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Environmental Health TABLE OF CONTENTS July/August 1987 Volum e 4 2 , Num ber 4 Peripheral Neurotoxicity in Workers Exposed to Inorganic Mercury Compounds Environmental and Occupational Exposures to Chrysotile Asbestos: A Comparative Microanalytic Study Exposure to Alcohol and Tobacco and the Risk of Laryngeal Cancer Pulmonary Impairment in a Cotton Textile Factory in Nigeria: Is Lifetime Alcohol Intake with Low Cigarette Smoking a Confounding Factor? A Retrospective Cohort Study of Mortality among New York State Farm Bureau Members Chronic Obstructive Pulmonary Disease Symptom Effects of Long-Term Cumulative Exposure to Ambient Levels of Total Suspended Particulates and Sulfur Dioxide in California Seventh-Day Adventist Residents Selenium Status, Lipid Peroxides Concentration, and Glutathione Peroxidase Activity in the Blood of Power Station and Rubber Factory Workers An Evaluation of Respiratory Effects Following Exposure to 2.0 ppm Formaldehyde in Asthmatics: Lung Function, Symptoms, and Airway Reactivity Brief Communication: Fibers in Idiopathic Retroperitoneal Fibrosis: A Case Report Letters to the Editor Raymond Singer, Jose Valciukas, Kenneth Rosenman Bruce Case, Patrick Sebastien Ross Brownson, Jian Chang U. Oleru Alice Stark, Hwa-Can Chang, Edward Fitzgerald, Karan Riccardi, Robert Stone Cary Euler, David Abbey, John Hodgkin. Allan Magie Bronislaw Zachara, Wojciech Wasowicz, Maria Sklodowska, Iolanta Cromadzinska Theodore Witek, E. Schchter. Tarik Tosun, Cerald Beck. Brian Leaderer Augustus Middleton, Renate Kimbrough 181 185 192 197 204 213 223 230 238 241 The Archives of Environmental Health (ISSN 000.3-9896) is the official publication of the Society for Occupational and Environmental Health. It is published bi-monthly by HELDREF PUBLICATIONS (Evron Kirkpatrick, president. 4000 Albemarle St.. N .W ., Washington. D .C . 20016) under the editorial leadership of the Society for Occupational and Environmental Health. Annual subscription rates S60 plus $7 postage for all subscriptions outside the U S. Single copies are $10.00. Second class postage paid at Washington. D C and other Post Offices. POSTMASTER: Send address changes to Archives o f Environmental Health, Rm. 500, 4000 Albermarle St., N .W ., Washington, D.C. 20016. Copyright 1986 by the Helen Dwight Reid Educational Foundation, 4000 Albemarle St., N.W . Washington. D.C 2001b. All business correspondence should be sent to this address Allow 6 weeks for shipment of the first copy. Claims concerning missing issues made within 6 months will be serviced free of charge Send all manuscripts to HELDREF PUBLICATIONS. 4000 Albemarle St., N .W .. Suite 504, Washington, D C. 20016 The Archives ot Environmental Health is either indexed or abstracted in the following: Cambridge Scientific Extracts: Environt(al) Index: Excerpta Medica; Hospital Literature Index (American Hospital Association); Index M edicus (HEW ); Industrial Hvgiene Digest (Industrial Health Foundation. 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Copyright is retained bv the author where noted 0003-9896/87 $1.00. t Letters to the Editor I wish to give two cheers for Ellen Silbergeld's editorial "The Fullness of Time in Epidemiology" in the March/ April 1987 issue of the A rchives o f Environmental Health. The real importance of her principal thesis is diminished by her unfortunate misuse of the Brown and Jones study results, and by her demonstration of her tenuous mastery of the principles of epidemiology. In the former case she has told part of the truth. She gives the impression that the only noteworthy finding of the initial study was an excess mortality from stomach cancer based on a "small number of deaths," leaving us to wonder what was found when the study was updated. She gives the further impression that an excess of liver and biliary cancer was first detected in Brown's update of the study. The whole truth is that an excess of liver and biliary cancer was found jn the first study and was widely mentioned. The update confirmed the excess, and con firmed the fact that it was inversely related to latency and duration of exposure. The "small number of deaths" from stomach cancer was, in fact, a single death, was not even mentioned by the authors, and disappeared in the update. There is no doubt that updating the Brown and Jones study was a desirable and productive effort which con firmed the ambiguity of the original findings. However, Silbergeld's selective citations of the results is an attempt Silbergeld's epidemiologic pronouncements seem to assume that short follow-up implies short latency. This is not true. She also states that some studies are often terminated "on the basis that sufficient time has elapsed." Since her initial pronouncement is wrong, terminating a study early would eliminate long latent periods only if the study were designed so as to make this happen. More important, the cheapest and most expedient termination date for a study is the most recent date.for which com plete information can be obtained. I challenge Silbergeld to name one example of a study which has done other wise. The bottom line of all of the above is that an important and relevant point was used, to its detriment, as a spring board to launch (a) misstatements about the results of a particular update and (b) pronouncements about epi demiology and epidemiology studies that are simply not true. Naive readers w ill swallow the baby with the bath water, to mix a metaphor. Careful and suspicious readers will find the misstatements and may as a result reject the main thesis also. I do not want either of these things to happen. William R. Gaffey, Ph.D. Epidemiology Director To the Editor: This letter is response to the letter received from Dr. W illiam Gaffey concerning my editorial, "The Fullness of Time in Epidemiology" which appeared in the March/ April 1987 issue of Archives. The purpose of the editorial was not to continue the prolonged scientific and political debate on the carcinogenicity of PCBs, but .rather to discuss the problems in environmental/occupational epidemiology which are associated with incomplete data. As the editorial states, the best solution to these problems is exemplified by the methods used in the paper by Malker and Gemme. In the absence of mechanisms which can exploit computerized linkages between dis ease and exposure registries, I commended the effort by Brown to reinvestigate the occupational cohort exposed to PCBs. The editorial did not imply that the follow-up study found radically different results from the first Brown study, but rather that the effect of time was to increase the number of observations available for analysis. The con sequence of this was to provide further resolution of the associations observed between occupational exposure and cancer. As stated by Brown and Jones, in their original paper (Arch. Environ Health 36: I 20, 1981), the observation of excess mortality for rectai and liver cancer was not statistically significant (contrary to the assertion in Gaffey's letter); moreover, to quote Brown and Jones: "Because a relatively small number of deaths were ob served, conclusions drawn from the results of this study are tentative." This is exactly the point of the editorial: july/August 1987 (Vol. 42, (No. 4)) that time by itself can reduce the tentativeness of a conclusion. Gaffey has misunderstood my comments on follow-up and latency. In fact, my concerns are that short follow-up times are inappropriate for diseases with long latency just because the full expression of the pathophysiologic pro cess may require more time than has elapsed between exposure and compilation of results. O bviously, a study canonly be done at the time at which it isdone, and notat some time in the future; however, the point of the edi torial is that when follow-up times are short, and when the number of observations is low, the investigator should as a matter of professional obligation undertake to revisit the cohort in the future. No experimental study would be considered acceptable if only 10% of the total possible observations were in fact available for analysis; epidemiology does not enjoy the advantages of the laboratory, but it can use the resolving power of time, particularly in the absence of the power of linkage analy sis. It is a shame that Gaffey did not see his way to endorsing the importance of the kind of epidemiological investigation* proposed by NIOSH which have been suppressed by O M B. This is more critical than raising somewhat tangential critiques of my editorial. Ellen K. Silbergeld, Ph.D. Environmental Defense Fund 241