((a)) ** .—** Not later than 160 days after the date on which the Secretary receives a recommendation to establish or modify a presumption of service connection under —

((1)) if the Secretary determines, in the discretion of the Secretary, that the presumption, or modification, is warranted, the Secretary shall—

((A)) commence issuing regulations in accordance with the provisions of subchapter II of chapter 5 of title 5 (commonly referred to as the Administrative Procedures Act) setting forth the presumption or commence revising regulations to carry out such modification; and

((B)) include in such regulations any time frame during which a health effect must become manifest; or

((2)) if the Secretary determines, in the discretion of the Secretary, that the presumption, or modification, is not warranted, the Secretary shall publish in the Federal Register a notice of the determination, including the reasons supporting the determination.

((b)) ** .—**

((1))

((A)) The Secretary may—

((i)) issue a regulation to remove an illness from a presumption of service connection previously established pursuant to a regulation issued under subsection (a); and

((ii)) issue a regulation to remove a presumption of service connection established pursuant to title IV of the Sergeant First Class Heath Robinson Honoring our Promise to Address Comprehensive Toxics Act of 2022 if the Secretary concludes that evidence suggests the lack of a positive association between the disease and the toxic exposure.

((B)) Under subparagraph (A)(ii), the Secretary shall not consider the lack of evidence as sufficient to support a decision for removal of a presumption.

((2)) Whenever an illness is removed from regulations pursuant to paragraph (1), or the periods and locations of exposure covered by a presumption of service connection are modified under subsection (a)—

((A)) a veteran who was awarded compensation under chapter 11 of this title for such illness on the basis of the presumption provided under such regulations before the effective date of the removal or modification shall continue to be entitled to receive compensation on that basis;

((B)) a survivor of a veteran who was awarded dependency and indemnity compensation under chapter 13 of this title for the death of a veteran resulting from such illness on the basis of such presumption shall continue to be entitled to receive dependency and indemnity compensation on such basis; and

((C)) no veteran or survivor covered under subparagraph (A) or (B) shall have their compensation reduced solely because of the removal of an illness pursuant to paragraph (1).