Mortality risk among workers with exposure to dioxins.

BACKGROUND: In several studies, dioxin exposure has been associated with increased risk from several causes of death. AIMS: To compare the mortality experience of workers exposed to dioxins during trichlorophenol (TCP) and pentachlorophenol (PCP) production to that of the general population and to examine mortality risk by estimated exposure levels. METHODS: A retrospective cohort study which followed up workers' vital status from 1940 to 2011, with serum surveys to support estimation of historical dioxin exposure levels. RESULTS: Among the 2192 study subjects, there were nine deaths in TCP workers from acute non-lymphatic leukaemia [standardized mortality ratio (SMR) = 2.88, 95% confidence interval (CI) 1.32-5.47], four mesothelioma deaths (SMR = 5.12, 95% CI 1.39-13.10) and four soft tissue sarcoma (STS) deaths (SMR = 3.08, 95% CI 0.84-7.87). In PCP workers, there were eight deaths from non-Hodgkin's lymphoma (SMR = 1.92, 95% CI 0.83-3.79), 150 from ischaemic heart disease (SMR = 1.20, 95% CI 1.01-7.89) and five from stomach ulcers (SMR = 3.38, 95% CI 1.10-7.89). There were no trends of increased mortality with increased dioxin exposure except for STS and 2,3,7,8-tetrachlorodibenzo-p-dioxin levels. This finding for STS should be interpreted with caution due to the small number of deaths and the uncertainty in diagnosis and nosology. CONCLUSIONS: While some causes of death were greater than expected, this study provides little evidence of increased risk when dioxin exposures are considered.

Slips, trips and falls at a chemical manufacturing company.

BACKGROUND: Slips, trips and falls (STF) are a major cause of workplace injury. AIMS: To examine risk factors for STF at a large US chemical manufacturing company. METHODS: We conducted a case-control study of occupational STF. Cases were identified from company injury records between 1 April 2009 and 1 May 2011. Four controls per case were randomly selected from all active company workers employed during the same time. Data were collected through a questionnaire and from company medical examinations. Logistic regression was used to calculate odds ratio (OR) and 95% confidence intervals (95% CI) for personal, environmental and health-related risk factors for STF. RESULTS: There were 74 cases and 309 controls. The response rate was 65% for the cases and 68% for the controls. Most STF were unrelated to production activities. When examining all factors in a logistic regression model, increased OR were observed for increased body mass index (OR = 1.44, 95% CI: 1.03-2.02), having arthritis (OR = 2.11, 95% CI: 1.01-4.37), lack of exercise (OR = 2.25, 95% CI: 1.01-5.05), carrying materials (OR = 3.01, 95% CI: 1.41-6.43) and being female (OR = 2.46, 95% CI: 1.17-5.19). Reduced risk of STF was observed for never having smoked (OR = 0.48, 95% CI: 0.24-0.95), long service (OR = 0.53, 95% CI: 0.34-0.81) and persons working over 8h a day (OR = 0.42, 95% CI: 0.20-0.88). CONCLUSIONS: Risk factors for STF in a large US chemical company are similar to those reported from other workplaces, but we found that staying fit and healthy is important for reducing risk.

The healthy worker effect in US chemical industry workers.

BACKGROUND: Occupational studies typically observe a 20% deficit in overall mortality, broadly characterized as the healthy worker effect (HWE). Components of the HWE may be addressed by various analytical approaches. AIMS: To explore the HWE in a modern industrial cohort. METHODS: Standardized mortality ratios (SMRs) were calculated for 114,683 US chemical industry employees, who worked at least 3 days between 1960 and 2005. RESULTS: SMRs were 79 (95% confidence interval 78-80) for all causes, 81 (95% confidence interval 79-82) for heart disease, 70 (95% confidence interval 67-73) for non-malignant respiratory disease, 83 (95% confidence interval 81-85) for smoking-related cancers (buccal, cervix, oesophagus, stomach, pancreas, lung, larynx, bladder and kidney) combined and 97 (95% confidence interval 95-100) for other cancers. CONCLUSIONS: The low SMRs observed in this study are likely due to differential smoking between the cohort and the background population. Future considerations to control for the HWE should take this into account.

Correlates of serum dioxin to self-reported exposure factors.

