Summary of External Peer Review and

Public Comments and Disposition

This document summarizes the public and external peer review comments that the EPA’s Office 

of Pollution Prevention and Toxics (OPPT) received for the draft work plan risk assessment for 

1,3,4,6,7,8-Hexahydro-4,6,6,7,8,8-hexamethylcyclopenta--2-benzopyran (HHCB). It also 

provides EPA/OPPT’s response to the comments received from the public and the peer review 

panel.

EPA/OPPT appreciates the valuable input provided by the public and peer review panel. The 

input resulted in significant revisions to the risk assessment.

Peer review charge questions1 are used to categorize the peer review and public comments into 

specific issues related to four main themes.

 General Issues on the Risk Assessment Document

 Environmental Exposure Assessment

 Hazard and Dose‐Response Assessments

 Risk Characterization

A separate section, Other Comments, organizes the response to those public comments that are 

unrelated to the charge question themes listed above.

 

1These are the questions that EPA/OPPT submitted to the panel to guide the peer review process.
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General Issues on the Risk Assessment Document

Charge Question 1-1: Please comment on whether the assessment provides a clear and logical summary of EPA’s approach and 

analysis. Please provide specific suggestions for improving the assessment.

Charge Question 1-2: Please comment on whether appropriate background information is provided and accurately characterized. 

Please provide any other significant literature, reports or data that would be useful to complete this characterization.

#

Summary of Peer Review and Public Comments for 

Specific Issues Related to 

Charge Questions 1-1 and 1-2

EPA/OPPT Response

1 The discussion of Problem Formulation and the purpose 

of the assessment are not clearly articulated.

There should be a Problem Formulation section (based on 

a systematic framework) that includes the Conceptual 

Model and outcomes. 

The purpose of the assessment and relation to risk 

management goals are missing.

Explain rationale for treatment of developmental toxicity 

and human health assessment.

Further explanation would be helpful as to why mammals 

and birds were beyond the scope of this assessment.

EPA/OPPT has made significant revisions to the HHCB risk assessment to 

improve the clarity of the document. 

Chapter 1 of the final risk assessment has been restructured to include 

additional sections describing Problem Formulation, Scope of the 

Assessment, Conceptual Model and the Analysis Plan for HHCB. In addition, 

the purpose and audience have been described in the Introduction section of 

Chapter 1, Section 1.1 of the final HHCB risk assessment.

A discussion of the rationale for excluding an assessment of risk to human 

health based on measured data has been included in Chapter 1, Background 

and Scope. A more detailed review of the available mammalian toxicity data 

and recently published biomonitoring data was conducted to determine if 

there are adequate data to conduct a human health assessment. The review 

found minimal developmental toxicity at relatively high oral exposures and 

no developmental toxicity at levels several times greater than detected in 

human breast milk. This information is summarized in Appendix A, Human 

Health Toxicity Studies, Biomonitoring Data, and Risk Assessment.

Additional explanation for excluding mammals and birds from the scope of 

this assessment is provided in Chapter 1, Background and Scope. Briefly, 

HHCB has a low to moderate potential to bioaccumulate and trophic transfer 

(biomagnification) does not appear to be a concern based on review of the 

bioaccumulation data, monitoring data in biota, and aquatic food-chain 

modeling is included in the final scope of the assessment. In addition, a plant 
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study cited in the 2008 EU Risk Assessment Report for HHCB indicates 

transfer of HHCB from soil to plants in not likely to represent a significant 

exposure pathway. In light of this available study data, modeling for 

assessing plant uptake and trophic transfer of HHCB to birds and mammals 

was deemed unnecessary. Furthermore, despite the comment, EPA did not 

find such models to be publicly available and validated for use in this 

assessment.

2 Pathways, data, and analyses should be added to the 

scope of the assessment.

The Conceptual Model should include other points of 

entry, a discussion of wastewater treatment processes, 

worst case scenarios, routes of exposure, and trophic 

transfer.

The Conceptual Model diagram is presented as Figure 1-1 in Section 1.3 of 

Chapter 1, Conceptual Model for HHCB and has been revised to clarify what 

was evaluated in this assessment. In addition, a new accompanying text 

section entitled Conceptual Model for Environmental Assessment has been 

added to more clearly articulate the scenarios that were evaluated. Points of 

entry, wastewater treatment processes, worst case scenarios, routes of 

exposure, and trophic transfer are also more fully discussed within the 

document. 
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3 Terminology, methods, and results are not clear.

This is a screening-level assessment or a screening 

deterministic hazard assessment. 

It is a hazard assessment, not a risk assessment. Use the 

term hazard quotient, not risk quotient. Hazard is the 

possibility of an occurrence; risk is the probability of

occurrence. An HQ≥1 only indicates “potential” concern.

Need to be consistent in terms used to characterize risk.

Various fate terms are not consistently used or defined. 

This assessment includes both exposure assessment and hazard assessment 

as well as risk estimation conducted by comparing exposures and hazards via 

a Risk Quotient approach; hence, it is a risk assessment. Comparing point 

exposure and effects via a ratio or quotient is a simple and commonly used

method for estimating risk, EPA (1998). The quotient method has long been 

used by EPA/OPPT in our new chemicals program. 

Reference:

EPA (1998). Guidelines for Ecological Risk Assessment. Fed. Regist. 

63(93):26846-26924. 

http://www.epa.gov/raf/publications/pdfs/ECOTXTBX.PDF. 

