Document 9mKZVbxmzkQKgzJQY0N6krd7

} 31 Is not possible to come to a reliable quantitative assessment'of the risk of malignancies for the general public. Present evidence docs not point to there being a threshold level of exposure, but there is very likely a practical level of exposure below which it will^b'e `impossible to detect any excess morta lity or morbidity due to asbestos, despite the presence of this mineral in the tissues, cxpecielly in the lung. Chapter XI presents various existing permissible limits, mainly for occupational exposure. In many countries permissible limits for workroom air are (or will be in the near future) ? fibrcs/ml (>5 pm); there is a tendency to lover these levels, particularly for crocidolite (in UK 0.? f/ml). These levels aim ot prwvntion of early asbcstosls, and not of malignancies; small fibres (>5 pm) are taken into account. With regard to the general environment adequate quantitative standards are scarcely available; most arc expressed in terms of required control practices. There is no way of extrapolating from oc cupational permissible limits to environmental permissible limits for ambient air, water, etc. Chapter XI3 evaluates the health risk of true environmental exposure. Two approaches arc discussed which try to extrapolate from the occupational to the public health risk. However, the approaches appear to be too deficient to allow quantitative extrapolation. Nevertheless, they both indicate that true ambient air exposure of the general p3^Hc_is__of_6n_crue_r of__two _tc> three magnitudes smaller than in wcl 1 cent_iol]_od industry. It seems possible that a factor of 1000 or more may be l^rgo tmvugh to reduce the ri;k of tumors to a negligible level compared to other risks. The 197? Conclusions of the Advisory Committee on Asbestos racers of the International Agency for Research on Cancer which state that there docs not exist evidence of an increased risk of mesothelial tumors in respiratory or gastrointestinal exposure of the general public arc not contradicted by the data presented in this report. On the other hand present evidence is not conclurive enough to make a statement in a positive wsy. The general conclusions of this chapter can be follows: - there exists enough reason to mj n i mi r.c_ i.iO^vptjcr^ f-j'.*rc cf the general public as much as possible; this is particularly the Cc:;e for croci there water couni too r. if U by nc the ) hour) the > JleJ : iatr* tent Chop gaps in k cy of the are nenti - ctud \ cut 1 t'fig ibt r t \)C * sL- cc n< cl- ln t Y\ : d i c:.t in umiip * X 600] 0 7 f1 ? PRODUCED BY FORD