Currently, facilities required to report on PCBs must report on all PCBs, not just the co planar PCBs or any other individual PCBs. The current listing includes all PCBs. Consequently EPA does not believe that the requirements of section 313( f)( 2) function as an impediment to its decision to withdraw its proposal to include the co planar PCBs in the dioxin and dioxin like compounds category. As discussed in Units II. B. and VI. A., EPA believes that it has satisfied the requirements of EPCRA section 313( f)( 2), without the need for quantitative support. c. Listing dioxin and dioxin like compounds as a category versus individual listing of each chemical. Some commenters contend that reporting dioxin and dioxin like compounds as one category would not provide useful information and asked that the individual compounds be reported. One commenter recommends that reporting on individual chemical species should be required when the information is available. One commenter who supports the individual reporting of all of the dioxin and dioxinlike compounds, states that the amounts of individual dioxin compounds released from facilities is part of the important public information needed to assist research and policy development. The commenter claims that reporting as a category will not provide the public with the information to assess the relative hazards of releases since one dioxin like compound can have a relative hazard several orders of magnitude less than 2,3,7,8 tetrachlorodibenzo p dioxin. This commenter also states that different sources often emit a different mix of dioxin compounds and that this information is widely used to trace dioxin contamination to specific root causes. The commenter states that the relative amounts of the many different dioxin like chemicals in a sample are compared to create a `` profile'' which might match the profile created by emission from a particular source. The commenter did not support the reporting of the category based on toxic equivalents (TEQs) but thought it important for the users of the data to be able to determine TEQs. Some other commenters make the same general argument that individual isomer reporting is needed to facilitate risk characterization including transport and fate of the different isomers. Some commenters contend that certain dioxin like compounds such as octachlorodibenzo p dioxin and octachlorodibenzofuran should not be reported since they are ubiquitous in the environment and are the least toxic under the toxic equivalent factors (TEFs). One commenter states that EPA should require reporting only for the most toxic congeners: the tetra, penta and hexa congeners and not the heptaand octa congeners which are less toxic and less relevant from a risk standpoint. Other commenters state that only 2,3,7,8 tetrachlorodibenzo p dioxin should be reported. Some commenters contend that reporting for these compounds should not be required at the same reporting threshold as the other dioxin and dioxin like compounds. Most commenters who would like to exclude certain dioxinlike compounds did not indicate that they wanted individual reporting of the remaining compounds. Some commenters support the reporting of dioxin and dioxin like compounds as a category, as EPA proposed. One commenter states that if reporting is not limited to just 2,3,7,8 tetrachlorodibenzo p dioxin, then the commeter supports EPA's proposal to limit the category to only the 7 dioxins and 10 furans listed in the proposed rule. After consideration of all of the comments on this issue, EPA has decided that the best way to report on dioxin and dioxin like compounds is to report them as a category. This is consistent with the way EPA has addressed other groups of chemicals that share the same toxic effect and in this case are also generated as complex mixtures. As discussed in Units VI. G. 1. d. and e., reporting as a category and based on TEQs would not provide users of the data with information on which compounds contribute the most to the TEQ total. In addition, requiring facilities to report each compound individually would impose an additional burden on the industries that will be required to report. However, EPA agrees that being able to determine the amounts of the individual dioxin and dioxin like compounds would make the data more useful. Therefore EPA will add a section to the Form R that will require the reporting facility to provide the distribution of dioxin and each dioxin like compound for the total quantity that the facility is reporting. If a facility has information on the distribution of the dioxin and dioxinlike compounds, the facility must report either the distribution that best represents the distribution of the total quantity of dioxin and dioxin like compounds released to all media from the facility; or its one best mediaspecific distribution. This information is only required if it is available from the data used to calculate thresholds, releases, and other waste management quantities, no additional analysis is required. As with all other reporting under EPCRA section 313, this information will only be required if the facility has information that can be used to make a reasonable estimate of the distribution from the available data. With the distribution of congeners reported on each Form R, the user of the data can determine the grams of dioxin and each individual dioxin like compound that makes up the total quantity reported on the Form R. Under this reporting mechanism, all of the information that the commenters have stated is important to determining the significance of quantities reported under this category will be provided to the public but the reporting facilities will still only have to file one report. Any of the other possible options, such as reporting in terms of TEQs or reporting each individual compound separately, either do not provide all of the information the commenters would like to have, or impose too great an additional reporting burden without providing the public with significant additional information. d. Using mass versus TEQs for reporting releases and other waste management quantities. Most of the commenters on this issue suggest that EPA should require that release and other waste management data for the dioxin and dioxin like compounds category be reported in terms of TEQs rather than in terms of absolute grams. The following list is a summary of the various reasons provided by the commenters in support of reporting dioxin and dioxin like compounds in terms of TEQs: (1) All dioxin data reported under other EPA programs as well as other Federal and state regulatory programs are reported in terms of toxicity equivalents; (2) the public is familiar with dioxin data reported in terms of TEQs and reporting in other units would cause confusion and be misleading; (3) TEQs provide more meaningful information than total weights since they take into account the relative toxicities of the various dioxinVerDate 58701 Federal Register / Vol. 64, No. 209 / Friday, October 29, 1999 / Rules and Regulations like compounds; (4) facilities that report under other regulatory programs are likely to rely upon TEQ data that they already have; (5) use of absolute mass may cause misleading comparisons between grams and grams TEQ; (6) releases reported in absolute mass make it difficult to assess the impacts these compounds may have on the environment due to the differences in their toxicities; and (7) reports based on TEQs would provide far more useful information about potential community risks than reports based on the total mass of compounds in the category since more risk information would be provided. One commenter argues that EPA's justification for adding the category is based on assumptions about the toxicity of the other dioxin like compounds relative to dioxin itself and that given these assumptions the reporting of TEQs makes sense. The commenter states that under current TEQ schemes, these dioxin like compounds are all less toxic than dioxin, as much as 1,000 times less, and that facilities should not simply sum emissions on the Form R for compounds with such drastically different toxicities. One commenter suggests that EPA require the reporting of both grams and TEQs and if not both, then just grams. This commenter asserts that if only grams are reported, the data will be somewhat difficult to interpret without any further information, but if only TEQs are required to be reported, then there are uncertainties about what and how much is discharged. Another commenter states that if EPA is going to require dioxin reporting as a group and not by specific chemicals, TEQ reporting is an unnecessary complication. The commenter states that the TEFs used to formulate the TEQs are constantly reviewed and changed, which would necessitate EPA review and possible reissuance of new TEFs each year. The commenter argues that this would make previous years' TRI data impossible to compare once the changes were made. While EPA recognizes that TEQs are a common way of expressing quantities of dioxin like compounds, EPA does not believe that reporting in these units would be the best or most appropriate way to report for the dioxin and dioxinlike compounds category under EPCRA section 313. Although some commenters believe that TEQ reporting should be used since not all of the dioxin like compounds are as toxic as dioxin itself, EPA has determined that all of the dioxin like compounds meet the listing criteria of EPCRA section 313. Since all of these compounds meet the listing criteria, the actual mass of each member of the category should be reported. To do otherwise would deny the public information on the actual quantities of toxic chemicals entering the environment. It would also be inconsistent with all other reporting of EPCRA section 313 toxic chemicals since none of them are reported based on relative toxicities. In addition, this would be inconsistent with EPCRA section 313( g)( 1)( C)( iv) which requires that `` the annual quantity of the toxic chemical entering each environmental medium'' be reported. Some of the commenters state that TEQs should be used because they provide more risk information to the public than just reporting mass. While TEQs do provide information on relative toxicity, EPA does not believe that increasing the amount of risk information is a basis for changing the EPCRA section 313 method for reporting from mass based to relative toxicitybased As discussed in Unit VI. F., EPCRA section 313 is not a risk based program, and reporting is not intended to communicate information about relative risks. Rather it provides local communities with data on release and other waste management quantities on listed toxic chemicals, so that they may use the data in conjunction with information on chemical properties (e. g., persistence and bioaccumulation) and site specific information to determine if releases present a potential risk. It is also not clear, as some commenters state, that the public is more familiar with dioxin data reported in terms of TEQs or that they will understand TEQs any better than grams. EPA does not believe that the fact that other programs require reporting in TEQs and that facilities will already have TEQ information is a significant reason to require TEQ reporting under EPCRA section 313. Since the first piece of information that is required to determine TEQs is the grams of dioxin and each dioxin like compound, these facilities should already have the grambased information they would need. In addition, as stated above, EPCRA section 313 reporting serves the purposes of EPCRA section 313; other programs, e. g., the CWA, are risk based command and control programs. Several commenters also disagree with the concerns that EPA raised in the proposed rule, which were:

. . .there are three significant disadvantages to reporting in TEQs. First, revisions in TEF factors for individual dioxin like compounds in future years would require changes to the calculations in the reported release and other waste management quantities, thus making year to year comparisons more difficult, unless the particular dioxin like compounds are identified. Second, some facilities may not be able to report in TEQs, since, although they may be able to estimate a mass quantity for the category as a whole, they may not have enough information to estimate the relative distribution of all category members. Third, TEQ reporting would be different from all other TRI reporting, which is mass based, and may cause additional confusion. (at 64 FR 712 713)