The aim of the current analysis was to examine the determinates of lipid-adjusted body levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) from occupational histories, age, body mass index, and self-reported information from a questionnaire. We collected serum from 346 workers at a New Zealand chemical plant that manufactured and formulated the herbicide, 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). Age, body mass index, and employment history were significant determinates of TCDD. The self-reported data on occupation, residence, and general diet were not predictive of serum levels and we observed no evidence of increased TCDD levels from living close to the site. For participants with putative occupational exposure, employment history and personal factors were important to understand the range of TCDD serum levels. For employees without direct occupational exposure, and resulting lower dioxin levels, we recommend further efforts to develop and validate questionnaires to better evaluate environmental sources of dioxins.

Have sperm counts been reduced 50 percent in 50 years? A statistical model revisited.

OBJECTIVE: To reanalyze data that were used in a linear model to predict that mean sperm counts have been reduced globally by approximately 50% in the last 50 years. DESIGN: The mean sperm counts and their temporal distribution were reanalyzed via several different statistical models (quadratic, spline fit, and stairstep). CONCLUSION: There are several reasons why a published linear regression model is inappropriate to infer a 50% reduction in mean sperm counts in the last 50 years. These include [1] the potential selection biases that may have occurred with the 61 assembled studies such that they are not representative of their underlying populations; [2] the likely variability in collection methods, in particular, the lack of adherence to a minimum prescribed abstinence period, as has been stated for the largest study, which contained 29.7% of all the subjects included in the analysis; [3] the paucity of data in the first 30 years of the 50-year trend analysis; [4] the fact that if the last 20 years of data are examined, which contains 78.7% of all the studies and 88.1% of the total number of subjects, there is no decrease in sperm counts, in fact, sperm counts were observed to have increased; [5] the conflicting data from a large individual laboratory, which was not prone to the collection variability that likely occurred between the 61 studies, that did not suggest a decline in mean sperm count or seminal volume during a comparable time period, even though this laboratory published the data that were largely responsible for the high historical values in the linear model; and, most importantly, [6] the variety of other mathematical models that perform statistically better at describing the recent data than the linear model and thus offer substantially different hypotheses. The data are only robust during the last 20 years of the analysis, in which all the models, except the linear model, suggest constant or slightly increasing sperm counts.

Lymphohaematopoietic cancer risk among chemical workers exposed to benzene.

AIMS: To determine cause specific mortality in a cohort of 2266 chemical workers exposed to benzene in various manufacturing processes after 1935. METHODS: The cohort has accumulated over 80 000 person-years of observation; about 70% of the workers were followed for more than 30 years since first exposure. RESULTS: Mortality from non-malignant diseases of the blood was increased (SMR 2.17, 95% CI 0.87 to 4.48), and correlated with duration of benzene exposure, although risk had decreased from the previous investigation of this cohort. The risk for leukaemia was slightly above background (SMR 1.14, obs 12, 95% CI 0.59 to 1.99) but has also decreased since the earlier study of this cohort. SMRs for acute non-lymphocytic leukaemia (ANLL), chronic lymphatic leukaemia, and non-Hodgkin's lymphoma were 1.11, 0.42, and 1.06 respectively. There was evidence of a weak trend of increasing SMRs for leukaemia and possibly ANLL with increasing low-level cumulative exposure but not with other measures. CONCLUSION: Leukaemia and ANLL results were consistent with the mildly increased risk estimates from lower exposure subgroups of the Pliofilm cohort.

A longitudinal study of respiratory health of toluene diisocyanate production workers.

A longitudinal comparison of 305 toluene diisocyanate (TDI) and 581 hydrocarbons workers employed at a Texas chemical manufacturing facility from 1971 through 1997 tested whether workplace exposure to TDI was associated with changes in any of the respiratory measures collected by the company's health surveillance program. Mean TDI exposures measured 96.9 ppb-months, or 2.3 ppb per job. At the end of the study, there were no differences in self-reported symptoms between the groups. Longitudinal analyses of symptoms and pulmonary function showed no correlation with TDI exposure, yielding an average annual decrease in forced expiratory volume at 1 second of 30 mL per year. We concluded that exposure to TDI at workplace concentrations was not associated with respiratory illnesses in this cohort, and consistent with other recent research, it seemed not to accelerate the normal age-related decline in pulmonary function.

Mortality among workers engaged in the development or manufacture of styrene-based products--an update.

