Biomedical subjects

N Sathiakumar

Publications and source records attributed to N Sathiakumar.

At least 19 recordsLinked to original sources

PubMed2006

Cancer incidence among semiconductor and electronic storage device workers.

AIMS: To evaluate cancer incidence among workers at two facilities in the USA that made semiconductors and electronic storage devices. METHODS: 89 054 men and women employed by International Business Machines (IBM) were included in the study. We compared employees' incidence rates with general population rates and examined incidence patterns by facility, duration of employment, time since first employment, manufacturing era, potential for exposure to workplace environments other than offices and work activity. RESULTS: For employees at the semiconductor manufacturing facility, the standardised incidence ratio (SIR) for all cancers combined was 81 (1541 observed cases, 95% confidence interval (CI) 77 to 85) and for those at the storage device manufacturing facility the SIR was 87 (1319 observed cases, 95% CI 82 to 92). The subgroups of employees with > or =15 years since hiring and > or =5 years worked had 6-16% fewer total incidents than expected. SIRs were increased for several cancers in certain employee subgroups, but analyses of incidence patterns by potential exposure and by years spent and time since starting in specific work activities did not clearly indicate that the excesses were due to occupational exposure. CONCLUSIONS: This study did not provide strong or consistent evidence of causal associations with employment factors. Data on employees with long potential induction time and many years worked were limited. Further follow-up will allow a more informative analysis of cancer incidence that might be plausibly related to workplace exposures in the cohort.

Adult↗

PubMed2005

An updated study of mortality among North American synthetic rubber industry workers.

AIM: This study evaluated the mortality experience of workers from the styrene-butadiene industry. METHODS: The authors added seven years of follow up to a previous investigation of mortality among 17 924 men employed in the North American synthetic rubber industry. Analyses used the standardised mortality ratios (SMRs) to compare styrene-butadiene rubber workers' cause specific mortality (1943-98) with those of the United States and the Ontario general populations. RESULTS: Overall, the observed/expected numbers of deaths were 6237/7242 for all causes (SMR = 86, 95% CI 84 to 88) and 1608/1741 for all cancers combined (SMR = 92, 95% CI 88 to 97), 71/61 for leukaemia, 53/53 for non-Hodgkin's lymphoma, and 26/27 for multiple myeloma. The 16% leukaemia increase was concentrated in hourly paid subjects with 20-29 years since hire and 10 or more years of employment in the industry (19/7.4, SMR = 258, 95% CI 156 to 403) and in subjects employed in polymerisation (18/8.8, SMR = 204, 95% CI 121 to 322), maintenance labour (15/7.4, SMR = 326, 95% CI 178 to 456), and laboratory operations (14/4.3, SMR = 326, 95% CI 178-546). CONCLUSION: The study found that some subgroups of synthetic rubber workers had an excess of mortality from leukaemia that was not limited to a particular form of leukaemia. Uncertainty remains about the specific agent(s) that might be responsible for the observed excesses and about the role of unidentified confounding factors. The study did not find any clear relation between employment in the industry and other forms of lymphohaematopoietic cancer. Some subgroups of subjects had more than expected deaths from colorectal and prostate cancers. These increases did not appear to be related to occupational exposure in the industry.

Aged↗

PubMed2004

A cross-sectional study of triallate exposure and neurological health among workers at a pesticide manufacturing and formulating facility.

AIMS: To evaluate the relation between an indicator of cumulative exposure to triallate and selected measures of neurological function, including nerve conduction, the prevalence of certain neurological deficits as determined by a medical examination, and vibration perception threshold testing in workers at a pesticide manufacturing plant. METHODS: Subjects were 50 workers with high estimated triallate exposure ("high triallate" group) and 50 workers with no or low triallate exposure ("no/low triallate" group). Industrial hygienists used existing work histories and personal knowledge of plant operations to develop a triallate score. In-person interviews elicited information on past medical history and on occupational and non-occupational exposures. A neurologist carried out nerve conduction tests of the sural and the peroneal nerves, a standardised neurological examination, and vibration sensation testing. RESULTS: Differences between the high and the no/low triallate groups were minimal for all but one of the six nerve conduction tests, for the prevalence of neurological abnormalities, and for vibration sensation perception. The high triallate group had lower mean sural nerve peak amplitude than the no/low triallate group (11.7 v 15.2 microV, p = 0.03). This difference was reduced when adjusted for other potential risk factors (12.5 v 14.5 microV, p = 0.25) and was not associated with cumulative triallate score. We also noted several associations between factors other than triallate and nerve conduction measures. CONCLUSION: The results were consistent with the absence of an association between triallate and measures of neurological function.