There is not clear consensus on whether a simple ratio or quotient should be 

referred to as a ‘hazard quotient’ or a ‘risk quotient’; however, in this 

assessment we are calling the ratio a ‘risk quotient’ to reflect that the ratio 

includes exposure and hazard components. This approach is consistent with 

long-standing practice in other EPA programs – to refer to the quotient as a 

Risk Quotient or RQ 

(http://www.epa.gov/oppefed1/ecorisk_ders/toera_risk.htm#Deterministic).

EPA/OPPT has made efforts to more consistently use appropriate fate 

terminology throughout the document and particularly in Chapter 2, Sources 

and Environmental Fate. Where terms were not clear, a brief definition is 

provided (see Chapter 2, Table 2-6 for example).
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4 Details of the QA/QC for the data sets are required.

It is difficult to assess bioaccumulation or environmental 

monitoring data without discussing the criteria used to 

validate a data set. 

QA/QC specifics regarding sampling and analysis need 

further clarification.

Multiple studies presented in this section (hazard) do not 

appear to have followed an internationally validated 

protocol and likely did not adhere to strict GLP 

procedures.

Acceptability criteria for the toxicity studies have not 

been provided.

Additional clarification regarding data adequacy criteria for environmental 

occurrence has been provided in Chapter 3, Section 3.2.2 Measured Levels of 

HHCB in the Environment. Additional descriptions regarding the QA/QC 

specifics of exposure monitoring data including reporting levels, detection 

limits, recovery and use of blanks has been added to Chapter 3, 

Environmental Exposure Assessment and Appendix G, Environmental 

Monitoring Data Analysis.

Toxicity tests would, ideally, have been conducted under optimum 

conditions and follow good laboratory practice (GLP). However, for the 

purpose of Work Plan Chemical Assessments, EPA/OPPT will consider 

guideline studies as well as studies using other protocols. For this risk 

assessment, studies were included if they met data adequacy criteria as 

described in Chapter 3, Section 3.3 and EPA/OPPT guidance, EPA (1999c):

Reference:

EPA (1999c). Determining the adequacy of existing data. US 

Environmental Protection Agency, Office of Pollution Prevention and 

Toxics. http://www.epa.gov/hpv/pubs/general/datadfin.htm.

Fate Assessment and Sources of HHCB

Charge Question 2-1: Please comment on whether the information (chemistry, environmental fate and transport, production and 

uses) is used appropriately in the risk characterization. Please provide any specific suggestions for improving the assessment.

#

Summary of Peer Review and Public Comments for 

Specific Issues Related to Charge Question 2-1

EPA/OPPT Response

5 Bioaccumulation analysis is incomplete.

Given the moderate Log Kow value (i.e., 5.3) and fish BCF 

value, a higher level bioaccumulation assessment would 

be appropriate.

A revised and more detailed discussion of bioaccumulation has been 

provided in Chapter 2, Section 2.3.2 Bioaccumulation and Bioconcentration. 

This discussion includes information provided during peer review.
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Suggested using field-derived BAF values and modeling to 

estimate BCFs. 

There was no mention of measured or estimated plant 

bioconcentration factors.

References:

- Reiner, J. L., and Kannan, K. (2011). Polycyclic musks in water, 

sediment, and fishes from the upper Hudson River, New York, USA. 

Water, Air, & Soil Pollution 214(1-4), 235-242. 

- Nakata, H., Sasak,i H., Takemura, A., Yoshioka, M., Tanabe, S., and 

Kannan, K. (2007). Bioaccumulation, temporal trend, and 

geographical distribution of synthetic musks in the marine 

environment. Environ. Sci. Technol. 41:2216-2222.

No additional bioaccumulation information was found in the Nakata

reference provided by peer reviewers. The suggested modeling was already 

performed.

Additional discussion regarding plant bioconcentration factors is provided in 

Chapter 2, Section 2.3.2.

6 No data or estimations of uptake for terrestrial plants.

There was no information provided for terrestrial plant 

concentrations and no attempt was made to predict 

values. 

It was stated that the long half-life in soil may result in 

HHCB being available for plant uptake but no estimates 

were made. There are several plant uptake estimation 

approaches that could be used.

Additional text describing an unpublished study by Muller et al. (2002) 

referenced in EC (2008) has been added to the assessment in Chapter 2,

Section 2.3.2. In brief, in spite of a high concentration of HHCB in biosolids, 

no relevant accumulation in leaves was observed. The low observed 

concentrations in the above ground parts of the carrot plant showed that 

there was no transport within the plant. It was concluded that there is little 

transfer of HHCB from the soil to plants under environmental conditions. In 

light of this measured data, applying plant uptake models to predict HHCB 

uptake was deemed unnecessary for this assessment. 

Models for assessing plant uptake and trophic transfer of HHCB to birds and 

mammals were not publicly available and validated for use in this 

assessment. Insufficient data were available calculate risk to terrestrial 

plants, and EPA/OPPT acknowledges this as an uncertainty of this 

assessment, noted in Chapter 3, Section 3.4.2.7.
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7 Metabolism and degradation discussion is not complete.

Metabolites need to be identified and discussed relative 

to potential hazard relative to the parent compound.

The assessment should speak to degradation products 

(e.g. lactone) or specify that they are out of scope.

There are also several predictive models that could be 

used to generate potential metabolites.

Any information on differences in biological activity or 

degradability between isomers? 

Additional literature provided on anaerobic degradation 

should be included in the assessment.

Additional information on HHCB-lactone, the primary degradation product of 

HHCB, has been added to the assessment in Chapter 2, Section 2.3, 

Environmental Fate, based on the suggested reference of Horii et al. (2007). 

Hazard information on metabolites of HHCB were not available, thus using 

predictive models to generate potential metabolites was not performed and 

due to lack of this information, discussion of the potential hazard relative to 

the parent compound was not included in the final assessment. Information 

(hazard and exposure) of HHCB isomers and metabolites is also discussed in 

Section 3.4.2, Key Sources of Uncertainty and Data Limitations.

