Incidence of lymphohaematopoietic malignancies in a petrochemical industry cohort: 1983-94 follow up.

OBJECTIVES: In response to a previous finding of increased mortality from lymphohaematopoietic (LH) malignancies, this study examines incidence of LH malignancy in a petrochemical industry cohort. Emphasis is on chronic lymphocytic leukaemia (CLL) and on comparisons by period of first employment. METHOD: The study cohort consists of 8942 employees who were active in the period 1970-92 and alive on 31 December 1982. Record linkage with the Louisiana tumour registry (LTR) provided information on cancer for cases occurring between 1983 and 1994. Standardised incidence ratios (SIR), with the south Louisiana population as a comparison, were computed for all cancers, all LH malignancies and specific LH subtypes. Analyses were conducted for sex and race categories, and by period of first employment, job type, duration of employment, and latency. RESULTS: 672 Cases of cancer were identified, including 59 LH malignancies. Women (n=1169) had an overall cancer SIR below unity and four LH malignancies versus 2.28 expected. Among the 7773 men, those first employed before 1950 had no overall cancer excess, a significant 1.4-fold increase in overall LH malignancies (43 observed versus 30.78 expected), and four CLL cases versus 3.27 expected. Findings for men first employed after 1950 are based on fewer cases, but there was no indication of excesses of overall cancer or LH malignancy. Numbers were too small in the group first employed after 1950 for meaningful analysis of LH malignancy subtypes such as CLL (one case). CONCLUSION: These findings do not suggest a continuing excess of CLL but do suggest a small increase in incidence of overall LH malignancy for workers first employed before 1950. This may reflect associations with earlier workplace conditions, although work related patterns are mixed. Interpretation is limited by the diverse group of diseases within LH malignancies, and the lack of control for non-work factors other than sex, age, race, and period of diagnosis. This study has a major advantage of more complete and reliable cancer ascertainment compared with the mortality investigation, and shows the feasibility and benefits of using cancer registry incidence data in an occupational cohort study.

Lymphopoietic cancer and other major causes of death among petrochemical researchers: an update.

This study updates lymphopoietic cancer (LHC) mortality statistics and other major causes of death through 1992 for 13,188 petrochemical researchers employed between 1964 and 1986. Significant deficits of deaths were observed for all causes, all cancers, ischaemic heart disease and all external causes. The subcategory of 'all other LHC' was elevated among males in an exposure class containing scientists and engineers. This finding was statistically significant based on national but not state comparison rates. Poisson regression analyses showed that increasing exposure classes were not associated with LHC, but a relationship was noted for total years worked. A non-significant increase in breast cancer among females was also observed but was concentrated among the lowest exposure class. This study and other similar investigations suggest various subcategories of LHC deaths are marginally elevated among chemical researchers and engineers. Evidence for a work-related LHC hazard for this population, however, has not been identified.

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.

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.

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.

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.

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.

Mortality, cancer incidence, and sickness-absence in photographic processors: an epidemiologic study.

An epidemiologic investigation of a 1964 cohort of 478 photographic processors in nine Eastman Kodak Color Print and Processing (CP&P) laboratories in the continental United States was undertaken. Analysis of pre-1965 environmental data indicated that chemical exposures were within the standards applicable at the time. The results showed no significant excess mortality, sickness-absence or cancer incidence. The processing cohort's mortality experience after 16 years of follow-up compared favorably with that of two industrial control populations. The present study represents (to our knowledge) the first published occupational epidemiology investigation that specifically examines the health of workers engaged in large-scale commercial photofinishing operations.

Diagnostic sensitivity bias -- an epidemiologic explanation for an apparent brain tumor excess.

Preliminary data showing over-representation of the Eastman Kodak Company (Rochester) on death certificates of brain tumor patients, and higher risk for older workers when compared to the general population, led to a case-control epidemiologic study. Chemical exposure histories of 56 workers with brain tumors were compared with those of other Kodak employees. No differences were found in exposure to a variety of chemicals. In addition, employees with brain tumors were compared to other upstate New York brain tumor patients; there was no difference in histology. However, the Kodak employees had diagnoses more frequently confirmed by histologic examination and more thorough diagnostic studies. Thus, the apparent initial excess of diagnosed tumors may have resulted from a "diagnostic sensitivity bias" arising from more complete medical evaluation of Kodak employees.

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.