Document ID: EPA-HQ-OPPT-2018-0314-0031
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2019-08-28T04:00Z

Office of Chemical Safety and 
                  United States	Pollution Prevention
                  Environmental Protection Agency	April 2019

	
                                       
                                       
                                       
Summary of External Peer Review and Public Comments and Disposition for the Exposure and Use Assessment for the Persistent, Bioaccumulative and Toxic (PBT) Chemicals

                 Draft to Support Proposed Rule: RIN 2070-AK34
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                  April 2019 
Summary of External Peer Review and Public Comments and Disposition for the Exposure and Use Assessment for the Persistent, Bioaccumulative and Toxic (PBT) Chemicals

This document summarizes the public and external peer review comments that the EPA's Office of Pollution Prevention and Toxics (OPPT) received for the exposure and use assessment for the persistent, bioaccumulative, and toxic (PBT) chemicals. 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 numerous revisions to the exposure and use assessment.

Peer review charge questions are used to categorize the peer review and public comments into specific issues related to nine main themes.  
 Organization and clarity of the document,
 Clarity in the description of the literature search, literature screening, and data evaluation,
 Consideration of additional data sources,
 Prioritization approach used to evaluate and extract data for Decabromodiphenyl ether,
 Selection of core data for use in the assessment,
 Read-across approach used to consider data for use in the Phenol, isopropylated, phosphate, (3:1) (PIP (3:1)) and 2,4,6-Tris(tert-butyl) phenol (2,4,6 TTBP) assessments,
 Characterization of exposure scenarios,
 Utility of including additional information from the monitoring studies, and 
 Strengths and weaknesses of datasets used in the assessment.

All peer review comments for the nine charge questions are presented first, organized by charge question in the following section. These are followed by the public comments. For each theme, general comments pertaining to all chemicals are presented first, and then additional comments pertaining to only one or several chemicals follows.

Organization and clarity of the document - Peer Review Comments
Charge question 1: This information, when finalized will inform a technical support document to support document to support EPA's regulatory activities on PBTs. Please comment on the organization and structure of this document to inform this use. Do you have specific recommendations to improve clarity and presentation of this information?
                                       #
Summary of Peer Review Comments for Specific Issues Related to Charge Question 1
                               EPA/OPPT Response
                                       1
Selection of chemicals: 
 Can EPA briefly summarize how these five chemicals were selected? 
 Can EPA summarize the data showing that they are persistent and bioaccumulative?
 EPA has added text to the approach section of the document that includes this information.
                                       2
Interpretation: 
 The document presents information but does not offer interpretation or conclusions. 
 How will the document be used within a regulatory context? 
 Can the Executive Summary provide an overview of interpretation? 
 This document contains interim conclusions based on logical extrapolations of the data found or speculation about industry practices.  These speculations may be useful but should be used cautiously as they may not agree with other data in other sections.
 EPA has added text to the approach section of the document to convey the section of TSCA that the documents satisfy to explain the regulatory context. 
 The Executive Summary has been updated to accommodate an overview of chemicals.
 Additional contextual interpretation was included based on published findings. 
                                       3
Document organization: 
 To improve the clarity and presentation of the document, the document should be reordered as follows:  1) uses 2) lifecycle and potential routes of exposure 3) physical chemical properties 4) expected environmental distribution 5) summary of review articles 6) overview of existing exposure assessment 7) Compare and contrast reviews with data collected in this document.  
 The document should avoid repeating text and strive to be concise wherever possible.
 The human health hazard document should be incorporated within the main document. It is difficult to judge the relevance of concentrations measured in compartments such as serum or other non-human data without context, specifically health hazard summary.  
 The organization and order of the document were developed after a thorough evaluation of scope and to communicate the assessment effectively.  In addition, several reviewer's suggestions were taken into consideration in order to develop the clarity of presentation. 
 Text has been edited to improve clarity and conciseness. 
 The purpose of the Exposure and Use Assessment is to show that are exposures are likely from each of the five PBT chemicals. The purpose of the Environmental and Human Health Hazard Summary is intended to be a survey of existing hazard data to provide a general characterization of the toxicity profile of the five PBT chemicals. Margins of exposure were not used to characterize hazards of the five PBT chemicals and thus adding the hazard summaries into the Exposure and Use Assessment would be redundant.
                                       4
Conditions of use data:
 A single table structure across all chemicals would help for clarity.
 All uses should be listed within this section.
 EPA has standardized use table structure across chemicals. The current table format contains a comprehensive list of uses. 
                                       5
Physical-Chemical property data:
 In some cases, providing more than one value for a given parameter is necessary (e.g., log Koa, which can vary substantially for different sources)
 All data should include a valid reference.
 EPA acknowledges that there is inherent variability associated with measured and estimated physical-chemical properties. Presenting a range of values for physical-chemical property data was not considered necessary for this evaluation.
 The physical-chemical property data have citations of appropriate references and/or have clarifications indicating how the values were calculated.
                                       6
Partitioning and persistence data: 
 For any PBT assessment, experimental or estimated values of persistence properties such as biodegradation, atmospheric oxidation, hydrolysis, etc. should be included. 
 The environmental partitioning sections were generally not very instructive. Inclusion of persistence properties would allow the discussion to be framed around a relatively simple Fugacity Level 1 or 2 calculation to help the reader make a relative comparison between the expected environmental distributions of the chemicals.  
 A comparison to a well-studied reference PBT chemical (one or more of the so called "dirty dozen" chemicals for example) would also help put this partitioning discussion into perspective.  
 Addition of persistence properties and trophic magnification factors (TMF) would help the reader understand the persistence and bioaccumulation potentials. 
 As indicated in the document that this report EPA has been prepared for the five chemical substances it has identified for proposed action under TSCA section 6(h).
 The purpose of the Exposure and Use Assessment is to evaluate the exposures that are likely from each of the five PBT chemicals. The scope of the TSCA section 6(h) rulemaking is determined according to specific criteria outlined in the statute and summarized in the Background section of this document. Persistence and bioaccumulation characteristics of the chemicals are such criteria and were considered previously in identifying the chemicals subject to the 6(h) action, as outlined in the Background section of this document. A PBT analysis was not conducted for section 6(h) rulemaking.  Further details regarding how the PBT chemicals were evaluated to be listed in the TSCA Work Plan can be found in EPA's TSCA Work Plan for Chemical Assessments: 2014 Update (web accessible at: https://www.epa.gov/sites/production/files/2015-01/documents/tsca_work_plan_chemicals_2014_update-final.pdf). 

                                       7
Presentation and description of monitoring data: 
 Generally, there is not enough information in figure captions and text to understand data presented. All figures captions should stand alone, should include references for all data presented, and should clearly indicate the units, location, etc. 
 It would have been helpful to summarize the finding of each graph so that when a reader makes comparisons to review papers, longitudinal studies, and modeled values or across matrices, the summaries will allow the reader a quicker reference of what each plot described. Overall significant differences in data should be explained when possible.  Many of the data plotted demonstrate orders of magnitude differences in concentrations.  
 There are many instances across chemicals where referenced data are not in the information provided in the HERO data base or are selectively drawn from referenced data without documentation. 
 Any instances where parameters are estimated or were modeled must be noted.  
 It would be helpful to the reader if the notation on the graph axes were more consistent. 
 Terms such as "influent", "effluent, "background", "high-end", and "diet" should be clearly defined.
 The "human  -  other" data type should be expanded to note the type of matrix for the data. 
 Additional information including country of origin are needed to adequately draw conclusions from the monitoring data. 
 Using the same approach to present data from both data-rich and data-poor chemicals is distracting. For any data-poor chemicals without enough data to support a figure, the figure should be eliminated. For example, looking at time trends over a short timescale is inappropriate.
 The environmental monitoring data would be much more instructive if studies that measured concentrations in multiple phases at the same time were included and summarized (e.g. sediment and pore water, soil and pore water, fish tissue and water, etc.).
 EPA has provided additional details within figure captions, in text, and in tables describing the figures to address each of the specific comment bullet points. 
 EPA believes that all data are accurately reflected as reported in the original data sources which can be located in the HERO database. 
 Terms have been defined at first use.
                                       8
Acronyms: 
 Please define all acronyms. In particular, chemical acronyms should be consistent throughout the document.
 All acronyms have been defined in the text when they are first used. 
                                       9
Legends and figure font: 
 Font size is too small to read in some figures.
 Specific comments on lifecycle figure font have been addressed wherever possible.
 Tables have been added to all monitoring figures, which provide additional detail corresponding to the data in figures.
                                      10
Frequency tables: 
 The frequency tables showing frequency of detection are not useful and should be eliminated.
 Frequency of detection provides important context when interpreting monitoring data. EPA included additional detail on frequency of detection, by study, along with additional information such as sample size and sample location. 
                                      11
Phenol, isopropylated, phosphate (3:1)-specific comments:
 There are multiple compounds including TPP that can act as surrogates for PIP in both usage and toxicity such as TBP, TCP etc.  It is also worth including their metabolites (a hydroxyl substitution for one ligand) in any human health hazard assessment as the metabolites are more reactive than the parent compounds.  This data should be included when available.
 The current assessment was restricted to the primary compounds and DPP, the primary urinary metabolite of TPP. The break-down and degradation products, as appropriate, had been included. 
                                      12
DecaBDE-specific comments:
 Characterization of the sampling year would be helpful in looking at trends and should definitely be included. DecaBDE is a chemical that was not tested in many older studies of PBDEs, which lead to the false impression that exposure was low or non-existent. This point may bear discussion in the report. 
 Tying various workplace exposures (dermal/oral and inhalation) to biomonitoring would enhance our understanding of the exposure potential.
 Sampling years, in addition to publication years, have been added to the DecaBDE figures. 
 All workplace exposures and monitoring data identified in EPA's literature search are included in the report. 