HHCB-lactone is the only degradate of HHCB that has been reported in 

environmental monitoring studies of wastewater and additional information 

has been added in Chapter 3, Section 3.2.2.1, Wastewater. Monitoring data 

identifying specific isomers of HHCB has not been reported.

Information on differences in biological activity or degradability between 

isomers is not available.

A review of the additional literature provided on anaerobic degradation was 

performed and the studies are discussed in Chapter 2, Section 2.3.1.1.

Reference: 

Horii, Y., Reiner, J. L., Loganathan, B. G., Senthil Kumar, K., Sajwan, 

K., and Kannan, K. (2007). Occurrence and fate of polycyclic musks in 

wastewater treatment plants in Kentucky and Georgia, USA. 

Chemosphere 68(11), 2011-2020.
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8 Some PChem properties are missing or need clarification.

Henry’s Law constant is missing

Melting point range, log Kow and solubility data need to be 

clarified.

Table 2-1, Physical-Chemical Properties of HHCB has been updated to include 

the Henry’s Law Constant and a brief explanation has been added to clarify

the melting point range as presented. The log KOW has been footnoted to 

clarify the source and the solubility data has been culled to present the 

measured solubility at pH7.

9 Volatilization as a process affecting the fate of HHCB 

needs more definitive treatment here. 

The document and this chapter in particular provide 

conflicting information regarding the importance of 

volatilization to HHCB fate. If possible, it would be helpful 

to the reader if some sort of consensuses view on the 

importance of volatilization could be provided.

EPI Suite’s WWTP model (STPWIN) predicts negligible removal due to 

volatilization. This is consistent with the experimental data presented in the 

assessment’s section on fate in wastewater treatment, Chapter 2, Section 

2.3.1.1. EPA/OPPT has made efforts to clarify the discussion of volatility in 

the above noted section and throughout the document.

EPA agrees that volatilization is an important fate process. As noted in the 

document, volatilization seems not to be a major process in activated sludge 

treatment, although available data are limited. Two studies are cited in the 

section on water, and they may appear at first glance to be in conflict. In one, 

40% of initial radioactivity was lost by volatilization in 300 hr (12.5 days); in 

the other, ≤16% was volatilized after 28 days. While this may appear to be 

conflicting information, the amount of volatilization in lab studies and in the 

environment is highly dependent on the test conditions; for lab studies, 

specifically, on design of test vessels, degree of mechanical aeration if any; 

and incubation temperature. Summaries of these studies are provided in 

Section 2.3.1.2, Fate in Water.

10 Increasing use may affect future risk.

How do you factor in the increasing use patterns and 

likely increasing environmental concentrations?

According to IFRA, there has been an increase in HHCB use in the US from 

2000-2008 (IFRA, 2012c). 

Reference:

IFRA (2012c). REACH Exposure scenarios for fragrance substances.

International Fragrance Association, Brussels, Belgium. 

EPA/OPPT’s Work Plan Chemical Assessments are conducted using currently 

available data and information, and forecasting future trends are generally 

beyond the scope of these assessments. In examining the range of 

Production/Import Volumes, as reported to the US EPA Inventory Update 

Reporting Rule (IUR) and Chemical Data Reporting (CDR) databases, EPA has 
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found that these volumes have been steady over the past 20 years; 

therefore, there is little information for on which to make trend predictions.

As discussed in Section 3.4.2, Key Sources of Uncertainty and Data 

Limitations, EPA acknowledges that variability in available environmental

concentrations may obscure trends such as use practices across the 

population, differences in sewage treatment plant inputs and removal 

efficiencies may all affect final concentrations present in any single location 

or point in time.

Risk quotients indicated current environmental exposure concentrations are 

approximately one to two orders of magnitude below hazard concentrations 

of concern. Unless environmental levels increase by 1-2 orders of magnitude, 

risks are expected to be low.

11 Modifying factors for exposure and toxicity are not 

considered.

Exposure and toxicity modifying factors were not 

mentioned or considered. There should be no effect of pH 

on HHCB solubility since it is non-ionizable.

Modifying factors were not applied due to the level of uncertainty this would 

introduce into the assessment in order to account for the diversity of 

“receiving environments” and were considered beyond the scope of this 

assessment. It should be noted that some of these parameters such as 

temperature, pH, salinity, dissolved oxygen, and water hardness, are noted 

during the course of the experiment which follows recommended guidelines.
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Environmental Exposure Assessment

Charge Question 3-1: Please comment on the use of data from multiple years and locations to characterize environmental 

concentrations in surface water and sediment in the US.

Charge Question 3-2: Please comment on the approach of using both the monitoring data from the literature and the USGS NWIS 

data.

#

Summary of Peer Review and Public Comments for 

Specific Issues Related to 

Charge Question 3-1 and 3-2

EPA/OPPT Response

12 Comparison of levels of HHCB in US to other countries

The representativeness of US data should have been 

compared to data from other parts of the world, in 

particular Europe. 

Revisions have been made to Chapter 3: Section A, Section 3.2 and to

Appendix G, Environmental monitoring Data Analysis. Additional summary 

statements for each media have been added to this section with comparative 

data from other countries. Levels of HHCB in the US were compared to levels 

in the EU Risk Assessment Report for HHCB, EC (2008), and levels in Asia as 

summarized by Lee et al., 2014. Levels of HHCB were also compared to 

those in Canada in this assessment where the data was available. 

References:

- Lee I.S., Kim U.J., Oh J.E., Choi M., Hwang D.W. (2014). 

