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Biomedical subjects

O Wong

Publications and source records attributed to O Wong.

At least 91 records · Page 5Linked to original sources
PubMed1988

Mortality of workers in two Minnesota taconite mining and milling operations.

Mortality during the years 1947 to 1983 was studied in 3,444 men employed for at least 3 months in Minnesota taconite mining operations during the years 1947 to 1958. During 86,307 person-years of observation, there were 801 deaths for a standardized mortality ratio (SMR) of 88 (US white male rates) or 98 (Minnesota rates). The 41 deaths from respiratory cancer were fewer than expected, the SMR being 61 (P less than or equal to .01) (US rates) and 85 (Minnesota rates). There were 25 respiratory cancers 20 or more years after first taconite employment, for an SMR of 57 (P less than or equal to .01) (US rates). SMRs for colon cancer, kidney cancer, and lymphopoietic cancer were elevated, but below the level of statistical significance. There was one death from pleural mesothelioma, 11 years after first taconite employment, in a man with long prior employment as a locomotive operator. The pattern of deaths did not suggest asbestos-related disease in taconite miners and millers.

Asbestos↗
PubMed1987

An industry wide mortality study of chemical workers occupationally exposed to benzene. I. General results.

The cohort (7676) of this historical prospective study consisted of a group of male chemical workers from seven plants who had been occupationally exposed (continuously or intermittently) to benzene for at least six months and a comparison group of male chemical workers from the same plants who had been employed for at least six months during the same period but were never occupationally exposed to benzene. The observed mortality of the cohort, by cause, was compared with the expected based on the US mortality rates, standardised for age, race, sex, and calendar time. Standardised mortality ratios (SMRs) from all lymphatic and haematopoietic (lymphopoietic) cancer combined, leukaemia, non-Hodgkin's lymphoma (lymphosarcoma, reticulosarcoma, and other lymphoma), and non-Hodgkin's lymphopoietic cancer (non-Hodgkin's lymphoma and leukaemia) for the exposed group were slightly, but not significantly, raised above the national norm. These SMRs were considerably higher than those in the comparison group. When the group with no occupational exposure was used for direct comparison, the continuously exposed group experienced a relative risk from lymphopoietic cancer of 3.20 (p less than 0.05). Furthermore, the Mantel-Haenszel chi-square showed that the association between continuous exposure to benzene and leukaemia was statistically significant (p less than 0.05).

Adult↗
PubMed1987

An industry wide mortality study of chemical workers occupationally exposed to benzene. II. Dose response analyses.

The data presented in this paper show statistically significant dose response relations between cumulative exposure to benzene (ppm-months) and mortality from both all lymphopoietic cancer combined and leukaemia. Chemical workers with a cumulative exposure to benzene of at least 720 ppm-months experienced a relative risk of 3.93 for lymphatic and haematopoietic cancer when compared with workers with no occupational exposure. The dose response relation between cumulative exposure and non-Hodgkin's lymphopoietic cancer was of borderline statistical significance (p = 0.06). No dose response relation was detected for any other causes of death.

Adult↗
PubMed1986

An epidemiological study of petroleum refinery employees.

A cohort study of 14179 current and former Chevron USA employees at the Richmond and El Segundo, California, refineries was conducted. The cohort consisted of everyone working at either refinery for a minimum of one year. The observed mortality of the cohort, by cause, was compared with the expected based on the United States mortality rates, standardised for age, race, sex, and calendar time. Analyses by refinery, job category, hire date, duration of employment, and latency were performed. For the entire cohort, mortality from all causes was 72.4% of that expected, a deficit that was statistically significant. In addition, a significantly lower mortality was found for all forms of cancer combined, digestive cancer, lung cancer, heart disease, non-malignant respiratory disease, diseases of the digestive system, and accidents. Only lymphopoietic cancer showed a pattern of increased risk suggestive of a possible relation to an occupational exposure. The excess appears confined to cancer of lymphatic tissue (not leukaemias) at Richmond, and only among those hired before 1948. A follow up case analysis of the deaths from lymphatic cancer failed to identify a common exposure pattern.

Brain Neoplasms↗
PubMed1985

An epidemiologic surveillance program for evaluating occupational reproductive hazards.

