Document J34wrvGDkeZm24yO1kzaE217e

considered, preliminary findings. The similarity of the figures reported by the various worXers does suggest that at least an order of magnitude has been established. Consider now the estimate of 3.2 ng/m3 calculated pre viously as the contribution from asbestos brake linings. Firstly, it should be stated that this figure is a conservative estimate and allowance has been made for the many factors which could re duce this figure. Secondly, although there is no reason to doubt the factor for the diffusion of lead, it should be realized that this figure is an average value for the whole of the city air. Consequently, much higher concentrations are to be expected in certain areas of high brake usage. For example, near inter sections, tollbooths, etc. In the light of the evidence here presented, one must conclude that asbestos emitted from brake linings may be a major contributing factor in the overall ambient air concen tration. Further work is necessary to establish more definitely the major contributors to urban asbestos concentration levels. Zt is not possible to state with assurance how much these low concentrations of asbestos constitute a threat to the health of the general public. Medical evidence and opinion is widely divergent on this issue. However, asbestos has been rated as a hazardous substande by the EPA and as such it should be.treated with due respect. Emissions should be reduced or curbed wherever this is possible. To this end it is worth briefly reviewing how this may be achieved. TECHNOLOGY OF ELIMINATING EMISSIONS The emission of asbestos to the atmosphere from asbestos containing brakes could be prevented in two ways: its use could be banned altogether, or, the brakes could be sealed. In the former case, an.alternate would have to be found. Ill RESEARCH INSTITUTE 70