Adult↗

PubMed2001

Leukemia and exposure to 1,3-butadiene, styrene and dimethyldithiocarbamate among workers in the synthetic rubber industry.

This study evaluated relations between exposure to 1,3-butadiene (BD), styrene (STY) and dimethyldithiocarbamate (DMDTC) and mortality from leukemia among synthetic rubber industry workers. Subjects were 13130 men employed for at least 1 year during 1943-1991 at any of six plants that manufactured synthetic rubber. Death certificates and medical records identified workers with leukemia. Cumulative exposure estimates were based on plant- and time period-specific process and task characteristics, linked to subjects' work histories. Poisson regression estimated relative rates (RRs) for workers exposed to each agent compared to unexposed workers. Leukemia (N=59) was positively associated with BD ppm-years (RRs of 1.0, 1.2, 2.0 and 3.8, for exposures of 0, >0-<86.3, 86.3-<362.2 and 362.2+ ppm-years; only the RR for the highest exposure category was statistically significant), STY ppm-years (RRs of 1.0, 1.2, 2.3 and 3.2, for exposures of 0, >0-<20.6, 20.6-<60.4 and 60.4+ ppm-years; only the RR for the highest exposure category was statistically significant) and DMDTC mg-years/cm (RRs of 1.0, 2.3, 4.9 and 2.9, for 0, >0-<566.6, 566.6-<1395.1 and 1395.1+ mg-years/cm; the RR for each non-zero exposure category was statistically significant) after adjusting for age and years since hire. After further adjusting each agent-specific set of RRs for the other two agents, a positive but imprecise relation remained for BD and DMDTC but not for STY. The association with BD was stronger for ppm-years due to exposure intensities >100 ppm than for ppm-years due to lower concentrations. BD and DMDTC, but not STY, were positively associated with leukemia in multivariable analyses. The independent effect of each agent was difficult to evaluate because of correlations with other agents and imprecision.

Butadienes↗

PubMed2001

Mortality among employees at a petrochemical research facility.

BACKGROUND: This retrospective follow-up study evaluated mortality during 1970-1996 among 6,956 employees at a petrochemical research facility in Illinois. METHODS: Standardized mortality ratios (SMRs) compared employees' mortality rates with those of the Illinois general population. Poisson regression procedures estimated rate ratios for various subject subgroups compared to other facility employees. RESULTS: Subjects had 267 observed/524 expected deaths (SMR = 51) from all causes combined and a large deficit of deaths from all cancers (76/136, SMR = 56) and from most other major diseases. Other results included fewer than expected brain cancers (1/4.0, SMR = 25) and a slight increase in colorectal cancer (20/14, SMR = 139) that was concentrated in white male scientists employed for one of the three main companies at the facility (SMR = 295, RR = 2.6). CONCLUSIONS: The deficit of brain cancer deaths contrasts with an excess incidence seen in a companion study. Subjects' generally favorable mortality experience probably reflects socioeconomic advantages of employees relative to the Illinois general population.

Adult↗

PubMed2001

Cancer incidence among employees at a petrochemical research facility.

This investigation evaluated cancer incidence among workers at a petrochemical research facility in Illinois. A cluster of brain cancer and other intracranial tumors had occurred at the facility before the study began. The subjects were 5641 people who had worked at the facility from 1970 through 1996 and who had lived in Illinois at any time between 1986 and 1997. Data on cancer cases came primarily from the Illinois State Cancer Registry. Analyses compared the 1986-to-1997 cancer incidence rates of employees with Illinois general population rates. Subjects had 18% fewer than expected total cancers (125 observed/153 expected cases; standardized incidence ratio [SIR], 82; 95% confidence interval [CI], 68 to 98), which was primarily attributed to a large deficit of lung cancer (10/26; SIR, 39; CI, 19 to 72). Brain cancer was increased in the overall study group (6/2.7; SIR, 222; CI, 81 to 484). This excess was restricted to white men who were scientists or technicians for one of the three companies at the facility (6/0.8; SIR, 750; CI, 275 to 1633); all cases in this group had worked in the "500 building complex" (6/0.6; SIR, 968; CI, 355 to 2106). Subjects also had an increased incidence of thyroid cancer (7/2.6; SIR, 265; CI, 106 to 546) that was not concentrated in particular occupational or building groups. The brain cancer incidence patterns indicated that an unidentified occupational exposure might have been responsible for the excess. Chance, socioeconomic factors leading to better case detection in facility employees than in the general population, and confounding by potential nonoccupational risk factors are plausible explanations of the observed increase in thyroid cancer.

