Biomedical subjects

Colleen Beall

Publications and source records attributed to Colleen Beall.

9 recordsLinked to original sources

PubMed2006

TCDD exposure-response analysis and risk assessment.

We examined the relation between cancer mortality and time-dependent cumulative exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) estimated from a concentration- and age-dependent kinetic model of elimination, and we estimated incremental cancer risks at age 75. Data from the National Institute for Occupational Safety and Health study of 3,538 workers with occupational exposure to TCDD were analyzed using standardized mortality ratios and Cox regression procedures. Analyses adjusted for potential confounding by age, year of birth, and race and considered exposure lag periods of 0, 10, or 15 years. Other potential confounders including smoking and other occupational exposures were evaluated indirectly. To explore the influence of extreme values of cumulative TCDD ppt-years, we restricted the analysis to observations with exposure below the 95th percentile or used logarithmic (ln) transformed exposure values. We applied penalized smoothing splines to examine variation in the exposure-response relation across the exposure range. TCDD was not statistically significantly associated with cancer mortality using the full data set, regardless of the lag period. When we restricted the analysis to observations with exposure below the 95th percentile, TCDD was associated positively with cancer mortality, particularly when a 15-year lag was applied (untransformed exposure data: regression coefficient , standard error (s.e.) = 1.4 x 10(-6), p < 0.05; ln-transformed exposure data: , s.e. = 2.9 x 10(-2), p < 0.05). The estimated incremental lifetime risk of mortality at age 75 from all cancers was about 6 to more than 10 times lower than previous estimates derived from this cohort using exposure models that did not consider the age and concentration dependence of TCDD elimination.

Aged↗

PubMed2005

Methodologic issues in follow-up studies of cancer incidence among occupational groups in the United States.

PURPOSE: Incidence studies of occupational factors and cancer in the United States are problematic because the use of population-based registries to identify cases requires development of historical data on subjects' residences and often severely restricts the time period of follow up. This article describes procedures for addressing these challenges. METHODS: We used data from studies of cancer incidence and mortality among microelectronics industry employees to assess various methods for developing residential histories and the relative informativeness of the two studies. RESULTS: We developed residential histories for 98% of 99,229 mortality study subjects. Analyses making alternative assumptions about residential histories yielded standardized incidence ratios varying by at most 6%. Use of postemployment residential histories increased person-years by up to 62% and increased the observed number of cancers by up to 28%. The proportion of mortality study person-years included in the cancer incidence study ranged from 40% to 77% among work activity subcohorts. The number of observed cancer cases in the incidence study was 60% higher than the number of observed cancer deaths in the mortality study. CONCLUSIONS: Assumptions about residential history had little impact on validity. Use of information sources with national coverage to develop residential histories increased the incidence study's precision. Despite geographic and temporal restrictions, incidence studies provide more data than mortality studies on cancers with good survival. However, the potential for selection bias in incidence studies may vary considerably among subcohorts, indicating the need for cautious interpretation of such research.

Adult↗

PubMed2005

Cancer incidence among a cohort of smokeless tobacco users (United States).

OBJECTIVE: Smokeless tobacco (ST) use remains a prevalent form of tobacco use among certain US populations. The purpose of this paper is to clarify its role in cancer development. METHODS: Using data from a prospective cohort of the US population, we categorized 6,779 subjects 45-75 years of age as ST users or non-ST users. Subjects were further stratified by cigarette smoking status in order to differentiate 'exclusive' ST users (n=414) from never tobacco users (n=2,979). RESULTS: In this cohort, exclusive ST use was not associated with increased incidence of all cancer in males (hazard ratio=0.8, 95% CI: 0.4, 1.6) or females (HR=1.2, 95% CI: 0.7-2.1) or oral cancer (standardized incidence ratio=30, 95% CI: 3, 95). No synergistic effect was observed between ST and cigarette smoking among male combined users (females were not analyzed for combined use) for the major cancers. CONCLUSIONS: In contrast to the well-known deleterious effects of cigarette smoking, ST use did not substantially increase the risk for cancer incidence above that of non-tobacco users, particularly among males. Although the use of tobacco in any form is to be discouraged, our data suggests that cancer risks are much lower from ST use than from cigarette smoking.

Aged↗

PubMed2005

Exposure assessment for retrospective follow-up studies of semiconductor- and storage device-manufacturing workers.

