The terms defined in COMAR 26.11.15 also apply throughout this chapter. Screening Analysis. Carcinogenic Effects. A person may demonstrate that emissions of a Class I TAP from a premises will not unreasonably endanger human health because of potential carcinogenic effects by a screening analysis showing that total allowable emissions from the premises will not cause increases in ambient levels that exceed the risk-based screening level for the TAP. Other Toxic Effects. A person may demonstrate that emissions of a Class I or Class II TAP from a premises do not unreasonably endanger human health because of potential toxic effects other than cancer by a screening analysis showing that total allowable emissions from the premises will not cause increases in ambient levels that exceed applicable TLV-based, threshold-based, or special screening levels. If a special screening level has been adopted, a TLV-based or threshold-based screening level may not be used for that TAP. A threshold-based screening level may be used only if there is no TLV, no special screening level, and no acceptable ambient level for a TAP. For a screening analysis, a person may use the dispersion modeling procedures in Air Management Administration Technical Memorandum 86-02 (TM 86-02), “Ambient Air Quality Impact Screening Analysis for Toxic Air Pollutants”, which is incorporated by reference, or other, more rigorous dispersion modeling procedures as provided in §C(1)(a) of this regulation. If concentrations predicted using TM 86-02 exceed applicable screening levels, more rigorous modeling techniques should be used in either a screening analysis or a more detailed analysis. Instead of using dispersion modeling, a person may conduct a screening analysis by showing that total allowable emissions of a TAP will be less than the most stringent applicable emission rate listed in the tables in this section. Multiple screening levels with different averaging periods may apply to a TAP. These tables may not be used with screening levels having averaging periods other than those listed in the tables. Emission rates labeled "10 Meter Stacks, No Downwash" may be used only if all emissions of the TAP are discharged from a stack or stacks at least 32.8 feet (10 meters) high under conditions preventing downwash. (TM 86-02 describes conditions causing downwash.) Except as provided in COMAR 26.11.15.06, these emission rates apply to the total allowable emissions from a premises. Second Tier Analysis. Carcinogenic Effects. A person may demonstrate that emissions of a Class I TAP from a premises will not unreasonably endanger human health because of potential carcinogenic effects by a second tier analysis showing that total allowable emissions from the premises will not cause increases in ambient levels that exceed an insignificant risk concentration (IRC) for the TAP, or by an approvable request for a special permit under Regulation .05 of this chapter. A second tier analysis would be appropriate if new information is available concerning carcinogenic dose-response relationships. A special permit should be requested if a person wishes to more accurately characterize exposure, to justify approval of risks greater than 1 × 10 superscript -5, or to otherwise modify assumptions to more accurately represent risks. Other Toxic Effects. A person may demonstrate that emissions of a Class I or Class II TAP from a premises will not unreasonably endanger human health because of toxic effects other than cancer by a second tier analysis showing that total allowable emissions from the premises will not contribute to concentrations exceeding the applicable acceptable ambient level (AAL) for the TAP. General Procedures for Compliance Demonstrations. Dispersion Modeling Procedures Required. A person using dispersion modeling to demonstrate compliance with COMAR 26.11.15.06 shall use procedures approved by the Department. The Department will approve dispersion modeling procedures that are consistent with the U.S. Environmental Protection Agency's guidance on dispersion modeling. For second tier analysis showing that total allowable emissions from a premises will not contribute to concentrations exceeding an acceptable ambient level, a person shall use available emissions data to model ambient impacts caused by other sources of the Class II TAP within 5 kilometers (3.1 miles) of the premises. The Department will assist persons modeling ambient concentrations for comparison to AALs by providing available information on emissions from other sources or on background levels. The Department may provide additional assistance as resources permit. Averaging Times. To demonstrate compliance with this chapter, a person shall use the averaging time consistent with the applicable screening level, AAL, or IRC unless the Department requires the use of a shorter averaging time. The Department will require that a shorter averaging time be used if it determines that the operating procedures of the source may cause a high concentration of a TAP for a