; and (B) the association has been observed in studies in which chance, bias, and confounding can be ruled out with reasonable confidence. (2) The term toxic substance has the meaning given that term in section 1710(e)(1)(G)(iv) of this title. . (b) Clerical amendment The table of sections at the beginning of chapter 11 of such title is amended by inserting after the item relating to section 1118 the following new item: 1119. Presumptions of service connection for diseases associated with exposure to certain toxic substances. . (c) Conforming amendment Section 1113 of such title is amended by striking or 1118 each place it appears and inserting 1118, or 1119 . II Research and review regarding exposure to toxic substances 201. Establishment of Toxic Exposure Review Commission (a) In general Subchapter III of chapter 5 of title 38, United States Code, is amended by adding at the end the following new section: 547. Toxic Exposure Review Commission (a) Establishment The Secretary shall establish an independent commission to be known as the Toxic Exposure Review Commission (in this section referred to as the Commission ). (b) Purpose The Commission shall— (1) advise the Secretary on questions relating to exposure to toxic substances that require scientific research