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Objectives: This cohort study is to assess the extent of cancer risks of betel quid chewing (without tobacco added) beyond oral cancer, as such information was limited from case-control studies., Methods: The cohort, selected from participants in a medical screening program since 1994, consisted of 177,271 adult men with 19.2% chewers of betel quid. As of 2006, out of 4,840 deaths, 1,901 cancer deaths were identified. Mortality hazard ratios (HR) were estimated by Cox proportional hazard model. Life expectancy was calculated by life table method., Results: One-third of smokers chewed (33%) but most of chewers smoked (90%). Risk for all cancer doubled among chewers (HR = 2.00). Risks of at least six cancer sites were increased among chewers: oral cavity (HR = 12.52), esophagus (HR = 5.64), liver (HR = 2.27), pancreas (HR = 2.67), larynx (HR = 6.24), and lung (HR = 2.43) with risks increased with increasing betel quid amount consumed. All-cancer age-adjusted mortality rates in Taiwan increased 25%, including 223% increase in oral cancer, during the last 20 years when chewing rate increased five- to tenfolds. Chewing on top of smoking increased the risks synergistically, and these two were responsible for at least half (50%) of all cancer deaths among 2 million chewers in Taiwan. Life expectancy of chewers was shorter than non-chewers by 5.93 years at age 20 and 5.55 years at age 40., Conclusion: In addition to oral cancer, significant increases were seen among chewers for cancer of the esophagus, liver, pancreas, larynx, lung, and all cancer. Chewing and smoking, as combined by most chewers, interacted synergistically and was responsible for half of all cancer deaths in this group. They were responsible for the recent increases in oral, esophageal, pancreatic, and liver cancer in Taiwan. Chewing and smoking shortened their life span by nearly 6 years.

Objective: Dieldrin and aldrin, pesticides widely used until the 1970s, have been under suspicion of being carcinogenic. In this study, overall and cause-specific mortality was assessed in a cohort of 570 employees occupationally exposed to the pesticides dieldrin and aldrin to investigate the long-term health effects, in particular carcinogenic effects., Methods: All of the employees worked in the production plants between January 1954 and January 1970 and were followed for cause-specific mortality until 30 April 2006. Based on dieldrin levels in blood samples taken from 343 workers during the exposure period, the total intake of dieldrin was estimated for each individual subjects in the cohort. The estimated total intake ranged from 11 to 7,755 mg of dieldrin, with an average of 737 mg., Results: Two hundred and twenty-six workers had died before 30 April 2006 compared with an expected number of 327.3, giving a standardized mortality ratio (SMR) of 69.0 (95% confidence interval (CI): 60.3-78.7). Overall cancer mortality was also significantly lower than expected (SMR: 76.4, 95% CI: 60.8-94.9). Also, none of the specific cancer sites showed a significant excess mortality and no association between exposure level and cancer mortality was found., Conclusion: The results from this study support findings from other epidemiological and recent animal studies concluding that dieldrin and aldrin are not likely human carcinogens.

Purpose: The purpose of this study is to determine the incidence of cancer among employees at two petrochemical facilities in south Louisiana, and to compare their cancer rates to those of the general population of south Louisiana., Methods: Records on 4639 active and former employees and retirees from the two plants were linked to the Louisiana Tumor Registry (LTR) database by LTR staff to ascertain incident cases of cancer. Standardized incidence ratios (SIRs) were then calculated using the south Louisiana population as the comparison and adjusted for age, race, and time period., Results: There was a significant 16% deficit of overall cancer cases for males in this cohort (SIR=0.84; 95% CI, 0.74-0.95). The only significantly elevated SIR in males was for cancer of the bone and joint (SIR=6.89; 95% CI, 1.42-20.1). This result was based on three non-fatal cases of bone cancer with different histologies, occurring in different parts of the body. These cases worked in different units of one plant. Significant deficits were seen for lung cancer, non-Hodgkin's lymphoma, and cancer of the oral cavity and pharynx. Cancer incidence among 719 female employees was non-significantly increased (SIR=1.24; 95% CI, 0.81-1.82). Breast cancer accounts for the excess (SIR=1.46; 95% CI, 0.73-2.61). Seventy percent of the breast cancer cases worked in an office setting., Conclusions: This study found little evidence of any association between cancer incidence and employment at these two petrochemical facilities. The increased incidence of bone cancer is unlikely to be due to occupational exposures. The non-significant excess of breast cancer may be due to early detection or other important unmeasured confounders, such as certain reproductive factors.

A previous report presented the 1948-1983 mortality patterns of the Shell Deer Park Manufacturing Complex employees who were employed for at least 3 months from 1948 through 1972. The present study updates the earlier investigation by extending the vital status follow-up through 1989 and by expanding the cohort to include employees hired after 1972. As in the previous study, the overall mortality and cancer mortality for both refinery and chemical employees were quite favorable compared to residents in the local population. Among refinery workers, cancers for which a suspicion of work-relatedness was raised in the previous study, i.e. leukemia and cancers of the central nervous system and biliary passage/liver, no supportive evidence was found in this update. For both refinery and chemical plant employees, the mortality rate due to cancers of all lymphopoietic tissue increased with increasing duration of employment; this finding was also noted by the original study. This was also evident for lymphoreticulosarcoma in refinery employees and for leukemia in chemical plant employees. However, elevations of cancers of all lymphatic and hematopoietic tissue are primarily confined to employees who started work at the complex before 1946. By contrast, deaths from cancer of all lymphatic and hematopoietic tissue for employees hired after 1945 were 22% lower than the comparison population. Seven deaths with mesothelioma mentioned on the death certificates were identified, with 3.2 deaths expected, resulting in a statistically nonsignificant SMR of 219.

