# NAS/NRC (1969) — "Guidelines for Estimating Toxicologically Insignificant Levels of Chemicals in Food"

**The institutional keystone of Strand I — the National Academy of Sciences recommending Frawley's proposal,
number and all, within a year of the FDA conference that called it "sheer nonsense."** Title borrows Frawley's
exact phrase; the report cites his 1967 paper; and the drafting Task Force *included Frawley himself.*

**Citation.** National Research Council, Food Protection Committee, *Guidelines for Estimating Toxicologically
Insignificant Levels of Chemicals in Food* (Washington, DC: National Academy of Sciences / National Academies
Press, 1969), 11 pp. DOI **10.17226/20376**. **Local primary:** `papers/1969 - Guidelines…Insignificant
Levels…pdf`; OCR `papers/nas1969.txt`. Reprinted as the Appendix to *Evaluating the Safety of Food Chemicals*
(NAS-NRC 1970). All quotes verbatim from the local OCR (page numbers from the monograph).

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## Who wrote it (Preface, p. ii)
> "This statement was developed for the Food Protection Committee by a special task force… The Task Force
> comprised: **H.F. Smyth, Jr., Chairman; J.M. Coon; J.P. Frawley; R.L. Hall; B.L. Oser; A.T. Schramm; and
> J.A. Zapp.**" (Food Protection Committee chaired by **William J. Darby**.)

*Nuance for the dossier:* Frawley's **12 July 1968** letter (UCSF Darby Papers `yhgd0228`) is recorded as
declining an *active drafting* part — yet the printed Preface still lists him on the Task Force. Both facts stand.

## Built on the previous essay's number (Introduction, p. 1)
> "the safe level is frequently expressed as **1/100 of the experimentally determined 'no-adverse-effect
> level.'** This ratio, 1:100, provides a conservative estimate of the safety factor…"

→ then proposes "guidelines for quantitatively defining levels of chemicals in food that can be administratively
considered as **toxicologically insignificant**." (The 1958 Committee had coined the phrase but left it
undefined; this 1969 statement supplies the numbers.)

## The operative recommendation (pp. 5–6) — Frawley's 0.1 ppm, by name
**A. Chemicals in commercial production** (≥5 yr, no hazard evidence, not a heavy metal, not used for biological
activity):
> "it is consistent with sound toxicological judgment to conclude that **a level of 0.1 ppm of the chemical in
> the diet of man is toxicologically insignificant.**"

**B. Pesticide degradation products** — below 0.1 ppm "insignificant and undeserving of laboratory investigation."

**C. Organic chemicals lacking data but meeting four structural criteria** (known structure/purity; structurally
simple; handled by known metabolic pathways; member of a low-toxicity group):
> "it may be presumed to be **toxicologically insignificant at a level of 1.0 ppm or less** in the human diet."

**D. Less closely related structures** — estimate by analogy: "**1/10**" (or, where safe levels differ, "**1/20**")
"of the estimated safe level."

*(Correction to the dossier's earlier [secondary] reading: 0.1 ppm — Frawley's exact figure — is the headline
threshold for commercial chemicals; the 1.0 ppm value applies only to the looser structural-analogy tier C.)*

## The rationale — Frawley's grievance, in the Academy's voice (Conclusion, p. 7)
> "The **principle of toxicological insignificance is a valid concept** for separating potential health hazards
> from predictably safe applications. Guidelines on toxicological insignificance are needed **to eliminate
> wasteful diversion of scientific resources** in university, industry, and government laboratories."

Compare Frawley, FDCLJ 23(5):260 (1968): the testing "was all wasted… the benefit to the consumer was zero."

## It cites Frawley
The report's footnotes cite **J.P. Frawley, "Scientific Evidence and Common Sense as a Basis for Food-Packaging
Regulations"** (the 1967 *Food Cosmet. Toxicol.* paper) and the 1958 *Food Drug Cosmetic Law Journal* note
"Insignificant Levels of Chemical Additives in Foods."