Clarity in the description of the literature search, literature screening, and data evaluation - Peer Review Comments
Charge question 2: Please comment on the clarity of the descriptions of how the data were searched for, screened, and evaluated for inclusion in the exposure assessment.
                                       #
             Summary of Peer Review Comments for Specific Issues 
                         Related to Charge Question 2
                               EPA/OPPT Response
                                      13
Presentation of the search strategy:
 Some text about the search strategies and screening should be included in the main body of the text, rather than only the supplemental information.
 There is no need to repeat this information for all five chemicals.  Just explain the general procedure for the collection and organization of the literature data for the first chemical and mention only differences or unique cases for all the other compounds.
 100 Google scholar results returned were used.  Did this include duplicate references?  Is there a reason why only 100 were used?
 Did the authors stop at 100 references for the other search targets e.g. Medline? 
 The supplemental document states that EPA will use TSCATS in the future but does not explain how or why. 
 Please clarify what you mean by "backward searching".
 For clarity, EPA elected to retain the full descriptions of literature searching and screening strategy in the supplemental information.
 While much of the processes were similar, the individual chemical sections include unique search and screen strategies and PRISMA diagrams for each chemical.
 Due to character limits, Google Scholar lacks the utility of a literature database; in this case it was used as a supplemental search and test of the search strategy.
 All results from PubMed, Web of Science, and Toxline were included in the search results.  
 TSCATS references were typically not exposure-related references and therefore there was not information to include in the Exposure and Use Assessment.
 Text was added to indicate: backwards searching..."to gather articles cited by these sources"

                                      14
Study quality criteria: 
 Descriptions of each search and screening criteria were easy to follow and understand in the supplement. The descriptions of why things were not included (study quality criteria), was much less so. At times study counts in the PRISMA diagram did not match data tables, indicating some studies may have been excluded without explanation.   
 References are generally cited without commentary as to general quality and without examination of plausibility of assumptions or results. Various exposure studies are lumped together without clear explanation that they may have examined different questions. EPA should provide a matrix that summarizes the literature in a manner that permits readers to better understand the scope of prior studies.
 Full explanation of inclusion/exclusion criteria and extraction data is found in Appendix I. PRISMA diagrams have been reviewed for accuracy and any discrepancies have been explained in the text.
 The secondary data including references have undergone QA/QC and as per approved QAPP and QMP. While the original studies were conducted to answer different questions, the monitoring and modelling data provide information which can also be used for these assessments and are included as appropriate. Where special circumstances are identified, such as modelled data or data collected from hot spots or near facilities, these are clearly identified and noted in figures and discussions.
                                      15
HCBD-specific comments:
 There was no apparent information in the main document on how data were selected for this compound.   
 Full explanation of inclusion/exclusion criteria and extraction data is found in Appendix I.
                                      16
Phenol, isopropylated, phosphate (3:1)-specific comments:
 There was little apparent information on how data for this compound was searched for in the main document, only a description that TPP was added as a search parameter.
 In the PRISMA document for PIP (3:1) Figure C-3, the search result numbers for PIP (3:1) should be separated from the related compounds, so that it is clear to the reader the amount of literature actually available for PIP (3:1).
 Full descriptions of the searches are available in the supplemental information.
 Search results are separated; see box within Figure C-3 on page 46 labeled:  "Data sources identified through open lit from similar chemicals" that shows the results of open literature search from similar compounds.
                                      17
PCTP-specific comments: 
 There are two biomonitoring studies cited for PCTP, To-Figueras et al. 1992 and 2000. However, in Appendix E, the PRISMA diagram (Figure E-2) states that 0 studies were extracted and passed evaluation criteria. This discrepancy should be repaired, or the status of the To-Figueras studies in Section 8.6.1 should be clarified. 
 Other related chemicals were included in the searches for TTBP and PIP (3:1). It should be stated why this wasn't also done for PCTP. Are there no relevant, related chemicals?
 The PRISMA and text were edited to explain the discrepancy.
 Thorough literature searches were performed throughout the development of this report. The secondary data quality requirements were followed as per the QAPP.
 Surrogate chemicals were selected based on availability of data, structural similarity, similar use, and close physical-chemical properties as presented in EPA's Chemistry Dashboard. Although PCTP was data poor, no surrogates were identified using these criteria.
                                      18
2,4,6 TTBP-specific comments:
 There was information on the supplemental search in the main document describing the use of BHT as a surrogate/read across based on its prevalence in environmental monitoring studies.  This is not a good inclusion criterion; there are different manufacturing, distribution and certainly routes of exposure. 
 An external commenter noted a significant contradiction in the solubility of this compound.  This needs to be addressed.  
 Based on this feedback, EPA is no longer using BHT as a surrogate chemical. Instead, 2,4,-di-tert-butylphenol (2,4 DTBP) was used as a surrogate for 2,4,6, TTBP and additional rationale for selection of surrogate is included  in the document.

Additional data sources for consideration for inclusion - Peer Review Comments
Charge question 3: Please identify any additional information and data sources that EPA should also consider.
                                       #
             Summary of Peer Review Comments for Specific Issues 
                         Related to Charge Question 3
                               EPA/OPPT Response
                                      19
Human biomonitoring data: 
 The Agency should revisit the human monitoring data and should not limit the studies to long term studies.  
 NHANES data should be included where applicable.
 Reasonably available data were considered and included in the assessment and not limited to long term studies.
 NHANES DecaBDE pooled serum samples have been included.
                                      20
Persistence data:
 Addition of persistence properties and trophic magnification factors (TMF) would help the reader understand the persistence and bioaccumulation potentials.  
 The purpose of the Exposure and Use Assessment is to evaluate the exposures that are likely from each of the five PBT chemicals. The scope of the TSCA section 6(h) rulemaking is determined according to specific criteria outlined in the statute and summarized in the Background section of this document. Persistence and bioaccumulation characteristics of the chemicals are such criteria and were considered previously in identifying the chemicals subject to the 6(h) action, as outlined in the Background section of this document. A PBT analysis was not conducted for section 6(h) rulemaking.  Further details regarding how the PBT chemicals were evaluated to be listed in the TSCA Work Plan can be found in EPA's TSCA Work Plan for Chemical Assessments: 2014 Update (web accessible at: https://www.epa.gov/sites/production/files/2015-01/documents/tsca_work_plan_chemicals_2014_update-final.pdf). 