Some commenters contend that EPA's first concern is not valid since the EPCRA section 313 reporting requirements have been changed several times in the past in spite of difficulties in comparing future reports to past performance. Two commenters state that this same logic could be applied to the use of AP± 42 factors which EPA acknowledges have been revised and refined over the years, and that this also diminishes the value of year to year reporting comparisons. One commenter suggests that EPA could minimize any confusion that might be caused by a subsequent change in one or more TEFs by each year specifically publishing or cross referencing the TEFs that must be used for that reporting period. One commenter contends that EPA's second and third concerns appeared weak in light of the much greater risk information provided by a TEQ approach. Some commenters contend that EPA's third concern is not valid since the reporting requirement being proposed for dioxin and dioxin like compounds is different whether TEQs are used or not. One commenter states that the third concern is clearly dwarfed by the confusion that would ensue if all dioxin like compounds were reported as equivalent, when the hazards vary by a factor of 500. One commenter states that reporting dioxin on a TEQ basis will cause more rather than less confusion if the public mistakenly compares data in grams with data presented in grams TEQ. Some commenters agreed with the concerns EPA expressed in the preamble. One commenter states that it agreed with these concerns but that the concern about year to year comparisons being more difficult also applies to the reporting of a single mass value for the entire category. The commenter contends that since the amounts of the individual dioxin like compounds would not be known, if TEFs change, one cannot adjust previously reported values to reflect the changes in TEFs. This commenter suggests that in order to make the information reported of greatest use, the mass of dioxin and each of the dioxin like compounds should be reported once a TEQ threshold is exceeded. One commenter argues that while TEQs are a valid and scientifically 58702 Federal Register / Vol. 64, No. 209 / Friday, October 29, 1999 / Rules and Regulations sound metric for reporting the likely health hazard of a compound, that was not the intended purpose of the EPCRA section 313 reporting requirement. The commenter claims that reporting dioxin and dioxin like compounds in TEQs will cause confusion, since all other reporting under EPCRA is done in terms of mass and does not take toxicity into account. EPA believes, as do some of the commenters, that the concerns that were expressed in the proposed rule for reporting dioxin and dioxin like compounds in terms of TEQs under EPCRA section 313 are valid. EPA disagrees with those commenters who claim that since other changes in reporting have occurred, such as revisions to AP 42 emission factors, there should be no concern for the changes that might occur in TEFs and the resulting TEQs. The fact that certain changes have occurred in reporting requirements or methods of estimation and that those changes may make certain year to year comparisons more difficult does not reduce the concern for knowingly selecting reporting units, based on relative toxicity as opposed to emission factors, that have changed in the past and may well change in the future. Also, EPA would be required to choose a particular set of TEFs (i. e., as of 1999) and would need to amend them by rulemaking each time the TEFs were revised. Changes in TEFs and the resulting TEQs would be unlike any of the past changes in EPCRA section 313 reporting since none of these reporting changes were related to the relative toxicity of chemicals that meet the listing criteria of EPCRA section 313. The cross referencing or publishing of the TEFs that must be used for each reporting period would still not allow year to year comparisons since without knowing a facility's distribution of each of the category members the TEQ cannot be recalculated. EPA's concerns that some facilities may not be able to report in terms of TEQs are also valid. Although most facilities that will be able to make reasonable estimations for the dioxin and dioxin like compounds category should be able to report in terms of TEQs, there may be some that can only report in actual mass units and they should not be exempt from reporting. EPA is also still concerned that TEQs would be different than other EPCRA section 313 reporting units, since they are not based on absolute mass, and that this could cause confusion. EPA does not agree with the commenters that state that this does not matter since the reporting for the dioxin and dioxin like compounds category is going to be different anyway. The only real reporting difference for the dioxin and dioxin like compounds category is that the reporting units are in grams rather than pounds. To determine the amounts in pounds all that one would have to do is multiply the grams by 0.002204. However, TEQ reporting would be much different since in order to understand the reported value one would need to understand the basis for TEFs, what they are, how they relate to dioxin, and how TEQs are calculated from the individual TEFs. This obviously requires more knowledge on the part of the data user than simply understanding different units of mass and does have the potential to cause some confusion. One commenter contends that neither total mass nor TEQ reporting provides sufficient information on reduction in potential exposure and risk. The commenter asserts that it is possible that a facility could reduce its dioxin TEQ while releasing a greater mass of dioxinlike compounds, but neither total mass nor TEQ reporting would really provide a good picture of what a facility was doing. The commenter suggests that if EPA wants to provide TEQ information to the public, it should also require facilities to report dioxins by individual chemical, rather than as a group. Another commenter that favors the reporting of dioxin and dioxin like compounds as individual chemicals claims that reporting as a category but in TEQs would still fail to reveal the amounts of individual dioxin compounds released. The commenter argues that this alternative would provide no information on individual compounds for use in tracing dioxin source profiles. The commenter contends that reporting in TEQs would provide better information on the relative toxicity hazard based upon today's toxicity information but that information on the relative toxicity of the many dioxin like chemicals is improving and thus toxicity factors for some of these compounds will change in the future. The commenter claims that in future years the Inventory would have to choose between keeping the old toxicity calculation (and becoming irrelevant in comparison with other research data), or changing the toxicity calculation (and becoming irrelevant for tracking changes in dioxin release rates over time). The commenter contends that the need to aid research and policy development based on current science and the need to track release rates over time are fundamental to the Inventory's purpose and that this alternative must be rejected as just another ill advised aggregate reporting scheme. The commenter recommends that EPA require the reporting of dioxin and dioxin like compounds in the way these compounds are measured and analyzed by scientists and government agencies, as individual chemicals, and consider an additional service by EPA to calculate and report dioxin toxicity as TEQ for the year to year data using the most recent toxicity information which becomes available. Several commenters make the point that for dioxin and dioxin like compounds neither reporting total mass nor reporting in terms of TEQs provides sufficient information on potential exposures and risks, and that neither would allow for the tracing of dioxin source profiles. EPA agrees that neither approach would provide all of the data that the commenters would like to have reported and that being able to determine TEQs would provide additional useful information. A common solution to the TEQ issue that the commenters suggest, was to report dioxin and each individual dioxin like compound separately rather than as a category. However, EPA believes that this approach would be overly burdensome and unnecessary to get the kind of data that would be the most useful. As discussed in the previous section of this unit, many other commenters requested that dioxin and dioxin like compounds be reported separately rather than as a category. After consideration of all of the comments on this issue, EPA has determined that the best way to report for the dioxin and dioxin like compounds category is to report in terms of absolute grams for the entire category. This is consistent with all other reporting under EPCRA section 313 and will provide the most consistent information from year toyear However, EPA agrees with most of the commenters that being able to determine TEQs from the reported data and being able to determine which individual chemicals are include in a facilities report would make the data more useful to the public. Therefore, as discussed in the previous section of this unit, EPA will add a section to the Form R that will require the reporting facility to provide the distribution of dioxin and each dioxin like compound for the total quantity that the facility is reporting. If a facility has information on the distribution of the dioxin and dioxinlike compounds, the facility must report either the distribution that best represents the distribution of the total quantity of dioxin and dioxin like compounds released to all media from the facility; or its one best mediaVerDate 58703 Federal Register / Vol. 64, No. 209 / Friday, October 29, 1999 / Rules and Regulations specific distribution. This information is only required if it is available from the data used to calculate thresholds, releases, and other waste management quantities, no additional analysis is required. As with all other reporting under EPCRA section 313, this information will only be required if the facility has information that can be used to make a reasonable estimate of the distribution from the available data. With the distribution of the individual members of the category reported on each Form R, the user of the data can determine the grams TEQ that correspond to the absolute grams reported and can adjust the grams TEQ as TEF values change over time. Under this reporting mechanism, all of the information that the commenters state is important to determining the significance of quantities reported for this category will be provided to the public on one Form R. This way all parties can express the data in whichever format they believe is best, and since the first thing that must be determined under any reporting method is the mass of each member of the category, there should be little, if any, additional burden associated with including the distribution. e. Using TEQs as the basis for reporting thresholds. All of the commenters on this issue requested that the reporting threshold for the dioxin and dioxin like compounds be set in terms of TEQs. Most of the commenters indicate that the reasons they support a TEQ based threshold were the same as the reasons they support reporting release and other waste management quantities in terms of TEQs (see the first paragraph of the preceding section of this unit). Two commenters argue that since EPA proposed to use TEQs for reporting release and other waste management quantities, that not basing the reporting threshold on TEQs would be inconsistent. The commenters contend that a facility may trigger reporting by having emissions that exceed the threshold (in terms of absolute weight) but have no significant reporting quantity (in terms of TEQ equivalent weight) and, therefore, no significant health risk. The commenters recommend the use of a consistent approach where TEQs are used for both threshold determinations and release and other waste management quantities. The commenters state that such an approach would be consistent with the health risk rationale for EPCRA reporting, yet not rely on site specific risk approaches that may evolve over time. Another commenter had similar concerns suggesting that it would be extremely burdensome and unnecessarily complex to have thresholds based on absolute grams and release and other waste management quantities reported in TEQs and recommends that EPA should use TEQs for both. One commenter claims that it may ease the reporting burden somewhat to base the EPCRA section 313 reporting threshold on a TEQ basis rather than attempting to develop mass based estimates. Another commenter contends that in order to determine the sum of the mass of the 17 dioxin and dioxin like compounds, one already will have determined the mass of each compound individually and that with data reported by compound, a TEQ can easily be calculated. The commenter also suggests that there are short term screening bioassays for determining the TEQ of a sample that are less expensive, more sensitive, and can be done more rapidly than traditional analytical chemistry methods. The commenter states that rather than facilities trying to guess what their releases may be, in an attempt to avoid spending money on expensive analytical chemistry methods, if the reporting threshold were based on TEQs, a facility can readily and more inexpensively screen its releases. The commenter argues that having a reporting threshold based on TEQ is more representative of potential health risks and recommends that EPA consider using some amount of TEQs as the reporting threshold. Another commenter suggests that one option would be to report releases of each dioxin like compound if the total, in TEQ, exceeds some chosen threshold. One commenter that suggests that TEQs should be used for thresholds, notes that reporting dioxin on a mass basis is quite different from reporting on a TEQ basis. The commenter asserts that since some of the dioxin like compounds have TEFs of 0.001 then the 0.1 gram threshold could require facilities that produce 0.0001 gram TEQ of dioxin to report. The commenter claims that when compared to the estimate that there are 2,973 grams TEQ of U. S. dioxin emissions such amounts are insignificant and meaningless. The commenter maintains that using TEQs instead of the mass of each compound for determining whether an EPCRA reporting threshold for dioxin and dioxin like compounds is exceeded would not deprive EPA or the public of information regarding meaningful releases of dioxin. The commenter also recommends that whatever units EPA decides to use should be the same for thresholds and for release and other waste management quantities. One commenter suggests that EPA should require sources to use toxicity factors in calculating the manufacturing threshold for dioxin and dioxin like compounds to avoid triggering the threshold based solely on non detection. The commenter states that the 17 dioxin like compounds to which the 0.1 gram proposed reporting threshold would apply vary in toxicity by a factor of 1,000 but that EPA does not take this variation in toxicity into consideration for the purpose of determining the manufacturing threshold. EPA did not propose to use TEQs as the units of measurement for the EPCRA section 313 reporting threshold for dioxin and dioxin like compounds. EPA has the same concerns for using TEQs for EPCRA section 313 thresholds as it does for reporting releases and other waste management quantities in terms of TEQs, and most of the issues raised here have been addressed in the preceding section of this unit. Most importantly, since EPA has determined that each of the dioxin like compounds meets the listing criteria of EPCRA section 313, the actual mass of each member of the category should be included in threshold determinations. Also, the fact that the TEFs and thus the TEQs can change over time, is even more important for thresholds since TEF changes would in effect change the threshold, because for example, the same mass quantity that would have exceeded the threshold before the change may not exceed the threshold after the change. As one of the commenters pointed out, using TEQs as the units for the reporting threshold is much different than using actual mass. The commenter showed how a 0.1 gram threshold for a dioxin like compound with a TEF of 0.001 would be equivalent to a 0.0001 gram TEQ threshold. The opposite of this is that if the 0.1 gram threshold were in units of TEQ, then for dioxinlike compounds with a 0.001 TEF, it would take 100 grams to reach the reporting threshold. Using TEQs as the units for the reporting threshold would thus be equivalent to establishing separate thresholds for each member of the dioxin and dioxin like compounds category based on their relative toxicity. EPA does not believe that any of the reporting requirements of EPCRA section 313 should be based on relative toxicities since, as discussed in Unit VI. F., EPCRA section 313 is not a riskbased program and reporting is not intended to communicate information about the Federal government's risk determinations for individual chemicals. Rather it provides local communities with data on release and 58704 Federal Register / Vol. 64, No. 209 / Friday, October 29, 1999 / Rules and Regulations other waste management quantities on listed toxic chemicals, so that they may use the data in conjunction with information on chemical properties (e. g. persistence and bioaccumulation) and site specific information to determine if releases present a potential risk. Several commenters express concern about consistency between the units of measurement for the threshold for the dioxin and dioxin like compounds category and the units of measurement used to report releases and other waste management quantities. While EPA is not adopting the use of TEQ as some commenters requested, EPA is being consistent since absolute gram quantities will be used for both thresholds and the reporting of releases and other waste management quantities. EPA does not agree with those commenters who state that the information collected under a 0.1 gram threshold would, in some cases, represent such a small portion of the estimated national amount of dioxin TEQs that the data would not be useful. On a facility by facility basis, the amounts reported may be a small percentage of the national total, but that does not mean that it will not be useful or meaningful to the public. One of the purposes of EPCRA section 313 is to provide information to communities about releases into their community. A small percentage of national releases may pose potential risks to local communities. Further, even information that shows little or no releases helps communities to understand what risks may be or may not be present in their communities and helps government agencies to target resources. In addition, since not all of the sources of dioxin and dioxin like compounds will be reporting under EPCRA section 313, the amount reported will be a larger portion of the total amount reported under EPCRA section 313 than it will be on a national basis. The issue of how many sources of dioxin and dioxin like compounds are captured by EPCRA section 313 are addressed in the Response to Comments document (Ref. 69) for this rulemaking. EPA does not agree that reporting in terms of TEQs would necessarily be less burdensome. As one commenter states, in order to determine the sum of the mass of the 17 dioxin and dioxin like compounds, one already will have determined the mass of each compounds individually and that with data reported by compound, a TEQ can easily be calculated. Since the TEQs are calculated from the relative amounts of dioxin and each dioxin like compound that is present, it is an additional step to present the data in terms of TEQs and therefore it should not be less burdensome. f. Reporting guidance for dioxin and dioxin like compounds. A number of commenters requested that EPA develop reporting guidance for the dioxin and dioxin like compounds category. EPA agrees that guidance should be provided to assist facilities in determining threshold and release quantities for the dioxin and dioxin like compounds category. As EPA stated in the proposed rule:

EPA intends to develop reporting guidance for industries that may fall within this reporting category. The guidance developed will be consistent with the methods and procedures that EPA has developed for determining if dioxin and dioxin like compounds are present in various industrial processes, including Method 23 (Ref. 77) developed for electric utilities. In developing the reporting guidance for the dioxin and dioxin like compounds category EPA will work with interested parties to provide the best possible guidance for reporting facilities (at 64 FR 712).

