Document 85Dr297Ea4Z2aKzbEkLRDr6rB

-3- i v_ / III e-iv occasions B and C in Table 3. The counts are expressed in terns of particles with diameter greater than Ip. and of fibres (i.e. particles with aspect ratio greater than 3:1 and length greater than 5p). LABORATORY INVESTIGATION In view of the relatively few fibres present in the air samples, a laboratory investigation was undertaken, comprising microscopic examination of samples from brake lining material (which was filed to produce dust) and brake drum dust (collected by spatula from brake drums immediately prior to blowing-out). The samples were sieved through 200-mesh screens and then examined before and after incineration. The results are shown as fibre proportions in Table 4. Samples of material collected from the brake drums of (a) an Anglia van, (b) a Mark II Cortina, and (c) an Anglia car were analysed by Dr S Holmes of Messrs.Turner Brothers Asbestos Co.Ltd., and his findings are shown in Table 5. DISCUSSION OF RESULTS (a) Standards of dustiness In June 1968, the British Occupational Hygiene Society published a Hygiene Standard for Chrysotile Asbestos Dust, which suggested that in order to reduoe the risk of contracting asbestosis to 1# of those with a lifetime's exposure to the dust, the accumulated exposure should not exceed 100 fibre-years/cc, i.e. 2 fibres/oo for SO years, or 4 fibres/cc for 25 years. In this standard, fibres are ... defined 8006 1205 HFM - 005791