chemical has a vapor pressure of 4.70E-5 torr at 21°C (USEPA, 2007b). OPPT has
established 0.001 torr as a value above which worker exposures to vapors should be estimated
for chemical assessments. Below this value, OPPT assumes exposure to vapor is negligible.
Based on IUR data, some of which may contain CBI, other types of worker exposures are
possible for this chemical. In fact, the Hazardous Substance Data Bank states that:
"Occupational exposure to 1,2,5,6,9,10-hexabromocyclododecane may occur through inhalation
of dusts and dermal contact with this compound at workplaces where 1,2,5,6,9,10-
hexabromocyclododecane is produced or used" (HSDB, 2008). HBCD does not have an OSHA
Permissible Exposure Limit (NIOSH, 2007a).
The National Occupational Exposure Survey (NOES), conducted from 1981 to 1983, has no data
for the total number of workers potentially exposed to HBCD under the CAS number 3194-55-6
(NIOSH, 2007b) but, the NOES estimated a total of 11,921 workers potentially exposed to this
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chemical under CAS number 25637-99-4 (NIOSH, 2007c). Based on IUR reporting, the
maximum total number of workers likely to be exposed to this chemical during manufacturing
and industrial processing and use is between 100 and 999. There may be additional potentially
exposed workers that are not included in this estimate since not all production volume has been
accounted, and there is at least one use that contains a "Not Readily Obtainable" (NRO) response
among the submissions. This estimate does not include potentially exposed commercial workers.
Differences between numbers of workers estimated by IUR submitters and by the NOES are
attributable to many factors, including time, scope, and method of the estimates. For example,
NOES estimates are for all workplaces while IUR are for industrial workplaces only, and NOES
used a survey and extrapolation method while IUR submitters simply provide their best estimates
based on available information for the specific reporting year.
Based on IUR data, specifically the number of potentially exposed workers and use codes, the
potential worker exposure is considered high.
Exposures to the General Population and the Environment
HBCD is not on the Toxics Release Inventory (USEPA, 2007a) and no direct information from
the other sources that were searched is available on environmental releases. Additionally,
HBCD's production and use as an additive flame retardant for extruded and expanded
polystyrene foam, as well as crystal and high-impact polystyrene, SAN (Styrene-AcryloNitrile)
resins, adhesives, and coatings, may result in releases to the environment through various waste
streams because, as an additive flame retardant, it is not incorporated into the matrix of the
material it protects and so has the potential to enter the environment (HSDB, 2008). Based on
the totality of the information and expert judgment, EPA assumes, for the purpose of this risk
based prioritization, that the potential for exposures to the general population and the
environment is high.
Exposures to Commercial Workers and Consumers
IUR information has some commercial/consumer products listed, such as, fabrics, textiles,
apparel, rubber and plastics. Depending on the product, commercial workers and consumers
may have potential exposure to the chemical. The likelihood that this chemical is used in
consumer/commercial products is high based on IUR data.
Exposures to Children
Information suggests either that HBCD will not be used in children's consumer products or that
this type of information is not readily available.
There is a moderate likelihood that this chemical is used in products intended to be used by
children but there is uncertainty in the IUR data.
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References
BFRIP, 2005. HPV Data Summary and Test Plan for Hexbromocyclododecane (HBCD).
Original Submission: December 20, 2001 - Updated September 2003, March 2005.
American Chemistry Council's Brominated Flame Retardant Industry Panel (BFRIP).
Accessed January 2008 at
http://www.epa.gov/chemrtk/pubs/summaries/cyclodod/cl3459rt.pdf
HP VIS, 2007. U.S. EPA. High Production Volume Information System.
http://www.epa.gov/hpv/hpvis/index.html.
HSDB,2008. Hazardous Substances Data Bank. As cited in HSDB record for
Hexabromocyclododecane, CAS 3194-55-6, accessed January 7, 2008.
http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen7HSDB.
NIOSH, 2007a OSHA PEL Project Documentation. Accessed August, 2007.
http://www.cdc.gov/niosh/pel88/npelcas.html.
NIOSH, 2007b. National Occupational Exposure Survey (Survey for 1981-1983, NOES).
