PART 1. TEXAS COMMISSION ON ENVIRONMENTAL QUALITY
CHAPTER 350. TEXAS RISK REDUCTION PROGRAM
SUBCHAPTER D. DEVELOPMENT OF PROTECTIVE CONCENTRATION LEVELS
The Texas Commission on Environmental Quality (TCEQ, agency, or commission) proposes amendments to §350.76, concerning Approaches for Specific Chemicals of Concern to Determine Human Health Protective Concentration Levels.
Background and Summary of the Factual Basis for the Proposed Rules
The purpose of this rulemaking is to amend 30 Texas Administrative Code (TAC) Chapter 350, Texas Risk Reduction Program (TRRP) rule §350.76, pertaining to the chemical-specific approaches used for developing and demonstrating attainment of the critical human health protective concentration levels (PCLs) for dioxins/furans and dioxin-like polychlorinated biphenyls (PCBs).
The TCEQ proposes to update the approach for developing soil PCLs for dioxins/furans and dioxin-like PCBs used for residential and commercial/industrial land use under TRRP. The current approach is covered in the TRRP rule in §350.76(d) and §350.76(e), and the current PCLs are specified in the TRRP rule at §350.76(e)(3). The PCLs contained in the existing TRRP rule were based on a then-current 1998 United States Environmental Protection Agency (EPA) policy memo (OSWER Directive 9200.4-26), which described an approach for addressing dioxins in soil. Since that time, the EPA completed a reassessment of this approach and derived an updated reference dose for dioxins. Based on more recent scientific evaluations, the TCEQ can support the use of a reference dose in the range of EPA's updated value, and that value will be reflected in the approach provided in this proposed rule revision. Upon the effective date of the adopted revisions, any activity conducted pursuant to TRRP must comply with the revised approach for developing dioxins/furans and dioxin-like PCBs and the soil PCLs used for residential and commercial/industrial land use under TRRP.
Additionally, the proposed rule revision updates the toxicity equivalency factors (TEFs) related to dioxins/furans and dioxin-like PCBs contained in §350.76(d)(2)(B). Dioxins/furans and dioxin-like PCBs are mixtures of chemical compounds (congeners) with different toxicities. TRRP §§350.76(d) and (e) use TEFs to assess the relative toxicity of the individual congeners compared to the toxicity of the most toxic congener, 2,3,7,8-tetrachlorodibenzodioxin (2,3,7,8-TCDD), within a mixture of dioxins/furans and dioxin-like PCBs. The TEFs are applied as a multiplier of the concentration of each measured congener to calculate a 2,3,7,8-TCDD toxicity equivalency quotient (TEQ) concentration. The resulting 2,3,7,8-TCDD TEQ concentrations for each congener are summed to derive a total 2,3,7,8-TCDD TEQ concentration for the entire mixture. The total 2,3,7,8-TCDD TEQ concentration is then compared to a 2,3,7,8-TCDD PCL to determine the nature and extent of contamination and whether a remedy is required. The TRRP rule provides specific TEFs for various dioxins/furans and dioxin-like PCB compounds and directs persons to use these TEF values when demonstrating attainment of the critical PCL.
When the TRRP rule was promulgated in 1999, the most recent TEF values established by the World Health Organization (WHO) in 1998 were listed in the rule. However, based on evolving science and current data, WHO updated the TEF values in 2005 and continues to develop the most current TEF values. EPA and other regulatory agencies have been using the 2005 WHO TEFs. The proposed TRRP §350.76 rule revision will allow cleanups being conducted under TRRP to adopt the 2005 WHO TEFs or more recent TEFs established by a scientifically valid source that have been reviewed and approved by the executive director. Upon the effective date of the adopted revisions, any activity conducted pursuant to TRRP must comply with the 2005 WHO TEFs, or more recent TEFs established by a scientifically valid source that have been reviewed and approved by the executive director, for dioxin-like PCBs and dioxins/furans.
The TRRP chemical-specific PCL approaches for dioxins/furans and dioxin-like PCBs need to be revised to reflect updated information on dioxin toxicity and address appropriate updates to the WHO TEFs for dioxins/furans and dioxin-like PCBs. Updating the rule will also provide TCEQ with the flexibility needed to evaluate and adopt more recent TEFs that have been derived since the TRRP rule was first adopted in 1999.
Section by Section Discussion
Subchapter D: Development of Protective Concentration Levels
The commission proposes to amend §350.76(d)(2)(B) by removing the figure and the directive for persons to use TEFs specified therein when determining a 2,3,7,8-TCDD TEQ for dioxin-like PCBs. The proposed rule would direct persons to apply the 2005 WHO TEFs, or more recent TEFs established by a scientifically valid source that have been reviewed and approved by the executive director, to the measured concentrations for each of the dioxin-like PCBs.