short period and that consideration of potential health effects due to peak exposures may be warranted for the TAP. Screening Levels for Toxic Effects Other than Cancer. TLV-Based Screening Levels. TLV-based screening levels shall be determined as follows: If a toxic air pollutant (TAP) has a threshold limit value-time weighted average (TLV-TWA), divide the TLV-TWA by 100 to calculate an 8-hour time-weighted average screening level; If a TAP has a ceiling TLV (TLV-C) or a short term exposure limit (TLV-STEL), divide the TLV-C or TLV-STEL by 100 to calculate a 1-hour time-weighted average screening level; If a TAP has both a TLV-TWA and TLV-STEL, calculate both 8-hour and 1-hour time-weighted average screening levels as described above. Threshold-Based Screening Levels. If a TAP has neither a TLV, nor a special screening level, nor an acceptable ambient level, then a person may use one of the following formulae, given in order of preference, to develop an 8-hour threshold-based screening level in milligrams/cubic meter. In these formulae, a NOEL is a No Observed Effect Level, and an LC50 or LD50 is a concentration or dose, respectively, expected to cause the death of 50 percent of an entire defined experimental animal population. The following are formulae to be used: Divide a 90-day inhalation NOEL in milligrams/cubic meter for rats, mice, or rabbits by 100; Multiply a 90-day oral NOEL in milligrams/kilograms for rats by 2.7 × 10-3rd), for mice by 9.0 × 10-4th), or for rabbits by 1.3 × 10-3rd); Divide a 7-day inhalation NOEL in milligrams/cubic meter for rats, mice, or rabbits by 700; Multiply a 7-day oral NOEL in milligrams/kilograms for rats by 3.8 × 10-4th), for mice by 1.3 × 10-4th), or for rabbits by 1.9 × 10-4th); Divide an LC50 in milligrams/cubic meter for rats, mice, or rabbits by 10,000; or Multiply an oral LD50 in milligrams/kilograms for rats by 4.1 × 10-5th), for mice by 1.4 × 10-5th), or for rabbits by 2.0 × 10-5th). When two or more animal test data acceptable to the Department are available for use under a subparagraph in §A(2)(a) of this regulation, the screening level shall be calculated using the data producing the lowest screening level. The above formulae are not the only ones appropriate for developing screening levels. These are acceptable formulae to the Department at this time. Other formulae may be used to calculate special screening levels. Special Screening Level. If a special screening level for a toxic air pollutant is listed in Regulation .09 of this chapter, the special screening level or levels in Regulation .09 of this chapter replace applicable TLV-based or threshold-based screening levels for that toxic air pollutant. General. The Department may adopt special screening levels for TAPs that ACGIH has identified as carcinogens. A person should contact the Air Management Administration before using a TLV-based screening level for any of these TAPs. The Department will provide information on TLV-based screening levels upon request. The Department will maintain a list of AALs under consideration pending their adoption into this chapter, and will make a list available upon request. Screening Level for Carcinogenic Effects. “Risk-based screening level” means the annual average concentration, in micrograms per cubic meter, that would increase a person's lifetime cancer risk by 1 in 100,000 (1 × 10-5th)) if the person were continuously exposed to the concentration for 70 years. The Department will calculate the risk-based screening level using: If available, a unit risk factor developed by the Cancer Assessment Group of the U.S. Environmental Protection Agency (termed a CAG unit risk factor); or If a CAG unit risk factor is not available, an upper bound unit risk factor developed in accordance with EPA's Risk Assessment Guidelines. The Department will maintain an up-to-date list of available risk-based screening levels and will provide information on these levels upon request. Ongoing Scientific Review. In order to use the best available scientific information, the Department will conduct an ongoing review of information concerning whether to add or delete toxic air pollutants under Regulations .06 and .07 of this chapter and concerning what screening levels or ambient concentrations should be used to review emissions of toxic air pollutants. In its ongoing review, the Department will consider scientific information developed by the U.S. Environmental Protection Agency, other states, or other scientific organizations. The Department will also consider scientific information provided by any person. In reviewing information about toxic air pollutants or requests to amend lists, screening levels, or ambient concentrations, the Department will request advice from the Governor's Science Advisory Council. Interim Levels Set During Permit Review. Requesting Approval. In order to demonstrate compliance with COMAR 26.11.15.06 when scientific evidence indicates a screening level adopted under this chapter should be revised, a person may request Departmental