Adult↗

PubMed2001

Cancer and benign tumor incidence among employees in a polymers research complex.

The detection of several intracranial tumors among employees in one building complex (C500) at a petrochemical research facility prompted investigation of a possible workplace cause. This retrospective follow-up study included 1847 subjects, of whom 1735 had worked in C500. Medical records, death certificates, and Illinois State Cancer Registry data confirmed self-reported cancers and tumors. Analyses compared the subjects' cancer and benign intracranial tumor incidence rates with national general population rates. C500 employees had 15% fewer than expected total cancers (92 observed/108 expected; standardized incidence ratio [SIR], 85; 95% confidence interval [95% CI], 69 to 104). An excess of brain cancer (6/2.0; SIR, 302; 95% CI, 111 to 657) was concentrated among white men who had 10 or more years since hire and 5 or more years of C500 employment (4/0.7; SIR, 602; 95% CI, 165 to 1552) and who had worked in a particular building of C500 (5/0.7; SIR, 735; 95% CI, 239 to 1716). An excess of benign intracranial tumors (6/1.6; SIR, 385; 95% CI, 142 to 839) was not restricted to a single type of tumor and was not concentrated in any particular building. Occupational exposure may have caused the increased rate of brain cancer but is a less likely explanation for the elevated rate of benign intracranial tumors.

Adult↗

PubMed2001

Case-control study of intracranial tumors among employees at a petrochemical research facility.

This case-control study evaluated the relation between potential exposure to chemical and physical agents and the occurrence of intracranial tumors among employees at a petrochemical research facility. Cases were employees with glioma (n = 6) or benign intracranial tumors (n = 6). Controls (n = 119) were individually matched to cases on gender and birth year, and they were alive and did not have an intracranial tumor at the case's diagnosis date. Exposure information came from interviews with subjects or surrogates and from corporate records on agents used in research projects. Analyses computed matched odds ratios (ORs) and corresponding 95% confidence intervals (CIs) for self-reported exposure to 15 agents and project-based estimates of exposure to 29 agents. For gliomas, the OR was elevated for self-reported exposure to ionizing radiation (OR, 15.7; CI, 1.4 to 179.4), n-hexane (OR, infinity; CI, 1.4 to infinity), organometallics (OR, 9.4; CI, 1.5 to 59.7), and amines other than nitrosamines (OR, 6.0; CI, 1.0 to 35.7). The OR also was elevated for project-based potential use of ionizing radiation (OR, 9.6; CI, 1.7 to 55.2) and for potential use of n-hexane lasting at least 4 years (OR, 16.2; CI, 1.1 to 227.6). For benign intracranial tumors, the OR was elevated only for self-reported exposure to ionizing radiation (OR, 5.4; CI, 1.7 to 43.1) and other amines (OR, 5.2; CI, 0.9 to 29.5). Occupational exposure may have contributed to the glioma excess, but the specific causal agents remain unknown. The study indicated that benign intracranial tumors were unlikely to be work-related.

Adult↗

PubMed2000

An updated mortality study of workers at a dye and resin manufacturing plant.