EPA will provide a guidance document to assist certain facilities in making thresholds and release determinations for the dioxin and dioxin like compounds category. The guidance document will be consistent with EPA established methods of measuring or estimating quantities of dioxin and dioxin like compounds, including Method 23. 2. Benzo( g, h, i) perylene (CAS No. 191 24 2) (Ref. 70). EPA proposed to add benzo( g, h, i) perylene to EPCRA section 313 pursuant to EPCRA section 313 (d)( 2)( C). One commenter states that EPA should not add benzo( g, h, i) perylene to the EPCRA section 313 list of toxic chemicals because there are insufficient data to support the EPCRA section 313( d)( 2)( C) determination. The commenter states that EPA used predicted aquatic toxicity values based on quantitative structure activity relationship (QSAR) analysis but did not provide any toxicity data. The commenter contends that EPA did not provide any evidence to support the statement that aquatic QSAR equations show a high correlation between predicted and measured toxicity values, and did not provide any other information to support use of QSAR for this type of chemical. EPA disagrees with the commenter's statements. EPA provided the following discussion in the proposed rule:

Three of the chemicals being proposed for listing (benzo( g, h, i) perylene, 3 methylcholanthene, and octachlorostyrene) have been found to meet the EPCRA section 313( d)( 2)( C) criteria for ecotoxicity based on predicted aquatic toxicity values generated from quantitative structure activity relationship (QSAR) equations and other predictive techniques. As previously stated (58 FR 63500, December 1, 1993), EPA believes that, where no or insufficient actual measured aquatic toxicity data exist upon which to base a decision, toxicity predictions generated by QSARs and other predictive techniques may constitute sufficient evidence that a chemical meets the section 313 listing criteria. EPA's authority to use such predictive techniques derives from section 313( d)( 2) of the statute, which states that EPA shall base its listing determinations on, inter alia, `` generally accepted scientific principles. '' EPA believes that the aquatic QSAR equations that are in widespread use and show a high correlation between predicted and measured aquatic toxicity values can be considered to be ''generally accepted scientific principles'' and can appropriately form the basis of a listing determination (Ref. 70). (at 64 FR 693)

EPA believes that QSAR data is valid predicted aquatic toxicity data and the fact that no actual toxicity studies were provided does not mean that the available data were insufficient to determine that benzo( g, h, i) perylene met the listing criteria of EPCRA section 313( d)( 2)( C). In addition, EPA did provide support for the statement that aquatic QSAR equations are in widespread use and show a high correlation between predicted and measured aquatic toxicity values. The docket for the proposed rule contained a document titled `` SAR/ QSAR in the Office of Pollution Prevention and Toxics'' In: Environmental Toxicology and Risk Assessment: 2nd Volume, STP 1216. One of the articles in this reference was titled Validation of Structure Activity Relationships Used By the USEPA's Office of Pollution Prevention and Toxics for the Environmental Hazard Assessment of Industrial Chemical. This includes the methods of SAR for the class of neutral organic chemicals which, as discussed in the support document, was used for benzo( g, h, i) perylene since it is a neutral organic chemical. Thus, EPA did provide support for its conclusions about QSAR analysis and for the use of QSAR for benzo( g, h, i) perylene. This commenter also states that EPA uses an estimated Log Kow in its aquatic toxicity prediction and argues that Log Kow is an inaccurate predictor for many chemicals particularly if it is estimated rather than measured. The commenter contends that EPA's basis for the listing of benzo( g, h, i) perylene is a prediction based upon a prediction, with no actual data and that this is not a sufficient basis for listing under EPCRA section 313 and it does not meet the statutory requirements for listing that a chemical is `` known to cause or can reasonably be 58705 Federal Register / Vol. 64, No. 209 / Friday, October 29, 1999 / Rules and Regulations anticipated to cause'' a significant adverse effect. EPA disagrees with the commenter's conclusions. The majority of the SAR calculations in the ECOSAR Class Program are based upon the octanol/ water partition coefficient (Kow or Log P) since there is a correlation between Log P and toxicity. Using the measured aquatic toxicity values and estimated Log P values, regression equations can be developed for a class of chemicals. Toxicity values for a chemical within that class may then be calculated by inserting the estimated Kow into the class regression equation and correcting the resultant value for the molecular weight of the compound. The ecological assessment guidelines for predicting the toxicity of chemicals with limited measured aquatic toxicity data have been used for over a decade (Ref. 35). The commenter has not provided the Agency with any concrete information or data indicating that this approach either is not a generally accepted scientific approach or is unreliable, and the Agency finds no reasonable basis to change these techniques at this time. In addition, the commenter did not provide any data to indicate that the predicted Log Kow for benzo( g, h, i) perylene was inaccurate. This commenter also contends that EPA's failure to consider exposure in this proposed rule is particularly important for benzo( g, h, i) perylene. The commenter argues that given the properties of benzo( g, h, i) perylene, any release into water will result in the vast majority (more than 99%) of the compound being partitioned to sediment or adsorbed onto suspended particulates and organics in the water column and thus the potential for this chemical to be in a toxic form and pose risk in natural systems is low. EPA disagrees with the commenters' contention that EPA should consider exposure in its determination that benzo( g, h, i) perylene meets the EPCRA section 313( d)( 2)( C) listing criteria. As discussed in Unit VI. F., EPA is only required to consider exposure under a limited set of circumstances. In the final chemical expansion rule (59 FR 61432), EPA further explained its policy on the use of exposure considerations under EPCRA section 313( d)( 2)( C) and the fact that the Agency does not consider exposure for chemicals that are highly ecotoxic. As EPA explained in the final rule:

The Agency believes that exposure considerations are not appropriate in making determinations (1) under section 313( d)( 2)( B) for chemicals that exhibit moderately high to high human toxicity (These terms, which do not directly correlate to the numerical screening values reflected in the Draft Hazard Assessment Guidelines, are defined in unit II.) based on a hazard assessment, and (2) under section 313( d)( 2)( C) for chemicals that are highly ecotoxic or induce wellestablished adverse environmental effects (at 59 FR 61441).

Although EPA does not believe that it would be appropriate to consider exposure, EPA also disagrees with the commenter's characterization of the fate of benzo( g, h, i) perylene. Environmental fate models show that the chemical will only partition about 60% to the sediment. Also, the Agency cannot rely on the environment to serve as a sink for this chemical. Other environmental conditions such as turbidity, biological activity, or the chemical activity in water could cause redistribution of the chemical into the water column again. Based upon QSAR equations and other predictive techniques, EPA has concluded that benzo( g, h, i) perylene is toxic. It has the potential to kill fish, daphnia, and algae, among other adverse effects, based on chemical and/ or biological interactions. Benzo( g, h, i) perylene can cause these toxic effects at relatively low concentrations. The predicted aquatic toxicity values for benzo( g, h, i) perylene, based upon QSAR analysis using the equation for neutral organics and an estimated Log Kow of 6.7, included calculated values of 0.030 milligrams per liter (mg/ L) for the fish 96± hour LC50 (i. e., the concentration that is lethal to 50% of test organisms) and 0.0002 mg/ L for fish chronic toxicity; 0.012 mg/ L for daphnia 48± hour LC50 and 0.027 mg/ L for the daphnid 16± day chronic LC50; and 0.03 mg/ L for the algae 96± hour EC50 (i. e., the concentration that is effective in producing a sublethal response in 50% of tests organisms) with an algal chronic toxicity of 0.012 mg/ L. Benzo( g, h, i) perylene can cause its toxic effects at relatively low concentrations, therefore EPA considers it to be highly toxic. Since benzo( g, h, i) perylene is toxic at relatively low concentrations EPA believes that it causes or can reasonably be anticipated to cause a significant adverse effect on the environment. In addition, because of the nature of the potential significant adverse effects, e. g., fish, daphnia, and algae kills, and the impacts such effects can have on ecological communities and ecosystems, EPA has determined that they are of sufficient seriousness to warrant reporting. EPA reaffirms that there is sufficient evidence for listing benzo( g, h, i) perylene on the EPCRA section 313 list of toxic chemicals pursuant to EPCRA section 313( d)( 2)( C)( i) based on the available ecotoxicity information for this chemical. Therefore, EPA is finalizing the addition of benzo( g, h, i) perylene on the EPCRA section 313 list. 3. Benzo( j, k) fluorene (fluoranthene) (CAS No. 206± 44± 0) (Ref 70). EPA proposed to add fluoranthene to EPCRA section 313 pursuant to EPCRA sections 313 (d)( 2)( B) and (C). EPA received no comments specific to the carcinogenicity data that EPA presented in the proposed rule in support of the addition of fluoranthene to the EPCRA section 313 list of toxic chemicals. Thus, EPA reaffirms that there is sufficient evidence for adding fluoranthene to this list of EPCRA section 313 toxic chemicals pursuant to EPCRA section 313( d)( 2)( B) based on the available carcinogenicity data for this chemical. One commenter argues that EPA should refrain from listing fluoranthene pending additional assessment of the data. The commenter contends that EPA's reported toxicity values for fluoranthene span a range of about two orders of magnitude and that for such a wide range, it is necessary to evaluate potential exposure to determine which scenarios, and therefore which types of data, are most relevant to this compound following a release. The commenter argues that fluoranthene is a highly lipophilic compound that will bind primarily to sediment and suspended organics, so it is not clear whether the reported toxicity values on which EPA relies for the listing are applicable to this compound in the environment. EPA assumes the commenter was referring to data used to support EPA's proposal to list fluoranthene pursuant to EPCRA section 313( d)( 2)( C). As discussed in Unit VI. F., EPA does not believe that it is appropriate to consider exposure for chemicals that are highly ecotoxic as the data for fluoranthene clearly shows it is. However, even if EPA were to consider exposure, the commenter provided no data to support the assumption that fluoranthene will bind primarily to sediments and suspended organics, and EPA believes that fluoranthene will partition to water as well as sediment. While the ecotoxicity data for fluoranthene does range over about two orders of magnitude that does not, in itself, form a basis for conducting an exposure assessment. There are data that clearly show that fluoranthene is highly ecotoxic. Thus, an exposure assessment is not required. While it does not impact EPA's assessment, EPA notes that of the ecotoxicity values presented in the proposed rule, 9 were within the same order of magnitude, 4 58706 Federal Register / Vol. 64, No. 209 / Friday, October 29, 1999 / Rules and Regulations were one order of magnitude higher, and 2 were two orders of magnitude higher. Thus, 60% are within the same order of magnitude and 87% are within one order of magnitude. EPA does not believe that this represents a very wide distribution as the commenter implies. Based on the available toxicity data, EPA has concluded that fluoranthene is toxic. It has the potential to kill mysid shrimp, a variety of freshwater benthic species and various saltwater species and it can also cause other adverse effects on fish and mysids, based on chemical and/ or biological interactions. Fluoranthene can cause these toxic effects at relatively low concentrations. Ecotoxicity values for fluoranthene include a calculated 96± hour LC50 of 0.04 mg/ L for mysid shrimp. Using standard acute toxicity tests, fluoranthene has been tested in 12 freshwater species from 11 genera. For freshwater benthic species, the acute 96± hour LC50 calculated values are 0.032 mg/ L for an amphipod (Gammarus minus), 0.070 mg/ L for a hydra (Hydra americana), 0.17 mg/ L for an annelid (Lumbriculus variegatus), and 0.17 mg/ L for a snail (Physella virgata). For saltwater species, the 96± hour LC50 values are 0.051 mg/ L for a mysid (Mysidopsis bahia), 0.066 mg/ L for an amphipod (Ampelisca abdita), 0.14 mg/ L for a grass shrimp (Palaemonetes pugio), and 0.50 mg/ L for an annelid (Neanthes arenaceodentata). Fathead minnows exposed to fluoranthene at a concentration of 0.0217 mg/ L for 28 days in a chronic early life stage test showed a reduction of 67% in survival and a 50.2% reduction in growth relative to the controls. In a 28± day chronic study, mysids exposed to 0.021 mg/ L of fluoranthene showed a 26.7% reduction in survival and a 91.7% reduction in reproduction; at 0.043 mg/ L all mysids died. In a 31± day study, mysids showed a reduction of 30% in survival, 12% in growth, and 100% in reproduction relative to controls at a concentration of 0.018 mg/ L of fluoranthene. Fluoranthene can cause its toxic effects at these relatively low concentrations, therefore EPA considers it to be highly toxic. Since fluoranthene is toxic at relatively low concentrations, EPA believes that it causes or can reasonably be anticipated to cause a significant adverse effect on the environment. In addition, because of the nature of the potential significant adverse effects, e. g., kills of mysid shrimp, a variety of freshwater benthic species, and various saltwater species, and the impacts such effects can have on ecological communities and ecosystems, EPA has determined that they are of sufficient seriousness to warrant reporting. Thus, EPA reaffirms that there is sufficient evidence for adding fluoranthene on the EPCRA section 313 list of toxic chemicals pursuant to EPCRA section 313( d)( 2)( C)( i) based on the available ecotoxicity information for this chemical. Therefore, EPA is finalizing the listing of fluoranthene on the EPCRA section 313 list. 4. 3 Methylcholanthrene (CAS No. 56± 49± 5) (Ref. 70). EPA proposed to add 3 methylcholanthrene to EPCRA section 313 pursuant to EPCRA sections 313( d)( 2)( B) and (C). EPA received no comments on the carcinogenicity data that EPA presented in the proposed rule in support of the addition of 3 methylcholanthrene to the EPCRA section 313 list of toxic chemicals. Thus, EPA reaffirms that there is sufficient evidence for adding 3 methylcholanthrene to the list of EPCRA section 313 toxic chemicals pursuant to EPCRA section 313( d)( 2)( B) based on the available carcinogenicity data for this chemical. No comments were received concerning the ecotoxicity data that EPA presented for 3 methylcholanthrene in the proposed rule. Based upon quantitative structure activity relationship (QSAR) equations and other predictive techniques, EPA has concluded that 3 methylcholanthrene is toxic. It has the potential to kill fish and daphnia as well as cause other adverse effects on fish, daphnia, and algae based on chemical and/ or biological interactions. 3 Methylcholanthrene can cause these toxic effects at relatively low concentrations. The predicted aquatic toxicity values for 3 methylcholanthrene, based on QSAR analysis using the equation for neutral organics and an estimated Log Kow of 7.05, include a calculated fish 96± hour LC50 of 0.009 mg/ L and a chronic fish toxicity value of 0.003 mg/ L, a daphnia 48± hour LC50 of 0.005 mg/ L and a 16± day chronic LC50 of 0.015 mg/ L, and an algae 96± hour EC50 of 0.0105 mg/ L with a calculated chronic toxicity value of 0.014 mg/ L. 3 Methylcholanthrene can cause its toxic effects at these relatively low concentrations; therefore, EPA considers it to be highly toxic. Since 3 methylcholanthrene is toxic at relatively low concentrations, EPA believes that it causes or can reasonably be anticipated to cause a significant adverse effect on the environment. In addition, because of the nature of the potential significant adverse effects, e. g., fish and daphnia kills, and the impacts such effects can have on ecological communities and ecosystems, EPA has determined that they are of sufficient seriousness to warrant reporting. Thus, EPA reaffirms that there is sufficient evidence for listing 3 methylcholanthrene on the EPCRA section 313 list of toxic chemicals pursuant to EPCRA section 313( d)( 2)( C)( i) based on the available ecotoxicity information for this chemical. Therefore, EPA is finalizing the listing of 3 methylcholanthrene on the EPCRA section 313 list. 5. Octachlorostyrene (CAS No. 29082± 74± 4) (Ref. 70). EPA proposed to add octachlorostyrene to EPCRA section 313 pursuant to EPCRA sections 313( d)( 2)( B) and (C). One commenter argues that octachlorostyrene (OCS) should not be included in the EPCRA section 313 PBT chemicals list. The commenter contends that OCS was included as a PBT chemical simply because it appears on several lists of persistent and bioaccumulative chemicals and not based on a thorough evaluation of its toxicity. The commenter argues that there is limited toxicity data for OCS and cited two statements that were in EPA's support document for the addition of OCS and the other chemicals being added in this rulemaking. The two statements the commenter cited were:

The health hazard data which support TRI listing are very limited. Human health data were not located. (Ref. 70 p. 48)

EPA disagrees with the commenters' conclusions. The commenter did not comment on the actual toxicity data that EPA provided as the basis for listing OCS pursuant to EPCRA section 313( d)( 2)( B). Rather the commenter takes two statements that were contained in the support document out of context to support their apparent contention that there are insufficient data to list OCS under EPCRA section 313( d)( 2)( B). The fact that the commenter has taken these statements out of context is demonstrated by the content of the rest of the paragraph that contained the statements the commenter cited:

Laboratory studies on rats suggest OCS may have acute and chronic effects on the liver, kidneys, and thyroid. In a long term study (one year) of rats a LOAEL of 0.31 mg/ kg/ day was determined based on significant histological effects on these organs. (Ref. 70)

The statements the commenter cited only acknowledged that there was not a vast amount of toxicity data for OCS and specifically, that there were no human studies; they do not support the commenters' conclusion that OCS does not meet listing criteria of EPCRA 58707 Federal Register / Vol. 64, No. 209 / Friday, October 29, 1999 / Rules and Regulations section 313( d)( 2)( B). In addition, these statements were from the summary section of the discussion on OCS, more detailed discussion of the toxicity data for OCS was contained in the other sections on OCS toxicity but the commenter provided no comments on this information. EPA reaffirms that there is sufficient evidence for adding OCS to the EPCRA section 313 list of toxic chemicals pursuant to EPCRA section 313( d)( 2)( B) based on the available hepatic, nephric, and thyroid toxicity data for this chemical. The same commenter also claims that the toxicity comparisons to hexachlorobenzene are not supported and that no references or rationale are provided to support basing the aquatic toxicity of OCS on that of hexachlorobenzene. As with the human health data, the commenter argues that there are limited environmental toxicity data for OCS and cited some statements that were in EPA's support document. The statements the commenter cited were:

So far as is known, after a search of former EEB chemical files, the ecological hazard of OCS has never been formally reviewed under TSCA section 4 or in the OPPT Risk Management (RM) process. OCS was briefly reviewed for aquatic toxicity in August 1986, as part of an OTS (now OPPT) chemical scoring project. Thus, available information on OCS is very limited. (Ref. 70, p. 52)

EPA disagrees with the commenter's conclusions. The commenter has not commented on the actual toxicity data but rather states that the data are limited and that hexachlorobenzene is not an appropriate analogue for predicting the aquatic toxicity data for OCS. The statements the commenter cited only acknowledged that there was not a vast amount of toxicity data for OCS, they do not support the commenter's conclusion that OCS does not meet the listing criteria of EPCRA section 313( d)( 2)( C). Contrary to the commenter's statement, EPA did provide a reference to the use of hexachlorobenzene as an appropriate analogue for OCS. As EPA stated in the same section of the support document the commenter cited:

OCS is one of 7 compounds in this chemical class (chlorinated styrenes) with the generic formula C8H8 xClx, where x equals 8 for OCS. This class is analogous to the chlorinated benzenes; for example hexachlorobenzene (HCB), is considered to be an appropriate analogue chemical for OCS (2). (Ref. 70, page 52).