Accessed December 2007.
http://www.cdc.gov/search.do?action=search&subset^noes&queryText=3194-55-
6&Go%21 =Go%21
NIOSH, 2007c. National Occupational Exposure Survey (Survey for 1981-1983, NOES).
Accessed December 2007. http://www.cdc.gov/noes/noes2/x2384occ.html
USEPA, 2006. 2006 Partial Updating of TSCA Chemical Inventory.
U.S. EPA, 2007a. Toxic Release Inventory. Accessed August, 2007.
http://www.epa.gov/tri/.
USEPA 2007b. Physical/Chemical and Environmental Fate Characterization for High Production
Volume Chemicals Chemical Name: Hexabromocyclododecane
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PHYSICAL/CHEMICAL AND ENVIRONMENTAL FATE CHARACTERIZATION
FOR HIGH PRODUCTION VOLUME CHEMICALS
CHEMICAL NAME:
1,2,5,6,9,10-HEXABROMOCYCLODODECANE (CAS NO. 3194-55-6)
FEBRUARY 12, 2008
Prepared by
Exposure Assessment Branch
Economics Exposure and Technology Division
Office of Pollution Prevention and Toxics
Environmental Protection Agency
1200 Pennsylvania Avenue, NW
Washington, DC 20460-0001
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1. Executive Summary
This report was prepared using the best available data from a number of sources. 1,2,5,6,9,10-
hexabromocyclododecane is a solid at room temperature. It has low water solubility, low vapor
pressure, and moderate volatility from water. It is not expected to hydrolyze but may photolyze
slowly. It is minimally mobile in soil and water systems. Recent information suggests that
HBCD is relatively biodegradable at environmentally relevant concentrations. Thus, HBCD is
considered highly bioaccumulative (B3) but not persistent (PI). In addition, the predicted
atmospheric oxidation half-life for HBCD meets the long-range transport criterion (half-life in
air of 2 days) of the UNECE-LRTAP and UNEP conventions.
2. Fate Characterization Summary for 1,2,5,6,9,10-Hexabromocyclododecane
The following summary of the fate of 1,2,5,6,9,10-hexabromocyclododecane (HBCD) is derived
from information contained within the Hazardous Substance Data Bank (HSDB, 2007), High
Production Volume Test Plans (ACC, 2002), EPISuite™ (USEPA, 2007b), and recent
publications by Davis et al. (2005; 2006).
As cited in HSDB (2007), 1,2,5,6,9,10-HBCD production and use as an additive flame retardant
may result in its release to the environment through various waste streams. If released to air, a
vapor pressure of 4.7xl0"7 mm Hg at 21° C indicates 1,2,5,6,9,10-HBCD will exist in both the
vapor and particulate phases. Vapor-phase 1,2,5,6,9,10-HBCD will be degraded in the
atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this
reaction in air is estimated to be 1-3 days. Particulate-phase 1,2,5,6,9,10-HBCD will be removed
from the atmosphere by wet and dry deposition. If released to soil, 1,2,5,6,9,10-HBCD is
expected to be minimally mobile based upon an estimated Koc values of 60,000 to 125,000.
Volatilization from moist soil surfaces may be an important fate process based upon an estimated
Henry's Law constant of 4.6xl0"5 atm-m3/mole; however, adsorption to soil is expected to greatly
attenuate volatilization. 1,2,5,6,9,10-HBCD is not expected to volatilize from dry soil surfaces
based upon its low vapor pressure. If released into water, 1,2,5,6,9,10-HBCD is expected to
adsorb to suspended solids and sediment based upon the estimated Koc. Volatilization from
water surfaces may be an important fate process based upon this compound's estimated Henry's
Law constant; however, adsorption is expected to severely attenuate volatilization. A BCF of
18,100, was measured in fathead minnows exposed to 6.2 [j,g/L of 1,2,5,6,9,10-HBCD over the
course of a 32-day incubation period. According to a classification scheme, this BCF suggests
the potential for bioconcentration in aquatic organisms is high.