A noninvasive and inexpensive epidemiologic program for evaluating the possible effects of occupational exposures on fertility is proposed. This surveillance program utilizes reproductive information obtainable from a short questionnaire (1-2 pages in length) or directly from existing medical, employment, or insurance records, and results can be generated readily on a routine basis. This program examines the reproductive experience of the exposed workers in terms of live births compared with that of the US general population with the proper statistical adjustments. It calculates the standardized birth ratios (SBR), adjusting for maternal age, parity, calendar time, and race. Such an analysis will detect whether there is a significant decrease in fertility among a group of employees, and is, therefore, a useful surveillance tool. The proposed method should be viewed as a mechanism to provide an early signal for any potential hazard and to direct priority for other more in-depth epidemiologic or physiologic studies. The procedure is illustrated with data from individuals exposed to EDB, DBCP, and waste-water treatment plant processes. The method can be modified to compare the reproductive performance of an exposed group to that of an internal control group. With an internal control group, additional confounding factors can be taken into consideration. The relative merits of this approach compared to another method of fertility evaluation, semen analysis, are discussed.

Adult↗
PubMed1985

Mortality of paint and coatings industry workers. A follow-up study.

Extensive follow-up of production workers in the paint and coatings industry failed to indicate any important hazard that was previously unsuspected. The authors are more confident of the results of their original study since studying a subsample of persons lost to follow-up in the original study. Some efforts to investigate certain diseases (skin and liver cancer) more vigorously met with failure, which illustrates the problem of attempting retrospective studies by using death certificates for case ascertainment. Of the successful studies, the leukemia case-control analysis showed a possible relationship to lacquer production, which probably included benzene exposure. For lung cancer, no exposure category was associated with increased risk. The bowel cancer excesses, concentrated in three plants, are probably not job related and in any case do not represent an industry-wide problem. Cerebrovascular accidents showed a mild elevation of risk for vehicle workers. Although strong statements concerning the safety of this industry probably await more studies or further follow-up of this cohort, there is every indication that it is an industry without a major excess of any job-related disease. In drawing this conclusion, however, one must be aware that an individual job or individual plant could harbor health problems that would not be detected by a study of this type.

California↗
PubMed1985

Mortality among members of a heavy construction equipment operators union with potential exposure to diesel exhaust emissions.

A historical prospective mortality study was conducted on a cohort of 34 156 male members of a heavy construction equipment operators union with potential exposure to diesel exhaust emissions. This cohort comprised all individuals who were members of the International Union of Operating Engineers, Locals 3 and 3A, for at least one year between 1 January 1964 and 31 December 1978. The mortality experience of the entire cohort and several subcohorts was compared with that of United States white men, adjusted for age and calendar time. The comparison statistic was the commonly used standardised mortality ratio (SMR). Historical environmental measurements did not exist, but partial work histories were available for some cohort members through the union dispatch computer tapes. An attempt was made to relate mortality experience to the union members' dispatch histories. Overall mortality for the entire cohort and several subgroups was significantly lower than expected. When cause specific mortality was examined, however, the study provided suggestive evidence for the existence of several potential health problems in this cohort. Mortality from liver cancer for the entire cohort was significantly high. Although mortality from lung cancer for the entire cohort was similar to expected, a positive trend by latency was observed for lung cancer. A significant excess of mortality from lung cancer was found among the retirees and the group for whom no dispatch histories were available. Other dispatch groups showed no evidence of lung cancer excess. In addition, the total cohort experienced significant mortality excess from emphysema and accidental deaths.

Accidents, Occupational↗
PubMed1985

Comparison of SMR, PMR, and PCMR in a cohort of union members potentially exposed to diesel exhaust emissions.

A comparison of cause specific standarised mortality ratios (SMRs) and proportionate mortality ratios (PMRs) or proportionate cancer mortality ratios (PCMRs) was made based on the mortality experience of a cohort of 34 156 members of a heavy equipment operators union. Two types of PMRs or PCMRs were used in the comparison: those based on all deaths and those based on deaths known to the union only. The comparison indicated that, for the entire cohort, both types of PMRs were poor indicators for cancer risk and produced a large number of false positives. On the other hand, PCMRs appeared to be better than PMRs for assessing the direction of site specific cancer risk, but they tended to overstate the magnitude of risk. Analysis by duration of union membership or latency indicated that PMRs or PCMRs based on deaths known to the union tended to overestimate the risk of lung cancer by disproportionately larger amounts in groups with shorter time than in groups with longer time. This differential bias had the net effect of reducing the gradient of any trend or eliminating the trend entirely. In conclusion, PMR or PCMR, based on reasonably sufficient death ascertainment, has a certain usefulness in generating hypotheses, but they are not useful or reliable in measuring the magnitude of risk or in detecting trends in dose response analysis. No conclusion should be drawn from either PMR or PCMR.

Air Pollutants, Occupational↗
PubMed1985

Mortality among employees of lead battery plants and lead-producing plants, 1947-1980.