                                      21
Modeled data:
 The assessment should include some modeled estimates of exposure that can be compared with the monitoring data.
 Data should be evaluated to see if they support a probabilistic assessment.
 EPA included additional information for how new targeted exposure modeling could be done to provide additional context when interpreting monitoring data and plans to take comment on this. In addition, EPA included and evaluated modeled estimates of exposure that were completed by others. Generating de novo modeled estimates was not necessary to identify likely exposure for the five PBT chemicals.  
 No probabilistic assessment has been carried out due to a general lack of sufficient input data to support the distributions.
                                      22
DecaBDE-specific comments:
EPA should include the following:
 Lorber (JESEE, 2008)
 Trudel et al. (ES&T, 2011) paper dealing with aggregate PBDE exposure; it includes information specifically about DecaBDE in the Supplemental Information.
 Relevant dermal absorption literature including Hughes et al., (Food Chem & Tox, 2001) and Knudsen et al. (Xenobiotica, 2017).
 PK-related studies of DecaBDE including Thuresson et al. (EH, 2006) and multiple rat studies. 
 PBDE 209 studies should be included because uses of PBDEs are usually made as formulations of PBDE mixtures.
 EPA Targeted National Sewage Sludge Survey EPA-822-R-08-014, wherein 74 wastewater treatment facilities were sampled for PBDEs, including decaBDE (BDE-209) collected in 2006-2007.
 Additional wildlife biomonitoring papers mentioned by reviewer Hale, including Chen et al. 2008 and Potter et al. 2009.
 Additional papers identified by reviewer Buckley:  Hakk, H., Larsen, G., Bergman, Å. and Örn, U., 2002., Sørmo, E.G., Salmer, M.P., Jenssen, B.M., Hop, H., Bæk, K., Kovacs, K.M., Lydersen, C., Falk‐Petersen, S., Gabrielsen, G.W., Lie, E. and Skaare, J.U., 2006. , McDonald, T.A., 2005.
 Each of the suggested papers were reviewed subject to EPA's inclusion and exclusion criteria, and if deemed acceptable, added to the assessments. 
                                      23
Phenol, isopropylated, phosphate (3:1)-specific comments:
 There are multiple compounds including TPP that can act as surrogates for PIP in both usage and toxicity such as TBP, TCP etc.  It is also worth including their metabolites (a hydroxyl substitution for one ligand) in any human health hazard assessment as the metabolites are more reactive than the parent compounds.  This data should be included when available.
 Section 6.1: The table list the Log Kow as 9.07, as estimated from EpiSuite. However, empirical values of around 5 are reported elsewhere (TSCATS 8HEQ-1179-0317; ChemID database). The vapor pressure is listed as 2.1x10[-8] mm Hg, based on EpiSuite. ChemID lists a modeled value of 3.5x10[-7], an order of magnitude lower. The water solubility also varies over numerous orders of magnitude in EpiSuite versus values cited by the U.K.
 Thorough literature searches were performed throughout the development of this report. The secondary data quality requirements were followed as per the QAPP. The break-down and degradation products, as appropriate, have been included. 
 Empirical measurements and modeled values for PIP (3:1) could vary depending on the composition of the tested mixture or the representative structure that is chosen. Since many chemical structures fit within the name, the physical chemical properties could vary. EPA recognizes and discusses this variability and rationale for the value presented in Section 6.1.

24
PCTP-specific comments: 
 The physical properties of pentachlorophenol and PCTP are likely to be similar so fate and transport and portioning are likely to be similar. PCP studies on the physical distribution could be included.  PCP is not a surrogate for PCTP.
 PCP did not meet the criteria of p-chem properties available from the open literature, modeled sources, or the EPA chemistry dashboard and was thus not used as a surrogate.
                                      25
2,4,6 TTBP-specific comments:
 The comments raised by the SI Group (both of which are available in the docket) do not appear to have been reflected in the 2,4,6-TTBP section, especially as pertains to water solubility and the use of BHT as a surrogate. Particularly concerning is the discrepancy between the SI submitted experimental value (0.0629 mg/L) and the value utilized in the assessment (35 mg/L). 
 The authors should have included a more significant discussion on differences between TTBP and BHT in both manufacture and fate and transport through the environment.  
 BHT is no longer included as a surrogate chemical. Instead, EPA identified 2,4,-di-tert-butylphenol (2,4 DTBP) as a surrogate. Rationale for selection and other relevant information are included in the document.
 Please see section on response to public comments for solubility discussion.

Prioritization approach used to evaluate and extract data for Decabromodiphenyl ether - Peer Review Comments
Charge question 4: Due to the large number of references identified during the literature search for Decabromodiphenyl ether, EPA used a prioritization approach to evaluate and extract exposure data for this chemical. Please comment on the prioritization approach that was used for Decabromodiphenyl ether (see section A.2.4 of the Supplemental Information for the Exposure and Use Assessment document). Please comment on whether further characterization lower priority studies is expected to significantly affect the exposure characterization for Decabromodiphenyl ether. Please comment on the strengths/limitations associated with prioritizing use of studies/data sources with larger sample sizes versus smaller sample sizes.
                                       #
Summary of Peer Review Comments for Specific Issues Related to Charge Question 4
                               EPA/OPPT Response
                                      26
Clarification questions:
 Can EPA clarify the first paragraph on page 18 of the supplemental document? It implies that EPA only applied the prioritization scheme only to the additional 13,000 articles identified in the chemical class (PBDE) search.
 What articles were not available as full text?  Were they just not retrievable with the software tool employed or did the full text article not exist?  How many articles does this represent?  
 Clarification text was included: Inclusion of search terms for the chemical class PBDEs to the DecaBDE search added approximately 10,500 results for a total of approximately 13,000 results; therefore, the relevant results of the title abstract screening of the DecaBDE search results were used to prioritize the approximately 10,500 results added by including this chemical class.
 Approximately 14% of articles were unobtainable, either due to being printed in a foreign language, conference proceedings, or not freely available to the EPA library.  
                                      27
Comments on assumptions:
 The title and abstract could match very well and not be on topic while a lesser match between title and abstract does not exclude the possibility that it is a good fit for inclusion.
 Reliance on information obtained from available tabular data, as opposed to graphs, is not optimal.  Upon further evaluation of the data presented in this document it is clear some useful studies were not included.  
 A different approach would be to exclude non-North American studies rather than using the prioritization method presented. If one excluded non-North American studies the available pool would be far smaller.
 EPA acknowledges that some titles and abstracts may have been screened out during the prioritization process that could be used to support the assessment but believes these have been identified via the peer and public review process. 
 Where priority studies were identified, data was extracted from graphs in additional to extracting tabular data. Due to time constraints, all graphical data could not be extracted. 
 EPA acknowledges that the representatives of monitoring data by geographic location is informed by many factors and likely varies by chemical and scenario. Rather than limit the number of studies considered, EPA chose to use all studies regardless of location. 

Selection of core data for use in the assessment - Peer Review Comments
Charge question 5: EPA identified specific core exposure data: environmental monitoring, biomonitoring, estimated environmental concentrations, or estimated doses. Please comment on any additional core data that EPA should evaluate for each chemical.
                                       #
Summary of Peer Review Comments for Specific Issues Related to Charge Question 5
                               EPA/OPPT Response
                                      28
Recommendations for additional core data:
 Persistence properties and trophic magnification factors (TMF) should be added.
 Modeling results should be obtained and considered.
 If lifecycle studies are available, they should be included as core data.
 ADME data should be obtained and presented.
 The purpose of the Exposure and Use Assessment is to evaluate the exposures that are likely from each of the five PBT chemicals. The scope of the TSCA section 6(h) rulemaking is determined according to specific criteria outlined in the statute and summarized in the Background section of this document. Persistence and bioaccumulation characteristics of the chemicals are such criteria and were considered previously in identifying the chemicals subject to the 6(h) action, as outlined in the Background section of this document. A PBT analysis was not conducted for section 6(h) rulemaking.  Further details regarding how the PBT chemicals were evaluated to be listed in the TSCA Work Plan can be found in EPA's TSCA Work Plan for Chemical Assessments: 2014 Update (web accessible at: https://www.epa.gov/sites/production/files/2015-01/documents/tsca_work_plan_chemicals_2014_update-final.pdf). Thorough literature searches were performed following data evaluation criteria to conduct exposure and use assessment for the five chemical substances for proposed action under TSCA section 6(h). The secondary data quality requirements were followed as per the QAPP. 
 Modeling results and data from peer-reviewed studies, and other secondary data that met data evaluation criteria are presented and discussed in the document.
 No lifecycle studies were identified during the literature search.
 