approval of an interim special screening level, interim AAL, or interim IRC for a TAP. The person shall submit written information on the health effects of the TAP, the levels at which health effects have occurred, and other supporting information requested by the Department. The Department may use an interim special screening level, interim AAL, or interim IRC, to establish allowable emissions of a TAP for a source until a special screening level, AAL, or IRC for the TAP has been adopted or amended under this chapter. Scientific and Public Review. In order to evaluate information concerning a proposed interim special screening level, an interim AAL, or interim IRC, the Department may convene a scientific review panel consisting of scientific experts from within or outside the Department. If the Department makes a determination to proceed with an interim special screening level, interim AAL, or interim IRC, it will notify the applicant. The applicant shall publish a notice of an opportunity for a public hearing on the interim special screening level, interim AAL, or interim IRC, using the procedures set forth at COMAR 26.11.02.12F, G for providing public notice and an opportunity for public hearing. If the Department is required or intends to provide an opportunity for a public hearing on a permit or approval for the source in question, the opportunity for a public hearing on the interim special screening level, interim AAL, or interim IRC, may be provided concurrently. Approval Criteria. The Department will approve an interim special screening level, interim AAL, or interim IRC, only if it meets the approval criteria listed under §D of this regulation. Petitions. Filing. In accordance with COMAR 26.01.03, any interested person may file a petition asking the Department to adopt or amend a special screening level, acceptable ambient level, or insignificant risk concentration for a TAP. The petitioner should submit information on the health effects expected to be caused by the TAP, the levels at which health effects occur, other information that supports adopting or changing a screening level, acceptable ambient level, or insignificant risk concentration. Scientific Review. In order to evaluate information submitted by a petitioner, the Department may convene a scientific review panel consisting of scientific experts from within or outside the Department. Approval Criteria. Special Screening Level. The Department will adopt a special screening level only if it determines that the level will not unreasonably endanger human health and provides a scientifically appropriate basis for screening analysis. In deciding whether to establish a special screening level for a TAP, the Department will consider the scientific basis for both the special screening level and any applicable TLV as well as other available information on the health effects of the TAP. Acceptable Ambient Level. The Department will adopt an AAL under this chapter only if the Department determines that concentrations at that level will provide a margin of safety to protect the public health from toxic effects of the TAP other than cancer. Insignificant Risk Concentration. The Department will adopt an IRC under this chapter only if the Department determines the IRC is calculated using procedures consistent with EPA's Risk Assessment Guidelines and is the annual average concentration, in micrograms per cubic meter, that would increase a person's lifetime cancer risk by not more than 1 in 100,000 (1 × 10-5th)) if the person were continuously exposed to the concentration for 70 years. In deciding whether to adopt an IRC, the Department will consider factors contributing to the uncertainty of the applicable upper bound unit risk factor, including: Whether it is appropriate to use a most likely estimate of risk rather than a 95 percent upper confidence limit in developing an IRC; Whether the IRC should be based on the highest unit risk factor developed from the most sensitive species; and Other pertinent information. Applicability. A person who cannot demonstrate that a premises discharging a Class I TAP complies with COMAR 26.11.15.06 using a risk-based screening level may submit a written request for the Department to establish allowable emissions for the premises in a special permit. The Department will issue a special permit to specify the maximum allowable emissions of any Class I TAP discharged from the premises. Except as provided by State Government Article, §10-404, Annotated Code of Maryland, a special permit expires 5 years from the date it is issued by the Department. Approval Criteria. The Department will approve a special permit only if it determines that emission controls represent at least T-BACT and emissions of toxic air pollutants will not unreasonably endanger human health. In making this determination, the Department will consider information submitted by the applicant, public comments, and other available and relevant information, including: The effectiveness, cost, feasibility, and timing of