Document ZJOm8mOQ12mnG6aykj0oGOq7Y

/ INTERNAL. C CORRMPONDINCI UNION CARBIDE CORPORATION olo riogebury road, danbury, ct obbi7 To <Nvn) Dr. Carol Stack Chaaieal Manufacturers Association 2501 M Street, MM Suita 200 Washington, DC 20037 Dot* Ongwiocmg D*0t> November 4, 1983 Copy co EHA Phasa II Proposal on Vinyl Chlorida Study (OCC South Charlaston and Taxas City) Daar Carolt As a follow-up to our phona convarsation of Octobar 31, 1983 I shall set iny coswents on tha EHA Phasa II Proposal to papar. In ordar of conearn thay ara as followsi 1. I do not faal that parsons previously classified as exposed should be considered "unexposed" on the basis of available information in 1983. Tha EHA proposal contains a suggestion to analyse tha data two ways, using the original classification as wall as tha ravised classification. Tha substantial nunbar of reclassified individuals for sons coapanies is definitely a causa for concern, however, I do not faal this will be resolved siaply by re-analysing tha data and contrasting it with results obtained using the original classification. I feel that this will only create problems in interpretation if the results are different. union Carbide's plant in West Virginia was affected by this reclassification problen. By searching tha aeaories of thosa who were involved in selecting tha original cohort for tha 1972 study, I an not convinced that thay did not have good reason to assune that parsons selected for the exposed group ware indeed exposed. It is very likely that they had data available to than which is no longer to be found. While it is true that we cannot confirn the xposure status on tha basis of records available to us today, it is entirely possible and even likely that if we ware to start de novo in creating an exposed cohort, this cohort would contain sons individuals not included in tha original study.-__ Therefore, I conclude that only one of two approaches is justified under tha cireunstanceat 1) analyse tha original cohort using the original classification criteria, and 2) start da nov and independently Identifying an exposure cohort using records available today. Under the EHA proposed approach, individuals included in the original cohorts could only be excluded} there is no provision for the inclusion of employees found to be inadvertently onnitted from the orignial cohort. This could lead to substantial bias. ucc 014873 - 2- 2. The coding of contributory cum from th death certificate is a worthwhile endeavor. All death certificates should be coded in this manner, not just those obtained in the Phase II study. 3. is the national death index (NDI) a reliable source for determining individuals known to bs * alive*? is it valid to assuae that if the person does not appear as a death after 15 aonths have elapsed, that this person aust be alive? I state these simply as questions as I do not have the necessary information to provide any answers. 4. I would prefer to see deaths which occurred during the tine period of the 8th and the 9th revisions of the International Classification of Diseases used in preference to coding back to the 7th revision. The "Monson* program allows for the conversion of codes fron the 8th to the 7th or from the 7tb to the 8th. It is always preferable to be as up to date as is practicable. I am sorry that I was unable to attend the last meeting. I lc k forward to seeing you at the next one! Sincerely, SGA/psb cct Mr. J. H. Barrett Mr. H. L. Greenberg Mr. T. E. Lawrence Dr. T. A. Lincoln Susan G. Austin, 8c.D. Corporate Director of Epidemiology / ucc 014874