Comprehensive monitoring of synthetic musk compounds from 

freshwater to coastal environments in Korea: with consideration of 

ecological concerns and bioaccumulation. Sci. Total Environ. 470-

471, 1502-1508.

- EC (2008). European Union risk assessment report for 1,3,4,6,7,8-

hexahydro-4,6,6,7,8,8-hexamethylcyclopenta-a-2-benzopyran 

(1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylin-deno[5,6-C]pyranHHCB), CAS No. 1222-05-5, EINECS No. 214-916-9, Risk assessment, 

final approved version. European Commission. Office for Official 

Publications of the European Communities, Luxembourg, The 

Netherlands.
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13 Data quality measures are not adequately described.

The use of measured data to determine the range of 

concentrations to which organisms may be exposed is 

appropriate; use of data from multiple years and locations 

is also appropriate provided upper range values are used 

for this screening exercise.

QA/QC specifics regarding sampling and analysis need 

further clarification.

EPA/OPPT agrees that upper range values should be used to evaluate risk. 

The maximum published surface water and sediment concentrations and 95th

percentile USGS values were used for this assessment.

Revisions to Chapter 3, Section 3.2 and Appendix G, Environmental 

Monitoring Data Analysis have been made to more fully describe the QA/QC 

specifics. Data quality criteria included currency, geographic scope, 

accuracy/reliability, representativeness, lack of bias, comparability and 

applicability. 

An additional reference has been added to clarify the USGS data collection 

guidelines. USGS data from the NWIS database was accepted with the 

assumption that their internal methodologies were consistent and robust. 

These data were presumed to be collected under the guidance of the USGS 

National Field Manual for the Collection of Water-Quality Data, a publication 

which documents the methods, protocols, procedures and recommended 

practices for the collection of water-quality data. Data reporting procedures 

were presumed to follow USGS guidance.

References:

- USGS (variously dated). National field manual for the collection of 

water-quality data: U.S. Geological Survey Techniques of WaterResources Investigations, book 9, chaps. A1-A9, available online at 

http://pubs.water.usgs.gov/twri9A.

- Oblinger Childress, C. J., Foreman, W. T., Connor, B. F., and Maloney, 

T. J. (1999). New reporting procedures based on long-term method 

detection levels and some considerations for interpretations of 

water-quality data provided by the US Geological Survey National 

Water Quality Laboratory. US Geological Survey. Open-File report 99-

193, 1-19.

14 Details on analytical methods are not provided.

HHCB is a ubiquitous chemical and frequently found in 

laboratory and field blanks. It would be helpful to capture 

that the general range of occurrence in blanks.

Additional information regarding the QA/QC specifics (reporting levels, 

detection limits, recovery and use of blanks), where provided in the studies 

from the open literature, have been incorporated into the appendix text for 
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Detection limits are not provided.

Extraction methods were not documented nor were 

Minimum Detection Limits.

Whether analytical methods employed are measuring all 

of the isomers of HHCB present or if only one primary 

isomer is analytically determined. 

each media. An additional reference to describe the QA/QC specifics for the 

USGS NWIS data sets has also been included as mentioned in Item 13 above.

The measurement of specific isomers of HHCB were not described in the 

USGS data set nor the studies reviewed for this assessment. Hazard as it 

relates to specific isomers of HHCB is also unknown. A brief statement has 

been added to the discussion in Chapter 3, Section 3.4.2, Key Sources of 

Uncertainty and Data Limitations.

15 For the USGS data analysis, more information would be 

useful.

An added column for percent or number of data points 

which are <LRL is desired.

It is clear from the descriptive statistics that some of the 

datasets were largely composed of substituted values. It 

would be useful to know the percent of each group that is 

<LRL.

As suggested by a peer reviewer, an additional table summarizing the 

laboratory reporting level (LRL) and substituted values has been included in 

Appendix G. Two additional columns have been added to Table G-8, 

Summary of Box Plots for USGS HHCB Data: the number of sample 

measurements (n), and the fraction of sample measurements lower than the 

laboratory reporting level (% <LRL). From these tables, it is more readily 

apparent that a large fraction (up to 100% in some cases) of the values were 

substituted low-end values as described in Appendix G. 

16 Probabilistic analysis of monitoring data is desirable.

Monte Carlo analyses or similar methods can certainly be 

used for the exposure assessment given the apparent 

large number of data points. Given the probabilistic data 

set from USGS, this seems like a more appropriate value 

to use with perhaps an uncertainty assessment (Monte 

Carlo or something similar Bayesian analyses?).

As described in Item 15 above, a large fraction of the values within the USGS 

dataset were substituted low-end values for many scenarios; therefore,

additional probabilistic analysis, such as Monte Carlo, would not be expected 

to alter the exposure estimates.

For the USGS effluent and outfall data sets the small size of the data set 

(generally 10-50) precluded a robust Monte Carlo analysis.

17 Analysis of non-detect data points is not clear.

The summary occurrence data should include information 

regarding the method reporting limits (MRLs) and how 

“non-detect” data were handled in the summary 

statistics.

For the box plot analyses and associated statistics, 

geometric mean and geometric standard deviation data 

would also be useful. For the categories with small n, and 

Additional information regarding reporting levels and detection limits, where 

provided in the studies from the open literature, have been incorporated 

into the appendix text for each media. Annotations have been added to the 

summary occurrence Table 3-1, Summary of Measured Concentrations of 

HHCB in Environmental Media and Biota, and associated tables in Appendix 

G. In addition, a notation in Chapter3, Section 3.2.2 referring the reader to 

the more detailed discussion in Appendix G has been added to guide the 

reader.
HHCB, August 26, 2014

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also not apparently all or mostly substituted <LRL values, 

a log-normal or other probability analysis with 

distribution fitting may be appropriate.