Two cohorts of male lead workers, 4 519 battery plant workers and 2 300 lead production workers, all of whom had been employed for at least one year during the period 1 January 1946 through 31 December 1970, were observed for mortality during the 34 years from 1 January 1947 through 31 December 1980. Vital status as of the closing date was determined for 94.7% of the former group and 91.6% of the latter. There were 1 718 deaths in the first cohort and 621 in the second. Mortality from all causes combined was significantly greater than expected in each cohort, the standardized mortality ratio (SMR) being 107 and 113, respectively. Among the battery plant workers the greater than expected mortality rate resulted in large part from a significant number of excess deaths from malignant neoplasms (SMR 113), other hypertensive disease (mainly renal) (SMR 320), chronic nephritis (SMR 222), and a group of ill-defined conditions (SMR 355). Among the lead production workers the pattern was similar, with a significant number of excess deaths from other hypertensive disease (SMR 475), hypertensive heart disease (SMR 203), chronic nephritis (SMR 265), and ill-defined conditions (SMR 214). There was also a significant excess of deaths from external causes (SMR 143). The SMR for total malignancies was 113, but this value was not significantly elevated at the 5% level. In neither cohort were deaths from cerebrovascular disease in significant excess, the SMR being 93 and 132, respectively. A proportionate mortality analysis showed that the excess deaths from cerebrovascular disease and from hypertensive heart disease among smelter workers were in part due to the high proportion of nonwhites in the smelter populations. The stomach, liver, and lungs were the sites responsible for most excess cancer deaths in both cohorts, but the elevated SMR values were statistically significant only for gastric and lung cancers in battery plant workers. There were no excess deaths from malignancies of the kidney, brain, or lymphopoietic system in either cohort. It is impossible to relate the observed mortality to levels of lead exposure; because of meager quantitative information prior to 1960. It is known that past exposures had been very high. Ethnicity, diet, alcohol, and cigarette smoking could not be ruled out as possible confounding etiologic factors for the cancer deaths.

Humans↗
PubMed1985

Long-term mortality study of oil refinery workers. IV. Exposure to the lubricating-dewaxing process.

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.

Butanones↗
PubMed1985

Asbestos and gastrointestinal cancer. A review of the literature.

Exposure to asbestos is among several factors cited as possible causes of esophageal, gastric and colorectal cancer. More than 45 published studies have presented mortality data on asbestos-exposed workers. For each cohort, we listed the observed and expected rates of deaths from types of gastrointestinal cancer based on the latest published follow-up. Summary standardized mortality ratios (SMRs) were then derived. Finally, we calculated summary SMRs for total gastrointestinal tract cancer for three occupational groups: asbestos factory workers, insulators/shipyard workers and asbestos miners. Statistically significant elevations in summary SMRs were found for esophageal, stomach and total gastrointestinal tract cancer in all asbestos-exposed workers. Esophageal cancer summary SMRs remained significantly elevated when data were reanalyzed to include only those cohorts with death certificate diagnoses for cause of observed deaths. However, summary SMRs were not statistically significant for stomach and total gastrointestinal tract cancer after reanalysis. Summary SMRs by occupational group showed a significant elevation for total gastrointestinal cancer in insulators/shipyard workers. The elevation was not significant after reanalysis. Based on the results after reanalysis, the elevations in summary SMRs for stomach and total gastrointestinal tract cancer are of a magnitude that could result from diagnostic and investigator error. We conclude that more studies are required before stomach and colorectal cancers are documented as asbestos-related diseases.

Asbestos↗
PubMed1984

Mortality of workers potentially exposed to organic and inorganic brominated chemicals, DBCP, TRIS, PBB, and DDT.

A historical prospective mortality study was conducted on 3579 white male workers employed between 1935 and 1976 with potential exposures to brominated compounds including 1,2-dibromo-3-chloropropane (DBCP), Tris (2,3-dibromopropyl) phosphate, polybrominated biphenyls (PBB), various organic and inorganic bromides, and DDT. The vital status as of 31 December 1976 was determined for 3384 (95%) of these workers: 2806 (79%) were still living and 578 (16%) had died. Death certificates were obtained for 541 deaths (94% of all deaths). The mortality experience of the entire cohort and several subcohorts was compared with that of United States white men adjusted for age and calendar time. The comparison statistic was the commonly used standardised mortality ratio (SMR). Historical industrial hygiene data were not available, and the workers were classified by their work areas or departments in order to estimate their potential exposures. Overall mortality for the entire cohort and several subgroups was significantly lower than expected. For the entire cohort, significant mortality deficits were observed in diseases of the circulatory system, non-malignant respiratory disease, and diseases of the digestive system. On the other hand, mortality from diabetes mellitus was significantly raised for the cohort. No significant overall or cause-specific mortality excess was detected among employees potentially exposed to either TRIS or DDT. A significant mortality excess due to diseases of the circulatory system was observed among workers potentially exposed to DBCP. Mortality from testicular cancer was significantly higher than expected among those potentially exposed to other organic bromides. The common potential exposure of those who had died of testicular cancer was methyl bromide. Owing to the lack of accurate historical exposure information and the fact that many workers were potentially exposed to a multitude of chemicals, it is difficult to draw definitive statements on the causations of the observed mortality excesses.

