Airborne asbestos exposure during light aircraft brake replacement.

Asbestos containing materials are a component of many vehicle brake systems, including those found in some light aircraft. To characterize the asbestos exposure that results from the installation and maintenance of these components, an aircraft fitted with asbestos containing brake pads had brake changes performed while both area and personal air samples were taken. The brake changing process took place in a closed, unventilated aircraft hanger and all operations were performed according to the manufacturer's recommended procedure. Personal air samples did not detect any measurable amount of asbestos fibers during the brake changing or subsequent cleanup procedures. Analysis of personal samples (n=9) using phase contrast microscopy indicated airborne fiber concentrations at or below 0.003f/ml as 8-h time weighted averages (TWAs) and less than 0.069f/ml averaged over 28-30min sampling periods. Airborne chrysotile fibers were detected by two area air samples with fiber concentrations remaining at or below 0.0013f/ml over an 8-h TWA. These results indicate that normal brake changing work practices on aircraft with asbestos containing brake pads does not produce a harmful level of asbestos exposure for aircraft mechanics.