For the summary statistics, “non-detect” data, or data below the LRL, were 

replaced by substituted values as described in Section G-7 of Appendix G. 

Briefly, for monitoring data sets where the geometric standard deviation was 

<3.0, values recorded as “less than LRL” or “estimated” were replaced by the 

LRL divided by the square root of two, as per the US EPA OPPT guidance 

document (EPA, 1994). Likewise, where the geometric standard deviation 

was >3.0, values recorded as “less than LRL” or “estimated” were replaced by 

the LRL divided by two, EPA (1994). 

Reference:

EPA (1994). Guidelines for statistical analysis of occupational 

exposure data. Final. US Environmental Protection Agency, Office of 

Pollution Prevention and Toxics 

http://www.epa.gov/oppt/exposure/pubs/stat_guide_occ.pdf.

For the data collected by the USGS, information regarding the LRLs is 

provided in Appendix G, USGS National Water Quality Information System 

Data. Additional information regarding geometric mean and geometric 

standard deviation was not added to the assessment. As stated in the 

assessment and endorsed by peer reviewers (see # 12 above) upper range 

values were used in the risk assessment and hence, the mean values were 

not necessary for the assessment.

For the data collected from the open literature, concentrations were 

reported as presented in the original reference (e.g. where the ‘mean’ or 

‘average’ value was reported, this was noted).

Further inspection of the limited number of categories with a small sample 

size (n) and not all substituted values, determined that the data did not fit 

standard distributions; therefore, distribution fitting was not performed. 

18 Variability in monitoring data is not described for 

different situations.

Environmental variability is accessed geographically, but 

only sparsely temporally.

For the data collected from the published literature, the year that the 

sampling was performed is provided in the summary tables of Chapter3, 

Section 3.2.2 and associated tables of Appendix G. The season that the 

sampling occurred was not readily available for many of these studies, thus 

additional analyses was not possible. 
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Attempts should be made to group data according to 

season and year if possible.

More specific investigation into the types of WWTPs that 

emit the highest and lowest levels of HHCB would be 

quite valuable in this document and would help better 

characterize the extent of the issue within the USA.

EPA/OPPT acknowledges that using data from all locations and seasons may 

obscure temporal or geographical trends, however, consistent and sufficient 

data with regard to these variables was not available to make this analysis. 

The sampling year is noted in the tables provided in Appendix G.

EPA/OPPT’s Work Plan Chemical Assessments are conducted using currently 

available data and information. Therefore an ‘investigation’ of the types of 

WWTPs that emit HHCB is outside the scope of this assessment. A brief 

discussion summarizing two currently available studies of the efficiency of 

WWTP processes with regard to removal of HHCB, has been added to 

Appendix G, Section G-1, Measured Concentrations in Wastewater. 

Additional discussion has been added to Chapter 3, Section 3.4.2, Key Sources 

of Uncertainty and Data Limitations.

References:

- Simonich, S. L., Federle, T. W., Eckhoff, W. S., Rottiers, A., Webb, S., 

Sabaliunas, D., and de Wolf, W. (2002). Removal of fragrance 

materials during U.S. and European wastewater treatment. Environ. 

Sci. Technol. 36(13), 2839-2847. 

- Smyth, S. A., Lishman, L. A., McBean, E. A., Kleywegt, S., Yang, J. J., 

Svoboda, M. L., Lee, H. B., and Seto, P. (2008). Seasonal occurrence 

and removal of polycyclic and nitro musks from wastewater 

treatment plants in Ontario, Canada. Journal of Environmental 

Engineering and Science 7(4), 299-317. 
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Hazard/Dose-Response Assessment

Charge Question 4-1: Please comment on the ecotoxicity studies selected to represent the most sensitive species in each of the risk 

scenarios (acute aquatic, chronic aquatic, chronic sediment, chronic terrestrial invertebrate, and chronic terrestrial plant). Please 

comment on the use of the marine copepod chronic value for chronic toxicity to aquatic species. Please provide discussion, 

suggestions, and references to support and recommendations for the hazard characterization.

#

Summary of Peer Review and Public Comments for 

Specific Issues Related to Charge Question 4-1

EPA/OPPT Response

19 The explanation for the selection and use of assessment 

factors is unclear.

Given the occurrence of chronic and acute data, an 

acute:chronic ratio may be a more appropriate metric.

It is not clear why uncertainty factors were used, where 

the different uncertainty factors (5 or 10) came from, nor 

why other alternatives such as the MOE (margin of 

exposure) approach were not considered.

In certain cases, EPA will use the acute to chronic ratio to calculate a chronic 

value for an ecological endpoint (i.e., fish, aquatic invertebrates, or green 

algae) when there are not data for the trophic level endpoint (i.e., the 

endpoint is a data gap). However, sufficient toxicity test data were available 

to identify the chronic hazard values for this assessment.

Additional discussion regarding the use of uncertainty factors are provided in

Chapter 3, Section 3.3, Environmental Hazard Assessment. The uncertainty 

factors that OPPT/EPA applies to ecotoxicity data in this assessment are 

those used in EPA’s New Chemicals Program. This practice/methodology is 

described in OPPT’s Sustainable Futures Interpretive Assistance Document, 

EPA (2013). 

In summary:

 Application of uncertainty factors based on established EPA/OPPT 

methods were used to calculate lower bound effect levels (referred to as 

the concentration of concern; COC) that would likely encompass more 

sensitive species not specifically represented by the available 

experimental data.