The commission proposes to add new subsection §350.76(d)(3). This subsection clarifies that a person may be required to evaluate the adequacy of a response action when the executive director determines that a substantial change in the TEFs alters the calculated TEQ in such a way that results in the actual toxicity of the dioxin-like PCB mixture not being protective of human health and the environment. The rule also specifies that it is possible that a person might not be required to conduct a response action in the case where a significant change in the TEFs affects the TEQ in such a way that reveals a response action is no longer warranted to protect human health and the environment. To maintain the numerical order of the rule, previous subsections (d)(3) and (d)(4) are being renumbered to (d)(4) and (d)(5), respectively.
The commission proposes to amend §350.76(e)(1) by removing the directive for persons to use TEFs specified in the figure included in subsection (d)(2)(B), when demonstrating attainment of the critical PCL for 2,3,7,8-TCDD. The proposed rule would direct persons to apply the 2005 WHO TEFs, or more recent TEFs established by a scientifically valid source that have been reviewed and approved by the executive director, to demonstrate attainment of the critical PCL for 2,3,7,8-TCDD.
The commission proposes to amend §350.76(e)(1)(B) to clarify that, when homologue-specific analytical data are available, persons shall apply the 2005 WHO TEFs or more recent TEFs established by a scientifically valid source that have been reviewed and approved by the executive director. Additionally, this subsection clarifies that if a homologue class has more than one TEF for different congeners, persons shall use the highest of the latest TEFs that have been reviewed and approved by the executive director for that congener class. Additionally, the proposed rule removes the language specifying that a TEF value of 0.5 be used for the pentachlorodibenzofuran homologue class.
The commission proposes to amend §350.76(e)(1)(C) to clarify that, when congener-specific analytical data are available, persons shall apply the 2005 WHO TEFs or more recent TEFs established by a scientifically valid source that have been reviewed and approved by the executive director.
The commission proposes to add new subsection §350.76(e)(1)(D). This subsection clarifies that a person may be required to evaluate the adequacy of a response action when the executive director determines that a substantial change in the TEFs alters the calculated TEQ in such a way that it results in the actual toxicity of the dioxin and furan mixture not being protective of human health and the environment. The rule also specifies that it is possible that a person might not be required to conduct a response action in the case where a significant change in the TEFs affects the TEQ in such a way that reveals a response action is no longer warranted to protect human health and the environment.
The commission proposes to amend §350.76(e)(3) by removing language that establishes the critical soil PCL for residential properties for all three tiers as 1 part per billion (ppb) and for commercial/industrial properties for all three tiers as 5 ppb. The proposed rule would specify that the critical soil PCLs for residential and commercial/industrial properties shall be calculated for a 2,3,7,8-TCDD TEQ according to the equations and rule provisions provided in §350.75.
Fiscal Note: Costs to State and Local Government
Kyle Girten, Analyst in the Budget and Planning Division, has determined that for the first five-year period the proposed rules are in effect, fiscal implications are anticipated for TCEQ and potentially a local governmental entity as a result of administration or enforcement of the proposed rule. Implementation of amendments to the proposed rule in §350.76 are anticipated to result in increased costs for the assessment and remediation of a small number of sites whose remediation is managed and funded by TCEQ and/or a municipality. The rulemaking is not anticipated to result in fiscal implications for other state or local governmental entities.
Costs for sample collection, laboratory analysis, and data analysis are anticipated to increase for these sites when they are being assessed. Given that this rulemaking will result in lower assessment levels for dioxins/furans and dioxin-like PCBs in soil, an increased number of samples would need to be collected at sites to delineate the horizontal and vertical extent of contamination. Laboratory analysis costs for these parameters could also increase significantly because laboratories would be required to use analytical methods that can meet the required level of performance based on the lowered PCL. Costs for remediation are also anticipated to increase because greater volumes of soil may need to be remediated to the lower PCLs.
Costs cannot be estimated because they will vary depending on the extent of contamination that is found and the remedy (e.g., excavation, capping, in-situ treatment) that is implemented; however, it is anticipated that any cost increases can be addressed at current appropriation levels.
Public Benefits and Costs
Mr. Girten determined that for each year of the first five years the proposed rules are in effect, the public benefit will be increased consistency with the latest science. Specifically, the critical soil PCLs for 2,3,7,8-TCDD and the approach for developing dioxin/furan and dioxin-like PCB soil PCLs would be implemented in a manner consistent with the latest scientific evaluations from EPA and other regulatory agencies.
This rulemaking is anticipated to result in increased costs for the assessment and remediation by responsible or other performing parties at a small number of sites. In addition, it is possible that closed sites may need to be revisited if a lower soil PCL was determined to be a substantial change in circumstance, or if risks of exposure to concentrations of dioxins/furans and dioxin-like PCBs above new soil PCLs needed to be addressed.