The reference EPA cited is a previous EPA analysis of this class of chemicals that also used hexachlorobenzene as an appropriate analogue for OCS. EPA believes that since OCS and hexachlorobenzene are both highly chlorinated derivatives of benzene they can reasonably be anticipated to have similar toxicities. However, in addition to aquatic toxicity data on hexachlorobenzene, EPA provided the results of a QSAR analysis of OCS, using a measured Log Kow of 7.7, that gave a predicted 14± day LC50 value of 6 mg/ L for guppies. Based upon QSAR equations and analogue data, EPA has concluded that OCS is toxic. It has the potential to kill fish and inhibit photosynthesis in algae, among other adverse effects, based on chemical and/ or biological interactions. OCS can cause these toxic effects at relatively low concentrations. The predicted aquatic toxicity value for OCS, based upon QSAR analysis using a measured Log Kow of 7.7, is an estimated 14± day LC50 of 6 mg/ L for guppies. Based on the chemical analogue hexachlorobenzene, OCS can reasonably be anticipated to inhibit photosynthesis in algae at a concentration of 30 mg/ L and have a calculated subchronic EC50 value of 16 mg/ L for daphnids. OCS can cause its toxic effects at these relatively low concentrations; therefore, EPA considers it to be highly toxic. Since OCS is toxic at relatively low concentrations, EPA believes that it causes or can reasonably be anticipated to cause a significant adverse effect on the environment. In addition, because of the nature of the potential significant adverse effects, e. g., fish kills, and inhibition of photosynthesis in algae and the impacts such effects can have on ecological communities and ecosystems, EPA has determined that they are of sufficient seriousness to warrant reporting. EPA reaffirms that there is sufficient evidence for listing OCS on the EPCRA section 313 list of toxic chemicals pursuant to EPCRA section 313( d)( 2)( C)( i) based on the available ecotoxicity information for this chemical. Therefore, EPA is finalizing the addition of OCS on the EPCRA section 313 list. 6. Pentachlorobenzene (CAS No. 609± 93± 5) (Ref. 70). EPA proposed to add pentachlorobenzene to EPCRA section 313 pursuant to EPCRA sections 313( d)( 2)( B) and (C). No comments were received concerning the human health toxicity data that EPA presented in the proposed rule. Thus, EPA reaffirms that there is sufficient evidence for adding pentachlorobenzene on EPCRA section 313 pursuant to EPCRA section 313( d)( 2)( B) based on the available hepatic, nephric, hematological, and developmental toxicity data for this chemical. No comments were received concerning the ecotoxicity data that EPA presented for pentachlorobenzene in the proposed rule. Based on the available toxicity data, EPA has concluded that pentachlorobenzene is toxic. It has the potential to kill fish and mysid shrimp as well as cause other adverse effects on algae and daphnia, based on chemical and/ or biological interactions. Pentachlorobenzene can cause these toxic effects at relatively low concentrations. Aquatic acute toxicity calculated values for pentachlorobenzene include a sheepshead minnow 96± hour LC50 of 0.83 mg/ L, bluegill sunfish 96± hour LC50s of 0.25 mg/ L and 0.3 mg/ L, a guppy 96± hour LC50 of 0.54 mg/ L, and a mysid shrimp 96± hour LC50 of 0.16 mg/ L. Because pentachlorobenzene can cause these toxic effects at these relatively low concentrations, EPA considers it to be highly toxic. Additional acute toxicity calculated values include algae 96± hour EC50s of 1.98 mg/ L and 6.78 mg/ L, and daphnia 48± hour EC50s of 1.3 mg/ L and 5.28 mg/ L. Considering pentachlorobenzene's persistence and bioaccumulation potential pentachlorobenzene is considered highly toxic to aquatic organism at these higher concentrations. As discussed above, pentachlorobenzene is highly toxic. Because pentachlorobenzene is highly toxic at relatively low concentrations, EPA believes that it causes or can reasonably be anticipated to cause a significant adverse effect on the environment. In addition, because of the nature of the potential significant adverse effects, e. g., fish and mysid shrimp kills as well as other adverse effects on algae and daphnia, and the impacts such effects can have on ecological communities and ecosystems, EPA has determined that they are of sufficient seriousness to warrant reporting. Thus, EPA reaffirms that there is sufficient evidence for adding pentachlorobenzene on the EPCRA section 313 list of toxic chemicals pursuant to EPCRA section 313( d)( 2)( C)( i), (ii), and (iii) based on the available ecotoxicity information for this chemical. Therefore, EPA is finalizing the listing of pentachlorobenzene on the EPCRA section 313 list. 7. Tetrabromobisphenol A (CAS No. 79± 94± 7) (Ref. 70). EPA proposed to add TBBPA to EPCRA section 313 pursuant to EPCRA sections 313( d)( 2)( B) and (C). One commenter claims that the study cited by EPA in support of its 58708 Federal Register / Vol. 64, No. 209 / Friday, October 29, 1999 / Rules and Regulations conclusion that TBBPA meets the EPCRA section 313( d)( 2)( B) criteria for listing based on developmental toxicity was not a study on TBBPA. The study in question was submitted to EPA by ICI Americas Inc. with a cover letter identifying Saytex 111, the product tested, as being TBBPA. The product was identified as TBBPA by both name and CAS number. EPA has determined that the product tested was not TBBPA as claimed by the submitter but has been unable to determine why it was misidentified by the submitter. ICI Americas is now Zeneca at the Delaware location that submitted the study. A Zeneca staff member researched the submission and found that the report was originally from Ethyl Corporation and that no other report on TBBPA was submitted to EPA on that date. Without the misidentified developmental study, no adequate toxicology studies or other data were located by EPA that support the addition of TBBPA pursuant to EPCRA section 313( d)( 2)( B). Thus, EPA is not adding TBBPA based on concerns for developmental toxicity or any other human health effects. The same commenter provides comments on the persistence and bioaccumulation of TBBPA and contends that there are insufficient data to conclude that TBBPA meets the listing criteria of EPCRA section 313( d)( 2)( C)( ii) and 313( d)( 2)( C)( iii). These two sections deal with EPA's authority to add a chemical based on its `` toxicity and persistence in the environment'' and its `` toxicity and tendency to bioaccumulate in the environment'' respectively. However, the commenter does not contend that TBBPA does not meet the listing criteria of EPCRA section 313( d)( 2)( C)( i) which addresses EPA's authority to add a chemical based on its `` toxicity'' without consideration of persistence and bioaccumulation. EPA believes that TBBPA is persistent and bioaccumulative as discussed in Unit VI. H. However, EPA did not propose to add TBBPA to the EPCRA section 313 list of toxic chemicals based on its persistence or bioaccumulation data, and neither of these properties were mentioned in the toxicity discussion of TBBPA in the proposed rule. Rather, EPA based its listing decision on the ecotoxicity data alone which indicated that TBBPA was highly toxic even without consideration of persistence or bioaccumulation. Based the available toxicity data, EPA has concluded that TBBPA is toxic. It has the potential to kill fish, daphnid, and mysid shrimp, among other adverse effects, based on chemical and/ or biological interactions. TBBPA can cause these toxic effects at relatively low concentrations. Aquatic acute toxicity calculated values for TBBPA include a fathead minnow 96± hour LC50 of 0.54 mg/ L, a rainbow trout 96± hour LC50 of 0.40 mg/ L, a bluegill sunfish 96± hour LC50 of 0.51 mg/ L, and a daphnid 48± hour LC50 of 0.96 mg/ L; mysid shrimp 96± hour LC50 values ranged from 0.86 to 1.2 mg/ L depending on the age of the shrimp. Aquatic chronic toxicity calculated values from a daphnia 21± day study resulted in a Maximum Acceptable Toxicant Concentration (MATC) that was between 0.30 and 0.98 mg/ L (geometric mean 0.54 mg/ L) based on a significant reduction in reproduction rates; a fathead minnow 35± day study resulted in a MATC that was calculated to be between 0.16 and 0.31 mg/ L (geometric mean 0.22 mg/ L) based on adverse effects on embryo and larval survival. TBBPA can cause its toxic effects at these relatively low concentrations; therefore, EPA considers it to be highly toxic. Since TBBPA is toxic at relatively low concentrations, EPA believes that it causes or can reasonably be anticipated to cause a significant adverse effect on the environment. In addition, because of the nature of the potential significant adverse effects, e. g., fish, daphnid, and mysid shrimp kills, and the impacts such effects can have on ecological communities and ecosystems, EPA has determined that they are of sufficient seriousness to warrant reporting. EPA reaffirms that there is sufficient evidence for listing TBBPA on the EPCRA section 313 list of toxic chemicals pursuant to EPCRA section 313( d)( 2)( C)( i) based on the available ecotoxicity information for this chemical. Therefore, EPA is finalizing the addition of TBBPA on the EPCRA section 313 list. 8. Vanadium and vanadium compounds. EPA proposed to add vanadium and vanadium compounds to EPCRA section 313 pursuant to EPCRA sections 313( d)( 2)( C). One commenter cited the following statement from the proposed rule, `` However, very few toxicity tests have been conducted with invertebrates. '' The commenter argues that, beyond vanadium pentoxide, the Agency appears to have very little toxicity data on vanadium compounds. The commenter contends that the paucity of toxicity data on many different forms of vanadium compounds in the proposal, as well as in the literature, does not appear to support the Agency's belief that `` the evidence is sufficient to list vanadium and vanadium compounds on EPCRA section 313 pursuant to EPCRA section 313( d)( 2)( C) based on the available ecotoxicity information on vanadium and vanadium compounds'' (at 64 FR 698). EPA disagrees with the commenters' conclusions. Although there is limited information on vanadium's toxicity on invertebrates, data that were available for invertebrates shows that vanadium is toxic to these species. Furthermore, EPA's assessment of vanadium's toxicity included algae and vertebrates, and showed that the chemical is highly toxic to aquatic organisms. The data on vanadium are not limited to vanadium pentoxide, the ecological data provided in the proposed rule for vanadium evaluates vanadium toxicity based on data for other vanadium compounds including: sodium metavanadate, sodium orthovanadate, vanadyl sulfate, and ammonium vanadate. In assessing the ecological toxicity of vanadium and vanadium compounds, EPA evaluated the parent metal (vanadium) and determined that it is highly toxic to some aquatic species and anticipated to cause a significant adverse effect on the environment of sufficient seriousness to warrant reporting. Thus, vanadium, the parent metal in vanadium compounds, is the concern, not the other components of each vanadium compound. Many metals are tested in the salt form because these forms are readily soluble in aqueous solutions. The toxicity data for vanadium shows that the metal is highly toxic (aquatic toxicity < 1 mg/ L) to the most sensitive species. This evaluation of vanadium's toxicity is acceptable according to traditional guidelines for the assessment of toxic substances as conducted by the Agency for over 2 decades. In addition, when consideration is given to vanadium's persistence it is also considered highly toxic at higher concentrations. Three commenters contend that since most vanadium compounds are practically insoluble, they consequently have very low bioavailability, and thus it is likely that they could qualify for delisting. The commenters argue that the delisting process is extremely cumbersome, time consuming and costly. One of these commenters contends that it is inappropriate to list all of vanadium compounds based on aquatic toxicity of the few compounds cited in the proposed rule. The bioavailability of metals such as vanadium was also raised as an issue at the public meetings held for this rulemaking. It was suggested that the parent metal will not be bioavailable from certain metal compounds that may be released into the environment and that therefore the compounds cannot be 58709 Federal Register / Vol. 64, No. 209 / Friday, October 29, 1999 / Rules and Regulations properly characterized as a PBT chemicals. EPA disagrees with these comments. First, it should be noted that EPA has not addressed whether vanadium and vanadium compounds can properly be classified as PBT chemicals in this rulemaking. The sole issue, therefore, is whether vanadium and vanadium compounds meet the EPCRA section 313( d)( 2)( C) listing criteria. EPA's analysis of the environmental fate of vanadium and vanadium compounds shows that under many environmental conditions vanadium will be available and thus is able to express its toxicity. The commenters have not provided EPA with any data or acceptable scientific studies indicating that vanadium in any particular compound will not become available in the environment. In fact, at least one commenter appears to indicate that these vanadium compounds may merely have low solubility. In these compounds, the parent metal vanadium can become available. While water soluble vanadium compounds would obviously provide vanadium in an immediately bioavailable form, solubility is not the only factor to consider in determining the bioavailability of vanadium from a vanadium compound. In addition to solubility, processes such as: hydrolysis at various pHs; solubilization in the environment at various pHs; photolysis; aerobic transformations (both abiotic and biotic); anaerobic transformation (both abiotic and biotic); and bioavailability when the compounds are ingested (solubilization in and/ or absorption from the gastrointestinal tract and solubilization in various organs) need to be considered. In Unit VI. C., EPA discusses in detail the persistence and bioavailability of metals in general. The issue of bioavailability has been addressed for EPCRA section 313 chemical assessments through EPA's policy and guidance concerning petitions to delist individual members of the metal compound categories on the EPCRA section 313 toxic chemical list (56 FR 23703). This policy states that if the metal in a metal compound cannot become available as a result of biotic or abiotic processes then the metal will not be available to express its toxicity. If the intact metal compound is not toxic and the metal is not available from the metal compound then such a chemical is a potential candidate for delisting. One commenter argued that the lowest toxicity value cited by EPA for a marine algal species was for Dunaliella marina with a 9± day LC50 of 0.5 mg/ L but that EPA omitted a study which tested the same species and reported no significant adverse effects at a concentration of 50 mg/ L. EPA believes that the study that reported the 9± day LC50 of 0.5 parts per million (ppm) on Dunaliella marina, is accurate and was acceptably conducted within the guidelines for ecological assessments of hazardous chemicals. This study shows the most sensitive species' response to the chemical. There are differences in the two studies that could explain the range of toxicity between the two. They are: (1) Differences in the exposure times, (2) the species used in the experiments, and (3) the form of vanadium that was exposed to the organisms. The exposure time in the study EPA cited reported a 9± day LC50 of 0.5 mg/ L. However, the study the commenter cites did not report an LC50 duration. Also, the species for the study EPA cited reported the test species to be Dunaliella marina (salina), but the study the commenter cited only reported the genus name for this organism. Furthermore, the study EPA cited reported the form of vanadium as sodium vanadate, but the study the commenter cites only reported using the vanadium compound without reporting the specific salt form. It is clear that any one of the three factors mentioned, or some combination of these factors, likely accounts for the variation in toxicity between the two studies. One commenter argues that a study, omitted in EPA's review of vanadium toxicity, on nine algal species showed no significant reduction in productivity (as measured by chlorophyll synthesis) at vanadium concentrations in excess of 10 mg/ L. The commenter also contends that the authors of the study also demonstrated that phosphate concentrations were critical in the toxicity of vanadium to algae. The Agency has not neglected to review the study cited by the commenter. However, EPA interprets the study cited by the commenter as describing the competition uptake between vanadium and phosphorus in an algal medium containing two different kinds of phosphorus concentrations (i. e., phosphorus deficient and phosphorus sufficient). Also, this study was performed only on freshwater algae and one form of vanadium (orthovanadate) which only exists in a pH range of 3 to 6. This study did report a moderately high toxicity value for Scenedesmus acutus between 5 and 177 M, which continues to support EPA's findings that vanadium is toxic to algae. Furthermore, EPA is aware that there are studies that were not included in the assessment that showed that the chemical was more toxic than the values reported in EPA's assessment. However, each study was carefully reviewed based on EPA's extensive evaluation process which reviews studies for conformance with generally accepted scientific standards and tests. The studies that were reported in EPA's assessment used generally accepted, validated scientific methods for evaluating aquatic toxicity. The toxicity values that were reported in the ecological assessment of vanadium toxicity were from well conducted studies. One commenter argues that it appears from a review of the data that the contention that vanadium is highly toxic to algae has no basis. The commenter contends that with the exception of one study on a single species, Ceratium hirundinella, none of the studies on freshwater algae showed significant toxicity at concentrations below 10 mg/ L. The commenter states that the lowest level of toxicity reported for a marine species (Dunaliella marina) was an LC50 of 0.5 mg/ L, but that there is conflicting evidence that the threshold of toxicity for this species may be higher than 50 mg/ L. The commenter concludes that there appears to be little evidence that vanadium is a highly toxic agent to algae. The commenter also argues that evaluating the toxicity of a compound based on the response of individual algal species can be misleading. The commenter contends that algae never exist within either marine or freshwater environments as monocultures, but rather as dynamic mixed populations. The commenter concludes that unless a compound can be shown to have a broad effect over an entire assemblage or over numerous species of either freshwater or marine species, it is not likely to have a significant effect within the natural environment. EPA's assessment on algae toxicity shows that vanadium is highly toxic based on the most sensitive species' response to the chemical. There is no conflict in the threshold of toxicity of Dunaliella marina. As stated above, there are three factors that most probably account for the differences between the study EPA cited and the study the commenter cites. After careful review of the available data, it is EPA's professional judgment that the study EPA cited provides accurate and valid data. Algae studies have been included in ecological risk assessments for over 2 decades. Several guidelines on different species have been written to show that these genera are important in the environment and show sensitivity in how chemicals affect the biota. EPA 58710 Federal Register / Vol. 64, No. 209 / Friday, October 29, 1999 / Rules and Regulations agrees that algae usually do not exist in monocultures in the marine or freshwater environment. However, testing monocultures species is the most accurate method to determine whether a chemical is directly harmful to that species. Therefore, if a compound is highly toxic to a particular species of algae or any species, its effects can be extrapolated to represent other species exposed to that chemical. This evaluation process has been used by the Agency and accepted by OECD for over two decades, and used on thousands of chemicals. Vanadium's toxicity ranges from highly toxic to moderately toxic for algae in EPA's assessment. It is reasonable from the evidence in EPA's assessment of vanadium that the species that is the most sensitive to the chemical can represent the toxicity for all other species based on this narrow range. EPA's final evaluation of any chemical's toxicity is based on the most sensitive species' response. One commenter contends that the study EPA cited that reported the 144± hour LC50 of 0.4 and 0.5 mg/ L for vanadyl sulfate (VOSO4) and ammonium metavanadate (NH4VO3), respectively, were actually values for VOSO4 and sodium metavanadate (NaVO3) respectively. The commenter contends that the 144± hour LC50 for NH4VO3 was l. 5 mg/ L. The commenter also argues that EPA neglected to report from the same study a 144± hour LC50 of 1.1 mg/ L for vanadate pentoxide (V2O5) for this species. The commenter also contends that the findings of 144± hour LC50s of 2.5 to 8.1 mg/ L in goldfish (Carassius auratus) for the same four vanadium species were also omitted. The comment concerning the vanadium compounds for the 144± hour LC50s of 0.4 and 0.5 mg/ L is correct. EPA inadvertently cited to the incorrect compound in the study. The correct vanadium compounds will be reflected in an update to the support document. However, sodium metavanadate, is still a vanadium compound and the study therefore continues to support EPA's findings that vanadium is highly toxic to fish. The other values of 2.5 and 8.1 mg/ L merely provide further support for EPA's finding that the vanadium is moderately toxic to fish. However, considering vanadium's persistence in the environment, EPA believes that it is highly toxic at concentrations between 1 and 10 mg/ L. Thus the goldfish values provide further support to EPA's finding that vanadium is highly toxic to some aquatic organisms. One commenter contends that in assessing the toxicity of vanadium to fish, EPA neglected to review the following studies: (1) Hamilton and Buhl (1997), who reported a 96± hour LC50 for the flannelmouth sucker (Catostomus latipinnis) of 11.7 mg/ L; (2) Taylor et al. (1985), who reported a 96± hour LC50 for English sole (Limanda limanda) of 26.8 mg/ L; (3) Ernst and Garside (1987), who reported a 96± hour LC50 for the brook trout (Salvelinus fontinaliis) alevins of 24 mg/ L and for yearlings of 7± 15 mg/ L (the authors also reported that the method by which stock solutions are formulated could have a dramatic effect on the toxicity of vanadium through its effects on the polymeric form of the metal in the test study); and (4) Hamilton and Buhl (1990), who reported a 96± hour LC50 for chinook salmon (Oncorhynchus tshawytscha) fry of 16.5 mg/ L. EPA undertook an exhaustive review of vanadium toxicity. The studies the commenter has listed show that vanadium compounds are moderately toxic to fish, which further support EPA's findings on the toxicity of vanadium. EPA's review of the studies cited in the proposed rule are not contradicted or undermined by the studies provided by the commenter, and continue to support the Agency's conclusion that vanadium and vanadium compounds are highly toxic to some aquatic species. One commenter states that the background document to support EPA's proposal to list vanadium and vanadium compounds indicates that the proposed listing is based on data for five vanadium compounds: vanadium pentoxide, sodium metavanadate, sodium orthovanadate, vanadyl sulfate, and ammonium vanadate. The commenter contends that EPA may consider listing under EPCRA section 313 for the individual compounds for which the Agency has data, but EPA is not justified in listing a broad `` vanadium and vanadium compounds'' category based on data for only five compounds. The commenter suggests that EPA consider individual listings for these compounds, or a category consisting only of the compounds for which the Agency has data. EPA disagrees with the commenter's characterization of the Agency's assessment of vanadium and vanadium compounds. In assessing the ecological toxicity of vanadium and vanadium compounds, EPA evaluated the parent metal (vanadium) and determined that it is highly toxic to some aquatic organisms and can reasonably be anticipated to cause a significant adverse effect on the environment of sufficient seriousness to warrant reporting pursuant to EPCRA section 313( d)( 2)( C). Thus, vanadium, the parent metal in vanadium compounds, is the concern, not the other components of each compound. Many metals are tested in the salt form because they are readily soluble in aqueous solutions. The toxicity data for vanadium shows that the metal is highly toxic (aquatic toxicity < 1 mg/ L) to the most sensitive species. In addition, because vanadium is persistent, EPA considers any toxicity values between 1 and 10 mg/ L as indicating high ecotoxicity. This evaluation of vanadium's toxicity is acceptable according to traditional guidelines for the assessment of toxic substances conducted by the Agency for over two decades. EPA has also provided sufficient basis for the inclusion of all vanadium compounds in the category. As EPA stated in the 1994 chemical expansion final rule:

The Agency believes it satisfies the statutory criteria to add a category to the list by identifying the toxic effect of concern for at least one member of the category and then showing why that effect may reasonably be expected to be caused by all other members of the category. (at 59 FR 61442) See also, Troy, supra at 277.

