Document KnD7mdeED6o4vJ98kRoQXRE6

Mr. H.A. Eschenbach Industrial Chemicals Group W.R. Grace & Co. 62 Whittemore Ave. Cambridge, MA 02140 Dear Harry, I am just back from my long stay in Europe and have your note of July 21 and the reprint of the paper by Kaplan on a mortality study in petroleum refineries. It is certainly most unusual to calculate standardized mortality ratios (SMR) for mesothelioma. This is partly because mesothelioma has been so incorrectly and inadequately coded in national mortality statistics and partly because even today it is a rare tumour. What Kaplan actually did, however, was a quite dubious procedure. You will see at the top of the methods section on page 514 that the SMR's for mesothelioma were based upon data from the Third National Cancer Survey supple mented by data from the SEER Program. These sources of data repre sent an extremely high level of case ascertainment, most people would say overascertainment by perhaps 50%. The 9 cases of mesothelioma in the cohort studied could not be considered comparable. Probably that is the reason that the SMR based on 9 deaths was only 241. I look forward to seeing* you in Cambridge on the 19th. Best wishes to all. Yours sincerely. J. Corbett McDonald MD FRCP Professor J CMcD/rb 10002167. 4 Postal address: Dust Disease Research Unit 1110 Pine Avenue West. Montreal, PQ, Canada H3A 1 A3