Asbestos exposure of brake repair workers in the United States

Measurements were made by optical microscopy of asbestos levels during brake repair and maintenance work in New York City. Both time weighted averages and peak levels showed significant asbestos exposure. Over four fifths of the total number of chrysotile fibers in brake drum dust were below 0.4μ in length and not visible by optical microscopy. Fiber concentrations for personal and background samples during blowing dust from drum brakes on automobiles show extensive variation, but the values at 3-5 feet are by far the highest, with a mean of 15.9 fibers/ml. For fiber concentrations of personal and background samples during renewing used linings by grinding truck brakes, the mean concentration for the personal sampler was 3.8 fibers/ml. Fiber concentrations for personal and background samples during beveling new linings for trucks show mean concentrations of 37.5 fibers/ml. Ten samples of bulk brake drum dust were analyzed to determine the percentage of short fibrils, defined as 250-500 A x 750-3750 A. A mean of 83% of all chrysotile fibers were in this category. Over one quarter of a group of experienced vehicular maintenance workers examined had evidence of x ray abnormalities consistent with asbestosis; one quarter also had restrictive pulmonary function test findings. While this preliminary study was limited in scope and was restricted to volunteers, and its results cannot therefore readily be ganeralized to all brake maintenance workers in the United States, the findings suggest that asbestos disease will be present among such workers and that appropriate control measures should be urgently instituted.