The Functional Relationship Between Dust Hazard and the Rate of Collecting Funds to Pay Compensation for Pneumoconiosis (3bbc6c56-78c8-4aca-84ca-a62e6a21a027)

Discussion: T. L. Gibbs,* (Honorary Vice-President and Fellow): In terms of the Pneumoconiosis Compensation Act of 1962, a Pneumoconiosis Risk Committee was established whose function it is to estimate (by whatever means the committee deems fit) in respect of every controlled mine the pneumoconiosis risk to which persons employed in a dusty atmosphere at that mine are exposed. In estimating such risk the committee may estimate different risks in respect of individual mines or parts of mines or classes or groups of mines or occupations or localities at mines. The pneumoconiosis risk may be reviewed and re-estimated at any time. The Act provides further that the General Council for Pneumoconiosis Compensation shall apportion the levy imposed on owners of controlled mines on the basis of the pneumoconiosis risk determined by the risk committee and the numbers of persons employed in a dusty atmosphere. The task of the risk committee is a most responsible one and also a very difficult and complex one in view of the many different types of mines, rock formations, dust conditions, etc. Quite obviously, comparisons between mines cannot be made on dust concentrations alone as different mineral dusts have different toxicity or pneumoconiosis response factors. However, with its present knowledge, the risk committee is satisfied that the risk at mines, other than coal mines, is related to the mean quartz-equivalent dust concentration to which persons are exposed and the estimation of risks is based on this relationship. From the above, it will be clear that the work done by Dr du Toit on the problem of basing the current rate of levies to provide for pneumoconiosis compensation on the current dust hazard at mines has been of immense value to the risk committee. Up to now the risk committee has not been able to obtain complete and accurate information on the dust exposure of persons at all mines - and, in fact, it is doubtful whether it will be economic or practicable to obtain this in the foreseeable future - but reasonable assessments have been possible from routine dust sampling in some cases and from periodic comprehensive dust surveys in others. As a temporary measure the risks of some mines were estimated initially on a group basis relating to average dust conditions and the type of rock and mineral mined, but as more information became available, differentiation between individual mines became possible. It is the aim of the risk committee to eventually apply such a differentiation in all cases and to ensure that within the bounds of practicability each mine pays for its risk and for its risk only. In this connection, the relationship between the levies and the amounts actually paid out in compensation are examined regularly. In conclusion, I wish to add my congratulations to the author on his excellent paper. His findings will assist materially in the just administration of that very important piece of beneficial legislation, the Pneumoconiosis Compensation Act. G. K. Sluis Cremer MD (Visitor): Dr du Toit has made a valiant attempt to relate dust hazard and the rate of collecting funds for the purpose of paying compensation for Pneumoconiosis. In doing so he has had to make a number of assumptious, some of which touch on the medical aspects of pneumoconiosis. It is worth discussing whether these assumptions are justifiable. Pneumoconiosis is defined in our Pneumoconiosis Act as permanent disease of the cardio-respiratory organs which is caused by the inhalation of mineral dust. To a non-medical person this definition has probably a clear cut meaning. The doctors however have to deal with such conditions as silicosis and asbestosis where there is a well defined dose response relationship to the inhalation of quartz and asbestos respectively and on the other hand chronic bronchitis where the relationship to dust inhalation is poorly defined and where certainly no clear dose response relationship has emerged after many investigations in this country and overseas. Nevertheless since 1953 about half of our certifications for Pneumoconiosis are on the grounds of chronic bronchitis i.e. the X-rays show no evidence of silicosis, asbestosis or other relevant disease. This fact must affect Dr du Toit's computations. The next assumption we should examine is the manner in which toxicity factors have been allocated to the various mineral species. These allocations have in part been based on a restricted number of animal experiments carried out overseas but mostly in South Africa by Webster at the Pneumoconiosis Research Unit. To extrapolate the findings in a relatively small number of animal experiments to the expected reactious in man is a notoriously dangerous exercise. Furthermore the bracketing together of all silicates (except asbestos) and the insoluble metal oxides is entirely unacceptable. Talc (a hydrated silicate of magnesium) and muscovite mica (a silicate of aluminium and potassium) cause pneumoconiosis in their own right. On the other hand