Costs for sample collection, laboratory analysis, and data analysis may increase for these sites when they are being assessed. Given that this rulemaking will result in lower assessment levels for dioxins/furans and dioxin-like PCBs in soil, an increased number of samples may need to be collected at sites to delineate the horizontal and vertical extent of contamination. Laboratory analysis costs for these parameters could also increase significantly because laboratories would be required to use analytical methods that can meet the required level of performance based on the lowered PCL. Costs for remediation may also increase as greater volumes of soil may need to be remediated because of the lower assessment levels and soil PCLs.
Costs cannot be estimated because they will vary depending on the extent of contamination that is found and the remedy (e.g., excavation, capping, in-situ treatment) that is implemented.
Local Employment Impact Statement
The commission reviewed this proposed rulemaking and determined that a Local Employment Impact Statement is not required because the proposed rulemaking does not adversely affect a local economy in a material way for the first five years that the proposed rule is in effect.
Rural Communities Impact Assessment
The commission reviewed this proposed rulemaking and determined that the proposed rulemaking does not adversely affect rural communities in a material way for the first five years that the proposed rules are in effect. The amendments would apply statewide and have the same effect in rural communities as in urban communities.
Small Business and Micro-Business Assessment
No adverse fiscal implications are anticipated for small or micro-businesses due to the implementation or administration of the proposed rule for the first five-year period the proposed rules are in effect.
Small Business Regulatory Flexibility Analysis
The commission reviewed this proposed rulemaking and determined that a Small Business Regulatory Flexibility Analysis is not required because the proposed rule does not adversely affect a small or micro-business in a material way for the first five years the proposed rules are in effect.
Government Growth Impact Statement
The commission prepared a Government Growth Impact Statement assessment for this proposed rulemaking. The proposed rulemaking does not create or eliminate a government program and will not require an increase or decrease in future legislative appropriations to the agency. The proposed rulemaking does not require the creation of new employee positions, eliminate current employee positions, nor require an increase or decrease in fees paid to the agency. The proposed rulemaking amends an existing regulation, and it does not create, expand, repeal, or limit this regulation. The proposed rulemaking does not increase or decrease the number of individuals subject to its applicability. During the first five years, the proposed rule should not impact positively or negatively the state's economy.
Draft Regulatory Impact Analysis Determination
The commission reviewed the proposed rulemaking in light of the regulatory analysis requirements of the Texas Government Code, §2001.0225. The commission determined that the action is not subject to Texas Government Code, §2001.0225, because it does not meet the definition of a "major environmental rule" as defined in that statute. A "major environmental rule" is a rule, the specific intent of which is to protect the environment or reduce risks to human health from environmental exposure, and that may adversely affect in a material way the economy, a sector of the economy, productivity, competition, jobs, the environment, or the public health and safety of the state or a sector of the state.
The specific intent of the proposed rule is to adjust TRRP §350.76 methods and measures related to dioxins/furans and dioxin-like PCBs to align with current accepted science. Specifically, the proposed rule would revise the dioxin/furan and dioxin-like PCB soil PCLs used for residential and commercial/industrial land use under TRRP and update TEFs related to dioxins/furans and dioxin-like PCBs contained in §350.76 in light of more recent scientific evaluation, evolving science, and current data. The proposed rule is not expected to adversely affect in a material way the economy, a sector of the economy, productivity, competition, jobs, the environment, or the public health and safety of the state or a sector of the state. Instead, the proposed rule may affect the costs and timeliness of cleanups of those sites where dioxins/furans or dioxin-like PCBs are the subject of investigation or remediation pursuant to TRRP. The proposed amendments do not rise to the level of material, but instead are limited to incorporating modifications to the current regulatory framework based on current science and data regarding dioxins/furans and dioxin-like PCBs. Therefore, the proposed rulemaking does not meet the definition of a major environmental rule.
Furthermore, even if the proposed rulemaking did meet the definition of a major environmental rule, the proposed rules do not meet any of the four applicability requirements listed in Texas Government Code, §2001.0225. Section 2001.0225 applies to a major environmental rule, the result of which is to: exceed a standard set by federal law, unless the rule is specifically required by state law; exceed an express requirement of state law, unless the rule is specifically required by federal law; exceed a requirement of a delegation agreement or contract between the state and an agency or representative of the federal government to implement a state and federal program; or adopt a rule solely under the general powers of the agency instead of under a specific state law. The proposed rulemaking does not meet any of the four applicability requirements listed in Texas Government Code, §2001.0225.
First, the rulemaking does not exceed a standard set by federal law. Second, the rulemaking does not propose requirements that are more stringent than existing state laws. Third, the proposed rulemaking does not exceed a requirement of a delegation agreement or contract between the state and an agency or representative of the federal government, where the delegation agreement or contract is to implement a state and federal program. Fourth, this rulemaking does not seek to adopt a rule solely under the general powers of the agency. Rather, sections of the TWC, Chapter 26, and Texas Health & Safety Code, Chapter 361, authorize this rulemaking, which are cited in the Statutory Authority.