EPA developed a hazard assessment for vanadium which reviewed the toxicity data for several vanadium compounds. The assessment indicated that the vanadium from these compounds is highly toxic to aquatic organisms. Since it is the vanadium from these compounds that is highly toxic rather than the intact chemical compound, EPA believes that all chemicals that are a source of vanadium meet the EPCRA section 313( d)( 2)( C) listing criteria. Thus, EPA has established the toxic effect of concern, the chemical species that causes the effect, and the basis for why it may reasonably be expected that all members of the vanadium compounds category can cause the effects of concern. Based on the available toxicity data, EPA has concluded that vanadium and vanadium compounds are toxic. They have the potential to kill fish, algae, and invertebrates as well as causing a range of other adverse effects on fish, algae, and invertebrates, based on chemical and/ or biological interactions. Vanadium and vanadium compounds can cause these toxic effects at relatively low concentrations. Toxicity data for vanadium and vanadium compounds include for algae, a 9± day LC50 of 0.5 mg/ L, a 15± day LC50 of 0.5 mg/ L, inhibition of growth at 0.1 ppm, adverse effects on cell division at 3 ppb, 20 ppb, and 0.5 ppm; and for fish, a 96± hour LC50 of 0.62 ppm, and growth and survival depression of larvae at 0.17 ppm. Because vanadium and vanadium 58711 Federal Register / Vol. 64, No. 209 / Friday, October 29, 1999 / Rules and Regulations compounds can cause these toxic effects at these relatively low concentrations, EPA considers these chemicals to be highly toxic. Additional toxicity values include for algae, 9± day LC50s of 2 and 3 ppm, and a 15± day LC50 of 2 mg/ L; for invertebrates, a 9± day LC50 of 10 ppm; and for fish, 96± hour LC50s of 6.4 ppm, 10 ppm, and 7 mg/ L, an LC50 of 5.6 mg/ L, an 11± day LC50 of 1.99 mg/ L, 14± day LC50s from 1.95 to 4.34 mg/ L, and 7± day LC50s from 1.9 to 6.0 ppm. Considering vanadium's persistence, vanadium and vanadium compounds are considered highly toxic to aquatic organism at these higher concentrations. As discussed above, vanadium and vanadium compounds are highly toxic. Because vanadium and vanadium compounds are toxic at relatively low concentrations, EPA believes that they cause or can reasonably be anticipated to cause a significant adverse effect on the environment. In addition, because of the nature of the potential significant adverse effects, e. g., fish, algae, and invertebrate kills as well as a range of other adverse effects on fish, algae, and invertebrates, and the impacts such effects can have on ecological communities and ecosystems, EPA has determined that they are of sufficient seriousness to warrant reporting. Thus, EPA reaffirms that there is sufficient evidence for adding vanadium and vanadium compounds on the EPCRA section 313 list of toxic chemicals pursuant to EPCRA section 313( d)( 2)( C)( i) and (ii), based on the available ecotoxicity information for vanadium and vanadium compounds. Therefore, EPA is finalizing the listing of vanadium and vanadium compounds on the EPCRA section 313 list. a. Reporting limitation of alloys. A number of commenters support EPA's proposed determination to defer the reporting of vanadium when contained in alloys (64 FR 717). Many commenters also suggest that the Agency adopt a reporting limitation for the other metals such as chromium, copper, manganese, and nickel which are commonly found in alloys. The commenters assert that alloys have significantly different bioavailability, bioaccumulation, and toxicity characteristics than other forms of metals, and thus should be treated separately. The commenters argue that alloys are inherently more stable than unalloyed materials, do not enter the environment as readily as unalloyed materials and hence do not interact as greatly with organisms, and should be considered safer from an environmental and human health perspective. The commenters suggested that alloys should be treated separately not only for threshold changes, but also for EPCRA section 313 listings in general and recommend excluding alloys from general EPCRA section 313 listings for metals. One commenter states in regard to the reporting of metals in alloys that it makes little or no sense to require the reporting of such `` useless'' information, since the information does not serve the purpose of informing the community. The commenter contends that not adding vanadium when contained in alloys would help to achieve EPCRA section 313's underlying purpose, i. e., to provide the public with meaningful information, while at the same time reducing the burden on reporting facilities. Another commenter argues that the proposed alloys exemption correctly recognizes that metals in alloys are not generally available for exposure or for toxic effects. The commenter argues that expansion of the exemption would improve the TRI data base by reporting only releases that may pose risks to human health and the environment, thereby providing the public with more meaningful data. Two commenters state that the definition of vanadium alloys should include `` fused alloy slag'' in the qualifier as well. The commenters contend that the state of the vanadium in a ferroalloy form is one of intimate chemical combination on the atomic level, not a simple mixture of individual components and it is inherently stable and cannot be dissociated by ordinary means. The commenters argue that likewise, the fused alloy slag formed represents an intimate chemical combination of materials as a result of the smelting operation. The commenters assert that these elemental materials may include various components such as gangue or ore, ash of fuel, refractory lining, or other stable oxides with the ultimate characterization resting upon the chemical stability of the resultant fused alloy bearing slag. Thus, the commenters argue, vanadium contained in either alloy or alloy slag form is fused in a stable compound and therefore, no releases of vanadium into the environment would occur from either substance. The commenters state that the true environmental issue to consider in the formulation of an activity qualifier is the leachability of the material in that state, and since in both of the aforementioned cases the vanadium is in a stable compound, leaching would not be expected. The commenters assert that without allowing an exemption for fused alloy slag, large volumes of steelmaking and ferroalloy slag will unnecessarily fall under this reporting requirement. The commenters request that EPA reconsider its position and expand the definition of alloy to include both vanadium alloys and vanadium alloy slags. EPA agrees with those commenters that support EPA's belief that it would be inappropriate, at this time, to change the status quo regarding reporting vanadium when contained in an alloy. As EPA stated in the proposed rule, the Agency is reviewing the issue of whether there should be any changes to the reporting requirements for metals contained in alloys. In the proposed rule, EPA did not state, and did not intend to imply, that EPA considers alloys to be `` safe, '' or as some commenters suggested, that EPA had `` correctly'' recognized that metals in alloys are not generally available for exposure or to express their toxic effects. EPA has not completed its review of the alloys issue and has made no conclusions regarding whether there should or should not be any type of limitation or exemption for any metals contained in alloys. EPA's proposal merely recognized that while this issue was under review, it would not be appropriate to add alloy forms of vanadium. The commenters contend that alloys have significantly different bioavailability, bioaccumulation, toxicity characteristics than other forms of metals and are inherently more stable than unalloyed materials and do not enter the environment as readily as unalloyed materials. EPA believes that the issue with alloys is primarily bioavailability, i. e., do the metals contained in alloys become available. This issue is the focus of EPA's current review. At this point in time, while EPA is in the process of a scientific review of the issues pertinent to alloys, the Agency is not prepared to make a final determination on whether vanadium in vanadium alloys meet the EPCRA section 313( d)( 2) toxicity criteria. The commenters did not provide any data to support their contention. The Agency does not believe that a metal compound in a slag necessarily will be environmentally unavailable; rather, the Agency's experience with a previous EPCRA section 313( d) review of manganese slags, indicates that at least in some cases the metal will be available (60 FR 44000, August 24, 1995) (FRL± 4954± 6). Some commenters suggested that EPA create an alloys reporting limitation for all metals contained in alloys. However, as EPA has stated, the review of whether any kind of exemption or reporting limitation should be granted for certain metals in alloys is still under review and until the Agency has thoroughly reviewed the available data, EPA is not 58712 Federal Register / Vol. 64, No. 209 / Friday, October 29, 1999 / Rules and Regulations prepared to extend the reporting limitation to any other metals. For example, EPA is not lowering the reporting threshold for cobalt and cobalt compounds, and therefore the Agency is taking no action with respect to a reporting limitation for cobalt when contained in alloys. One commenter asserts that for reasons of consistency which helps ensure data quality with existing EPCRA section 313 metal compound categories, they oppose adding the qualifier `` except when contained in an alloy'' in any new listing for vanadium. EPA has not completed its review of the alloys issue and has made no conclusions regarding whether there should be any type of general limitation or exemption for any metals contained in alloys. EPA merely recognized that while this issue was under review it would not be appropriate to increase the reporting requirements for those facilities that would otherwise submit reports for vanadium contained in alloys. Therefore, as discussed earlier in this section, EPA has expanded the EPCRA section 313 listing for vanadium by removing the `` fume or dust'' qualifier for vanadium, but has not added the alloy forms of vanadium. Until EPA has the opportunity to fully evaluate the available data, the Agency is not prepared to make a final determination whether vanadium contained in alloys meets the EPCRA section 313( d)( 2) listing criteria and should therefore be added. EPA believes that consistency, in this context, does not provide a sufficient basis to require reporting of vanadium contained in alloys.

H. Persistence and Bioaccumulation The persistence and bioaccumulation data for the PBT chemicals covered by this final rule are listed in Table 3. A discussion of these data follows Table 3.