 When deriving acute concentrations of concern (COC), EPA/OPPT applies

(divides by) a factor of 5 to fish, aquatic invertebrate and algae toxicity 

values to account for inter-species and lab-to-field uncertainty.

 When deriving chronic concentrations of concern (COC), EPA/OPPT 

applies a factor of 10 to the chronic effect value for fish, aquatic 

invertebrates, and aquatic plants to account for inter-species and lab-to-
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field uncertainty. This factor of 10 is consistent with factors reported in 

the literature or those used by other countries.

 The difference in approaches for setting concern levels for acute risk 

versus chronic risk is based on comparison of data sets and species 

sensitivity distributions among acute and chronic studies. It has been 

shown that the median variability among species in chronic toxicity is 

about four times greater than the median variability among species for 

acute toxicity (Forbes and Calow, 2002).

 For aquatic plants, EPA/OPPT typically sets the acute COC at the reported 

ChV value or NOEC effect level, if a ChV cannot be determined. The 

difference in assessment factors for aquatic plants is related to study 

design. For unicellular algae, which usually constitute the most common 

test organisms, the tests cover several generations and in most cases 

acute (EC50) and chronic (ChV) are obtained from the same study. 

Additionally, the effects levels are set not based on observations of 

lethality, but rather on more sensitive endpoints of growth rate and/or 

biomass production.

References:

- EPA (2013) Interpretive Assistance Document for the Assessment of 

Discrete Organic Chemicals. U.S. Environmental Protection Agency, 

Office of Chemical Safety and Pollution Prevention. 

http://www.epa.gov/oppt/sf/pubs/iad_discretes_june2013.pdf

- EPA (2012f) Sustainable Futures P2 Framework Manual. U.S. 

Environmental Protection Agency, Office of Chemical Safety and 

Pollution Prevention. EPA-748-B12-001, 

http://www.epa.gov/oppt/sf/pubs/sf-p2-manual.html

- Forbes, V., and Calow, P. (2002) Extrapolation in Ecological Risk 

Assessment: Balancing Pragmatism and Precaution in Chemical 

Control Legislation. BioScience, Vol 52-3, pp 249 – 257.
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EPA/OPPT is currently evaluating the feasibility of applying alternative 

approaches for assessing potential risks using the margin of exposure or 

MOE approach; however, these approaches are still under development.

20 It is not clear why the section on “Additional Studies” is 

provided.

While it is helpful to summarize these additional sublethal 

studies, there is no discussion putting these data into the 

context of the rest of the risk assessment.

The information regarding additional studies should be 

incorporated into an AOP which could focus the Hazard 

assessment on specific endpoints or justify specific 

uncertainty/safety factors.

EPA/OPPT agrees that the additional studies have not been used in the risk 

assessment, but did identify them in developing the risk assessment. This has 

been acknowledged in the Problem Formulation section and the descriptions

of these studies have been moved to Appendix F, Additional Studies.

Development of an Adverse Outcome Pathway (AOP) is beyond the scope of 

this risk assessment. 

21 The dataset is too small for definitive conclusions. 

Worst case screening decisions relative to hazard not risk 

can be made for fresh waters, fresh water sediments, and 

for soil invertebrates but not for terrestrial plants, marine 

waters, or sediments.

The document is not correct in stating that there are 

“robust ecotoxicology data for multiple species”.

The available ecotoxicity information for HHCB is summarized in Chapter 3, 

Section 3.3.

Acute and chronic toxicity data for HHCB exist for freshwater fish, daphnia, 

and algae, and for marine copepods. For sediment toxicity, data exist for five

invertebrates: an amphipod, a midge, an oligochaete, a polychaete, and a 

mud snail. For soil invertebrates the toxicity data include springtail, 

earthworm, and nematode. Two toxicity studies were conducted in the 

wheat plant. Relative to typical datasets available for many industrial 

chemicals, this is a rather large dataset; however, EPA/OPPT acknowledges 

that several of the studies have methodological limitations, therefore the 

characterization of “robust” has been removed. EPA/OPPT agrees that the 

dataset for plants and the marine environment is insufficient for assessment. 

The document has been revised to more clearly reflect which data are 

adequate and which are not.

22 Criteria for study evaluation and selection are not 

described adequately. Endpoint selection and 

justification for considering freshwater and marine 

species together are not clear.

EPA/OPPT followed the guidance for adequacy of toxicity studies described 

in EPA (1999c).

Reference:

EPA (1999c). Determining the adequacy of existing data. US 

Environmental Protection Agency, Office of Pollution Prevention 
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The examples provided do not cover all data acceptability 

parameters.

Multiple studies presented in this section do not appear 

to have followed an internationally validated protocol and 

likely did not adhere to strict GLP procedures.

It would also be helpful to provide what endpoint is

measured in the table (growth, survival or reproduction).

It appears that US EPA did not consider potential 

differences in the effects of HHCB between fresh and 

marine organisms. There are significant differences 

between saltwater and freshwater organisms. They 

should be evaluated separately.

US EPA has sufficient data for screening and determining 

hazard (not risk) for freshwater ecosystems,

not marine or estuarine ecosystems; marine and 

freshwater toxicity data should not be used

interchangeably.

and Toxics. http://www.epa.gov/hpv/pubs/general/datadfin.htm. 

Accessed September 27, 2012.

Toxicity tests would, ideally, have been conducted under optimum 

conditions and follow good laboratory practice (GLP). However, for the 

purpose of Work Plan Chemical Assessments, it is important to consider 

existing information that might not have been generated under ideal 

conditions. In other words, EPA/OPPT will consider guideline studies as well 

as studies using other protocols. For this risk assessment, studies were 

included if they met data quality criteria as described in Chapter 3, Section 

3.3 and EPA/OPPT guidance, EPA (1999c).