This investigation evaluated the mortality experience of workers at a dye and resin manufacturing plant in New Jersey. The retrospective follow-up study included 3266 workers employed for at least 6 months at the plant. Plant production areas were South Dyes, where anthraquinone dyes and intermediates were produced; North Dyes, where azo dyes and intermediates were produced; and plastics and additives, where various resins and additives for plastics were made. Analyses used standardized mortality ratio (SMRs) to compare the cohort's cause-specific mortality rates during 1952 to 1995 with the rates of the New Jersey population. There were fewer than expected deaths from all causes combined (728 observed vs 810 expected) and similar numbers of observed and expected cancer deaths (225 vs 232). Statistically significant work area-specific cancer excesses were limited to white men and included an excess of lung cancer in Maintenance workers (40 observed vs 26 expected; SMR, 153; 95% confidence interval [CI], 109 to 208) and in South Dyes workers (32 observed vs 19 expected; SMR, 168; CI, 115 to 237) and an excess of stomach cancer (5 observed vs 1.3 expected; SMR, 386; CI, 125 to 901), bladder cancer (4 observed vs 0.8 expected; SMR, 515; CI, 140 to 1318) and central nervous system cancer (5 observed vs 1 expected; SMR, 517; CI, 168 to 1206) in North Dyes workers. None of these increases was concentrated in work area subgroups with long duration of employment and long potential induction time. It was concluded that the excess of bladder cancer probably was due to exposure to carcinogenic arylamines at another facility, where some employees had worked before coming to the study plant. The other cancer increases may be attributable to chance, to uncontrolled confounding by smoking, or to an unidentified occupational exposure.

Cause of Death↗

PubMed1998

Using the National Death Index to obtain underlying cause of death codes.

This study evaluated the comparability of underlying cause of death codes obtained from NDI Plus, a new feature of the National Death Index (NDI), with codes assigned by two study nosologists or by a National Center for Health Statistics (NCHS) nosologist. Two study nosologists and an NCHS nosologist independently reviewed the death certificates of 493 decedents and assigned each an International Classification of Diseases code for the underlying cause of death. Using the NCHS codes as the reference standard, we determined discrepancy rates for NDI Plus codes; for each study nosologist's original codes; and for "final study codes," derived by comparing the two sets of study nosologists' codes and resolving discrepancies by using the NCHS code. For all causes of death combined, the discrepancy rate was 4% for NDI Plus codes, 4% for the final study codes and 6%-7% for the study nosologists' original codes. The discrepancy rate for selecting the appropriate cancer site was 1% for NDI Plus codes and 3% for the final study codes. For noncancer conditions, the discrepancy rate was 5% for NDI Plus codes and 4% for the final study codes. NDI Plus underlying cause of death codes are comparable to codes developed using standard but more cumbersome procedures. The use of NDI Plus codes may enhance the validity of comparisons of an occupational cohort's mortality rates with national or state rates.

Cause of Death↗

PubMed1998

Mortality from cancer and other causes of death among synthetic rubber workers.

OBJECTIVES: This study evaluated the mortality experience of workers from the styrene-butadiene rubber industry. Concerns about a possible association of 1,3-butadiene and styrene with lymphohaematopoietic, gastrointestinal, and lung cancers prompted the investigation. METHODS: A retrospective follow up study was conducted of 15,649 men employed for at least one year at any of eight North American styrene-butadiene rubber plants. Analyses used standardised mortality ratios (SMRs) to compare styrene-butadiene rubber workers' cause specific mortalities (1943-91) with those of the United States and Ontario general populations. RESULTS: On average, there were 25 years of follow up per subject. The standardised mortality ratio (SMR) was 87 (95% confidence interval (95% CI) 85 to 90) for all causes of death combined and was 93 (95% CI 87 to 99) for all cancers. There was an excess of leukaemia (SMR 131, 95% CI 97 to 174), restricted to hourly workers (SMR 143, 95% CI 104 to 191). For causes of death other than leukaemia, SMRs were close to or below the null value of 100. Results by work area (process group) were unremarkable for non-Hodgkin's lymphoma, multiple myeloma, and stomach cancer. Maintenance workers had a slight increase in deaths from lung cancer, and certain subgroups of workers had more than expected deaths from cancer of the large intestine and the larynx. CONCLUSION: This study found an excess of leukaemia that is likely to be due to exposure to butadiene or to butadiene plus other chemicals. Deaths from non-Hodgkin's lymphoma, multiple myeloma, and stomach cancer did not seem to be related to occupational exposure. The excess deaths from lung cancer among maintenance workers may be due in part to confounding by smoking, which was not controlled for, and in part to an unidentified occupational exposure other than butadiene or styrene. Increases in cancer of the large intestine and larynx were based on small numbers, did not seem to be due to exposure to butadiene or styrene, and may be chance observations.