The commission invites public comment regarding the Draft Regulatory Impact Analysis Determination during the public comment period. Written comments on the Draft Regulatory Impact Analysis Determination may be submitted to the contact person at the address listed under the Submittal of Comments section of this preamble.
Takings Impact Assessment
The commission evaluated the proposed rules and performed analysis of whether the proposed rules constitute a taking under Texas Government Code, Chapter 2007. The specific purpose of the proposed rules is to adjust TRRP §350.76 methods and measures related to dioxins/furans and dioxin-like PCBs to align with current accepted science. The proposed rules would substantially advance this stated purpose by revising the soil PCLs and updating the TEFs related to these constituents.
Promulgation and enforcement of these proposed rules would be neither a statutory nor a constitutional taking of private real property. Specifically, the subject proposed regulations do not affect a landowner's rights in private real property because this rulemaking does not burden (constitutionally); nor restrict or limit the owner's right to property and reduce its value by 25% or more beyond that which would otherwise exist in the absence of the regulations. In other words, the proposed rules will not burden private real property because they incorporate modifications to the current regulatory framework based on current science and data regarding dioxins/furans and dioxin-like PCBs.
Consistency with the Coastal Management Program
This rulemaking is not applicable to the Coastal Management Program.
Announcement of Hearing
The commission will hold a hold a hybrid virtual and in-person public hearing on this proposal in Austin on Monday, September 30, 2024, at 9 a.m. in Building F, Room 2210 at the commission's central office located at 12100 Park 35 Circle. The hearing is structured for the receipt of oral or written comments by interested persons. Individuals may present oral statements when called upon in order of registration. Open discussion will not be permitted during the hearing; however, commission staff members will be available to discuss the proposal 30 minutes prior to the hearing.
Individuals who plan to attend the hearing virtually and want to provide oral comments and/or want their attendance on record must register by Thursday, September 26, 2024. To register for the hearing, please email Rules@tceq.texas.gov and provide the following information: your name, your affiliation, your email address, your phone number, and whether or not you plan to provide oral comments during the hearing. Instructions for participating in the hearing will be sent on Friday, September 27, 2024, to those who register for the hearing.
For the public who do not wish to provide oral comments but would like to view the hearing may do so at no cost at:
https://teams.microsoft.com/l/meetup-join/19%3ameeting_MzY3YmVhNjItZWIxOS00OWEyLWI5ZTgtZjYyY2NhNzcwNjg1%40thread.v2/0?context=%7b%22Tid%22%3a%22871a83a4-a1ce-4b7a-8156-3bcd93a08fba%22%2c%22Oid%22%3a%22e74a40ea-69d4-469d-a8ef-06f2c9ac2a80%22%7d
Persons who have special communication or other accommodation needs who are planning to attend the hearing should contact Sandy Wong, Office of Legal Services at (512) 239-1802 or 1-800-RELAY-TX (TDD). Requests should be made as far in advance as possible.
Submittal of Comments
Written comments may be submitted to Gwen Ricco, MC 205, Office of Legal Services, Texas Commission on Environmental Quality, P.O. Box 13087, Austin, Texas 78711-3087, or faxed to fax4808@tceq.texas.gov. Electronic comments may be submitted at: https://tceq.commentinput.com/comment/search. File size restrictions may apply to comments being submitted via the TCEQ Public Comments system. All comments should reference Rule Project Number 2024-023-350-WS. The comment period opens on August 30, 2024, and closes at 11:59 p.m. on October 1, 2024. Please choose one of the methods provided to submit your written comments.
Copies of the proposed rulemaking can be obtained from the commission's website at https://www.tceq.texas.gov/rules/propose_adopt.html . For further information, please contact Scott Settemeyer, Rule Project Manager, Remediation Division, (512) 239-3429.