Table 3.Ð Persistence and Bioaccumulation Data Chemical Category/ Chemical Name CASRN BCF BAF Air Half life Surface Water Halflife Soil Half life Dioxin/ Dioxin Like Compounds Polychlorinated dibenzo p dioxins 1,2,3,4,6,7,8 heptachlorodibenzo p dioxin 35822± 46± 9 1,466 12.2± 4.2 hrs ~20 yrs 1,2,3,4,7,8 hexachlorodibenzo p dioxin 39227± 28± 6 5,176 12.4± 2.7 hrs ~20 yrs 1,2,3,6,7,8 hexachlorodibenzo p dioxin 57653± 85± 7 3,981 12.4± 2.7 hrs ~20 yrs 1,2,3,7,8,9 hexachlorodibenzo p dioxin 19408± 74± 3 1,426 12.4± 2.7 hrs ~20 yrs 1,2,3,4,6,7,8,9 octachlorodibenzo p dioxin 3268± 87± 9 2,239 20.4± 4.8 hrs ~20 yrs 1,2,3,7,8 pentachlorodibenzo p dioxin 40321± 76± 4 10,890 14.8± 2.0 hrs ~20 yrs 2,3,7,8 tetrachlorodibenzo p dioxin 1746± 01± 6 5,755 9.6± 1.2 hrs 20± 1.5 yrs Polychlorinated dibenzofurans 1,2,3,4,6,7,8 heptachlorodibenzofuran 67562± 39± 4 3,545 25.0± 4.3 hrs ~20 yrs 1,2,3,4,7,8,9 heptachlorodibenzofuran 55673± 89± 7 3,545 25.0± 4.3 hrs ~20 yrs 1,2,3,4,7,8 hexachlorodibenzofuran 70648± 26± 9 3,586 13.3± 3 hrs ~20 yrs 1,2,3,6,7,8 hexachlorodibenzofuran 57117± 44± 9 3,586 13.3± 3 hrs ~20 yrs 1,2,3,7,8,9 hexachlorodibenzofuran 72918± 21± 9 10,300 13.3± 3 hrs ~20 yrs 2,3,4,6,7,8 hexachlorodibenzofuran 60851± 34± 5 3,586 13.3± 3 hrs ~20 yrs 1,2,3,4,6,7,8,9 octachlorodibenzofuran 39001± 02± 0 1,259 29.4± 13.7 hrs ~20 yrs 1,2,3,7,8 pentachlorodibenzofuran 57117± 41± 6 33,750 11.6± 1.2 hrs ~20 yrs 2,3,4,7,8 pentachlorodibenzofuran 57117± 31± 4 42,500 11.6± 1.2 hrs ~20 yrs 2,3,7,8 tetrachlorodibenzofuran 51207± 31± 9 2,042 11.5± 2.1 hrs ~20 yrs Pesticides Aldrin 309± 00± 2 3,715 10 hrs± 1 hr 24 days 1 9 yrs± 291 days Chlordane 57± 74± 9 11,050 >6,000,000 2 5 days± 12 hrs 239 days 8 0.4 yrs Heptachlor 76± 44± 8 19,953 10.5 hrs± 1 hr 129.4± 23.1 hrs 4 yrs± 8 days Isodrin 465± 73± 6 20,180 10 hrs± 1 hr 5 yrs± 180 days Methoxychlor 72± 43± 5 8,128 12 hrs± 1 hr 15.2± 5 days 136± 81 days Pendimethalin 40487± 42± 1 1,944 21± 2 hrs 1300± 54 days Toxaphene 8001± 35± 2 34,050 16 days± 19 hrs 5 yrs± 1 yr 11± 1 yrs Trifluralin 1582± 09± 8 5,674 3.2± 0.42 hrs 36.5± 4.5 days 1 394± 99 days Polycyclic Aromatic Compounds 58713 Federal Register / Vol. 64, No. 209 / Friday, October 29, 1999 / Rules and Regulations Table 3.Ð Persistence and Bioaccumulation DataÐ Continued Chemical Category/ Chemical Name CASRN BCF BAF Air Half life Surface Water Halflife Soil Half life Benzo( a) pyrene 50± 32± 8 912 2.4 hrs 17.3± 5.4 yrs 14.6 yrs± 151 days Benzo( b) fluoranthene 205± 99± 2 5,631 1.4 days± 3.4 hrs ³100 days 14.2 yrs± 87 days Benzo( r, s, t) pentaphene 189± 55± 9 26,280 13 hrs± 1 hr 371± 232 days Benzo( a) anthracene 56± 55± 3 800 13 hrs± 1 hr 3 1.2 yrs 2.0 yrs± 240 days 7,12 Dimethylbenz( a) anthracene 57± 97± 6 5,834 4± 0.4 hrs 6 yrs± 1 yr 28± 20 days Dibenzo( a, h) anthracene 53± 70± 3 31,440 13 hrs± 1 hr ³100 days 2 yrs± 240 days 3 Methylcholanthrene 56± 49± 5 17,510 3± 0.3 hrs 3.8± 1.7 yrs 7H Dibenzo( c, g) carbazole 194± 59± 2 16,900 23± 2 hrs >160 days Benzo( k) fluoranthene 207± 08± 9 10,090 12 hrs± 1 hr 11 yrs± 139 days Benzo( j) fluoranthene 205± 82± 3 10,090 12 hrs± 1 hr 10.5 yrs Dibenzo( a, e) pyrene 192± 65± 4 6,875 13 hrs± 1 hr 371± 232 days Dibenzo( a, h) pyrene 189± 64± 4 26,280 13 hrs± 1 hr 371± 232 days Indeno( 1,2,3 cd) pyrene 193± 39± 5 28,620 7.6± 0.34 hrs 730± 58 days Dibenz( a, h) acridine 226± 36± 8 3,500 13 hrs± 1 hr >160 days Dibenz( a, j) acridine 224± 42± 0 18,470 23± 2 hrs >160 days Benzo( g, h, i) perylene 191± 24± 2 25,420 10.0± 0.31 hrs ³100 days 1.8 yrs± 173 days Dibenzo( a, e) fluoranthene 5385± 75± 1 26,280 10 hrs± 1 hr 371± 232 days 3 5 Methylchrysene 3697± 24± 3 9,388 5± 0.5 hrs 3.8 yrs± 79 days 4 2.7 yrs± 255 days 4 Dibenzo( a, l) pyrene 191± 30± 0 6,875 13 hrs± 1 hr 371± 232 days Benzo( a) phenanthrene 218± 01± 9 800 13 hrs± 1 hr 3.8 yrs± 79 days 2.7 yrs± 255 days 1 Nitropyrene 5522± 43± 0 908 4 days± 10 hrs 44 yrs± 16 yrs Benzo( j, k) fluorene (fluoranthene) 206± 44± 0 5,100 20± 2 hrs 13 yrs± 110 days Metals/ Metal Compounds Mercury 5 and Mercury compounds 7439± 97± 6 7,000 36,000 see footnote 5 see footnote 5 see footnote 5 Polychlorinated Biphenyl (PCBs) 1336± 36± 3 >200,000 2,6 2,3,3¢, 4,4¢, 5,5¢ heptachlorobiphenyl 39635± 31± 9 4,922 191± 19 days >56 days >5± 3.92 yrs 2,3,3¢, 4,4¢, 5 hexachlorobiphenyl 38380± 08± 4 37,590 127± 13 days >56 days >5± 3.42 yrs 2,3,3¢, 4,4¢, 5¢ hexachlorobiphenyl 69782± 90± 7 37,590 114± 11 days >56 days >5± 3.42 yrs 58714 Federal Register / Vol. 64, No. 209 / Friday, October 29, 1999 / Rules and Regulations Table 3.Ð Persistence and Bioaccumulation DataÐ Continued Chemical Category/ Chemical Name CASRN BCF BAF Air Half life Surface Water Halflife Soil Half life 2,3¢, 4,4¢, 5,5¢ hexachlorobiphenyl 52663± 72± 6 37,590 114± 11 days >56 days >5± 3.42 yrs 3,3¢, 4,4¢, 5,5¢ hexachlorobiphenyl 32774± 16± 6 73,840 88± 9 days >56 days >5± 3.42 yrs 2,3,3¢, 4,4¢ pentachlorobiphenyl 32598± 14± 4 196,900 >134,000,000 2 80 8 days >56 days 7.25± 0.91 yrs 2,3,4,4¢, 5 pentachlorobiphenyl 74472± 37± 0 196,900 67± 7 days >56 days 7.25± 0.91 yrs 2,3¢, 4,4¢, 5 pentachlorobiphenyl 31508± 00± 6 184,300 >141,000,000 2 80± 8 days >56 days 7.25± 0.91 yrs 2¢, 3,4,4¢, 5 pentachlorobiphenyl 65510± 44± 3 196,900 50± 5 days >56 days 7.25± 0.91 yrs 3,3¢, 4,4¢, 5 pentachlorobiphenyl 57465± 28± 8 196,900 57± 6 days >56 days 7.25± 0.91 yrs 3,3¢, 4,4¢ tetrachlorobiphenyl 32598± 13± 3 105,900 37± 4 days >98 days 4.83± 0.91 yrs Other Chemicals Hexachlorobenzene 118± 74± 1 29,600 66,000 >2,500,000 2 1,582± 158 days 5.7± 2.7 yrs Octachlorostyrene 29082± 74± 4 33,113 >117,000,000 2 10 hrs± 1 hr 5.7± 2.7 yrs7 Pentachlorobenzene 608± 93± 5 8,318 >640,000 2 460± 46 days 194 days± >22 yrs Tetrabromobisphenol A 79± 94± 7 780; 1,200; 3,200 9 days± 1 day 84± 48 days 44± 179 days 1 The reported half life data for water are suspected to include significant removal from the medium by processes other than degradation (e. g., volatilization). 2 Values are for Piscivorous Fish. 3 Since data could not be found for this chemical, the data for the dibenzopyrenes (192± 65± 4; 189± 64± 0; 191± 30± 0), which are structural analogues was used. 4 Since data could not be found for this chemical, the data for benzo( a) phenanthrene (218± 01± 9), a structural analogue was used. 5 The bioaccumulation potential for the parent metals is assumed to be equivalent to the associated metal compounds since in the environment the parent metals may be converted to a metal compound. Since metals are not destroyed in the environment they persist longer than 6 months. 6 Lowest value reported for a dichlorinated PCB. 7 Since no data could be found for this chemical, the data for the structural analogues hexachlorobenzene (118± 74± 1) and pentachlorobenzene (608± 93± 5) was used.

1. PersistenceÐ a. Dioxin and dioxinlike compounds. In the proposal, EPA preliminarily determined that dioxin and dioxin like compounds have persistence half life values in soil that ranged from 1.5 years to more than 20 with all but one chemical having a soil half life of more than 20 years. EPA has reviewed information and all comments received on dioxin and dioxin like compounds' persistence characteristics. Taking into account this information, as indicated in Table 3, EPA finds that dioxin and dioxin like compounds persist in the environment with halflives of 2 months or greater and therefore meet the persistence criterion established in this rulemaking. A complete discussion of EPA's findings on this chemical category can be found in EPA's Response to Comments document for this rulemaking (Ref. 69) and/ or in EPA's support documents for this rulemaking (Ref. 7). In addition, dioxin and dioxin like compounds persist in the environment with a halflife of greater than 6 months making it highly persistent. This, plus other factors, supports EPA's decision to lower the threshold to 0.1 gram. b. Aldrin. In the proposal, EPA preliminarily determined that aldrin has persistence half life values in soil of 291 days to 9 years and a persistence halflife value in water of 24 days. EPA has reviewed information and all comments received on aldrin's persistence characteristics. Taking into account this information, as indicated in Table 3, EPA finds that aldrin persists in the environment with a half life of 2 months or greater and therefore meets the persistence criterion established in this rulemaking. A complete discussion of EPA's findings on this chemical can be found in EPA's Response to Comments document for this rulemaking (Ref. 69) and/ or in EPA's support documents for this rulemaking (Ref. 7). c. Chlordane. In the proposal, EPA preliminarily determined that chlordane has persistence half life values in soil of 0.4± 8 years and a persistence half life value in water of 239 days. EPA has reviewed information and all comments received on chlordane's persistence characteristics. Taking into account this information, as indicated in Table 3, EPA finds that chlordane persists in the environment with a half life of 2 months or greater and therefore meets the persistence criterion established in this rulemaking. A complete discussion of EPA's findings on this chemical can be found in EPA's Response to Comments document for this rulemaking (Ref. 69) 58715 Federal Register / Vol. 64, No. 209 / Friday, October 29, 1999 / Rules and Regulations and/ or in EPA's support documents for this rulemaking (Ref. 7). In addition, chlordane persists in the environment with a half life of greater than 6 months which supports EPA's decision to lower the threshold to 10 pounds. d. Heptachlor. In the proposal, EPA preliminarily determined that heptachlor has persistence half life values in soil of 8 days to 4 years and a persistence half life value in water of 23.1± 129.4 hours. EPA has reviewed information and all comments received on heptachlor's persistence characteristics. Taking into account this information, as indicated in Table 3, EPA finds that heptachlor persists in the environment with a half life of 2 months or greater and therefore meets the persistence criterion established in this rulemaking. A complete discussion of EPA's findings on this chemical can be found in EPA's Response to Comments document for this rulemaking (Ref. 69) and/ or in EPA's support documents for this rulemaking (Ref. 7). In addition, heptachlor persists in the environment with a half life of greater than 6 months which supports EPA's decision to lower the threshold to 10 pounds. e. Isodrin. In the proposal, EPA preliminarily determined that isodrin has persistence half life values in soil of 180 days to 5 years. EPA has reviewed information and all comments received on isodrin's persistence characteristics. Taking into account this information, as indicated in Table 3, EPA finds that isodrin persists in the environment with a half life of 2 months or greater and therefore meets the persistence criterion established in this rulemaking. A complete discussion of EPA's findings on this chemical can be found in EPA's Response to Comments document for this rulemaking (Ref. 69) and/ or in EPA's support documents for this rulemaking (Ref. 7). In addition, isodrin persists in the environment with a halflife of greater than 6 months which supports EPA's decision to lower the threshold to 10 pounds. f. Methoxychlor. In the proposal, EPA preliminarily determined that methoxychlor has persistence half life values in soil of 81 to 136 days and a persistence half life value in water of 5 to 15.2 days. EPA has reviewed information and all comments received on methoxychlor's persistence characteristics. Taking into account this information, as indicated in Table 3, EPA finds that methoxychlor persists in the environment with a half life of 2 months or greater and therefore meets the persistence criterion established in this rulemaking. A complete discussion of EPA's findings on this chemical can be found in EPA's Response to Comments document for this rulemaking (Ref. 69) and/ or in EPA's support documents for this rulemaking (Ref. 7). g. Pendimethalin. In the proposal, EPA preliminarily determined that pendimethalin has a persistence halflife value in soil of 54 to 1,300 days. EPA received several significant comments addressing pendimethalin's persistence potential which are addressed below. EPA has reviewed information and all comments received on pendimethalin's persistence characteristics. Taking into account this information, as indicated in Table 3, EPA finds that pendimethalin persists in the environment with a half life of 2 months or greater and therefore meets the persistence criterion established in this rulemaking. A complete discussion of EPA's findings on this chemical can be found in EPA's Response to Comments document for this rulemaking (Ref. 69) and/ or in EPA's support documents for this rulemaking (Ref. 7). One commenter contends that EPA has miscategorized pendimethalin as a PBT chemical based on limited screening data which conflicts with conclusions reached by EPA in its risk assessment under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). The commenter believes that the characterization of pendimethalin is inaccurate and will lead to misplaced effort and misplaced focus on listed chemicals, and that there will be no benefit to the public or the environment in lowering the reporting threshold for pendimethalin. EPA disagrees with the commenter. EPA did not base its determination that pendimethalin meets the EPCRA section 313 persistence criteria, nor that pendimethalin is highly persistent on `` screening'' data. EPA's conclusion that pendimethalin persists with a half life greater than 6 months is based on a well conducted study in which pendimethalin degrades in soil with a half life of 1,322 days. Further, even if these data were discounted, there are numerous data submitted in support of reregistration of pendimethalin under FIFRA that provide strong evidence that pendimethalin meets the EPCRA section 313 persistence criteria, i. e., a half life greater than 2 months. A more detailed discussion of these data is presented in the following responses. Contrary to the assertion by the commenter, the categorization of pendimethalin as a PBT chemical as described in the proposed rule is not in conflict with the conclusions reached by EPA during the FIFRA assessment. In addition, EPA disagrees that there will be no benefits to the public or the environment from lowering the thresholds for pendimethalin. EPA believes that pendimethalin, like all PBT chemicals, is of special concern because it has the potential to cause adverse effects even when released to the environment in small quantities because it can bioaccumulate in organisms to levels much greater than those present in the environment. EPA believes that lowering the reporting threshold for pendimethalin will provide information to the public that will increase their awareness of low levels of releases to the environment which have the potential to concentrate in organisms and cause adverse effects, which is fully consistent with the purposes of EPCRA section 313. The commenter states that EPA has ignored bioavailability in designating pendimethalin as a PBT chemical and argues that the true bioaccumulation potential for pendimethalin is greatly overestimated based on the results of the standard laboratory fish bioconcentration study. The commenter asserts that when data on bioavailability, degradation, and depuration are all considered, the `` real world'' bioconcentration potential for pendimethalin is low and, therefore pendimethalin should not be mischaracterized as a PBT chemical. The bioavailability data the commenter refers to was not specifically identified. Bioavailability of a chemical will vary from environment to environment and soil type to soil type. Caution must be taken, however, not to draw the erroneous conclusion that because a chemical has been shown to have a high affinity to sorb to sediments in aquatic environments that it will not be available for uptake by aquatic organisms. Examples like the PCBs (see Unit VI. F. for a further discussion on this issue) indicate that although some of these compounds have sorption coefficients much greater than pendimethalin, they are still widely found in the tissues of aquatic organisms in contaminated waters. Further, it would be erroneous to state that pendimethalin is not bioavailable because if it were not bioavailable it could not function as an herbicide. The commenter claims that using EPA's own criteria (half lifes longer than 2 months in water, sediment, or soil, or a half life longer than 2 days in air) pendimethalin cannot be classified as persistent. Rather the commenter contends that pendimethalin has `` low'' or `` low to moderate'' persistence. The commenter is incorrect. The Agency has set persistence criteria of half lifes for soil, sediment, and water 58716 Federal Register / Vol. 64, No. 209 / Friday, October 29, 1999 / Rules and Regulations greater than 2 months and a half life in air of greater than 2 days. Chemicals meeting these criteria are considered persistent for purposes of EPCRA section 313. There are, in fact, no qualifiers such as `` low, '' `` moderate, '' or `` high'' associated with the persistence criteria. The commenter's characterization of the persistence of pendimethalin as `` low'' or `` low to moderate'' is thus not particularly relevant. It appears, based on the comments, that the commenter defines low to moderate persistence as a halflife of greater than 2 days in air and greater than 2 months in soil, sediment, or water. If this is the case, then the commenter in fact concurs with EPA's assessment of pendimethalin as persistent (half life greater than 2 months in soil or water and greater than 2 days in air). If the commenter, instead, meant that pendimethalin has half lifes of less than 2 months in soil or water, and 2 days in air, EPA notes that the commenter has failed to provide data to support that assertion, and that EPA's review of the data support the Agency's conclusion. A commenter cites numerous laboratory and field dissipation studies in support of the claim that pendimethalin does not meet the persistence criteria. EPA disagrees that the degree of persistence of pendimethalin can be characterized by the field dissipation studies cited by the commenter. Field dissipation studies are not equivalent to the studies which measure the half life for destruction of a chemical in a specific medium (i. e., soil, water, or air). Field dissipation studies are designed to measure the rate or extent of chemical loss from the medium after application of the chemical. The processes by which the chemical is lost may include not only those that result in destruction of the chemical, but those which only transport the chemical from one medium to another such as volatilization. The studies cited by the commenter measure the dissipation of pendimethalin from soil. For a relatively volatile chemical such as pendimethalin, field dissipation studies are of limited use in assessing persistence because an unknown amount of pendimethalin will be transported from soil to air, resulting in a measured loss from that medium, but not destruction. Thus, the field dissipation studies cited by the commenter will underestimate the persistence of pendimethalin in soil. The commenter cites several laboratory experiments on the degradation of pendimethalin in soil to support the argument that pendimethalin does not meet the persistence criteria. For example, they state that laboratory aerobic soil degradation studies have been conducted in which pendimethalin was applied to soil grab samples and incubated under controlled conditions. Pendimethalin degraded in laboratory soil studies with half lifes ranging from 31 to 1,322 days. In the Reregistration Eligibility Decision (RED) for Pendimethalin (Ref 63) document, EPA explained that 172 days was used instead of 1,322 days because:

