The record
The FDA proposed in the Federal Register on September 28, 1973 that talc failing to meet specifications be deemed adulterated, using a polarizing-microscope method intended to ensure purity at least 99.9% free of amphibole asbestos fibers and at least 99.99% free of chrysotile asbestos fibers.
Claim scope
The exact numeric detection standard the FDA proposed, and its date. PMID 31095409's endnote 25 identifies the primary document as: Department of Health, Education, and Welfare, FDA, “Asbestos Particles in Food and Drugs, Notice of Proposed Rulemaking,” Federal Register 38 (September 28, 1973): 27079-80.
What this source does not establish
I did NOT independently retrieve 38 Fed. Reg. 27079 (Sept. 28, 1973) in this session. The volume/page/date come from the peer-reviewed paper's endnote. The paper is a citable primary source under house rules by virtue of being PubMed-indexed, but the Federal Register citation itself is second-hand here and should be verified against govinfo before the page asserts it as an FR cite.
Limitations
MANDATORY DISCLOSURE whenever this paper is cited: its own conflict-of-interest statement reads “David Rosner and Gerald Markowitz wrote a 2017 Report to the Court in a legal case that formed the original basis of this article. They received funding from plaintiffs' law firms for research and writing.” Its documentary base is litigation-discovery material hosted on toxicdocs.org. It is peer-reviewed and PubMed-indexed, which satisfies house citation standards, but it is not a neutral archival study. Verify 38 Fed. Reg. 27079 directly on govinfo before citing it as a Federal Register document rather than as a quotation from PMID 31095409.
Source
Pmid — 31095409