Statutory Authority
The rule change is proposed under the authority of Texas Water Code (TWC), §5.102, concerning general powers of the commission; TWC, §5.103, which authorizes the commission to adopt any rules necessary to carry out its power and duties; TWC, §5.105, which authorizes the commission to establish and approve all general policy of the commission by rule; TWC, §26.011, which authorizes the commission to administer the provisions of TWC, Chapter 26; TWC, §26.039, which states that activities which are inherently or potentially capable of causing or resulting in the spillage or accidental discharge of waste or other substances and which pose serious or significant threats of pollution are subject to reasonable rules establishing safety and preventative measures which the commission may adopt or issue; TWC, §26.121, which prohibits persons from discharging wastes into or adjacent to any water in the state unless authorized to do so and prohibits persons from engaging in any other activity which causes pollution of any water in the state; TWC, §§26.262 and 26.264, which state it is the policy of this state to prevent the spill or discharge of hazardous substances into the waters in the state and authorizes the commission to issue rules to carry out the policy; TWC, §§26.341 and 26.345, which state it is the policy of this state to maintain and protect quality of groundwater and surface water resources from pollution from certain substances in underground and above-ground storage tanks and authorizes the commission to adopt rules to carry out the policy; TWC, §26.401, which states that it is the policy of this state that discharges of pollutants, disposal of wastes, or other activities subject to state regulation be conducted in a manner to maintain and not impair groundwater uses or pose a public health hazard, and that groundwater quality be restored if feasible; Texas Health & Safety Code (THSC), §§361.017 and 361.024, which establish the commission's jurisdiction over all aspects of the management of industrial solid waste and hazardous municipal waste with all power necessary or convenient to carry out the responsibilities of that jurisdiction and authorizes the commission to adopt rules; and THSC, Chapter 361, Subchapter F, which authorizes the commission to identify, assess, and remediate facilities that may constitute an imminent and substantial endangerment to public health and safety or the environment due to a release or threatened release of hazardous substances into the environment.
The proposed rules implement TWC, Chapter 26, and THSC, Chapter 361.
§350.76.Approaches for Specific Chemicals of Concern to Determine Human Health Protective Concentration Levels.
(a) General.
(1) Due to the unique nature of the toxicity and/or exposure, the person shall use the COC-specific approaches described in this section for the following COCs:
(A) cadmium;
(B) lead;
(C) polychlorinated biphenyls;
(D) polychlorinated dibenzodioxins and dibenzofurans;
(E) polycyclic aromatic hydrocarbons; and
(F) total petroleum hydrocarbons.
(2) Except for the specific provisions contained in this section, the person shall establish RBELs and PCLs in accordance with the standard procedures outlined in the previous sections of this subchapter.
(3) This section addresses only those exposure pathways for which PCL equations are provided in this subchapter. When dealing with other exposure pathways as required in §350.71(c) of this title (relating to General Requirements), the executive director will specify how those pathways should be addressed for these COCs using the best available science.
(4) The person shall use the figures as required in subsections (b) - (g) of this section.
(b) Cadmium.
(1) In calculating residential soil PCLs that are protective for noncarcinogenic effects for all tiers, the person shall incorporate age-adjusted exposure assumptions for the soil ingestion, vegetable ingestion, and dermal soil exposure pathways. Accordingly, 30 years of cadmium exposure shall be partitioned into three specific exposure periods: <1 - 6 years, 6 - 18 years, and 18 - 30 years. Cadmium intake shall be calculated for each of these periods, based on the period-specific exposure assumptions. The soil PCL for cadmium shall be a function of the final integrated intake estimate, which shall be determined by time-weighting intake from each of the three exposure periods. The age-adjusted RBEL equations and default parameters to be used for cadmium are provided in the following figure. The soil PCL for cadmium shall be calculated by combining the pathway-specific PCLs as outlined in §350.75(i)(6) of this title (relating to Tiered Human Health Protective Concentration Level Evaluation).
Figure: 30 TAC §350.76(b)(1) (No change.)
(2) In calculating residential and commercial/industrial soil PCLs for all tiers, the person shall use the reference dose values for cadmium in food in evaluating exposures to cadmium through the soil ingestion, vegetable ingestion, and dermal soil exposure pathways.
(c) Lead.
(1) The Tier 1 residential soil PCL (TotSoilComb) for lead is 500 mg/kg.
(2) Subject to prior approval by the executive director, the person may use property-specific data in conjunction with a lead model approved by the executive director (e.g., EPA Integrated Exposure Uptake Biokinetic model for lead in children (version 1.0 from 2005)) to calculate a Tier 3 residential soil PCL (TotSoilComb) for lead. The person shall submit information to the executive director which demonstrates that variance from default model inputs is supported by property-specific information (e.g., data from a scientifically valid bioavailability study using property-specific soils). Property-specific model input values must be approved by the executive director. Consistent with the development of residential RBELs for COCs without chemical-specific approaches in accordance with §350.74 of this title (Development of Risk-Based Exposure Limits), variance from certain model default exposure factors such as soil/dust ingestion rates and exposure frequency to less conservative (i.e., lower) numerical values shall not be allowed.
(3) The commercial/industrial soil PCL (TotSoilComb) is based only on the soil ingestion pathway (SoilSoilIng). The person shall use the exposure algorithm and default exposure factors in the following figure for calculating the Tier 1 commercial/industrial SoilRBELIng value.
Figure: 30 TAC §350.76(c)(3) (No change).