Mortality was updated another 11 years through 1986 for a previously studied cohort of 2904 male chemical workers who were potentially exposed to styrene and related materials for a year or more between 1937 and 1971. Substantial deficits in mortality from all causes and total cancer were observed in the cohort when it was compared with white males in the United States, and also other chemical workers who were unexposed to styrene-based products. Mortality from leukemia was slightly less than expected during the updated period, in contrast to an excess of lymphatic leukemia observed in the original period. Yet small elevations in risk of other types of lymphatic cancer, particularly multiple myeloma, persisted. The risk of these cancers did not increase with estimated intensity or duration of styrene exposure. The findings are discussed in context with those of studies of similarly exposed workers in related industries.

The experience of an occupational health centre during a prolonged work stoppage.

We describe the experience of the occupational health centre at the Sarnia Division of Dow Chemical Canada prior to, during and after a work stoppage of seven months duration. A descriptive analysis was performed of the occupational health case load during the work stoppage compared to the same period one year earlier. Total visits as well as those for dermatologic, upper respiratory, musculoskeletal and those associated with a non-occupationally related situation (e.g., sunburn) exceeded normal frequencies during the first ten weeks of the work stoppage. In particular, there was a peak number of visits during the first two weeks when a 'lock-in' prevented employees from visiting their own physicians except for emergency situations. In the Discussion section, recommendations are outlined to lessen the chance of adverse health effects in workers responsible for operating a chemical plant during a work stoppage.

A cross-sectional study of ethylene glycol monomethyl ether process employees.

Human exposures to ethylene glycol monomethyl ether have been associated with hematological and neurological abnormalities. Recent animal toxicology studies have also reported testicular atrophy. To determine whether employees potentially exposed to ethylene glycol monomethyl ether during manufacturing and packaging had a higher prevalence of anemia, leukopenia, or sterility than an in-plant comparison group, a cross-sectional study was conducted at the Michigan Division of Dow Chemical U.S.A. Blood samples on 65 of 97 potentially exposed and control white males, and semen samples from a subset of 15 were analyzed. With the possible exception of smaller testicular size, no gross abnormalities or clinically meaningful differences in hematological or fertility indices were noted. Results of regression modeling suggested that white blood cells and hemoglobin might be decreased at higher exposure levels.

A thirty-eight year comparison of cancer incidence and mortality among employees at a Connecticut chemical plant.

An important aspect of occupational mortality is the fact that death registration is complete and has good specificity and sensitivity for those cancers with poor survival. However, if available and complete, cancer incidence data are preferable. A unique opportunity presented itself at The Dow Chemical Company's Allyn's Point plant (Gales Ferry, Connecticut) to conduct a cancer incidence and mortality study since the plant began operation in 1951, several years after the establishment of the Connecticut Tumor Registry. All male employees (N = 666) with one or more years of service from 1951-1989 were eligible for the study. Altogether there were 47 primary incident cancers which represented 40 individuals. The Standardized Incidence Ratio (SIR) for all cancer was 124 (95% confidence interval [CI] 91-165). There were 23 deaths reported for all cancers (Standardized Mortality Ratio [SMR] 87, 95% CI 55-131). Only laryngeal cancer incidence was statistically significant (Standardized Incidence Ratio [SIR] 417, 95% CI 135-972). After review of the work history records, this association was found to be inconsistent with a common exposure hazard at the plant.

"Intrinsic" elimination rate and dietary intake estimates for selected indicator PCBs: toxicokinetic modeling using serial sampling data in US subjects, 2005-2010.

Changes in measured concentrations of persistent compounds such as polychlorinated biphenyls (PCBs) in an individual over time reflect not only intrinsic elimination rates but also any ongoing intake of the compounds and changes in the volume of distribution. Thus, "apparent" elimination rates calculated from data on changes in serum lipid-adjusted concentration may over- or under-estimate the "intrinsic" elimination rates for such compounds. Serum PCB concentrations were measured in 43 individuals approximately 5years apart. Changes in measured concentrations and body weights were used to estimate mass-based apparent elimination rates. The changes in estimated body mass of PCBs 105, 118, 138, 153, and 180 were input into a simple first-order model employing previously estimated intrinsic elimination rates to estimate congener-specific average dietary intake rates over the period between samples. Calculated median dietary intakes were compared to previous estimates. Intrinsic elimination rates were adjusted for two congeners. The analyses support central tendencies of intrinsic elimination rates of approximately 5years for PCBs 105 and 118, 11years for PCB 138, 14.4years for PCB 153, and 20years or more for PCB 180. Estimated dietary intakes for this population and time period depend on the assumed intrinsic elimination rates and range from 0.1ngkg(-1)d(-1) for PCB 105 to approximately 1-2ngkg(-1)d(-1) for PCB 180. Estimated body burdens of PCB 180 changed very little over the five-year period, suggesting near steady-state exposure levels. As a result, estimates for both elimination half-life and ongoing intake rates for this congener are highly uncertain.