This paper reports the mortality experience from 1948 to 1989 of 2,504 maintenance employees who had a minimum of one year of employment in jobs with potential exposure to asbestos at a Texas refinery and petrochemical plant. For the purposes of this study, "potential exposure" is equated with those jobs or crafts having the greatest direct potential proximity to, or which worked directly with, asbestos-containing materials, especially asbestos-containing thermal insulation. Approximately one-half of the study population had 10 years or longer potential exposure, and 80% had their first potential exposure before 1970. The total population exhibited significantly lower mortality for all causes, the standardized mortality ratio (SMR = 77); and for all cancer (SMR = 85), as compared to residents in the surrounding communities. Statistically significant deficits in mortality were also observed in a number of noncancerous diseases such as heart disease (SMR = 78; 95% CI = 69-88), nonmalignant respiratory disease (SMR = 70; 95% CI = 50-95), and cirrhosis of the liver (SMR = 44; 95% CI = 22-79). Mortality among employees who had 20 years or longer since their first potential exposure was also examined; the pattern of mortality was similar to that exhibited by the total cohort, with a slight increase in the SMR for most of the causes. The only statistically significant excess of mortality found was a fourfold increase in mesothelioma (5 observed and 1.2 expected deaths) the SMR was 428 (95% CI = 139-996) for the total cohort and was 469 (95% CI = 152-1093) for those who had 20 years or more since first potential exposure. In contrast to asbestos industry worker studies, mortality for lung cancer was substantially lower than the general population (SMR = 81; 95% CI = 63-103). The observed number of deaths for cancer of the larynx was virtually the same as expected (3 observed vs. 2.8 expected). This study also showed decreased mortality for cancers of gastrointestinal organs such as the esophagus (SMR = 78), stomach (SMR = 63), large intestine (SMR = 91), rectum (SMR = 55), or pancreas (SMR = 90)--cancers that have been reported to be elevated in studies of various industry workers directly exposed to asbestos.

This paper develops a method for adjustment of competing causes of death in the calculation of relative risk. It has identified three factors determining the significance of competing risks: (1) the magnitude of the overall mortality risk of the study population; (2) differential risk (or the adjustment factor) for mortality other than cause of interest between two populations; and (3) age intervals used in the mortality calculation. Thus, the impact of competing risks is increased if the study cohort has a high mortality risk, if the mortality other than the cause of interest has a large differential risk or if the mortality calculation uses wide age intervals. Two examples from a refinery cohort and the US national population show that among certain age groups unadjusted for competing risks the relative risk is overestimated by 9%. The impact of competing risks in these two particular examples is relatively small. Furthermore, if relative risk is expressed in terms of the ratio of mortality rates, competing risks can be ignored.

This longitudinal study examined the mortality and cancer experience of workers at the Gulf Oil refinery located in Port Arthur, Texas. The cohort was studied over a period of 41 years, from 1937 to 1978, and consisted of 16,880 employees, with an accumulation of 406,198 person-years; 4361 deaths were observed. Emphasis of this study was placed on the experience of the hourly and salaried male workers employed one day or more and those with a minimum of one year employment. The standardized mortality ratio analysis revealed generally favorable mortality experience of the refinery workers, including that of overall cancer. Statistically significant deficits in mortality were found for several cancer sites including bladder, liver, and esophageal cancer. Many of the increased cancer risks suggested in the literature were not confirmed in this study. Although bone cancer was found to be increased significantly, review of those death certificates raises questions as to the accuracy of the recording and coding of this cancer. Sample size of this study is capable of providing sufficient statistical power for the detection of a twofold increase in mortality risk for many cancers, if such risk exists.

A retrospective cohort mortality study of 1,008 male oil refinery workers who ever worked on the lubricating-dewaxing process of the lube oil department and who have been followed for a period of 43 years is presented. These workers were exposed to a number of solvents, primarily methyl ethyl ketone [(MEK) CAS: 78-93-3] and toluene (CAS: 108-88-3), but at levels far below the current Occupational Safety and Health Administration's standard. The standardized mortality ratio (SMR) for all causes (0.70) and the SMR for cancer (0.86) are much lower than unity when they are compared to the mortality experience of the U.S. population. Also observed in this study were 8 prostate cancer deaths (4.4 expected) with an SMR of 1.82, which was not statistically significant (P = .16). Seven of these 8 prostate cancer deaths occurred among nonwhite males, who showed an SMR of 2.47 (P = 0.53). However, only 1 prostate cancer death was seen among workers specifically assigned to the MEK units. The remaining deaths occurred among maintenance workers who had lube oil department-wide assignments. This cancer risk increased with increasing duration of employment in the lube oil department. A latency of 20 years or more was also observed for these prostate cancer deaths. In this study the processing of lubricating oils was found to be at least as important as the MEK solvents, and department-wide maintenance workers were as much at risk as the MEK unit workers. In view of this finding and findings obtained by others, it seems prudent to continue to study lubricating-dewaxing process workers, including the medical monitoring of all such workers for prostate cancer.

Potential gains in life expectancies among Texas population by partial elimination of 3 major causes of death are examined on the basis of the available statistics from the population census and mortality statistics for 1970. Contrary to the popular anticipation of longer potential gains, the results are not particularly encouraging. The number of years of life that would be gained during the working ages by 50% elimination of major cardiovascular diseases is less than 1/2 of 1 year, about 1/4 of 1 year by 50% elimination of malignant neoplasms, and less than 1/4 of 1 year by 50% elimination of motor vehicle accidents. Even with a scientific breakthrough in combating those causes of death it appears that future gains in life expectancies for working ages will not be spectacular. The implications of the results in relation to the current debate on the national health policy are discussed.