In the final assessment, Section 3, the toxicity testing summary tables now 

include designation of the endpoint that was measured in the toxicity test.

In the final assessment toxicity testing summary tables now include 

designation of freshwater and marine organisms and they are divided into 

separate section within the tables.

EPA/OPPT notes that although differences in sensitivity between freshwater 

and marine organisms appears, based on available data, to be less than an 

order of magnitude, several peer reviewers expressed that the two types of 

species should not be combined in the assessment of HHCB. In separating 

out marine species, EPA/OPPT concurs with the commenters expressing the 

view that data are insufficient to assess marine or estuarine ecosystems. 

Therefore, the final risk assessment is focused on freshwater species only 

and the lack of assessment of marine species is noted as an uncertainty.

23 Selection of key chronic aquatic toxicity study is not 

supported.

Chronic toxicity responses could include reproduction or 

other chronic responses such as growth.

The use of the marine copepod chronic value for chronic 

toxicity to aquatic species is inappropriate. The marine 

copepod study followed an OECD Draft Guideline.

EPA/OPPT has considered the multiple comments advising against 

considering both freshwater and marine species together (i.e., lumping) 

when selecting a study from which to derive an RQ and regarding the 

inappropriateness of using the marine copepod to derive a chronic RQ for 

aquatic organisms. 

Although EPA notes that the differences in sensitivity between freshwater 

and marine organisms appears, based on available data, to be less than an 

order of magnitude, EPA/OPPT agrees that the fathead minnow is a more 
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The impacts of salinity acclimation in anadromous and 

catadromous species, as well as some estuarine species 

have significant impacts on hormonal/endocrine 

pathways. Worst case screening decisions relative to

hazard, not risk, can be made for fresh waters, fresh 

water sediments, and for soil invertebrates but not for

terrestrial plants, marine waters, or sediments.

representative species for this assessment because the available monitoring 

data used for estimating exposures is largely freshwater. Furthermore, the 

study is reliable and demonstrates the chronic effects (i.e., survival and 

growth) using appropriate, reproducible protocols. 

EPA also agrees that available toxicity data are insufficient to robustly assess 

risks to marine or estuarine environments.

24 Selection of key sediment toxicity study is not 

appropriate.

For sediments data exist for 5 invertebrates: an 

amphipod, a midge, an oligochaete, a polychaete, and a

mud snail. Inclusion of the mud snail data are suspect. 

Further, the New Zealand mud snail, on which the 

sediment chronic COC is based, is an invasive species that 

is not welcome in the US (authorities are working to limit 

its distribution and, where it is now found, to

eradicate it). 

During the January 09, 2014 peer review, it was suggested 

that the Hyalella azteca data may be more appropriate 

for the sediment assessment than P. antipodarum. USEPA 

should consider this suggestion. 

EPA/OPPT has considered the comments regarding freshwater vs. marine 

species and the multiple peer review suggestion to use Hyalella azteca data 

in the sediment assessment. Although EPA notes that the differences in 

sensitivity between freshwater and marine organisms appears, based on 

available data, to be less than an order of magnitude, EPA/OPPT agrees that 

Hyallela azteca is a more representative species for this assessment because 

the available monitoring data used for estimating exposures is largely 

freshwater. Furthermore, the study is reliable and demonstrates the chronic 

effects (i.e., survival and growth) using appropriate, reproducible protocols. 

EPA also agrees that data are insufficient to robustly assess risks to marine or 

estuarine environments and hence, use of P. antipodarum as the sedimentdwelling organism for assessment is not the best choice. 

Chapter 3, Section 3.3.3 has been revised to derive the sediment COC based 

on the Hyalella azteca study. 

25 NOECs and LOECs are not preferred endpoints.

ECx values are preferred endpoints.

ECX (generally EC50s) were used to evaluate the acute toxicity of the chemical 

on aquatic and sediment organisms. 

However, NOEC and LOEC, and the MATC, are endpoints for chronic studies

recommended in internationally agreed to test guidelines for evaluating the 

chronic effects (e.g., growth, survival, and reproduction) of a chemical in the 

aquatic and sediment environments (OPPT TGs 850.1400, 850.1500, 

850.1300, 850.1350, 850.1740, 850.1735, and OCSPP 850.4500; OECD 201, 

204, 210, 215, 211, 218, and 219). 
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26 Species Sensitivity Distribution could be done to improve 

hazard data.

It would appear there are enough values on Table 3-3 for 

an ICE study for the other scenarios.

EPA/OPPT has considered this comment; however, given that ICE estimates 

acute toxicity (only for aquatic species and terrestrial birds and mammals) 

and EPA/OPPT has identified adequate measured acute toxicity tests for 

aquatic organisms, it is unclear what “other scenarios” the commenter 

envisioned ICE would be used for. 

Risk Characterization and Uncertainty/Variability Discussion

Charge Question 5-1: Please comment on the calculation of risk derived from different datasets and how they account for 

environmental variability. Please provide specific recommendations as needed for improving the risk characterization and 

references to support any recommendations.

#

Summary of Peer Review and Public Comments for 

Specific Issues Related to Charge Question 5-1

EPA/OPPT Response

27 Worst case risk scenarios were not included.

Comparison of toxicity data to “worst case” data in the 

form of maximum concentrations is appropriate.

Several additional worse case scenarios should be 

considered including: WWTP effluent dominated steams 

that are relatively common in the arid US west, reclaimed 

wastewater and biosolids land application.

