26.11.16.04

.04 Scientific Review and Amendment of Various Levels and Lists.

A. Ongoing Scientific Review.

(1) 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.

(2) 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.

B. Interim Levels Set During Permit Review.

(1) Requesting Approval.

(a) 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.

(b) 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.

(2) Scientific and Public Review.

(a) 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.

(b) 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.

(c) 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.

(3) 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.

C. Petitions.

(1) 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.

(2) 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.

D. Approval Criteria.

(1) 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.

(2) 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.

(3) Insignificant Risk Concentration.

(a) 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.

(b) 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:

(i) Whether it is appropriate to use a most likely estimate of risk rather than a 95 percent upper confidence limit in developing an IRC;

(ii) Whether the IRC should be based on the highest unit risk factor developed from the most sensitive species; and

(iii) Other pertinent information.