Butadienes↗

PubMed1997

A review of epidemiologic studies of triazine herbicides and cancer.

We evaluated epidemiologic evidence pertaining to the human carcinogenic potential of triazine herbicides in general and of atrazine, the most common triazine. Cancers for which data are available included non-Hodgkin's lymphoma, Hodgkin's disease, leukemia, multiple myeloma, soft tissue sarcoma, colon cancer, and ovarian cancer. The investigations had methodologic limitations, including lack of in-depth exposure measurements and small numbers of subjects with heavy exposure and/or with many years since starting exposure, possibly required for the induction of cancer. The relation between triazines and non-Hodgkin's lymphoma has been assessed in four independent population-based case-control studies, reporting odds ratios ranging from 1.2 to 2.5. However, chance and/or confounding by other agricultural exposures may have produced these weak statistical associations. Furthermore, a pooled analysis of three of the case-control studies and the combined analysis of two retrospective follow-up studies did not demonstrate the types of dose-response or induction time patterns that would be expected if triazines were causal factors. The epidemiologic data pertaining to Hodgkin's disease, leukemia, multiple myeloma, soft tissue sarcoma, colon cancer, and ovarian cancer were inadequate for determining whether associations with atrazine or triazines exist in humans. For each of these cancers, only one or two studies evaluating the relationship were available, and the results of the studies typically were imprecise.

Carcinogens↗

PubMed1997

Epidemiologic evidence on the relationship between mists containing sulfuric acid and respiratory tract cancer.

This review identified and evaluated 25 epidemiologic studies pertaining to the carcinogenicity of mists containing sulfuric acid (MSA). Few studies were designed with acid mists as the principal exposure under investigation, and in all studies exposure assessment was limited. The results of the follow-up studies from industries with high or moderate exposure potential and the case-control studies indicate, in aggregate, a moderate association between MSA and larynx cancer. The data suggest a dose-response relationship. However, many of the results from individual studies are imprecise, and confounding by smoking, alcohol, and other occupational agents is not adequately adjusted for. The biologic plausibility and the possible carcinogenic mechanism remain uncertain. There is little evidence in support of a causal relationship between exposure to MSA and lung cancer. Information is inadequate for drawing any meaningful inference about the association between exposure to MSA and nasal cancer.

Aerosols↗

PubMed1996

A follow-up study of synthetic rubber workers.

Although 1,3-butadiene (BD) has been classified as an animal carcinogen, epidemiologic research has reported inconsistent results on the relationship between BD and lymphopoietic and other cancers in humans. This study evaluated the mortality experience of 15649 men employed for at least 1 year at any of eight North American styrene-butadiene rubber (SBR) plants. About 75% of the subjects were exposed to BD; 83% were exposed to styrene (STY). During 1943-1991, the cohort had a total of 386172 and an average of 25 person-years of follow-up, with 3976 deaths observed compared to 4553 deaths expected based on general population mortality rates (standardized mortality ratio (SMR) = 87, 95% confidence interval (CI) = 85-90). More than expected leukemia deaths occurred in the overall cohort (48 observed/37 expected, SMR = 131, CI = 97-174) and among ever hourly subjects (45/32, SMR = 143, CI = 104-191). The excess was concentrated among ever hourly subjects with 10+ years worked and 20+ years since hire (28/13, SMR = 224, CI = 149-323) and among subjects in polymerization (15/6.0, SMR = 251, CI = 140-414), maintenance labor (13/4.9, SMR = 265, CI = 141-453) and laboratories (10/2.3, SMR = 431, CI = 207-793), three areas with potential for relatively high exposure to BD or STY monomers. Some cohort sub-groups had slight increases in deaths from lymphopoietic cancers other than leukemia, but mortality patterns by race, years worked and process group within the SBR industry did not indicate a causal association with occupational exposures. These results indicate that exposures in the SBR industry cause leukemia.

Butadienes↗

PubMed1996

Leukemia and cumulative exposure to butadiene, styrene and benzene among workers in the synthetic rubber industry.