                                      29
HCBD-specific comments:
 Read-across data should have been presented.
 Modeling results and data from peer-reviewed studies, and other secondary data that met data evaluation criteria are presented and discussed in the document.
                                      30
2,4,6 TTBP-specific comments:
 If any studies exist linking the two compounds such as a metabolism or degradation study of TTBP, that would have been a high priority document to target for supplemental searches and inclusion.  The searches should also include degradation and metabolism studies for all PBTs.  If none were located, that should be included in a statement.
 Thorough literature searches were performed following data evaluation criteria to conduct exposure and use assessment for the five chemical substances for proposed action under TSCA section 6(h). The secondary data quality requirements were followed as per the QAPP. The degradation products are discussed, as appropriate. 

Read-across approach used to consider data for use in the Phenol, isopropylated, phosphate, (3:1) (PIP (3:1)) and 2,4,6-Tris(tert-butyl) phenol (2,4,6 TTBP) assessments - Peer Review Comments
Charge question 6: Please comment on the approach to consider read-across of data from similar chemical substances for Phenol, isopropylated, phosphate (3:1) (PIP (3:1)) and 2,4,6-Tris(tert-butyl) phenol (2,4,6 TTBP).
                                       #
Summary of Peer Review Comments for Specific Issues Related to Charge Question 6
                               EPA/OPPT Response
                                      31
General comment:
 Read across is acceptable if there is a documented approach for showing how the structures are determined to be "similar".  This was not done in this document.
 Text was added to the approach document to discuss how EPA chose surrogates and how they demonstrate sufficient similarity for use. 
                                      32
Phenol, isopropylated, phosphate (3:1)-specific comments:
 The use of TPP for a surrogate for PIP (3:1) is well supported but the relationship between the two is unclear, especially when presenting concentration ranges. Recommend that there be an expansion of the discussion to elucidate this more effectively and that figures be annotated to distinguish which data is being reported.
 Text was added to explain that TPP can show patterns of environmental fate behavior for PIP but should not be considered to be a precise read-across for environmental levels, rather it provides an indication of the general magnitude and trends of potential occurrence. 
                                      33
2,4,6 TTBP-specific comments:
 BHT was a food additive and would not be introduced into the environment through any of the same pathways as TTBP. While the physical properties are similar, the use of BHT as a read-across chemical is inappropriate.
 BHT is no longer used as a surrogate chemical. 2,4,-di-tert-butylphenol (2,4 DTBP) was used as a surrogate.

Characterization of exposure scenarios - Peer Review Comments
Charge question 7: Please comment on whether EPA has appropriately captured the exposure scenarios. Please identify any existing exposure scenarios EPA may have missed. Please keep in mind the purpose of this document is to inform regulatory decisions under TSCA only.
                                       #
Summary of Peer Review Comments for Specific Issues Related to Charge Question 7
                               EPA/OPPT Response
                                      34
General comments:
 There is too much reliance in this review on prior publications to identify key exposure pathways.
 EPA must consider all conditions of use: This includes so-called legacy-related use and disposal as well as conditions of use related to recycling and imported articles. In keeping with the lifecycle diagrams, a full lifecycle analysis should be performed, including disposal.
 Potentially unique exposures to special subpopulations described in several of the comments that were received should also be evaluated (e.g., tribes and fire fighters).
 Overall, the assessment for compartmentalization and distribution of PBT (e.g. soil vs air vs water) based on the physical properties of the compound (Kow, Koc etc.) is a logical approach but should be coupled with manufacturing and deployment practices by noting any studies that support the approach.  They should also note places where literature reported studies contradict those assumptions, for example HCBD concentrations were expected to decrease based on manufacturing practices but did not in environmental monitoring studies.
 Dermal exposure is represented by the relatively uncertain absorption fraction method and is inadequate.

 EPA has considered all additional pathways mentioned by both the peer reviewers and the public commenters to fill any data gaps.
 Most use scenarios involve chemical transformation into new chemical forms. Retrospective use and transformation product disposal scenarios were not considered in this assessment.
 Additional language has been added to the representative exposures section for each chemical to emphasize the impact of potential exposure pathways on susceptible populations such as subsistence fishers and farmers.
   
                                      35
DecaBDE-specific comments:
 Additional release/exposure paths are wear, weathering, and unintentional destruction of products, e.g. accidental fires.  A substantial portion of these PBTs may be chemically altered, e.g. the formation of halogenated dioxins and furans. Because it degrades in the environment, decachlorodiphenyl ether and known transformation products should be included to be conservative.
 Organizing by receptor (Eco, Consumer, etc.) is helpful, but the text format makes it difficult to identify specific scenarios such as diet and indoor dust. Perhaps a table, with receptors in rows and scenarios in columns, or a figure (mental model) would be helpful.  Figure 4-1 is helpful, but does not capture the details of the exposure scenarios.
 Releases from fire events of chemical transformation products are not included in this assessment because those chemicals are not subject to this rulemaking effort. 
 Releases during product life to indoor environments are discussed in the representative exposure scenarios
 Quantitative modeling of end-of-life product disposal scenarios are considered beyond the scope of the current assessment.
 Describing exposure scenario in narrative form was important for integrating the results of this qualitative assessment. EPA chose not to further break-out components of the exposure scenarios into additional tables. 
                                      36
HCBD-specific comments:
 The modeled data used to estimate dose is the only means for estimating risk and would benefit from read across data as comparison.
 Information in the draft points to contaminated soil which presumably causes contaminated well water as presenting perhaps one of the highest non-occupational exposure potential to HCDB.  Also, Crump et al 2004 shows homes on contaminated soil have elevated levels of HCDB in their indoor air.  ATSDR 2013 shows relatively high levels of HCDB in drinking and bathing water.  As such, the scenario of a home on contaminated soil with contaminated well water should definitely be included, including exposure from HCDB in potable, drinking and bathing water.
 The purpose of the Exposure and Use Assessment is to evaluate the exposures that are likely from each of the five PBT chemicals. The purpose is not for estimating risks. A suitable surrogate chemical was not identified, so modeling data continues to serve as the dominant exposure evidence.
 The two referenced studies were added to the indoor air section monitoring section. The exposure from contaminated soil and from potable, drinking, and bathing water was not added to the analysis; the existing exposure scenarios presented were deemed sufficient to demonstrate evidence of exposure.
                                      37
Phenol, isopropylated, phosphate (3:1)-specific comments:
 The exposure scenarios have been adequately captured and described. Additional details on indoor exposures (home, office, automobiles) would be helpful. This could include possible time trends in the use of PIP in furniture, automobiles, and electronics.
 Since PIP appears to be used in hydraulic fluids common in military equipment, the military should be mentioned specifically.
 The purpose of the Exposure and Use Assessment is to evaluate the exposures that are likely from each of the five PBT chemicals. Additional details on indoor exposures including time trends is not necessary to support the purpose of the assessment in support of 6(h).
 Occupational exposures in the representative exposure scenarios are described in terms of functional use. Specific occupations are not exhaustively listed.
                                      38
PCTP-specific comments: 
 Specific consumer exposures in products like footwear and crumb rubber, which is used in athletic fields, as mulch, and in playground surfaces should be considered. Another significant use of PCTP is in the manufacture of golf balls. The report indicates that PCTP is used and mostly reacts during the manufacture of golf balls.  It is unclear but highly likely that some residual, unreacted PCTP may remain in the golf balls.  
 No monitoring data or laboratory studies were available to characterize the existence of PCTP residuals in or leaching out of matrices in the products referenced by the commenter. A single study (Callaway, 2018) was available to characterize residual PCTP leaching out of golf balls in the environment. The study reported that the leaching was only likely to occur if golf balls were quartered or ground; even if that occurred, the levels of leaching were expected to be close to the level of quantitation (5 ug/L). The study concluded that the overall magnitude of PCTP leaching from golf balls is relatively low. Other monitoring data or lab studies were not available to characterize the risk of residual PCTP leaching out of golf balls in the environment. The details of this study have been added to section 8.10.
                                      39
2,4,6 TTBP-specific comments:
 BHT is not a suitable alternative for TTBP as much larger concentrations of BHT should be present and ingestion would be a primary route of exposure for BHT and perhaps nonexistent for TTBP.
 Inhalation from or dermal contact with fuel additives should be added as a viable exposure scenario.
 BHT is no longer used as an exposure surrogate. 2,4,-di-tert-butylphenol (2,4 DTBP) was used as a surrogate for 2,4,6, TTBP.
 Inhalation and dermal contact to 2,4,6 TTBP are considered in the exposure scenarios.