Phenoxy herbicides and cancer: insufficient epidemiologic evidence for a causal relationship.

The question as to whether or not any or all of the phenoxy herbicides are carcinogenic to humans continues to be evaluated. We review the evidence available from the retrospective cohort and case-control epidemiology studies. Graphs of the individual probability densities for the odds ratios from the eight case-control studies of soft-tissue sarcoma, Hodgkin's disease, or non-Hodgkin's lymphoma demonstrate gross inconsistencies which are not likely to be attributable to chance. Early studies, conducted in Sweden, had indicated strong associations, but subsequent work from New Zealand and the United States has failed to substantiate those findings. The reasons for the discordant results may relate more to methodologic problems in the earlier studies than to qualitative or quantitative differences in the exposures of the underlying populations. The retrospective cohort studies offer the advantage of having focused on occupational groups believed to have had the highest exposures, although they have been criticized as being individually too small to assess the risks of the rarer forms of cancer. Consideration of the combined cohort studies of workers exposed to the phenoxy herbicides per se provides little or no evidence of carcinogenicity. Thus, the total weight of evidence currently available does not support a conclusion that the phenoxy herbicides present a carcinogenic hazard to humans.

Validation of work histories obtained from interviews.

There have been few attempts to assess the validity of occupational histories obtained from interviews. A nested case-control study of lung cancer conducted in 1985 among a cohort of 19,608 male workers at a Texas chemical production facility provided such an opportunity. Telephone interviews were attempted with 308 lung cancer patients and 588 matched controls or their next of kin in order to gather information on tobacco use, diet, places of residence, and occupations. Interview data from 734 respondents (143 subjects and 591 next of kin) were then compared with the records of work area assignments maintained by the company and with exposure profiles developed by an industrial hygienist. Respondents recalled 48.4 per cent of all documented work area assignments, but only 2.6 per cent of the chemical agents judged as likely exposures. Recall of usual work area assignment was 70.8 per cent. Among the factors found to have most influenced recall were the number and durations of assignments, a subjective assessment of the quality of the interview, and the relationship of the interview respondent to the subject. The elapsed time from job assignment to interview was also found to affect recall of the longest assignment of the subject.

Cancer risk for chemical workers exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin.

AIMS: To describe the long term mortality experience of a cohort of 2187 male chemical production workers previously exposed to substantial levels of dioxin. METHODS: Vital status for a previously identified cohort was determined for an additional 10 years, to 1995. Dioxin exposures took place before 1983 and were sufficient to result in chloracne in 245 individuals. Mortality rates were compared with national figures and with a large pool of co-workers in unrelated production jobs. RESULTS: All cancers combined (standardised mortality ratio (SMR) = 1.0, 95% CI 0.8 to 1.1) and lung cancer (SMR = 0.8, 95% CI 0.6 to 1.1) were at or below expected levels. Rates for soft tissue sarcoma (SMR = 2.4, 95% CI 0.3 to 8.6) and non-Hodgkin's lymphoma (SMR = 1.4, 95% CI 0.6 to 2.7) were greater than expected overall, but below expectation in the update period. No trend of increasing risk with increasing exposure was observed for these cancers. Workers who developed chloracne had very low all-cancer rates (SMR = 0.5, 95% CI 0.3 to 1.0), and lung cancer rates (SMR = 0.3, 95% CI 0.0 to 1.1). CONCLUSIONS: We found no coherent evidence of increased cancer risk from dioxin exposure in this cohort. Our study highlights the wide range of cancer rates and the lack of consistency across dioxin studies.

The incidence of spontaneous cytogenetic aberrations in lymphocytes cultured from normal humans for 48 and 72 h.

