Influence of the calcium content of the diet offered to leopard tortoises (Geochelone pardalis).

Twenty-four juvenile leopard tortoises were divided into four groups of six; one group was fed a basic low-calcium feed for six months, and the other three groups were fed the same basic diet supplemented with one, three and nine times the amount of calcium recommended as a supplement to the diet of reptiles. The animals' bone mineral content and bone mineral density were estimated by dual energy x-ray absorptiometry, and blood samples were taken at the start and at the conclusion of the study. One tortoise from each group was examined postmortem. There was a clear depletion of calcium in the body of the tortoises receiving no calcium supplement, and the shell of the tortoises receiving the recommended calcium supplement did not calcify to the extent expected. The tortoises that received three times the recommended calcium supplementation had the highest growth rate and were thriving. However, metastatic calcifications were observed postmortem in the two groups that were given the highest doses of calcium.

Mortality and cancer morbidity in a cohort of Canadian petroleum workers.

AIMS: To assess mortality and cancer morbidity in Canadian petroleum workers and explore exposure-response relations for specific petroleum agents. METHODS: A total of 25 292 employees hired between 1964 and 1994 were linked to the Canadian tumour registry and national mortality database. Exposure-response trends were assessed for hydrocarbon solvents/fuels, hydrocarbon lubricants, petroleum coke/spent catalyst, and hydrogen sulphide (H2S). RESULTS: External comparison analyses (mortality and incidence) showed deficits for all causes and all malignant neoplasms combined and were consistent with expectation for most malignant and non-malignant sites analysed. Gall bladder cancer mortality was increased among males based on four deaths, but cases had no common job assignments and the increase was focused in workers employed <10 years. Mesothelioma incidence was increased. Most exposure-specific analyses were compromised by small numbers. Statistically significant increases were observed for H2S exposure and a subgroup of accidental deaths as well as for petroleum coke/spent catalyst exposure and lung cancer. While both findings have a degree of biologic plausibility, the H2S association, which exhibited a clearer exposure-response pattern, could be subject to unmeasured confounders. Additionally, interpretation was complicated by the high correlation between hydrocarbon and H2S exposures. With regard to lung cancer, the analysis could not adequately control for smoking, was based on small numbers, and exhibited a tenuous exposure-response pattern. CONCLUSION: The findings for mesothelioma suggest the need for continued attention to asbestos in the petroleum industry. The relation between accidental deaths and H2S exposure deserves closer scrutiny in similarly exposed populations. Further analyses of lung cancer are underway and will be reported separately.

Updated mortality among diverse operating segments of a petroleum company.

OBJECTIVES: To update mortality for 34 560 employees from diverse operating segments of a Canadian petroleum company; and to investigate potential relations with occupational factors. METHODS: Employees from 1964-83 were linked to the Canadian mortality data base to provide 11 years additional follow up. There were 6760 deaths and 750 683 person-years of follow up compared with 3909 and 428 190, respectively, in the earlier study. Analyses used standardised mortality ratios (SMRs) to compare worker cause specific mortality with the Canadian general population. Duration of employment and latency analyses were performed for causes previously found to be increased in this and other petroleum cohorts, as well as any findings of interest. RESULTS: For the period 1964-94, employees experienced significantly low overall mortality (SMR=0.86 men, SMR=0.80 women). Kidney cancer, which has been increased in some studies of petroleum workers, was not increased. Acute non-lymphocytic leukaemia in exposed operating segments was consistent with the expected or only slightly, non-significantly increased. The most notable finding was increased deaths from mesothelioma among refinery and petrochemical workers (SMR 8.68; 95% confidence interval (95% CI) 5.51 to 13.03), most of whom were long term employees in jobs with presumed exposure to asbestos (mechanical and pipefitters). Deaths from multiple myeloma among marketing and distribution workers, which were previously increased, remained increased (SMR 2.08; 95% CI 0.95 to 3.95) in the update period 1984-94; however, there was no clear pattern by duration of employment or latency. Aortic aneurysms, which also were previously significantly increased among marketing and distribution workers approached the expected in the update period (SMR 1.18; 95% CI 0. 65-1.98). Analyses by duration of employment showed suggestive trends for aortic aneurysms, but earlier studies of this cohort have not found a relation between aortic aneurysms and exposure to hydrocarbons. CONCLUSION: The additional 2851 deaths and 322 493 person-years of follow up strengthened the assessment of mortality patterns relative to occupational factors. With the exception of mesothelioma, no clear work related increases in disease were identified.