Utility of including additional information from the monitoring studies - Peer Review Comments
Charge question 8: Please comment on whether inclusion of additional information on monitoring data would significantly enhance the exposure assessment for the intended purpose of this document. For example, characterization of sampling year vs. study year, characterization of free vs. particle bound chemicals in water and air, lipid normalization for biomonitoring data, and further characterization of studies that had incomplete reporting for their limits of detection. Please identify any specific chemicals for which this additional information would be helpful.
                                       #
Summary of Peer Review Comments for Specific Issues Related to Charge Question 8
                               EPA/OPPT Response
                                      40
 Characterization of the sampling year would be helpful in looking at trends and should definitely be included. The other kinds of information are always helpful for quantitative exposure and risk assessment, although they probably are not needed for the current purpose.
 Additional information on analytical methods and quantitation limits are necessary to enable an accurate comparison between studies.  
 Organic carbon normalized sorption data are needed to adequately compare concentrations between soils and sediments for the neutral forms of hydrophobic chemicals.  Difference between freely dissolved and particle concentrations would also enable better intra-study comparisons.  
 For environmental monitoring and biomonitoring datasets for all 5 of the PBT chemicals, the EPA only includes studies or databases where the chemical was measured above the limit of detection. This includes both the studies used for data extraction, as well as for the total study count. EPA should include all reliable studies where the PBT chemical was measured for, because it is very important in an exposure assessment to understand both where the chemical was found, and where it was not found.
 The weakness of all the monitoring studies is that most, if not all, failed to quantitatively characterize the potential sources for the HCBD.  This is vital information to link the strength and time-course of the source(s) as a predictor(s) of the exposure levels.  It should be specifically sought after and noted as not available if that is the case.
 The exposure assessment should include a more critical review of the prior studies and associated data.
 One area of potential concern is the approach used on presenting the monitoring data from peer-reviewed literature and that as presented would cast a misleading and biased picture. My recommendation would be to indicate that there may be a sampling bias in the data collection, with a focus on chemicals expected to be of highest concern.
 Data have been updated and are presented by both sampling year and publication year. 
 The purpose of the Exposure and Use Assessment is to evaluate the exposures that are likely from each of the five PBT chemicals. To meet the purpose and objectives of the document, the analytical method data and linkage to specific sources were not necessary.
 Particle and dissolved chemical measurements have been added to allow for ease of comparison. 
 EPA acknowledges that the data are left censored due to studies that measured but did not report non-detects. In cases where the surrogate was measured, but the PBT chemical was not, this is reported. 

                                      41
DecaBDE-specific comments:
 Characterization of the sampling year would be helpful in looking at trends and should definitely be included. DecaBDE is a chemical that was not tested in many older studies of PBDEs, which lead to the false impression that exposure was low or non-existent. This point may bear discussion in the report. 
 Tying various workplace exposures (dermal/oral and inhalation) to biomonitoring would enhance our understanding of the exposure potential.
 Sampling years, in addition to publication years, have been added to the DecaBDE figures. 
 All workplace exposure and biomonitoring data identified have been included in the assessment. 
                                      42
HCBD-specific comments:
 Once a specific area presents itself as perhaps a dominant source, e.g., contaminated soil and well water, further effort should be made to uncover all of the available information in that area.
 The purpose of the Exposure and Use Assessment is to evaluate the exposures that are likely from each of the five PBT chemicals. Identification of site-specific sources of contamination is outside the scope of this assessment. EPA has conducted a systematic literature search with a broad scope and believes that the Agency has identified a majority of available peer-reviewed and gray literature.
                                      43
Phenol, isopropylated, phosphate (3:1)-specific comments:
 The available and reported exposure data from PIP 3:1 or TPP as a surrogate is of little value.  Thus, we do not have very much real information on the exposure to PIP 3:1.  New studies specific to PIP 3:1 are clearly needed.
 In the meantime, given very little in the way of monitored exposure, modeling could provide some valuable insight and even provide some estimates of exposure potential. On what appears to be a critical source of exposure to PIP 3:1, modeling of migration and subsequent dust concentrations and exposure potential as a function of time tied to the characterization of sources. 
 EPA recognizes that the lack of PIP data introduces uncertainty in to the assessment. All available data that have been identified are presented. Modeling of exposure sources and scenarios are discussed for this exposure and use assessment for the proposed action under TSCA section 6(h) as appropriate. 
 EPA believes the existing data are sufficient to conclude whether exposures are likely and hence, new studies are not necessary.

                                      44
PCTP-specific comments: 
  On what appears to be a critical source of exposure to TTPE, characterizing the dustiness or source potential of TTPE dust in manufacturing should be a critical early task.  These data could be used for the modeling of dust concentrations and exposure potential as a function of time tied to the characterization of sources. 
 Tying various workplace exposures (dermal/oral and inhalation) to biomonitoring would enhance our understanding of the exposure potential.
 Modeling of dust concentrations and exposure potential are discussed for this exposure and use assessment for the proposed action under TSCA section 6(h) as appropriate. 
 All workplace exposure and biomonitoring data identified have been included in the assessment.
                                      45
2,4,6 TTBP-specific comments:
 It is difficult to determine whether additional studies would change any of the conclusions about TTBP as there were really not enough to draw any conclusions at all.  By inference any additional data/studies are more than likely to help.  As proposed by an external commenter, the bulk of TTBP may be consumed in production and not available for secondary release.  Additional data here is critical in determining whether this is true.
 EPA recognizes that the lack of TTBP data introduces uncertainty in to the assessment. The secondary data that met data evaluation criteria as per QAPP have been identified and reported.
 The purpose of the Exposure and Use Assessment is to evaluate the exposures that are likely from each of the five PBT chemicals. EPA believes the available data are sufficient to conclude whether exposures are likely and make this qualitative finding.

Strengths and weaknesses of datasets used in the assessment - Peer Review Comments
Charge question 9: Please comment on the reliability and relevance of the identified data sets for each chemical and on the strengths and weaknesses of individual data sets that will help to better inform future regulatory actions. 
                                       #
Summary of Peer Review Comments for Specific Issues Related to Charge Question 9
                               EPA/OPPT Response
All Chemicals
                                      46
 The overall lack of empirical data places significant uncertainty in any attempt to regulate by modeling effects from modelled characteristics and will require significant safety factors to mitigate these uncertainties.  The two most likely and equally troubling reasons for the omission of these data are failure of the registrant (producer) to provide them, or insufficient resources being provided to the Agency to compile data from available sources. 
 Additional information is needed for datasets presented in figures to allow the reader to determine how well they can be compared and interpreted.
 EPA has presented all monitoring and modeling data identified to support these assessments. Some of the PBT chemicals are data poor and this is recognized as a source of uncertainty. However, the purpose of the Exposure and Use Assessment is to evaluate the exposures that are likely from each of the five PBT chemicals. EPA believes the available data are sufficient to conclude whether exposures are likely and make this qualitative finding.