OBJECTIVE: This exposure assessment was conducted in the first large study of mortality and cancer incidence in semiconductor and storage device manufacturing. METHODS: Unique combinations of division, department and job codes and names (DDJ) from work history records were assigned to work groups and exposure categories. Agent exposure matrices assessed differences in potential exposures between groups. Changes in exposure over time were tracked by dividing the production history into manufacturing eras. RESULTS: Nineteen work groups were developed to capture 310,351 unique DDJs from 1965-1999. Agent exposure matrices contrasted exposure potential to solvents, metals, and work in cleanrooms between groups, and three manufacturing eras were identified for each site. CONCLUSIONS: The work groups, manufacturing eras and agent matrices have been used to classify workers in the study of cancer incidence and mortality.

Computer Storage Devices↗

PubMed2005

Mortality among semiconductor and storage device-manufacturing workers.

PROBLEM: We evaluated mortality during 1965 to 1999 among 126,836 workers at two semiconductor facilities and one storage device facility. METHOD: We compared employees' cause-specific mortality rates with general population rates and examined mortality patterns by facility, duration of employment, time since first employment, and work activity. RESULTS: Employees had lower-than-expected mortality overall (6579 observed deaths, standardized mortality ratio [SMR] = 65; 95% confidence interval [CI] = 64-67), for all cancers combined (2159 observed, SMR = 78, 95% CI = 75-81) and for other major diseases. Central nervous system cancer was associated with process equipment maintenance at one of the semiconductor facilities (10 observed, SMR = 247, 95% CI = 118-454). Prostate cancer was associated with facilities/laboratories at the storage device facility (18 observed, SMR = 198, (5% CI = 117-313). CONCLUSIONS: Further evaluation of workplace exposures or independent investigations of similar occupational groups may clarify the interpretation of associations observed in this study.

Adult↗

PubMed2005

Exposure reconstruction for the TCDD-exposed NIOSH cohort using a concentration- and age-dependent model of elimination.

Recent studies demonstrating a concentration dependence of elimination of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) suggest that previous estimates of exposure for occupationally exposed cohorts may have underestimated actual exposure, resulting in a potential overestimate of the carcinogenic potency of TCDD in humans based on the mortality data for these cohorts. Using a database on U.S. chemical manufacturing workers potentially exposed to TCDD compiled by the National Institute for Occupational Safety and Health (NIOSH), we evaluated the impact of using a concentration- and age-dependent elimination model (CADM) (Aylward et al., 2005) on estimates of serum lipid area under the curve (AUC) for the NIOSH cohort. These data were used previously by Steenland et al. (2001) in combination with a first-order elimination model with an 8.7-year half-life to estimate cumulative serum lipid concentration (equivalent to AUC) for these workers for use in cancer dose-response assessment. Serum lipid TCDD measurements taken in 1988 for a subset of the cohort were combined with the NIOSH job exposure matrix and work histories to estimate dose rates per unit of exposure score. We evaluated the effect of choices in regression model (regression on untransformed vs. ln-transformed data and inclusion of a nonzero regression intercept) as well as the impact of choices of elimination models and parameters on estimated AUCs for the cohort. Central estimates for dose rate parameters derived from the serum-sampled subcohort were applied with the elimination models to time-specific exposure scores for the entire cohort to generate AUC estimates for all cohort members. Use of the CADM resulted in improved model fits to the serum sampling data compared to the first-order models. Dose rates varied by a factor of 50 among different combinations of elimination model, parameter sets, and regression models. Use of a CADM results in increases of up to five-fold in AUC estimates for the more highly exposed members of the cohort compared to estimates obtained using the first-order model with 8.7-year half-life. This degree of variation in the AUC estimates for this cohort would affect substantially the cancer potency estimates derived from the mortality data from this cohort. Such variability and uncertainty in the reconstructed serum lipid AUC estimates for this cohort, depending on elimination model, parameter set, and regression model, have not been described previously and are critical components in evaluating the dose-response data from the occupationally exposed populations.

Adult↗

PubMed2005

Need to educate primary caregivers about the risk factor profile of smokeless tobacco users.