3. Disposition in Land, Water, Air
Terrestrial Fate (as cited in HSDB, 2007a, EPA 2007a)
Based on a classification scheme, estimated Koc values in the range of 60,000 to 125,000
indicates that 1,2,5,6,9,10-HBCD is expected to be minimally mobile in soil. Volatilization of
1,2,5,6,9,10-HBCD from moist soil surfaces may be an important fate process given an estimated
Henry's Law constant of 4.6xl0"5 atm-m3/mole derived from its vapor pressure, 4.7xl0"7 mm Hg
at 21° C, and water solubility of 8.6 (J,g/L. However, adsorption to soil is expected to attenuate
volatilization. 1,2,5,6,9,10-HBCD is not expected to volatilize from dry soil surfaces based upon
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its estimated vapor pressure. 1,2,5,6,9,10-HBCD achieved 0% of its theoretical BOD in a Closed
Bottle aerobic biodegradation test over a 28 day incubation period. Based upon these results,
biodegradation of 1,2,5,6,9,10-HBCD is classified as not readily biodegradable. However,
recent work (Davis et al. 2005, 2006) suggests that it is relatively biodegradable at
environmentally relevant concentrations. This work showed that HBCD was degraded in soil
and aquatic sediment under aerobic and anaerobic conditions by a combination of abiotic and
biotic processes, with half-lives of 2 days to 2 months.
Aquatic Fate (as cited in HSDB, 2007a, EPA 2007a)
Based on a classification scheme, estimated Koc values of 60,000 to 125,000, indicate that
1,2,5,6,9,10-HBCD is expected to adsorb to suspended solids and sediment. Volatilization from
water surfaces may occur based upon a estimated Henry's Law constant of 4.6xl0"5 atm-m3/mole
derived from its vapor pressure, 4.7xl0"7 mm Hg at 21° C, and water solubility of 8.6 (J,g/L;
however, adsorption is expected to attenuate volatilization. A BCF of 18,100, measured in
fathead minnows, suggests the potential for bioconcentration in aquatic organisms is high. In
addition, recent work (Davis et al. 2005, 2006) suggests that it is relatively biodegradable at
environmentally relevant concentrations. This work showed that HBCD was degraded in aquatic
sediment and soil under aerobic and anaerobic conditions by a combination of abiotic and biotic
processes, with half-lives of 2 days to 2 months.
Atmospheric Fate (as cited in HSDB, 2007a, EPA 2007a)
According to a model of gas/particle partitioning of semivolatile organic compounds in the
atmosphere, 1,2,5,6,9,10-HBCD, which has a vapor pressure of 4.7xl0"7 mm Hg at 21° C, is
expected to exist in both the vapor and particulate phases in the ambient atmosphere. Vapor-
phase 1,2,5,6,9,10-HBCD is degraded in the atmosphere by reaction with photochemically-
produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 1-3 days
Particulate-phase 1,2,5,6,9,10-HBCD may be removed from the air by wet and dry deposition.
Sorption to the atmospheric particulate phase may increase resistance of atmospheric HBCD to
oxidation, and thus enhance its potential for long-range transport.
4. Persistence and Bioaccumulation
Persistence and bioaccumulation are qualitatively characterized according to the criteria set forth
in the PMN program (FR, 1999). Recent studies show that HBCD is degraded in aquatic
sediment and soil under aerobic and anaerobic conditions by a combination of abiotic and biotic
processes, with half-lives of 2 days to 2 months. Therefore, it is rated as not persistent (i.e. PI).
However, a BCF value of 18,100 indicates that 1,2,5,6,9,10-HBCD is highly bioaccumulative
(B3).
5. Data Gaps
No data gaps were identified.
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6. Summary of Physical Chemical Properties
Figure 1 shows the structure of 1,2,5,6,9,10-HBCD. Basic physical-chemical properties of
1,2,5,6,9,10-HBCD are presented in Table 1, and environmental fate properties are given in
Table 2. The persistence-bioaccumulation rankings are given in Table 3, showing a ranking of
P1B3 for 1,2,5,6,9,10-HBCD.
Figure 1. Structure of 1,2,5,6,9,10-Hexabromocyclododecane (USEPA, 2007b)
Table 1. Physical-Chemical Properties of 1,2,5,6,9,10-Hexabromocyclododecane.