                                      47
DecaBDE-specific comments:
 It would be interesting to change the inclusion (and exclusion) criteria in the search algorithms to see how much it changes the result.  
 The document has been prepared to address the exposure and use assessment for the five chemical substances for proposed action under TSCA section 6(h). The change in the inclusion/exclusion criteria analytical method data and associate information were not relevant and data evaluation criteria for the secondary data have been followed as appropriate. The DecaBDE dataset was deemed sufficient to draw conclusions without exploring the screening criteria.
                                      48
HCBD-specific comments:
 Relying on modeled data for estimating risk is inherently noisy and arguably unreliable.  In the absence of other available data on levels of exposure, it may be the only way to estimate risk.  
 Another difficulty on the reliability of data used is reflected in magnitude differences in much of the data presented.  If your data varies by 12 orders of magnitude (see comment above), the underlying data are uncertain. 
 EPA considered modeling and monitoring data in the absence of human biomonitoring data. 
 The purpose of the Exposure and Use Assessment is to evaluate the exposures that are likely from each of the five PBT chemicals. EPA believes the available data are sufficient to conclude whether exposures are likely and make this qualitative finding.
                                      49
Phenol, isopropylated, phosphate (3:1)-specific comments:
 This compound favors a read across approach to substitute for actual measurement data.  I recommend expanding the search parameters to include all OPFRs and plasticizers instead of using speculation on usage distribution or toxicity data, in the absence of peer review literature.  While the modeled data seems reasonable it should not trump read across data for PIP.  
 The document has been prepared to address the exposure and use assessment for the five chemical substances for proposed action under TSCA section 6(h). The existing surrogate data were deemed sufficient to determine whether exposure is likely. Data evaluation criteria were followed for the secondary data.
 The Exposure and Use Assessment does not address toxicity data.
                                      50
PCTP-specific comments: 
 There are not really enough data sets to comment on or even make predictions on the reliability of the data used.  The two studies used for the human biomonitoring both appear to be reasonable.
 The purpose of the Exposure and Use Assessment is to evaluate the exposures that are likely from each of the five PBT chemicals. EPA believes the available data are sufficient to conclude whether exposures are likely and make this qualitative finding.
                                      51
2,4,6 TTBP-specific comments:
 The only real challenge to reliability came from the use of BHT as a surrogate.  Any conclusions draw from such sparse coverage in the literature should not carry significant confidence.
 BHT is no longer used as a surrogate ((2,4 DTBP) is used as a surrogate).

 
Organization and clarity of the document  -  Public Comments
Charge question 1: This information, when finalized will inform a technical support document to support document to support EPA's regulatory activities on PBTs. Please comment on the organization and structure of this document to inform this use. Do you have specific recommendations to improve clarity and presentation of this information?
                                       #
  Summary of Public Comments for Specific Issues Related to Charge Question 1
                               EPA/OPPT Response
                                       1
Document organization:
 ACC: A conceptual model for potential exposures and hazards based on each of the four representative exposures types (occupational, consumer, general population, ecological), much like those included in the risk evaluations on the initial 10 chemicals, would be a useful addition.
 ACC: The core exposure data sources (e.g., environmental monitoring, biomonitoring, etc.) should be organized in a manner indicating which representative exposure type (e.g., occupational exposure, ecological exposure, etc.) it is intended to address.
 The purpose of the Exposure and Use Assessment is to evaluate the exposures that are likely from each of the five PBT chemicals. EPA did not conduct risk evaluations and therefore not all methodologies used in risk evaluations were not conducted in support of 6(h) rulemaking. 
 Data can be associated with multiple types of representative exposures, for example soil can be relevant to both general population and ecological exposures. EPA decided to retain the format of the document. 
                                       2
Scope of Assessment
 ACC: EPA should apply a similar structural and analytical approach to the Section 6(h) PBT chemicals even though EPA is not required to conduct a risk evaluation on those chemicals. EPA should ensure that it understands how other federal laws not administered by EPA may already be managing the risks of these PBT chemicals for certain exposure pathways. Again, EPA should assess the risks associated with these chemicals under certain exposure pathways in order to do so.
 ACC: EPA should leverage the information generated from the first 10 chemicals for risk evaluation where it can. For example, it was noted that hexachlorobutadiene (HCBD) is primarily generated as a by-product of the manufacture of chlorinated hydrocarbons, particularly perchloroethylene, trichloroethylene and carbon tetrachloride -- each of which is the subject of one of the first ten risk evaluations. EPA should consider information associated with relevant risk evaluations where appropriate.
 The document included the relevant regulatory issues at the executive summary, introduction, and throughout the document.
 EPA followed the systematic review criteria used in the risk evaluations considering other assessments as well as thorough literature review.
 The purpose of the Exposure and Use Assessment is to evaluate the exposures that are likely from each of the five PBT chemicals. EPA believes the available data are sufficient to conclude whether exposures are likely and make this qualitative finding.
                                       3
Interpretation of data: 
 EDF: EPA statements suggesting certain exposures are low lack sufficient evidence: Certain EPA statements invoking existing regulations (sometimes in countries other than the U.S.), suggesting reductions in use over time, or characterizing specific scenarios suggest that some exposures to PBT chemicals are low or have declined. For reasons discussed in our comments, these statements are questionable or lack sufficient evidence.
 EDF: Exposure reduction is a key driver: The data and analyses need to support EPA's promulgation of rules that meet the requirement to "reduce exposure to the extent practicable" as well as to eliminate unreasonable risk. For many uses, meeting the exposure reduction requirement can and should drive deeper cuts in use of PBT chemicals than simply eliminating unreasonable risk, up to and including bans on some or all uses. For example, where a viable alternative exists, a ban would be necessary to comply with the requirement that EPA "reduce exposure to the chemical substance to the extent practicable."
 EDF: Exposure is likely to each of the five PBTs: The draft exposure and use assessment confirms that exposure "is likely" for each of the five PBT chemicals EPA has identified. Each of these chemicals is, by definition, persistent and bioaccumulative, which means people and other organisms can remain exposed to it for a very long time, with those higher up the food chain more heavily exposed. All five of these PBT chemicals appear to still be active in commerce. And monitoring data show that exposure is likely to each of the five chemicals.
 EPA acknowledges there are multiple interpretations of the data. 
 The purpose of the Exposure and Use Assessment is to evaluate the exposures that are likely from each of the five PBT chemicals. EPA believes the available data are sufficient to conclude whether exposures are likely and make this qualitative finding. EPA will further use the information from the Exposure and Use Assessment to inform exposure management.
 EPA agrees exposure is likely for each of the five PBT chemicals.
                                       4
Conditions of use data:
 EDF: EPA must consider all conditions of use: This includes so-called legacy-related use and disposal as well as conditions of use related to recycling and imported articles. 
 NTTC: Consider disposal as a condition of use, including
          Unlined landfills (207 unlined landfills in Alaska)
          Recycling/reuse of all or parts of consumer products and articles (vehicles, furniture, etc.)
          Air emissions from open waste burning
 EPA has a standardized use table structure across chemicals. The current table format contains a comprehensive list of uses including each of the items noted. 

                                       5
Description of monitoring data: 
 ACC: In those cases where it is stated "EPA did not identify any studies with detectable levels of ..." (e.g., Section 5.6.1 Human blood (serum), p. 88), EPA should indicate whether there were studies where the compound of interest was an analyte, but was not detected.
 ACC: All relevant monitoring data should be reported. In some cases, "only studies or databases that reported measurements of the chemical of interest above the limit of detection were extracted and included in the # of studies count" (p. 79, HCBD discussion). The number of studies that tested for the substance but did not find it should also be included. Data from studies where both absence or presence of a substance are relevant to understand its exposure potential should be included.
 ACC: Soil, sediment, flora and fauna monitoring data should indicate whether it is presented in units of wet weight or dry weight, and wet weight data should be reported separately from dry weight data.
 ACC: Monitoring data should be reported separately from modeled data. Alternatively, the title for the Environmental Monitoring section of the report should be modified to accurately reflect what is being presented. (In some cases, data from modeling exercises has been reported in the Environmental Monitoring section (Figure 5.7, p. 83).)
 Studies with reported data were prioritized for extraction over studies without reported data or with data present only below detection limits. The secondary data presented met the data evaluation criteria. No studies were identified reporting HCBD in human blood (serum).
 Samples are now presented on a dry weight and wet weight basis. 
 Modeling data is differentiated in the figures and text from monitoring data. 

                                       6
Presentation of monitoring data: 
 ACC: For the figures associated with Environmental Monitoring and Biomonitoring, the data are shown in a range. It would be useful to identify the number of data points (N) associated with each data range.
 ACC: For the figures associated with Environmental Monitoring and Biomonitoring, the data associated with any source should be reported according to the sample collection date rather than the publication date of the study article. Additionally, the source of the data may be used to reference the study.
 ACC: For the figures associated with Influent/Effluent data, the influent data should be represented separately from the effluent data, not aggregated.
 Further adding sample counts to the monitoring figures created presentations that were overly messy and difficult to interpret. These values are included in tables underneath the monitoring figures. 

Data are presented in the text and figures by both publication year and year of sample collection.
 EPA did not further differentiate the wastewater data as it did not influence overall magnitude and trends of observed exposure patterns. All conversion and/or calculations of data that met the secondary data evaluation criteria were presented.
 
