Document ykMLz5rB9NB93M6v4bjMe9e16

l. ESTIMATION OF BRAZE LIKING ASBESTOS DILUTIOH 9 URBAN A2MDSXBERE Sic concentration of asbestos fiber from the brake lining war debris is assumed to be the sane as vas found In the "normal usage" dynamometer test and to be dispersed and have the aaae residence times as the lead emitted from the engine. Assume an average mileage of 1$ HPG from ears vhich emit 75$ of the lead to the atmosphere. Wien gasoline averaged 2.52 grams of lead per gallon, the typical lead concentrations in urban atmospheres vere abort 2yftg/m9 (JAPCA, Sep. I969, lg, p. 68k). Typical U. S. cars vear 202 grams of lining per year and drive 10,000 miles per year. The "normal use" dynamometer tests provided asbestos fiber amounting to 0.0023$ (2.3 x 10'5) of the brake lining worn. Allowing a factor of ten to provide an upper bound in this determina tion, the asbestos concentration in urban atmospheres from brake vear should be less than C1100((22..33XX1100*=))vu>10i02008 al";)Lr?4>fa5a^rb/tt't(iijS7M5)PO),] 0.07 a* Urban atmospheres vary in asbestos fiber concentration from city to city, vithin a city, and from or.e tine to another. This variation does not correlate vith expected automobile brake usage. The concentration has been reported to reach 100 jj (2). Thus it appears that the vear of brake lining produces, at moat, a small fraction of the asbestos fiber in urban air. This is not aurprising when one considers that brake lining veer involves only 1.*' of U. 8. asbestos usage and that brake usage converts over 99.95$ of this to non-fibrous dust. 9000 0105