(4) The person may use a different exposure algorithm as presented in the following figure that considers soil and dust separately for calculating the Tier 2 and 3 commercial/industrial SoilSoilIng value in cases where the person has adequate direct measurement data on the concentrations of lead in both soil and dust at the affected property. In addition, in calculating Tier 2 or 3 SoilSoilIng values, the person may deviate from the default exposure factors as shown in the figure in paragraph (3) of this subsection and the following figure if property-specific or defensible alternative data (e.g., from open literature or privately funded studies) adequately support such an approach. The specific exposure factors for which the person may use property-specific or scientifically defensible alternative values are the following:
Figure: 30 TAC §350.76(c)(4) (No change.)
(A) individual geometric standard deviation (GSDI);
(B) baseline blood lead (PbBO);
(C) absolute absorption fraction of lead in soil/dust (Afsd);
(D) absolute absorption fraction of lead in soil (AFs); and
(E) absolute absorption fraction of lead in dust (Afd).
(d) Polychlorinated Biphenyls.
(1) In calculating Tier 1 residential and commercial/industrial soil and groundwater PCLs, the person shall use the upper-reference point of the upper-bound slope factors (2 (mg/kg-day)-1) for the soil ingestion, dermal contact with soil, vegetable ingestion, and inhalation (both vapor and particulate phases) exposure pathways.
(2) For Tiers 2 and 3, the person may use alternative slope factors when the following conditions are met:
(A) The person may use the lower reference point of the upper bound slope factors (0.4 (mg/kg-day)-1) to calculate an inhalation unit risk factor when evaluating inhalation exposures to volatilized polychlorinated biphenyls. The person must still use the upper reference point of the upper bound slope factors (2 (mg/kg-day)-1) to evaluate inhalation exposures to particulate phase polychlorinated biphenyls.
(B) The person may conduct congener or isomer analyses.
The person may use the lowest reference point of the upper-bound slope
factors (0.07 (mg/kg-day)-1) for the
soil ingestion, dermal contact with soil, and inhalation exposure
pathways if congener or isomer analyses verify that congeners with
more than four chlorines comprise less than one-half percent of total
polychlorinated biphenyls in a given exposure medium. The upper reference
point of the upper-bound slope factors (2 (mg/kg-day)-1) shall be used for all other exposure pathways
regardless of the results of the congener- or isomer-specific analyses.
If congener or isomer analyses indicate that congeners with more than
four chlorines comprise greater than one-half percent of total polychlorinated
biphenyls in a given exposure medium, then the person shall use the
upper-reference point of the upper-bound slope factors (2 (mg/kg-day)-1) for all pathways for that specific exposure
medium. Further, when congener concentrations are available, the contribution
of dioxin-like polychlorinated biphenyls to total dioxin equivalents
shall be considered. The person shall determine the constituents
considered to be dioxin-like polychlorinated biphenyls from the list
established by the World Health Organization in 2005, or a more recent
list of constituents established by a scientifically valid source
that has been reviewed and approved by the executive director. The
person shall apply the toxicity equivalency factors established
by the World Health Organization in 2005, or more recent toxicity
equivalency factors established by a scientifically valid source that
have been reviewed and approved by the executive director, [specified
in the following figure] to the measured concentrations for
each of the dioxin-like polychlorinated biphenyls. These values shall
then be summed to obtain a 2,3,7,8-TCDD toxicity equivalency quotient.
Toxicity equivalency quotients for dioxin-like polychlorinated biphenyls
shall then be added to those for other dioxin-like compounds as specified
in subsection (e) of this section to yield a total toxicity equivalency
quotient concentration. This total toxicity equivalency [quotients] quotient concentration shall then be compared with the critical
PCL for TCDD, 2,3,7,8-(dioxin). When addressing dioxin-like polychlorinated
biphenyls in this manner, the person shall subtract the concentration
of dioxin-like polychlorinated biphenyls from the total polychlorinated
biphenyls concentration to avoid overestimating dioxin-like polychlorinated
biphenyls by evaluating them twice.
[Figure: 30 TAC §350.76(d)(2)(B)]
(3) The executive director may determine that a change in a toxicity equivalency factor has been of such magnitude that the calculated toxicity equivalency quotient would not be representative of the actual toxicity of the dioxin-like polychlorinated biphenyl mixture and not protective of human health and the environment. If the executive director makes such a determination, then the person must evaluate the adequacy of the response action. If the executive director determines that a change in a toxicity equivalency factor is of such magnitude that the calculated toxicity equivalency quotient would not be representative of the actual toxicity of the dioxin-like polychlorinated biphenyl mixture such that the proposed response action is no longer warranted to protect human health and the environment, then a response action based on the previous toxicity equivalency quotient shall no longer be required.