Clarity in the description of the literature search, literature screening, and data evaluation  -  Public Comments
Charge question 2: Please comment on the clarity of the descriptions of how the data were searched for, screened, and evaluated for inclusion in the exposure assessment.
                                       #
  Summary of Public Comments for Specific Issues Related to Charge Question 2
                               EPA/OPPT Response
                                       
No comments were received for this charge question. 

Additional data sources for consideration for inclusion  -  Public Comments
Charge question 3: Please identify any additional information and data sources that EPA should also consider.
                                       #
  Summary of Public Comments for Specific Issues Related to Charge Question 3
                               EPA/OPPT Response
                                       7
 EDF: EPA can and should use its authorities to address gaps in available information: TSCA gives EPA ample authority to require testing or monitoring and to collect existing information in order to fill gaps in hazard and exposure or use information. EPA should use these authorities where needed to inform robust exposure reduction rules for the five PBT chemicals.
 EDF: EPA has inappropriately excluded reasonably available information, including through its literature search strategy: EPA has not yet summarized relevant information it already received on the PBT chemicals under its TSCA sections 4 and 8 authorities. EPA has also excluded large numbers of studies due to "time constraints" (see draft supplemental document). EPA should immediately provide a list of references to all excluded studies to peer reviewers and the public in advance of the upcoming peer review. EPA should also promptly initiate efforts to acquire and make public copies of the full studies as soon as possible.
 The purpose of the Exposure and Use Assessment is to evaluate the exposures that are likely from each of the five PBT chemicals. EPA believes the available data are sufficient to conclude whether exposures are likely and make this qualitative finding.
 Full explanation of data inclusion/exclusion criteria and extraction data is found in Appendix I. PRISMA diagrams have been developed and reviewed for accuracy and any discrepancies have been explained in the document. References have also undergone QA/QC review and as per approved QAPP and QMP. Information has been added to the Exposure and Use Assessment after the peer review and public comments were received.

Prioritization approach used to evaluate and extract data for Decabromodiphenyl ether  -  Public Comments
Charge question 4: Due to the large number of references identified during the literature search for Decabromodiphenyl ether, EPA used a prioritization approach to evaluate and extract exposure data for this chemical. Please comment on the prioritization approach that was used for Decabromodiphenyl ether (see section A.2.4 of the Supplemental Information for the Exposure and Use Assessment document). Please comment on whether further characterization lower priority studies is expected to significantly affect the exposure characterization for Decabromodiphenyl ether. Please comment on the strengths/limitations associated with prioritizing use of studies/data sources with larger sample sizes versus smaller sample sizes.
                                       #
  Summary of Public Comments for Specific Issues Related to Charge Question 4
                               EPA/OPPT Response
                                       
No comments were received for this charge question. 
   

Selection of core data for use in the assessment  -  Public Comments
Charge question 5: EPA identified specific core exposure data: environmental monitoring, biomonitoring, estimated environmental concentrations, or estimated doses. Please comment on any additional core data that EPA should evaluate for each chemical.
                                       #
  Summary of Public Comments for Specific Issues Related to Charge Question 5
                               EPA/OPPT Response
                                       8
 ACC: EPA is not required to conduct a risk evaluation for Section 6(h) PBT chemicals, nor is it required to apply systematic review to the data associated with the Section 6(h) PBT chemicals. EPA should apply, however, the data quality criteria from its Application of Systematic Review in TSCA Risk Evaluations to the environmental and human health hazard data to enable the public to understand which data may be of sufficient reliability and relevance for regulatory decision-making.
 All data presented and discussed in the Exposure and Use Assessment followed secondary data evaluation criteria.
 Comment is not applicable to the Exposure and Use Assessment in support of rulemaking under 6(h).  
                                       9
2,4,6 TTBP-specific comments (SI Group):
 Sections 7.5.1, 7.5.2, 7.5.3, 7.5.4, 7.5.5 Data is from outside the US, and it is unclear whether these countries have similar conditions of use of 2, 4, 6,- TTBP.(11/19)
 Section 7.5.6.  -  p. 138 In Figure 7-8 (ref. USGS 2012) both 2,4,6-TTBP and BHT were not analytes reported in the reference cited by EPA, so it is unclear what data are being presented.
 Section 7.6.1  -  p. 140 In Figure 7-9 (ref. USGS 1991) 2,4,6-TTBP was not detected at the method detection limit (MDL) in fish tissue, but the data is not presented by EPA as such. The draft document should be corrected to clarify that all data were below the MDL for 2,4,6-TTBP.
 Section 7.10; The vast majority of 2,4,6-TTBP manufactured is consumed as an intermediate in manufacturing other chemicals (94%) or through energy recovery being sold as a fuel (4%). The remaining 2% of the 2,4,6-TTBP manufactured is sold as a liquid antioxidant mixture (present at 9 - 13%) primarily for fuel  -  predominately military jet fuel. Additionally, 2,4,6-TTBP is manufactured in liquid form, and it is never isolated as a neat substance. 2,4,6-TTBP is not manufactured as a solid; therefore, dermal exposures and fugitive air emissions to dusts are not possible.
 Section 7.1.  -  p. 128 An experimental value for water solubility (0.0629 mg/L) has been calculated and previously provided to EPA. This value should be utilized for all interpretations since 2,4,6-TTBP is negligibly soluble in water. EPA did not include this value and was inconsistent in the draft assessment since 2,4,6- TTBP was stated to be both highly water soluble (p. 132) and have low water solubility (p. 133).
 Due to a lack of data, EPA decided to present all monitoring data, regardless of country of collection. 
 The document, text, and figures have been updated to address the discrepancies identified by the reviewers including updating the influent/effluent and fish sections. 
 Liquid and aerosols could sorb on air-borne particles and other colloids.
 The water solubility at 25 deg C has been reported in the document with appropriate peer-reviewed references are cited and noted. The solubility referred in Section 7.4.2 (Manufacturing and Processing as a Reactant/Chemical Intermediate) is a qualifier when the chemical is adhered to equipment and/or other surfaces.  Adhered organics on typical manufacturing/processing surfaces require hydrophobic solvent to dissolve/detach from the surfaces to provide effective cleaning. Water as a cleanser of adhered TTBP from surfaces would not be effective due to surface affinity and solubility.

Read-across approach used to consider data for use in the Phenol, isopropylated, phosphate, (3:1) (PIP (3:1)) and 2,4,6-Tris(tert-butyl) phenol (2,4,6 TTBP) assessments  -  Public Comments
Charge question 6: Please comment on the approach to consider read-across of data from similar chemical substances for Phenol, isopropylated, phosphate (3:1) (PIP (3:1)) and 2,4,6-Tris(tert-butyl) phenol (2,4,6 TTBP).
                                       #
  Summary of Public Comments for Specific Issues Related to Charge Question 6
                               EPA/OPPT Response
                                      10
ACC: The proposal to use a read-across approach to apply exposure data among similar chemical substances is problematic. ACC strongly urges EPA to re-consider this approach for the reasons discussed below.
According to the European Chemicals Agency (ECHA), "Read-across involves the use of relevant information from analogous substance(s) (the `source' information) to predict properties for the `target' substance(s) under consideration." Typically, read-across has been used in hazard characterization. The Organization of Economic Cooperation and Development (OECD) states that "[i]n principle, read-across can be used to assess physicochemical properties, toxicity, environmental fate and ecotoxicity." Use of read-across for exposure characterization beyond environmental fate is not mentioned in that OECD document and is not typically applied. The OECD Guidance on Grouping of Chemicals and the ECHA Read-Across Assessment Framework provide principles for developing a hypothesis-driven justification of why data from one substance can be used to fill the data needs for another substance for hazard assessment.
We commend the extension of this principle to the area of exposure characterization. However, EPA has not identified those characteristics that would make a surrogate chemical suitable for read-across for exposure. Physical-chemical similarity alone is not sufficient to apply read-across for exposure. Other factors should be considered for exposure, depending upon the type of information being considered. For example, for ecological or human biomonitoring data, the Agency proposed butylated hydroxytoluene (BHT) as a surrogate chemical for 2,4,6 TTBP based on structural similarity alone. However, the use pattern for BHT is not similar to that of 2,4,6 TTBP. BHT is an approved food additive and commonly found as a preservative in food where 2,4,6 TTBP is not. Therefore, one might expect a different human exposure potential from BHT than would be characteristic of exposures to 2,4,6 TTBP.
 Text was added to the approach document to discuss how EPA chose surrogate chemicals and how they demonstrate sufficient similarity for use. BHT is no longer used as a surrogate ((2,4 DTBP) is used as a surrogate).