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.

Mortality among three refinery/petrochemical plant cohorts. I. 1970 to 1982 active/terminated workers.

This study updates mortality rates for 19,075 active and terminated workers at three refinery/petrochemical plants. Mortality rates of the workers were compared with both national and state rates. The results indicated deficits of deaths for all causes, all malignant neoplasms, and respiratory and prostate cancer. The noteworthy finding was a statistically significant increase in leukemia among Louisiana male subjects (standardized mortality ratio [SMR], 181; 95% confidence interval [CI], 122 to 259), which showed suggestive trends of increasing SMRs with increasing tenure. This excess was largely due to increased chronic lymphocytic leukemia (SMR, 351; 95% CI, 168 to 645). The rate of kidney cancer remained elevated among Louisiana male subjects, but this finding was no longer significant, and there were no patterns in SMRs by tenure and latency. Mesothelioma was increased at the Louisiana (SMR, 198; 95% CI, 72 to 430) and Texas (SMR, 246; 95% CI, 99 to 507) locations. The leukemia findings have prompted a study of leukemia incidence at the Louisiana location.

Mortality among three refinery/petrochemical plant cohorts. II. Retirees.

This study updates mortality data for 6238 retirees from three refinery/petrochemical plants. Almost 90% of the cohort was deceased. Deaths from all causes (standardized mortality ratio, 104; 95% confidence interval, 102 to 107) and all cancers (standardized mortality ratio, 109; 95% confidence interval, 102 to 116) were elevated. Increased deaths due to kidney cancer, mesothelioma, and the category of other lymphohemopoietic cancers also were observed. The rate of leukemia was not increased. There was little internal or external consistency to support an occupational relationship for kidney cancer, but findings for mesothelioma and other lymphohemopoietic cancers are consistent with reports for other petroleum cohorts. Analyses by age indicated significantly higher all-cause mortality rates among persons retiring before age 65. The results suggest that continued surveillance of mesothelioma and lymphohemopoietic cancer malignancies in younger workers with more contemporary exposures may be warranted. Furthermore, age at retirement should be considered when analyzing occupational cohorts.

Mortality experience of a young petrochemical industry cohort. 1979-1992 follow-up study of US-based employees.

This retrospective study examines the mortality patterns of a relatively young cohort of 81,746 former and current petrochemical company employees. Standardized mortality ratios (SMR) for 1979 through 1992 are generally from about unity to well below unity for major causes and numerous specific causes of death studied by gender/race/job subgroups. Findings of note include a SMR (based on incidence rates) of 1.94 (95% confidence interval [CI], 1.04 to 3.33) for mesothelioma, and a SMR of 1.81 (95% CI, 0.90 to 3.24) for chronic lymphocytic leukemia, both among males hired before 1960. All male semiskilled operatives have a 1.6-fold increase (95% CI, 1.07 to 2.29) in motor vehicle accident deaths, with declining rates since the mid-1980s. The overall SMR for acquired immunodeficiency syndrome (AIDS) is at unity (69 deaths), with excesses in technician and office worker subgroups. Four decedents with lymphoma (code 202.8 in 9th revision ICD) had AIDS as a secondary cause of death, suggesting the need to examine secondary causes when studying lymphopoietic conditions. This routine surveillance activity provides leads regarding the presence or absence of excess mortality risk.