The half lifes for aerobic soil metabolism ranged from 42 563 days in the literature studies referenced below with a guideline study reporting a half life of 1,322 days for a total of 27 total observations. Because of the range of half life values, statistical analyses of the available data were performed. The mean, median, and modal half lifes are 126, 122, and 122 days, respectively, with a standard deviation of 66 days (n= 24). The half life values of 409, 563, and 1,322 days were not included in the final statistical analyses because they were greater than three standard deviations from the mean. Based on soils and crops that are normally treated with pendimethalin, the reviewer assumed that temperatures would likely range from 20± 30 °C and soil moisture contents from 50 75% Field Capacity (FC). The range of observed half lifes in the above experimental conditions was 72± 172 days.

The commenter contends that the 1,322± day half life value is assumed to be an outlier (Ref. 5), the range was 31 to 172 days. Thus, it is claimed that laboratory studies also indicate that pendimethalin has a low to moderate persistence according to the EPCRA section 313 persistence criteria. EPA believes that the guideline study that reported a half life of 1,322 days represents an accurate and representative value for the assessment of the persistence of pendimethalin in the environment. In situations where multiple values for half lifes are submitted under FIFRA to EPA's Office of Pesticide Program (OPP), statistical analysis may be conducted to determine mean values and standard deviations. The analysis permits the use of a value for exposure assessment modeling that takes into account the variability in data, and allows the exclusion of values more than three standard deviations outside the mean as `` outliers. '' The designation as an outlier does not invalidate the study, and in fact, EPA maintains that even a study designated as an `` outlier, '' if valid, gives useful half life information. In their assessment of the persistence of chemicals in soils, OPP focuses on studies using soil types, soil moisture contents, and temperatures consistent with the field application of the chemical in its intended use. In the OPP review of the studies, the reviewer assumed that in the field application of the chemical, temperatures would likely range from 20 30 °C and that soil moisture would range from 50 to 75% field capacity. The consideration of data from studies conducted under these conditions resulted in a half life range of 72 to 172 days for pendimethalin. It should be noted that even after the elimination of outliers and consideration of studies relevant to normal field application, the entire halflife range is above 2 months, clearly meeting the criteria for persistence in soil, i. e., a half life of 2 months. The releases of pendimethalin subject to EPCRA section 313 reporting, in many cases, will not be to agricultural soils under typical application scenarios. EPA, therefore, contends that even though some soil half life values were not considered by OPP, either because they were derived using studies that did not represent the desired field conditions, or because they were labeled as statistical outliers, the study conditions still represent realistic scenarios for releases reported under EPCRA section 313 and are valid for use in the determination of persistence. The commenter cites studies conducted using flooded soils to support the argument that pendimethalin does not meet the persistence criteria. The commenter asserts that the studies involved the use of pendimethalin spiked into soil grab samples covered with a shallow layer of water and incubated in the laboratory under controlled conditions. In laboratory flooded soil studies, pendimethalin degradation half lifes ranged from seven to 104 days with the majority of studies giving half lifes of less than 2 months. Degradation of pendimethalin was more rapid in flooded soils than in nonflooded soils in most instances. The commenter asserts that these results demonstrate that pendimethalin has a low to moderate persistence in flooded soils according to the EPCRA section 313 persistence criteria. EPA agrees that the reported degradation half lifes in laboratory flooded soils studies range from 7 to 104 days. The studies were reviewed for quality and preferred methodologies. Of the studies that are of acceptable quality, EPA chose the highest value (most protective) of the range to determine if the chemical meets the EPCRA section 313 persistence criteria. In this case, the value of 104 days would be used to characterize pendimethalin as persistent in flooded soils. However, 58717 Federal Register / Vol. 64, No. 209 / Friday, October 29, 1999 / Rules and Regulations there is not a separate persistence criterion for flooded soils, nor are data on flooded soils preferable to other soil data. EPA notes that other soil studies, as discussed above in this section, indicate a half life of 1,322 days in soils. The commenter states that while pendimethalin is stable to hydrolysis, it will degrade in natural water and water/ sediment systems under laboratory conditions with degradation half lifes ranging from 4 to 22 days. Photodegradation is also rapid with half lifes of approximately 3.5 days. The commenter concludes that these results indicate that pendimethalin has a low persistence in both water and its underlying sediment according to the EPCRA section 313 persistence criteria. Two of the aerobic aquatic degradation studies cited by the commenter were not provided to the Agency or are not publicly available, (i. e., they are internal American Cyanamid studies). It is unclear from the summary provided whether the cited studies measured destruction of pendimethalin or its loss from the medium by non destructive water to air transport processes. If the latter is the case, the `` dissipation half lifes'' cited cannot be used to characterize persistence. EPA agrees that if the halflifes reported for aerobic aquatic degradation represent half lifes for destruction of the chemical, they do not meet the criteria for persistence in water. However, as noted, the full studies were not available for review and as such, EPA cannot assume that the studies followed destruction of pendimethalin, or that the studies meet the quality criteria outlined in this rule. The commenter cites a half life range of 6 to 22 days derived from an anaerobic aquatic degradation study to support the argument that pendimethalin has a low persistence in both water and its underlying sediment according to the EPCRA section 313 persistence criteria. EPA agrees that the persistence half life values cited by the commenter do not meet the EPCRA section 313 persistence criteria, but points out that additional data submitted in support of the reregistration of pendimethalin indicated that half lifes in aquatic environments could be longer. OPP used flooded soil degradation studies to assess the persistence of pendimethalin under anaerobic aquatic conditions. Half lifes in these studies ranged from 6 to 105 days. In its discussion of the potential impact of pendimethalin on water resources, OPP in the RED notes that pendimethalin has an anaerobic aquatic metabolism half life of 60 days. EPA believes that after review of the available data on its persistence in water pendimethalin meets the EPCRA section 313 persistence criteria. EPA agrees that rapid aqueous photodegradation under laboratory studies has been reported for pendimethalin. However, the photolysis screening tests used are designed to allow the determination of rates of photolysis at shallow depths in pure water as a function of lattitude and season. EPA believes that the environmental relevence of these tests should be considered in their use to determine persistence, and that the results are most applicable to shallow, clear waters. EPA believes that the application of the results beyond these environments is tenuous due to the attenuation of light by suspended matter and increasing depth in the aquatic environment. EPA believes that pendimethalin's tendency to sorb to soil and sediments may result, under some circumstances, in its deposition in benthic environments beyond the effects of aqueous photolysis. Therefore, EPA does not believe that the half life for pendimethalin in water should be based on aqueous photolysis. The commenter claims pendimethalin will not persist in air according to the EPCRA section 313 persistence criteria for air since it has a half life of less than 2 days. The commenter discusses the estimation of pendimethalin's atmospheric half life and a study on its photodegradation in air. The commenter cites the results of a calculation according to the method of Atkinson performed to determine the rate constant for reaction of pendimethalin with OH radicals in the gas phase (Ref 42). A tropospheric half life of 3.4 hours was calculated using the method. The photolysis of pendimethalin was investigated by Bossan, et al., 1995 (Ref. 15), who reported on the photoreactivity of pendimethalin on airborne fly ash and kaolin using simulated sunlight. Approximately 70% of applied pendimethalin degraded within 30 minutes when adsorbed to fly ash but little degradation was observed after 100 minutes when pendimethalin was bound to kaolin. EPA agrees that pendimethalin does not meet the persistence half life criteria for air of greater than 2 days, but because it meets the persistence criteria for soil and water, this does not affect EPA's conclusion. As noted in the proposed final rule (at 64 FR 702), a chemical need only meet one of the media specific criteria to be considered persistent. The commenter cites EPA's pendimethalin RED document and cites its conclusion in support of the argument that pendimethalin does not meet the persistence criteria. The commenter describes the RED conclusions as follows:

Pendimethalin dissipates in the environment by binding to soil, microbiallymediated metabolism and volatilization. It is essentially immobile in soil. Based on laboratory studies and limited field study information, pendimethalin is slightly to moderately persistent in aerobic soil environments. Persistence decreases with increased temperature, increased moisture and decreased soil organic carbon.