Document 5k14Ozn73mE9Eno9XmvND4OLz

Sources of Emission - Emission of asbestos from friction materials results from normal day-to-day usage. An idee of the scope of this source can be gained from the estimation that the average automobile wears out 3 to 4 sets of brake linings, and '* 1 to 2 sets of clutch facings during its lifetime and that commercial public transport vehicles wear out many more sets. Data concerning motor vehicle brake linings for the whole of the United States are given in the followings Vehicle miles during 1968 Mileage life of brake linings Brake lining sets on new vehicles Pounds of asbestos per set of brake linings 1,010,000,000,000 . 27,500 10,718,000 3 Tests performed -on brake linings have indicated that under conditions of. normal usage, considerable alteration of the asbestos occurs. It is reported that. most, of-the dust, collected from hrake drums appears non-fibrous and is similar in appearance to thermally degraded -asbestos. The suggestion is that high temperatures at the brake lining/drum contact points actually reach degradation levels. Tests cn brake linings, brake discs and clutches have demonstrated that the quantity of fiber emitted is some function-- of the severity of* the braking conditions (see Teble 3)'. Howevec, -even at -the level-of TjC, Tfhe "total, emissions must be considerable when the total tonnage in use is considered. Further, the emissions are likely to occur at places of high density population and restricted ventilation. That is, in busy main streets o'f towns surrounded by large buildings. The effect of different braking conditions and' different types of friction materials on asbestos emissions is the subject of a study being sponsored by the Environmental Protection Acency. Other studies are being conducted in California and some work on .roadsides has been done at Mt. Sinai, New York. The E?A study will establish the extent and nature of the asbestos MT RESEARCH J NSTITUTE