Document wg8Qo8BQj3QVo9BKLmrQdKKxB

Letters For example, sentence one of paragraph two of the abstract is a state- , .I___ _ , .{vent of fact, i.e. as lone as readers do DY COPYRIGHT LAffi get confused regarding a "study tdit<WLE 17 u. s. CODc. population" and the "population at risk"; the latter being the one on which inferences are made and presumably the Readers are invited to submit letters lor publication in this department. Submit to Ir ving R Tabershaw, MO., Editor, P.O. Box 2169, Rockville, MO 20852. Letters should be typewritten, double spaced and should be designated "For Publication". population of importance -- in most epidemiological efforts. Very interesting, but what can we make of the statement? Not much, really, for the real inference to the "population at risk" can be found under (2) in the 3rd paragraph of the ab stract. The last sentence of the abstract Vinyl Chloride and Its Potymegs suggests that vinyl chloride may be Letter-to-the-Editor. -- This is in associated with cancer of multiple sites. reference to the article by Tabershaw Nonsense; no such a suggestion exists. and Gaffey: Mortality Study of Workers In the same light, vinyl chloride may not in the Manufacture of Vinyl Chloride be associated with cancer of multiple and its Polymers, /OM 16, August 1974. sites. These high SMR's may well be a I find this article to be quite interesting consequence of sampling variability and as well as intriguing. Although it appears in fact, the authors were unable to infer that the methodology employed could that significant excesses occur in the risk withstand a great deal of scrutiny, I am population. not at all convinced regarding the in The discussion on page 513 presents terpretation. of the resuits. rationale in support of the conclusions - '* found in the abstract. While the authors intuitive judgment may well be correct, the results are inconclusive. Using statistical justification as support for their conclusions is most certainly invalid. Robert B. Reger Chief, Statistics Branch NIOSH-ALFORD Morgantown, WV 26505 Reply to Robert B. Reger's Letter Reger's first comment on our paper makes a distinction between "population exposed to risk" and "study population," with which we agree. In every epidemiological study of which we are aware, the study population is, usually by design, a subgroup of the total population exposed to risk. Unless that subgroup is chosen by some kind of probability sampling, which is rarely the case, generalization from the study population to the population at risk is not a purely statistical process. It is Hmediated mon sense data bearit generalizat this comm The secc elusions o on which statistically responses points, we most relev The first this case Mint cc plete; V single r Model 1703 How effective is your hearing conservation program? Your audiometer is the Pleas* sand m* more Information on Graaon-Stadlar audiometers. final authority. NAME. FIRM/INSTITUTION .. ADDRESS____________ CITY__________________ .STATE- -ZIP- Mail this coupon to GRASON-STADLER COMPANY. 56 WINTHROP STREET. CONCORD. MASS., 01742 15 B-ECEnCEJL No matter how thorough yppr firm's noise reduction or protection program, the only way you can verify that it is effective is to keep-reliable records of the hearing threshold of all employees involved. This means audiometric measurements performed with accurately calibrated and reliable audiometers such as the Grason-Stadler Automatic 1703 or the Manual 1707. Grason-Stadler H A OR COMPANY BfioB 58 Winthrop St., Concord, Massachusetts 01742. T*i:j617/ 369-3787, TWX: 710-347-1050. 772 JUN1 81980 ; Hr!ey D. Conner Tl W le 11 D P ti Journal of ` the authors COfrerl Wn J'siflji 'n for fhCl, 'V 'nvaltfj 'qer ICS Branch IRQ ' VW 2hS0i Ks our paper between ind "sludi agree In of which ulahon n >p of the tk. Unless ne kind o( rarely the ie study at risk is 'SS. It is ^iated by a certain amount of coin er, sense, and the existence of other bearing on the plausibility of the cneralization. Our investigation shares in,s common defect The second comment attacks our conC Uiions on the ground that the SMR's n which they are based are not (jtisncally significant. Of the several ^ponses which might be made to this n.-,mts, we believe the following two are -ost relevant. The first is that the evidence at hand in ,his case is a complex of facts; (a) malignant neoplasms do in fact occur more often than expected, while other causes of death, with trivial exceptions, do not; (b) the deaths from malignancies which cause this excess are generally in the high exposure groups, and the more stringent the criterion for high exposure the greater the concentration of excess deaths; (c) for one site, digestive can cers, the observations agree with what is known from other evidence. We can measure the statistical significance of each SMR, but we know of no way to put a numerical measure on the significance of the above pattern. The second is that the interpretation of a non-significant, as opposed to a significant, SMR is not as simple as Reger implies. There is ample evidence that most employed groups have a lower mortality than the general population, so that there is a question as to what the "expected" SMR should really be There is no problem when the SMR is significantly greater than 100, but when it is not, one enters muddy waters, statistically speaking. We still believe that we are |ustified in what we consider to be a temperate conclusion from data which are ad mittedly less than overwhelming. Irving R, Tabershaw, M D William R. Gatfey, Ph O JOM BACK ISSUES Mint condition issues of the JOURNAL OF OCCUPATIONAL MEDICINE are available for Vol. 14 (1972) com plete; Vol. 15 (1973) with the exception of numbers 3, 4 and 9; and complete sets of the current year. Price S3 single copy orders. Complete year sets $34. JOM - BACK ISSUES , Mayo Publications P.O. Box 247 * Downers Grove, IL 60515 %is m i? he ty- ludion verify of the jrmed leters nr the :,617/ --------------------(g)-------------------' MEDICAL DIRECTOR The Bettis Atomic Power Laboratory, a division of Westinghouse Electric Corporation, one of the nation's leading design and development centers of nuclear reac tors, has an immediate openini tor a Division Medical Director. Position requires a full range uf occupational health ac tivities including periodic examinations oriented to control of radiation exposure, occupational disability care, health counseling and preventive services. Background in radiation medicine a plus. United States citizenship is required. This is a major career opportunity offering an attractive salary and benefits. If interested, please send resume in confidence to; Daniel T. Masta, Supervisor Professional Employment, Dept JO 11-74 Westinghouse BETTIS ATOMIC POWER LABORATORY operator tor tin atomic Eimtq Commission by WcsNmhouso Electric Corporation ML On 71 Wo* MiftHni, h. 15122 An Equtl Opportunity Employer Journal of Occupational Medicine/VoL 16, No. 12/December 1974 773