BACKGROUND: Many cancer risk factors are correlated with one another, and the presence of 1 risk factor may be a marker for other unhealthy behaviors. In this article, we focus on smokeless tobacco (ST), a known risk factor for oral leukoplakia and oral cancer, and the cancer risk factors associated with its use. METHODS: We analyzed cross-sectional data from the National Health and Nutrition Examination Survey (NHANES) I and the 1982-1984 NHANES I Epidemiologic Follow-up Study. Risk factor information was available on individuals 25-74 years of age, most of whom would be middle age or elderly today. RESULTS: Older subjects, Black males, and those living in the Southern Unite States had the highest prevalence of ST use. ST use was associated with current smoking (odds ratio [OR], 1.3; 95% confidence interval [CI], 1.1-1.5), former smoking (OR, 1.6; 95% CI, 1.4-2.0), low fruit and vegetable intake, low SES, increased alcohol consumption (among nonsmoking ST users), and increased body mass index, all of which elevate cancer risk. CONCLUSION. Physicians and dentists should ask their patients about current or former ST use. Identification of ST users should prompt the physician or dentist to inquire about other chronic disease risk factors that the patient may have and to educate the ST using patient about ways to reduce their risk of cancer.

Adult↗

PubMed2002

Chronic disease mortality in a cohort of smokeless tobacco users.

The purpose of this study was to characterize the relation between smokeless tobacco use and the risk of all-cause and disease-specific mortality. Using data from the First National Health and Nutrition Examination Survey Epidemiologic Followup Study, the authors assessed the 20-year mortality experience of smokeless tobacco users. Subjects aged 45 years or more at baseline (1971-1975) were categorized as either smokeless tobacco users (n = 1,068) or non-smokeless tobacco users (n = 5,737). Subjects were further stratified by smoking status and gender. Proportional hazard ratios were used to assess associations. After adjustment for confounders, no association between smokeless tobacco use and all-cause (hazard ratio = 1.1, 95% confidence interval (CI): 0.9, 1.3), all cancer (hazard ratio = 1.1, 95% CI: 0.6, 1.9), or all cardiovascular (hazard ratio = 1.1, 95% CI: 0.8, 1.5) mortality was found. There was an increase in all cancer mortality of borderline significance among female smokeless tobacco users (hazard ratio = 1.7, 95% CI: 1.0, 2.8). The lung cancer mortality rate among combined users (smokeless tobacco and cigarettes), based on the rates for exclusive smokeless tobacco users and exclusive smokers, was higher than expected, possibly because of heavier smoking among these subjects. The mortality experience of smokeless tobacco users was not significantly greater than that of non-tobacco users and was appreciably less than that of cigarette smokers. Furthermore, combined use of smokeless tobacco and cigarettes did not increase overall mortality beyond that expected from use of the individual products.

Adult↗

PubMed2002

Mortality among workers at a talc mining and milling facility.

BACKGROUND: This study evaluated mortality among workers at a talc mining and milling facility. METHODS: Subjects were white men actively employed between 1948 and 1989 and known to have been alive in or after 1950. Analyses assessed cancer mortality during the period 1950-89 (809 subjects) and non-cancer mortality during 1960-89 (782 subjects). RESULTS: Comparisons with regional general population death rates for 1960-89 indicated that the workers had more than expected deaths from all causes combined [209 observed/160 expected, standardized mortality ratio (SMR) = 131, 95% confidence interval (CI) = 114-150], due mainly to increased mortality from lung cancer (31/13, SMR = 232, CI = 157-329) and non-malignant respiratory disease (NMRD) (28/13, SMR = 221, CI = 147-320). The lung cancer excess was concentrated in miners (18/4.6, SMR = 394, CI = 233-622); millers had only a small increase (7/5.5, SMR = 128, CI = 51-263). An excess of NMRD occurred both in miners (10/4.2, SMR = 241, CI = 116-444) and in millers (11/4.8, SMR = 227, CI = 113-407). The median estimated exposure to respirable dust was 511 mg/m(3)-days for all exposed employees, 739 mg/m(3)-days for mine workers and 683 mg/m(3)-days for mill workers. Employees with high, compared with low, estimated exposure to dust had a rate ratio of 0.5 (CI = 0.2-1.3) for lung cancer and of 11.8 (CI = 3.1-44.9) for pulmonary fibrosis. CONCLUSIONS: Exposure to talc ore dust may not have been responsible for the lung cancer excess among these workers but probably contributed to the elevated rate of NMRD, particularly pulmonary fibrosis.

Dust↗