Arkansas↗
PubMed1983

Retrospective mortality and medical surveillance studies of workers in benzene areas of refineries.

The mortality and health experiences of refinery workers employed in benzene processes or operations are described. A retrospective cohort mortality study of benzene workers employed from 1952 to 1978 revealed no excess in overall general mortality or in cancer mortality compared either with the experience of the U.S. general population or with that of an internal control group. Ascertainment of vital status was accomplished for 99% of the cohort. Recent industrial hygiene data that included 1,394 personal samples indicated that 84% of all benzene exposures were less than 1 part per million (ppm), with a median exposure of 0.14 ppm for the refinery workers, and 0.53 ppm for those in the benzene-related units. Among these workers, no deaths from leukemia were observed. A medical surveillance program for benzene workers is also described, with special emphasis on the effectiveness of laboratory screening. Evaluation of data for a 21-year period showed no significant changes in the blood indices of the workers as a group. The limited value of establishing screening guidelines without the support of epidemiological studies is discussed.

Adult↗
PubMed1982

Clinical and metabolic abnormalities associated with occupational exposure to polychlorinated biphenyls (PCBs).

A cross-sectional study of 120 male workers was conducted to determine the prevalence of increased polychlorinated biphenyl (PCB) absorption as well as the presence of potentially related clinical and metabolic abnormalities. Three exposure categories ("exposed", "nominally exposed", "nonexposed") were defined. Complete work histories, clinical histories, physical examinations and laboratory tests, including plasma PCB determinations were obtained. In addition, fat PCB levels were determined in randomly selected subjects in each exposed group. Evidence of dermatotoxicity was observed and elevated PCB levels were noted more frequently in the exposed group (p less than .0001), correlating well with age and duration of employment. These correlations were stronger for fat (p less than .001) than for plasma (p less than .01) PCB levels. In the exposed group, significant correlations were found between plasma PCB and serum triglyceride (p less than .0001) and serum glutamic oxaloacetic transaminase (SGOT) levels (p less than .01). These correlations remained significant after controlling for either age or length of employment. No significant correlations were found between PCB levels and levels of cholesterol, high-density lipoprotein cholesterol or levels studied on liver function tests other than SGOT. Further analyses relating frequency of reported direct contact with PCB levels suggested a dermal route of exposure. An analysis by union affiliation demonstrated that those in crafts involving greater direct exposure had correspondingly higher elevations of PCB levels.

Adolescent↗
PubMed1982

Methodological issues involving the standardized mortality ratio and proportionate mortality ratio in occupational studies.

The algebraic relationship between the standardized mortality ratio (SMR) and the proportionate mortality ratio (PMR) is derived. This relationship clearly shows that the validity of PMR as a risk assessment index depends on the homogeneity of the age-specific overall SMRs and the value of the "average" overall SMR (usually estimated by the age-adjusted overall SMR). Based on actual data from various epidemiologic studies, the adequacy, or lack of it, of using the PMR or the converted SMR is examined. Variations of the PMR method using different bases can be useful. Incomplete death ascertainment, which is a common problem in PMR studies, can lead to biased estimates.

Adult↗
PubMed1981

Hodgkin's disease in South African children.

Thirty South African children with Hodgkin's disease were studied over a 7-year period (1970 - 1977). Males outnumbered females by 5:1. The most frequent histological pattern encountered was mixed cellularity (72%). Fourteen patients with stage I, II or IIIA disease were treated with radiation therapy alone, and all achieved a complete remission with a median duration of remission in excess of 48 months. Sixteen patients with stage III or IV disease received combination chemotherapy (MOPP regimen), and 13 achieved a complete remission with a median duration of remission in excess of 48 months. The overall median survival was in excess of 60 months. Seven patients died during the study period, 4 of Hodgkin's disease and 3 of other causes. There was no significant difference in treatment response or survival between Black and White children.

Adolescent↗