American Conference of Governmental Industrial Hygienists, Threshold Limit Value Booklets Collected as Johns-Manville Trial Exhibits (1952–1981)

A 949-page compilation of the yearly lists of threshold limit values adopted by the American Conference of Governmental Industrial Hygienists (ACGIH), from 1952 to 1981, with the years 1958, 1972 and 1980 missing. Several are stamped as Johns-Manville Sales Corporation defense exhibits in "Civil No. 55624." The early lists are a few pages each; the later booklets add notices of intended changes, appendices on carcinogens and limits for physical agents such as noise and heat. Asbestos is listed from the start: in 1952 at 5 million particles per cubic foot of air, and in the 1981 booklet among the "Human Carcinogens" with separate fiber limits for amosite (0.5 fiber per cubic centimeter), chrysotile (2), crocidolite (0.2) and other forms (2).

What it shows

Read together, the booklets trace how the published limit for asbestos changed: a dust-count figure unchanged from the 1940s into the late 1960s, then fiber counts, and by 1981 a listing as a human carcinogen with a lower limit for the amphiboles. From at least 1961 the booklets repeat that the limits "should not be regarded as fine lines between safe and dangerous concentrations." The Library has two of these lists as separate pages, the 1947 limits and the 1970 booklet, and J-M's own reprint of the missing 1958 list in its Manual of Standard Practices.

About this copy

The booklets are not in date order in the file: 1961, 1964 and most of the years from 1967 to 1979 come first, followed by 1963, 1952 to 1960, 1962, 1965, 1978, 1981 and 1966. The exhibit stamps read "Defendant JMSC Exhibit," with numbers such as 13606 (1952) and 13631 (1978). Because the ACGIH lists are copyrighted, this page gives a summary only.