(4) [(3)] In evaluating inhalation
exposures under Tiers 2 or 3, the person shall convert the appropriate
slope factor to an inhalation unit risk factor, based on the following
equation: Inhalation Unit Risk Factor (risk per µg/m3)= oral slope factor x 20 m3/day divided by 70 kg x 10-3mg/µg.
(5) [(4)] In Tiers 2 and 3, and
only when applicable for a specific site, the person may set soil
PCLs based on the requirements of the Toxic Substances Control Act,
40 Code of Federal Regulations Parts 750 and 761, as amended. Sites
must comply fully with all applicable Toxic Substances Control Act,
as amended, requirements when establishing the soil PCL for polychlorinated
biphenyls in this manner.
(e) Polychlorinated Dibenzo-p-Dioxins and Dibenzofurans.
(1) In demonstrating attainment of the critical PCL
for TCDD, 2,3,7,8-(dioxin), the person shall determine the constituents
considered to be dioxins and furans from the list established by the
World Health Organization in 2005, or a more recent list of constituents
established by a scientifically valid source that has been reviewed
and approved by the executive director. The person shall apply
the toxicity equivalency factors established by the World Health
Organization in 2005, or more recent toxicity equivalency factors
established by a scientifically valid source that have been reviewed
and approved by the executive director [factor directorship
shown in the figure in subsection (d)(2)(B) of this section]
to the measured concentrations of the dioxins and furans in
accordance with the following procedures.
(A) When analytical data are only available for total dioxins/furans, the person shall assume that the mixture consists solely of 2,3,7,8-TCDD, and a toxicity equivalency factor value of 1.0 shall be applied to the measured concentration to yield the 2,3,7,8-TCDD toxicity equivalency quotient concentration for the sample.
(B) When homologue-specific analytical data are available
(e.g., tetrachlorodibenzodioxins), the person shall assume that each
homologue class is comprised solely of 2,3,7,8-substituted congeners,
and shall apply the toxicity equivalency factors established
by the World Health Organization in 2005, or more recent toxicity
equivalency factors established by a scientifically valid source that
have been reviewed and approved by the executive director, [specified
for the 2, 3, 7, 8-substituted congeners in the homologue class shall
be applied] to the measured concentrations for that homologue
class. If a homologue class has more than one toxicity equivalency
factor for different congeners, the highest toxicity equivalency factor
that has been reviewed and approved by the executive director shall
be used for that congener class. [A toxicity equivalency
factor value of 0.5 should be used for the pentachlorodibenzofuran
homologue class.] The toxicity equivalency quotient concentrations
for each homologue class shall be summed to obtain a total toxicity
equivalency quotient concentration for the sample.
(C) When congener-specific analytical data are available
(e.g., 1, 2, 3, 4, 7, 8-hexachlorodibenzofuran), the person shall determine
the constituents considered to be dioxins and furans from the list
established by the World Health Organization in 2005, or a more recent
list of constituents established by a scientifically valid source
that has been reviewed and approved by the executive director. The
person shall apply the toxicity equivalency factors established
by the World Health Organization in 2005, or more recent toxicity
equivalency factors established by a scientifically valid source that
have been reviewed and approved by the executive director [factor
] for the 2, 3, 7, 8-substituted congeners, to the measured
concentrations. The toxicity equivalency quotient concentrations for
each 2, 3, 7, 8-substituted congener shall then be summed to obtain
a total toxicity equivalency quotient concentration for the sample.
(D) The executive director may determine that a change in a toxicity equivalency factor has been of such magnitude that the calculated toxicity equivalency quotient would not be representative of the actual toxicity of the dioxin and furan mixture and not protective of human health and the environment. If the executive director makes such a determination, the person must evaluate the adequacy of the response action. If the executive director determines that a change in a toxicity equivalency factor is of such magnitude that the calculated toxicity equivalency quotient would not be representative of the actual toxicity of the dioxin and furan mixture such that the proposed response action is no longer warranted to protect human health and the environment, then a response action based on the previous toxicity equivalency quotient shall no longer be required.
(2) The person shall then compare the total toxicity equivalency quotient concentration established in paragraph (1) of this subsection to the critical PCL for TCDD, 2, 3, 7, 8-(dioxins).
(3) The person shall calculate [The] the critical soil PCLs [PCL] for residential and commercial/industrial properties for a 2,3,7,8-TCDD
toxicity equivalency quotient according to the equations and rule
provisions provided in §350.75 of this title (relating to Tiered
Human Health Protective Concentration Level Evaluation). [for
all three tiers is 1 part per billion (ppb) and for commercial/industrial
properties for all three tiers is 5 ppb.]
(f) Polycyclic Aromatic Hydrocarbons.
(1) In calculating residential and commercial/industrial PCLs for all tiers, the person shall evaluate the following seven polycyclic aromatic hydrocarbons as carcinogens:
(A) benzo {a} anthracene;
(B) benzo {b} fluoranthene;
(C) benzo {k} fluoranthene;
(D) benzo {a} pyrene (B {a} P);
(E) chrysene;
(F) dibenzo {a, h} anthracene; and
(G) indeno {1, 2, 3-c, d} pyrene.
