USPHS Membrane Filter Method for Evaluating Airborne Asbestos Fibers (Draft) (1973)

This document is not a study of people. It is a technical method describing how the U.S. Public Health Service sampled and counted airborne asbestos fibers; the text supplied is a 1973 draft. A battery-powered pump worn by the worker drew air through a 37 mm membrane filter at about 2 liters per minute. A filter wedge was then made transparent and examined by phase-contrast microscopy. Only fibers longer than 5 micrometers and at least three times as long as wide were counted. Where other fibrous materials might be present, other analytical methods were needed if concentrations appeared high and it was doubtful that they reflected asbestos exposure. Citing Holland and Conway, the document reported standard deviations of 16.2% for precision and 21.4% for accuracy of a 100-fiber count, on filters without abundant fine fibers. A report coauthored by Leidel estimated the standard deviation at about 15.2% for counts of about 100 fibers, with 95% confidence limits of plus or minus 30.4%. The authors stated that uniform procedures were needed for reproducible results.

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From J-M's medical library

This copy comes from the Johns-Manville medical library. J-M listed it in its medical library index as no. 004890.