Spontaneously occurring cytogenetic aberrations were compared in 48- and 72-h human lymphocyte cultures from a group of 20 normal male volunteers. Mitotic indices for both cultures times were also evaluated. BUdR (5-bromo, 2-deoxyuridine) labelled metaphases from three men were utilized to determine the cell cycle kinetics in the medium used. There was no statistically significant difference between 48- and 72-h cultures among the majority of aberration categories considered. Possibly, the lymphocyte populations at the two different culture times maintained a consistent yield level. Mitotic indices in 72-h cultures were invariably higher than those in 48-h cultures. An overwhelming number of first division metaphases were observed at 48 h of incubation; however, approximately 22% of the lymphocytes did not enter into mitosis until 72 h in culture. A number of difficulties with regard to utilizing BUdR-labelled first division metaphases for cytogenetic analyses are discussed.

Preliminary evaluation of an employer-sponsored mammography screening program.

Recognizing the importance of early detection of breast cancer, the Dow Chemical Company initiated a breast cancer awareness program in 1988. Evaluation of operational aspects of mammography screening component revealed that about half (53%) of 1186 eligible women in the evaluation cohort took part, although participation was three times higher for active than for retired employees. Eleven per cent of participants were considered to have "positive" screens, ie, had roentgenogram films with suspicious areas, and at least 82% of these women had follow-up medical services within 1 year of screening, as determined by a review of group insurance claims records. Two women with positive mammograms were subsequently diagnosed and treated for breast cancer within 2 months of screening. None of the women with negative mammograms developed breast cancer in the subsequent year. The suitability of group insurance data resources for responding to health care delivery questions is discussed.

Update of the mortality experience of employees with occupational exposure to 1,2-dibromo-3-chloropropane (DBCP).

DBCP (1,2-dibromo-3-chloropropane), a nematocide, was used in the United States from the mid-1950s until 1977. The U.S. Environmental Protection Agency (EPA) restricted and eventually banned its use after the 1977 discovery of DBCP-induced sterility in production workers. The present study is an update of the mortality (1957-1989) experience of a cohort of 548 male employees who had potential for exposure in the production and formulation of DBCP. While adjusting for age, calendar-year, and pay status of all other Midland-area Dow Chemical male employees, there were 68 total observed deaths in the cohort compared to 72.1 expected (Mantel Haenszel Relative Risk 0.9, 95% Confidence Interval 0.7-1.2) and 19 deaths from all malignancies compared to 19.0 expected (RR 1.0, 95% CI 0.6-1.6). Of the a priori anatomic cancer sites of interest, there were no deaths from stomach, liver, kidney, testes, or nasal cavity cancers. Altogether, there were 7 deaths from lung cancer compared to 6.6 expected (RR 1.1, 95% CI 0.5-2.3). Among the 81 employees with exposure categorized as direct for 1 or more years, there were 3 observed lung cancer deaths compared to 0.9 expected (RR 3.3, 95% CI 1.1-9.6). Smoking was a confounding factor in the interpretation of this observation. Although the present analysis nearly doubled the number of person-years from the original study, the conclusions remain limited by the cohort's size and duration of follow-up.

Determinants of spermatogenesis recovery among workers exposed to 1,2-dibromo-3-chloropropane.

The purpose of this study was to investigate the determinants of spermatogenesis recovery among 30 azoospermic and 17 oligospermic workers who had a maximum of 18 months of exposure to 1,2-dibromo-3-chloropropane during 1976 to 1977. A maximum of 11 years of follow-up data were examined. Of the 26 azoospermic subjects who voluntarily participated in follow-up, 19 (73.0%) showed evidence of spermatogenesis recovery. Thirteen azoospermic subjects recovered to normospermic levels; however, their mean most recent sperm count (44.4 million/mL) was significantly lower (P less than .01) than the mean (88.8 million/mL) of the 17 oligospermic subjects who recovered to normospermic levels. The lack of spermatogenesis recovery was definitively shown to be job (drumming and canning) and, possibly, age related. Duration of exposure and the initial 1977 categorization of exposure (high, moderate, and low) were not predictive of recovery. Testicular atrophy was observed with azoospermia, and the testicles subsequently increased in size among those azoospermic subjects who returned to normospermic levels. The follicle-stimulating hormone level in 1977 was significantly associated with azoospermia as well as the likelihood of return to normospermia among the azoospermic subjects.