                                      11
2,4,6 TTBP-specific comments (SI Group):
 Section 7.5.  -  p. 135 Condition of Use for 2,4,6-Tri-Tert-Butyl Phenol (2, 4, 6-TTBP) is not similar to BHT so it should not be compared together. 2, 4, 6-TTBP is predominantly used as chemical feedstock in applications resulting in its destruction, where people are intentionally exposed to BHT via foodstuffs, pharmaceuticals and cosmetics.

 BHT is no longer used as a surrogate for TTBP in the assessment (2,4 DTBP is used as a surrogate).

Characterization of exposure scenarios  -  Public Comments
Charge question 7: Please comment on whether EPA has appropriately captured the exposure scenarios. Please identify any existing exposure scenarios EPA may have missed. Please keep in mind the purpose of this document is to inform regulatory decisions under TSCA only.
                                       #
  Summary of Public Comments for Specific Issues Related to Charge Question 7
                               EPA/OPPT Response
                                      12
Susceptible populations
 EDF: Need to identify potentially exposed or susceptible subpopulations: EPA has not included, and should add, a section to each document identifying the relevant potentially exposed or susceptible subpopulations it can now identify based on the information it has already provided in the documents, and EPA should update these as more information is developed.
 NTTC: Exposure scenarios representative of the highly exposed population of tribes should be considered, including the following:
       ingestion of traditional materials: basket grass softening via mouth, chewing reeds, sinew, fish skins
       increased biota consumption; (fish, plants, animals, large land mammals, shell fish, marine mammals (higher than standard population); smoking fish/ meats, hides
       increased traditional water use, untreated water collection, consumption, steamed baths, increased wading and constant soaking of water, drinking local surface water 
       increased hunting, fishing, gathering
       ceremonial objects (feathers, art/ tools in the form of clay pots, reed baskets, baleen carving; dust from handcrafts, burning out canoes; cultural burning to stimulate material production, shaping wood and sweat lodges
       living conditions: adobe houses present durable dust and soil ingestion exposures; open burning of community dump sites; animal, fish dried and stored without protective barrier next to vehicle care products and paints; the proximity of tribal populations to emissions and contaminated sites, incomplete plumbing and overcrowding
       occupational exposure- Native American silversmiths used asbestos mats to insulate worktables making silver jewelry
 NTTC: Exposure factors representative of the highly exposed population of tribes should be considered, including the following:
          multiple resource use (tribes may use plants for medicines, as well as basketry)
          frequency
          duration
          contact rate
          Age: young children hunt and gather, elders are active in the environment compared to general population
 NTTC: Consider exposure factors from Lifeline Group Developed Lifeline software (probabilistic software tool for US and Canadian populations and subpopulations): Lifeline is a people based modeling software that accounts for non-standard diets consisting of wild foods and interactions and exposure with all media in the environment.
 NTTC: Durability of environmental exposures may be orders of magnitude higher because Tribal people hunt and gather locally, then consume locally compared to the general population which may just consume from any number of different sources and those locations vary over time

 While EPA acknowledges that higher exposures may occur with tribal or other populations, the qualitative assessment of the exposure and use assessment for the five chemical substances is sufficient to fulfill the objectives and purposes as outlined in the document. To the extent practicable, EPA has proposed measures that will reduce exposures to susceptible subpopulations. The level of detail suggested is not necessary to make the TSCA section 6(h)(1)(B) exposure finding.
 The detailed and specific parameters identified for risk evaluations are not included in this evaluation.
   
                                      13
Representative Exposure Scenarios: 
ACC: Not all representative exposure scenarios are consistent with the uses reported for the chemicals. For example, an occupational exposure scenario is reported for the manufacture of PCTP, but it is also reported that "No company has reported manufacture and/or import of pentachlorothiophenol (PCTP) in the U.S. above the reporting threshold of the Chemical Data Reporting (CDR) Rule for 2016." Therefore, this exposure scenario does not appear to be relevant to the conditions of use of the chemical in the United States. The Representative Exposure Scenarios for each chemical should be consistent with the TSCA-regulated uses in the U.S.
 The exposure and use assessment for the five chemical substances have been focused on the objectives and purposes as outlined in the document.  The representative scenarios and data were presented in this document met the secondary data evaluation criteria.
 PCTP is imported in the ZnPCTP formulation and PCTP could be imported or manufactured under the volume required for reporting to CDR.

Utility of including additional information from the monitoring studies  -  Public Comments
Charge question 8: Please comment on whether inclusion of additional information on monitoring data would significantly enhance the exposure assessment for the intended purpose of this document. For example, characterization of sampling year vs. study year, characterization of free vs. particle bound chemicals in water and air, lipid normalization for biomonitoring data, and further characterization of studies that had incomplete reporting for their limits of detection. Please identify any specific chemicals for which this additional information would be helpful.
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  Summary of Public Comments for Specific Issues Related to Charge Question 8
                               EPA/OPPT Response
                                      14
 ACC: EPA has conducted a comprehensive search of relevant publicly available use and exposure information. However, there is no temporal or geographical context to the data presented. For instance:
 Geographical Context: A number of the core exposure studies cited by EPA are from sources outside the U.S. Before EPA uses studies of human or ecological exposure or environmental occurrence from outside the U.S., the Agency should establish whether they are relevant to potential risks of injury to health and the environment that result from conditions of use regulated by TSCA. EPA should determine whether TSCA-regulated uses in the U.S. are the likely source of environmental monitoring observations outside of the U.S. Likewise, EPA should determine whether uses in foreign countries are similar to those uses in the U.S. such that environmental monitoring and biomonitoring observations outside the U.S. could be considered representative of conditions within the U.S.
 Temporal Relevance: The core exposure studies cited by EPA cover at least four decades. The conditions of use for the Section 6(h) PBT chemicals have, however, been variable over that same time period. In the Trends in Monitoring Data section of EPA's document, some temporal trends in environmental monitoring data and biomonitoring data are described, but are not put into context with the use pattern of the chemical. For example, according to tables in the EPA document, EPA Chemical Data Reporting (CDR) production volumes for DecaBDE declined from 10-50 million pounds per year in 2010-2012 to less than 25,000 pounds in 2015 (Table 4-2, p. 27). However, the biomonitoring data appear to show substantial declines in concentrations of DecaBDE in fish (Figure 4-29, p. 53; Figure 4-41, p. 61) and bird eggs (Figure 4-42, p. 62) well before what appears to be a near phase-out in production in the U.S. in approximately 2013; further, the sediment monitoring data for DecaBDE (Figure 4-38, p. 59) seem to contradict the declining trend in fish tissues.
      EPA should establish that critical core exposure studies have a temporal relevance to current conditions of use regulated by TSCA. Also, any data to evaluate trends should be evaluated based upon the year of data collection rather than the year of study publication.
 Geographical context: The country of data collection is included in the figures and text.  
 Temporal context: Data have been updated and are presented by both sampling year and publication year. 
 Data collected recently and within the US were prioritized for review and presentation. Due to the scarcity of data, particularly for some chemicals, all available data is presented and is not censored by location or timescale. 

Strengths and weaknesses of datasets used in the assessment  -  Public Comments
Charge question 9: Please comment on the reliability and relevance of the identified data sets for each chemical and on the strengths and weaknesses of individual data sets that will help to better inform future regulatory actions. 
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  Summary of Public Comments for Specific Issues Related to Charge Question 9
                               EPA/OPPT Response
All Chemicals
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 ACC: EPA is not required to conduct a risk evaluation for Section 6(h) PBT chemicals, nor is it required to apply systematic review to the data associated with the Section 6(h) PBT chemicals. EPA should apply the data quality criteria from its document Application of Systematic Review in TSCA Risk Evaluations to the environmental monitoring data and biomonitoring data. This will enable the public to better understand which data may be of sufficient reliability and relevance for regulatory decision-making.
 All data presented in this document have undergone QA/QC review and met the secondary data evaluation criteria and as per approved QAPP and QMP.