Calculation of the acute aquatic RQ was based on the maximum reported 

value for surface water from the literature, the 95th percentile USGS NWIS 

value for surface water at effluent sites, and the highest mean value overall, 

in an effort to capture the full range of concentrations observed in this data 

set. These values encompass the upper range of measured environmental 

concentrations and are considered to be sufficiently conservative. 

Additionally, a comparison of the maximum published effluent value and the 

95th percentile value for effluent (stream or outfall site) from the USGS NWIS 

dataset to the acute benchmark for aquatic species also indicates a ratio of 

less than 1.

A biosolids or reclaimed wastewater to land application scenario was not 

included in this assessment due to the lack of an available, validated model 

to estimate environmental concentrations resulting from such uses. 

Sufficient and robust datasets to specifically assess WWTP effluent 

dominated streams of the US West and reclaimed wastewater scenarios 

were not available.
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28 Data gaps preclude risk conclusions for all scenarios.

Worst case screening decisions relative to hazard, not 

risk, can be made for fresh waters, fresh water sediments, 

and for soil invertebrates but not for terrestrial plants, 

marine waters, or sediments.

Upon consideration of peer review comments, EPA/OPPT agrees that risk 

quotients cannot be calculated for terrestrial plants. Data gaps for the 

terrestrial plant, terrestrial soil invertebrate, marine water and sediment 

scenarios are discussed in the uncertainty discussion in Chapter 3, Section 

3.4.2, Key Sources of Uncertainty and Data Limitations. 

29 Probabilistic analysis of data was not done.

RQs are presented for a range of exposure values. This 

brackets the range of RQs given the data so far and the 

analyses of that data. 

This may be an opportunity to use Monte Carlo-type 

analysis. But if that analysis is not feasible for statistical 

reasons, then the report already describes a range of RQs 

given different exposures. If only one variable, exposure, 

is treated as a random variable, a Monte Carlo analysis 

may not add much useful information. 

The majority of the data points (>40%) in the USGS datasets were comprised 

of values below the laboratory reporting level (LRL), and were thus replaced 

with substituted values, as discussed more fully in Appendix G, Section G-7. 

Additional probabilistic analysis, such as Monte Carlo, would not be expected 

to alter the risk conclusions. Also, the exposure assessment component of 

this risk assessment was based on the use of all available measured data. The 

use of all data obscures the ability to discern the contribution of any one 

variable to the measured environmental concentrations, and this is 

acknowledged in Section 3.4.2 Key Sources of Uncertainty and Data 

Limitations. For these reasons, EPA agrees that Monte Carlos analysis would 

not add much useful information and therefore was not performed.

30 Risk characterization terms are not consistent.

Levels of risk (negligible, acceptable, etc) used in the 

document are not explained or justified and may be 

inappropriate.

Terminology with respect to levels of risk have been revised throughout the 

document. Risk quotient values have been calculated and are provided. The 

use of qualifiers has been removed. 
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Other Comments

# Summary of Other Comments EPA/OPPT Response

31 Literature on endocrine disruptors should be included in 

“other studies”

Studies on potential endocrine effects are provided in Appendix A, Additional 

Information and summarized in Table A-1 of this same section. 

32 Additional analysis provided using iSTREEM model for DtD 

uses was provided by the American Cleaning Institute.

EPA/OPPT appreciates the submission of additional analysis provided using 

the iSTREEM model. EPA/OPPT’s exposure assessment was based on 

measured data collected by the USGS NWIS and published studies. These 

values represent a variety of discrete locations, times, WWTP processes and 

therefore it is not known how they may compare to the modeled values 

provided.

33 One peer reviewer submitted several studies of air 

concentrations, including one in a cosmetics 

manufacturing plant in China and several from indoor air 

and dust from apartments, kindergartens and women’s 

sports centers in Berlin, Germany.

The exposure monitoring data provided is not a cause for altering 

EPA/OPPT’s conclusions about worker risks, which are based largely on the 

EU RAR for HHCB (EC, 2008). The data reported in Chen et al., 2007 is 

comparable to the assessment results reported in the EU RAR. The maximum 

HHCB inhalation exposure concentration that was reported for the 

manufacturing plant in China (Chen et al., 2007) is equal to 4,504.97 ± 941.10 

ng/m3 and the associated exposure time is 8 hours per day. In comparison, 

the assessed inhalation exposure concentrations reported in the EU RAR for 

workers at compounding plants are equal to 0.013 to 0.065 mg/m3 and the 

maximum assessed worker exposure time reported in the EU RAR is 8 hours 

per day. Therefore the submitted data does not alter EPA/OPPT's conclusion 

about risk to the human health of workers.

References:

- Chen, D., Zeng, X., Sheng, Y., Bi, X., Gui, H., Sheng, G., Fu, J. (2007). 

The concentrations and distribution of polycyclic musks in a typical 

cosmetic plant, Chemosphere 66, 252-258.

- EC (2008). European Union risk assessment report for 1,3,4,6,7,8-

hexahydro-4,6,6,7,8,8-hexamethylcyclopenta-a-2-benzopyran 

(1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylin-deno[5,6-C]pyran-
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HHCB), CAS No. 1222-05-5, EINECS No. 214-916-9, Risk assessment, 

final approved version. European Commission. Office for Official 

Publications of the European Communities, Luxembourg, The 

Netherlands.

For the reasons described in Section 1.2, Problem Formulation, EPA 

determined that human health exposures need not be addressed in this 

assessment and defined the scope of this assessment to focus on the 

assessment of environmental risk to the aquatic environments from the use 

of HHCB as a fragrance ingredient in commercial and consumer products, as 

described in Section 1.2, Problem Formulation. Therefore, the evaluation of 

indoor air and dust is outside the scope of this assessment.