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August 1, 1994: EPA Specifies Methodology for Testing Asbestos in Air

1994-08-01

The EPA issues an advisory specifying the methodology that should be used to test for asbestos in air samples under the Asbestos Hazard Emergency Response Act (AHERA). The guidance recommends that transmission electron microscopy (TEM) be used rather than the older, less sensitive polarized light microscopy (PLM) method, which cannot detect ultrafine fibers below .25 micrometers. The advisory also states that when a PLM test is negative for asbestos, the sample should be retested using the TEM method. [Environmental Protection Agency, 8/1/1994]