American Conference of Governmental Industrial Hygienists, Threshold Limit Values for 1970, with a Proposed Asbestos Limit of 5 Fibers (1970)

The American Conference of Governmental Industrial Hygienists' booklet "Threshold Limit Values of Airborne Contaminants and Intended Changes Adopted by ACGIH for 1970." In the adopted list of mineral dusts, asbestos (all types) stays at 5 million particles per cubic foot of air, marked to see the notice of intended changes. That notice proposes a new asbestos limit of 5 fibers per milliliter longer than 5 microns, counted by the membrane filter method, with concentrations above 5 but not over 10 fibers allowed for 15-minute periods up to five times a day.

What it shows

The preface describes threshold limits as levels at which "nearly all workers may be repeatedly exposed day after day without adverse effect," but says they "should not be used as fine lines between safe and dangerous concentrations." Under the conference's rules, a proposed change was a trial limit for at least two years while the old limit stayed in effect. J-M's Environmental Control Subcommittee had expected the 5-fiber figure in January 1970 and recommended adopting it as the company's respirator level. The particle count limit for asbestos had stood since 1947. See Threshold Limit Value (TLV) and Fibers per Cubic Centimeter (f-cc).

In Johns-Manville's chronology

Johns-Manville's own chronology of what the company knew describes this document as follows:

ACGIH adopts 12 f/cc Standard.

Editor's note: J-M's description says the ACGIH adopted a 12 f/cc standard. The 1970 booklet keeps the adopted asbestos limit at 5 million particles per cubic foot and gives notice of an intended change to 5 fibers per milliliter; 12 f/cc does not appear.

Related documents

• E. M. Fenner's Report of the Environmental Control Subcommittee Meeting on Electron Microscope Counts and a New Fiber Limit (1970)