Reconciling old and new findings on dioxin.
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Dioxins↗
Biomedical subjects
B R Friedlander
Publications and source records attributed to B R Friedlander.
Three basic principles for improving epidemiology: an industry view.
Three principles are presented that will improve the quality of epidemiologic studies now being done. These principles are: (1) that outcome foreknowledge should be disclosed and discussed; (2) that key data in the study should be well understood to include what influences it and its inherent variability; and (3) that detailed exposure characterization, whether it be occupational or personal risk factors, should be an integral part of all studies. The quality of epidemiologic studies resides in meticulous planning and execution, because not considering important confounders or poorly measuring an effect can mask or magnify associations.
Epidemiologic Methods↗
A study of the hematologic effects of chronic low-level exposure to benzene.
A study of 200 persons working with benzene showed no differences in commonly measured hematologic outcomes when compared with 268 nonbenzene workers in the same plant. Exposures ranged from 0.01 ppm to a high of 1.40 ppm 8-hour time weighted average over a 10-year period. Several other factors (age, sex, race, and smoking), however, were associated with these outcomes, indicating the importance of considering confounding factors when comparing hematology results. Exposure to low levels of benzene does not appear to produce an increased level of abnormal hematology measures detectable in routine medical surveillance.
Adult↗
Absence of toxic effects in silver reclamation workers.
Recent reports have alleged that silver presents a toxic hazard to exposed workers. To define the potential risks of long-term exposure to silver better, a cross-sectional investigation was conducted of 27 Caucasian males occupationally exposed to primarily insoluble silver compounds and 27 matched referents. Physical examination and electron microscopy of skin biopsies revealed no cases of generalized argyria. Measurements of facial discoloration, judged from color photographs by panels of laymen and physicians, showed no significant difference between the two groups. Although 29% of the silver workers and none of the referents exhibited ocular silver deposition, optometric and contrast sensitivity test results revealed no significant deficits in visual performance. The kidney and respiratory findings were essentially normal in both populations. Despite the increased presence of silver in the blood, feces, and hair of the recovery workers versus the referents, there was no evidence that chronic silver exposure adversely affected the health of these employees.
Air Pollutants, Occupational↗
Methylene chloride mortality study: dose-response characterization and animal model comparison.
To assess the potential chronic health effects of methylene chloride, the mortality experience of a maturing 1964 to 1970 cohort of 1,013 hourly men was evaluated through 1984. On average, employees were exposed at a rate of 26 ppm (eight-hour time-weighted average) for 22 years; median latency was 30 years. Compared with the general population, no statistically significant excesses were observed for such hypothesized causes as lung cancer (14 observed v 21.0 expected), liver cancer (0 v 0.8), and ischemic heart disease (69 v 98.1); dose-response relationships based on career methylene chloride exposure and latency were not demonstrated. Among nonhypothesized causes, a significant deficit was reported for total deaths (176 v 253.2). None of the industrial referent comparisons achieved statistical significance. Sufficient power was available to detect relative risks of 1.6 for lung malignancy and 1.3 for ischemic heart disease. In contrast, there was inadequate power to identify meaningful risk levels for hepatic cancer. With 14 combined lung and liver cancer deaths observed v 36.3 predicted (P less than .0001), the mortality estimate projected from a mathematical model derived from an animal bioassay substantially overestimated cancer mortality for these sites. This inconsistency emphasizes the need to incorporate epidemiologic evidence in assessing the human health risks associated with long-term exposure to this widely used solvent.
Air Pollutants, Occupational↗
Mortality study of men employed at a large chemical plant, 1972 through 1982.
The mortality experience of a cohort of approximately 9,000 traced men employed at a Tennessee chemical plant was examined between 1972 and 1982. Statistically significant total mortality deficits of 41% to 46% and 14%, respectively, were observed compared with general population and occupational controls. Cancer deaths were 22% (significant) below expectation based on state and national vital statistics, whereas comparison with an employed group showed no difference. Significantly low mortality differentials were also reported for other major causes, including diseases of the circulatory, respiratory, and digestive systems. Analysis of the data by length of employment, payroll status, and chemical production division demonstrated no unusual patterns. The cohort's favorable mortality experience may be attributed to such factors as employee selectivity, health maintenance, accessibility to medical care, and less cigarette smoking.
Chemical Industry↗
Epidemiologic investigation of employees chronically exposed to methylene chloride. Mortality analysis.
A large male employee population with continuous low level work exposures to methylene chloride for up to 30 years was examined for mortality experience using non-concurrent prospective and proportionate mortality techniques. Mortality of the study group was consistent with industrial controls and less than the New York State general population. Life table analysis of the 1964 methylene chloride exposed cohort was followed through 1976 and demonstrated age group specific probabilities or 13 year survivorship equal to or better than that of three control male populations: Kodak Park, New York State, and United States.
Adolescent↗
Put on your epidemiologist's hat.
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Environmental Exposure↗