Retrospective, quantitative estimates of exposure to 1,3-butadiene, styrene and benzene were developed for a follow-up study of leukemia mortality among 16610 subjects employed at six North American styrene-butadiene rubber manufacturing plants (418846 person-years, 58 leukemia deaths). The estimation procedure entailed identifying work areas within each manufacturing process, historical changes in exposure potential and specific tasks involving exposure, and using mathematical models to calculate job- and time-period-specific average exposures. The resulting estimates were linked with the subjects' work histories to obtain cumulative exposure estimates, which were employed in stratified and Poisson regression analyses of mortality rates. Mantel-Haenszel rate ratios adjusted by race, age, and cumulative styrene exposure increase with cumulative butadiene exposure from 1 in the nonexposed category to 4.5 in the category of 80 ppm-years or more (P = 0.01). The risk pattern is less clear and statistically nonsignificant for styrene exposure. A trend of increasing risk with butadiene exposure is still present after exclusion of the nonexposed category (P = 0.03). A parsimonious interpretation of the findings presented here, in light of previous epidemiologic studies, is that exposure to butadiene in the synthetic rubber industry produces a dose-related increase in the occurrence of leukemia.

Benzene↗

PubMed1996

Mortality among workers at two triazine herbicide manufacturing plants.

Triazine herbicides, used extensively in the United States, have not been assessed adequately for carcinogenicity in humans. This study evaluated the mortality experience during the period 1960-1986 of 2,683 men with definite or probable manufacturing exposure to triazine herbicides and 2,234 men with possible exposure to triazines. Standardized mortality ratios (SMRs) were computed as the observed numbers of deaths among study subjects divided by the numbers expected on the basis of general population mortality rates. Subjects with definite or probable exposure to triazines had a favorable mortality experience, compared with U.S. men [all causes, SMR = 72, 95% confidence interval (CI) = 58-89; all cancer, SMR = 85, CI = 46-142]. This group had an increase in deaths from non-Hodgkin's lymphoma (NHL) (3 observed/0.78 expected, SMR = 385, CI = 79-1,124). Two of the decedents with NHL had worked for less than 1 year in triazine-related jobs. Among the 2,234 subjects with possible triazine-related work, the mortality rate for all causes combined was similar to the rates of U.S. men. There was only one confirmed death from NHL. On balance, the results were consistent with previous investigations, which have found no convincing evidence of a causal link between triazines and cancer. However, the exposed cohorts were relatively young and had, on average, only 18 years of follow-up. In particular, results were imprecise for subjects having both a long duration of exposure and long potential induction periods.

Adult↗

PubMed1995

Mortality among workers at a pesticide manufacturing plant.

This study evaluated the mortality experience of 2384 workers at a plant in Colorado that produced aldrin, azodrin, vapona, and other pesticides. Subjects were followed up for a median of 29 years, from 1952 through 1990. Comparisons of the cohort's mortality rates with those of the Colorado population indicated that observed and expected numbers of deaths were similar for all causes (465 observed/473 expected) and for all cancers (113/106). Standardized mortality ratios were elevated for hepatobiliary cancer (5/2.0; standardized mortality ratio, 249, 95% confidence interval, 81 to 581), due to an excess of biliary duct/gall bladder cancer, and for pneumonia (20/13; standardized mortality ratio, 150, 95% confidence interval, 92 to 232). These increases were limited to white men in hourly jobs but were not limited to any particular production unit and did not display duration-response trends. It is unlikely that these excesses are due to occupational exposures at the plant.

Adult↗

PubMed1995

A case-control study of leukemia among petroleum workers.

This case-control study evaluates the relationship between leukemia and the work histories of active and retired employees of a large petroleum company. The study includes 69 cases with leukemia and 284 matched controls. Employment in production-related work in the oil and gas division was associated with myelogenous leukemia (odds ratio [OR] = 2.0, 95% confidence interval [CI] = .97 to 4.2) and particularly with acute myelogenous leukemia (OR = 2.8, 95% CI = 1.1 to 7.3). The association with acute myelogenous leukemia was strongest for subjects in the highest tertile (32+ years) of duration of employment in oil- and gas production-related work (OR = 8.7, 95% CI = 2.0 to 37), and there was a consistent trend of increasing ORs with increasing duration of employment (P = .01). No clear association was observed for refining division work and leukemia. This is the first epidemiologic study reporting a positive association between oil and gas field work and acute myelogenous leukemia.

Adult↗