Property
Value/Quality
References
CAS No.
3194-55-6

IUPAC
1,2,5,6,9,10-HBCD

Molecular Weight
631.69
ACC (2002)
Physical State
Solid
ACC (2002)
Melting Point
175-190° Ca
ACC (2002)
Boiling Point
462° C (estimated); 230 °C (decomposes)
ACC (2002)
Vapor Pressure
4.7xl0"7 mm Hg at 21° C (measured)
ACC (2002)
Water Solubility
3.4 |ig/L at 25° C (measured)
ACC (2002)

8.6 |ig/L at 25° C (measured)
HSDB 2007
Density
No data

Log Kow
5.625 at 25° C (measured)
ACC (2002)
a Range of melting points provided by the commercial manufacturers.
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Table 2. Environmental Fate Properties of 1,2,5,6,9,10-Hexabromocyclododecane.
Property
Value/Quality
References
Photodegradation
Half-life = 25.6 hours (calculated)
Half-life = 3 days (calculated)
ACC (2002)
HSDB 2007
Aerobic Degradation
No biodegradation observed (closed-bottle test
over a 28-day incubation period at 18-20° C)
Half-lives for aquatic sediment = 11-32 days;
soil = 63 days
ACC (2002)
Davis et al. (2005, 2006)
Anaerobic Degradation
Half-lives for aquatic sediment = 1.1-1.5 days;
soil = 6.9 days
Davis et al. (2005, 2006)
Hydrolysis
1.8xl05 years pH 8 (calculated)
1.8xl06 years pH 7 (calculated)
ACC (2002)
Bioaccumulation
BCF = 18,100 measured in fathead minnows
HSDB 2007
Henry's Law Constant
6.4xl0"n atm-m3/mole at 25° C (estimated)
4.6xl0"5atm-m3/mole (estimated)
ACC (2002)
HSDB 2007
Direct photolysis
Not significant
ACC (2002)
Koc
1.25xl0+s mL/g (estimated)
60,000 mL/g (estimated)
ACC (2002)
HSDB 2007
Fugacity
Air: 0.0007%
Water: 2.1%
Soil: 40%
Sediment: 58%
USEPA (2007)a
ACC (2002)
a The model was run using the default values of the EPI Suite Level III (USEPA, 2007b).
Table 3. Persistence and Bioaccumulation of 1,2,5,6,9,10-Hexabromocyclododecane.
Property
Value/Quality
References
Persistence
PI (high)
FR (1999)
Bioaccumulation
B3 (high)
FR (1999)
6. References
ACC, 2002. Robust Summaries & Test Plans: Cyclododecane. HPV Test Plan. Submitted by
American Chemistry Council (ACC) Brominated Flame Retardant Industry Panel (BFRIP). U.S.
Environmental Protection Agency: Washington, DC. Accessed August 23, 2007.
http://www.epa.gov/chemrtk/pubs/summaries/cvclodod/cl3459tc.htm.
Davis JW, S Gonsior, G Marty, J Ariano. 2005. The transformation of hexabromocyclododecane
in aerobic and anaerobic soils and aquatic sediments. Water Res. 39:1075-1084.
Davis JW, SJ Gonsior, DA Markham, URS Friederich, RW Hunziker, JM Ariano. 2006.
Biodegradation and product identification of [14C]hexabromocyclododecane in wastewater
sludge and freshwater sediment. Environ. Sci. Technol. 40:5395-5401.
FR 1999, Category for Persistent, Bioaccumulative, and Toxic New Chemical Substances.
Federal Register 64, Number 213 (November 4, 1999) Page 60194-60204
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HSDB. 2007. Hazard Substances Data Base. As cited in HSDB record for 1,2,5,6,9,10-Hexa-
bromocyclododecane. Accessed August 23, 2007. http://toxnet.nlm.nih.gov/cgi-
bin/sis/htmlgen?HSDB.
USEPA. 2007. EPI Suite v3.2 PC-Computer software developed by the EPA Office of Pollution
Prevention Toxics and Syracuse Research Corporation.
http://www.epa. gov/opptintr/exposure/pub s/epi suite.htm.
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