additional risk reductions, including consideration of process changes or relocation of the source; Estimated public health risks; Environmental and social consequences of granting or denying the permit; and Uncertainty in data or analysis. Application. Required Information. A person applying for a special permit shall submit the following information to the Department in addition to any other information required by COMAR 26.11.02: A demonstration that emission controls on installations at the premises that discharge the Class I TAP in question represent T-BACT; A description and assessment of the effectiveness, cost, and feasibility of potential methods for achieving additional risk reductions; An assessment of the increased risk of cancer caused by allowable emissions from the premises, determined using procedures consistent with EPA's Risk Assessment Guidelines and approved by the Department; A description of current or future populations that may be affected by the premises' emissions; An assessment of other environmental health stresses borne by the affected population; and Other information requested by the Department and pertinent to the Department's decision to grant or deny the special permit. Risk Assessment. The risk assessment submitted under §C(1)(c) of this regulation shall include: A discussion of overall uncertainty in data and analysis; and An estimate of the increase in individual risk from a continuous 70-year exposure to the highest annual average concentration off the property. The risk assessment submitted under §C(1)(c) of this regulation includes one or more alternative characterizations of risk, such as: The estimated increase in individual risk at the location of the most exposed individual; The estimated increase in individual risk from each year of exposure; The maximum number of cancers in the exposed population that would be expected due to operation of the premises; or Other risk estimates more accurately characterizing exposure from emissions from the premises. The risk assessment submitted under §C(1)(c) of this regulation may use alternative unit risk factors, alternative dispersion modeling techniques, or other alternative risk assessment procedures approved by the Department and consistent with EPA's Risk Assessment Guidelines. Scientific Review and Public Hearing. Optional Scientific Review Panel. If the Department makes a preliminary decision to consider an application for a special permit, it may convene a scientific review panel consisting of experts from within or outside the Department to evaluate information submitted as part of the application. Public Notice and Opportunity for Public Hearing. Except as provided in §D(2)(b) of this regulation, if the Department makes a determination to proceed with the application, it will follow the procedures under COMAR 26.11.02.12F and G for providing public notice and an opportunity for public hearing. Unless public notice and an opportunity for public hearing are required by Environment Article, §2-204, Annotated Code of Maryland, or by other State or federal regulations, the Department will waive the requirement for public notice and opportunity for public hearing under this section if the Department determines that all of the following conditions are met: T-BACT is being used to reduce emissions of the TAP from the premises; Emissions from the premises will not unreasonably endanger human health; Emissions from the premises will cause increases in ambient levels of the TAP that are greater than the risk-based screening level for the TAP only on property that is zoned and used for industrial purposes; and Increases in ambient levels of the TAP on property that is zoned and used for industrial purposes will increase a person's lifetime cancer risk by not more than 1 in 100,000 (1 X 10 superscript -5) using assumptions that are consistent with EPA's Risk Assessment Guidelines and that the Department concludes accurately characterize worst plausible exposure and risk in those areas. For areas zoned and used for industrial purposes, the Department will assume a person is continuously exposed to the TAP for 40 hours a week for 40 years unless the Department concludes that other exposure assumptions would more accurately characterize worst plausible exposures in a particular instance. Known Human Carcinogens. Probable Human Carcinogens. Potential Human Carcinogens. Class I Toxic Air Pollutants Requiring Ambient Impact Analysis by Existing Sources. Class II Toxic Air Pollutants Requiring Emission Estimates or Ambient Impact Analysis by Existing Sources. The substances listed in §B of this regulation are examples of nuisance particulates and simple asphyxiants. List of Substances. Special Screening Levels (SSL) and Acceptable Ambient Levels (AAL). Environment Article, §§1-101, 1-404, 2-101—2-103, 2-301—2-303, 10-102, and 10-103, Annotated Code of Maryland Effective date: Chapter revised and recodified from COMAR 26.11.15.07B—.14 to COMAR 26.11.16 effective October 5, 1998 (25:20 Md. R. 1533)