(2) The person shall use the relative potency factors outlined in the following figure to estimate cancer slope factors and unit risk estimates for each of the polycyclic aromatic hydrocarbons identified in paragraph (1) of this subsection for all exposure pathways (e.g., the soil ingestion, vegetable ingestion, inhalation, dermal contact with soil, and groundwater ingestion (in the absence of a primary MCL) exposure pathways):
Figure: 30 TAC §350.76(f)(2) (No change.)
(3) The cancer slope factors and inhalation unit risk factors for the seven carcinogenic polycyclic aromatic hydrocarbons, shall be calculated according to the equations set forth in the following figure:
Figure: 30 TAC §350.76(f)(3) (No change.)
(4) The person shall not apply the relative potency factor for any pathways when evaluating noncarcinogenic endpoints.
(5) For class 1 or 2 groundwater, the person shall establish PCLs according to the procedures in subparagraphs (A) and (B) of this paragraph.
(A) In evaluating residential and commercial/industrial exposures to class 1 and 2 groundwater for all tiers, the person shall use the most currently available primary MCL for benzo{a}pyrene as GWGWIng for benzo{a}pyrene.
(B) In establishing GWGWIng for class 1 and 2 groundwater for the six remaining carcinogenic polycyclic aromatic hydrocarbons, the person shall use the higher of the calculated GWRBELIng or the primary MCL for B{a}P as GWGWIng for that specific polycyclic aromatic hydrocarbon. In the event that primary MCLs for the other carcinogenic polycyclic aromatic hydrocarbons become available, those MCLs would serve as GWGWIng for these compounds.
(g) Total Petroleum Hydrocarbons.
(1) The person shall follow the methodology prescribed by this subsection to establish PCLs for total petroleum hydrocarbons, unless the executive director approves the use of an alternate method.
(2) In order to establish PCLs for total petroleum hydrocarbons, the person shall establish PCLs for each of the aliphatic and aromatic hydrocarbon fractions listed in the following figure (e.g., aliphatic >C6 -C8) for the mandatory and complete or reasonably anticipated to be completed exposure pathways as required in §350.71(c) of this title (relating to General Requirements):
Figure: 30 TAC §350.76(g)(2) (No change.)
(3) The person shall use the specific toxicity factors for the specific surrogates as shown in the figure in paragraph (2) of this subsection for a hydrocarbon fraction. If a reference concentration is not available, then the person shall not be required to comply with §350.73(c) of this title (relating to Determination and Use of Human Toxicity Factors and Chemical Properties). The PCLs established under this subsection shall be based on noncarcinogenic effects.
(4) The person shall ensure that the PCLs established for each hydrocarbon fraction comply with the hazard quotient criteria as set forth in §350.72 of this title (relating to Carcinogenic Risk Levels and Hazard Indices for Human Health Exposure Pathways).
(5) The person shall ensure that the PCLs established for the total petroleum hydrocarbons comply with the hazard index criteria as set forth in §350.72 of this title considering only the hydrocarbon fractions as shown in the figure in paragraph (2) of this subsection. The person shall follow the methodology prescribed in §350.72(d) of this title to adjust the hydrocarbon fraction PCLs to meet the hazard index criteria for the total petroleum hydrocarbons.
(6) The person shall use an analytical method approved by the executive director to determine the concentration of the hydrocarbon fractions at the affected property.
(7) When the bulk total petroleum hydrocarbons composition can be assumed to be relatively consistent based on process knowledge, the person may establish mixture-specific (e.g., gasoline, diesel, transformer mineral oil, or other petroleum product) PCLs based on property-specific mixture compositions or mixture compositions considered to be representative of the mixture. The person shall comply with the other provisions of this subsection in the development of the mixture-specific PCLs, but the person shall be allowed to determine compliance with the mixture-specific total petroleum hydrocarbons PCL with a bulk total petroleum hydrocarbons analytical method acceptable to the executive director in lieu of analysis of the concentration of each hydrocarbon fraction.
(8) The PCLs established for each individual aliphatic and aromatic hydrocarbon fraction used to establish the mixture specific PCLs shall not exceed a hazard quotient of 1 and the mixture-specific PCL shall not exceed a hazard index of 10.
The agency certifies that legal counsel has reviewed the proposal and found it to be within the state agency's legal authority to adopt.
Filed with the Office of the Secretary of State on August 16, 2024.
TRD-202403776
Charmaine Backens
Deputy Director, Environmental Law Division
Texas Commission on Environmental Quality
Earliest possible date of adoption: September 29, 2024
For further information, please call: (512) 239-0634