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Biomedical subjects

S Barnhart

Publications and source records attributed to S Barnhart.

At least 19 recordsLinked to original sources
PubMed2004

Comparison of local risk factors for children's atopic symptoms in Hanoi, Vietnam.

BACKGROUND: A 1999 study in Hanoi, Vietnam using the International Study on Asthma and Allergies in Childhood (ISAAC) questionnaire showed a high prevalence of atopic symptoms. Identifying risk factors for symptoms in these children may help in understanding the causes for these high estimates. METHODS: An ISAAC questionnaire with supplemental questions on environmental variables was distributed to 5495 school children in Hanoi and a suburban district, Dong Anh. The response rate was 65.7%. RESULTS: In Dong Anh, the following were among the significant age and gender adjusted associations: pig ownership [odds ratio (OR) (95% confidence interval), OR = 1.79 (1.18-2.70) for doctor-diagnosed asthma (DDA), OR = 1.72 (1.08-2.78) for doctor diagnosed hay fever (DDHF)] and farming [OR = 1.67 (1.27-2.19) for ever asthma, OR = 1.51 (1.09-2.09) for DDHF]. In multivariate models, tuberculosis (TB) was a significant predictor of atopic symptoms [Hanoi: OR = 3.09 (1.10-8.70) for DDA, Dong Anh: OR = 3.71 (1.40-9.84) for DDA, OR = 4.66 (1.88-11.57) for DDHF]. CONCLUSIONS: These findings are contrary to the "hygiene hypothesis". Recent immunologic and epidemiologic studies refute the inverse association between allergy and TB and may be one explanation for the positive association in this study. The positive association with pig ownership and farming may be because of exposures on farms in a developing country that may be different from exposures in farms of developed countries.

Adolescent↗
PubMed1999

Respiratory protective devices: rates of medical clearance and causes for work restrictions.

BACKGROUND: There are no published data on the outcomes and benefits of medical evaluations for the use of respiratory protective devices. We, therefore, conducted a retrospective database and chart review to assess the rates of medical clearance and causes for work restrictions at a Department of Energy complex. METHODS: All workers with work restrictions or denied clearance over a one-year period were identified and their medical records abstracted. RESULTS: Of the 5,569 workers who received medical evaluation, only 71 (1.3%) received limitations on respirator use documented in their medical record. Of the 65 workers with sufficient medical records for additional analysis, 9 of the 5,569 workers (0.2%) were denied medical clearance, while 56 workers (1.1%) received work restrictions. Pregnancy was the most common cause for denying medical clearance for respirator use. Lung disease, cardiovascular disease, and claustrophobia were the most common causes for work restrictions. Physical examination and spirometry added little to the detection of relevant medical conditions. CONCLUSIONS: We conclude that few workers fail medical clearance for respirator use or receive work restrictions. Data on adverse events from respirator use are needed to help design appropriate medical evaluations and uniform criteria for work restrictions or denial of medical clearance.

Adult↗
PubMed1999

Medical clearance for respirator use: sensitivity and specificity of a questionnaire.

BACKGROUND: OSHA regulations require that workers receive medical clearance prior to respirator use, and recently, a detailed questionnaire has been provided to assist with this purpose. However, there are limited published data on the sensitivity and specificity of self-administered questionnaires for identifying individuals who may safely wear a respirator. METHODS: We tested 474 consecutive workers at a Department of Energy complex. After completing the self-administered questionnaire, all workers received a standardized physician evaluation including interview, physical examination, and spirometry. The outcomes of the questionnaire assessment were compared to the outcomes of physician evaluation. RESULTS: Data for analysis were available from 413 of workers (87%). All workers received medical clearance; only 10 workers (2.4%) received work restrictions. The questionnaire demonstrated 100% sensitivity in identifying workers who required work restrictions, but had specificity of only 19%. Compared to physician evaluation, the questionnaire had modest sensitivity to the detection of chronic medical conditions. CONCLUSIONS: These data suggest that the rates of medical clearance for respirator use are very high, and that a self-administered questionnaire may be appropriate for medical clearance in certain settings. It is recommended that the policy of routine physician evaluation and spirometry for respirator clearance be re-examined.

Adult↗
PubMed1999

Structure and function of occupational health services within selected Department of Energy sites.

The mission of the United States Department of Energy sites has recently changed from nuclear weapons production to site remediation. Considering the mass of radiological and chemical contaminants at these sites, ensuring the health and safety of workers is a major challenge. This study used the findings from a written survey to describe occupational health services at 10 Department of Energy sites. The study aims were to describe and compare: (1) the primary hazards associated with the site activities; (2) the occupational safety and health structure, including service providers; and (3) the occupational health and safety functions, including surveillance, training, and service provision. Although explosions and radiological agents were identified as the hazards with the greatest associated risks, workers at these sites were most likely to be exposed to physical hazards, ergonomic hazards, and/or chemicals, including asbestos. Physicians accounted for 2.4% of service providers, nurses for 5.5%, industrial hygienists for 12.2%, safety personnel for 11.8%, and health physicists for 64.9%. It was concluded that there is an imbalance between the most important hazards and the types of health and safety personnel at these sites.

Delivery of Health Care↗
PubMed1999

Longitudinal decline in measured firefighter single-breath diffusing capacity of carbon monoxide values. A respiratory surveillance dilemma.

Seattle firefighters participate in a voluntary annual medical surveillance program including measurements of ventilatory capacity (FVC and FEV1) and single-breath diffusing capacity of carbon monoxide (DLCO). From 1989 to 1996, average % predicted DLCO (Crapo) for all participating firefighters declined from 94.4% (95% confidence interval [CI]: 93.4% to 95.5%) to 87.3% (95% CI: 86.2% to 88.3%), with no significant change in average FVC or FEV1. A random-effects regression model based on data from 812 firefighters with at least two annual sets of DLCO measurements showed the expected associations between DLCO and age, height, gender, race, ventilatory capacity, and smoking. In addition, two important temporal changes were observed, including, for an average firefighter, a large mean decline in DLCO of -1.02 ml/min/mm Hg associated with year of measurement, and a relatively smaller decline of -0.006 ml/min/mm Hg associated with number of fires fought. Although the stability of ventilatory capacity over time is reassuring, the marked temporal decline in diffusing capacity among this population of firefighters raises issues of concern. Interpretation of the observed decline poses a dilemma in terms of the reliability and efficacy of diffusing capacity as a screening tool, in whether DLCO is subject to unacceptable technical variability or whether it might provide more sensitive detection of early adverse respiratory effects of smoke inhalation.

Adult↗
PubMed1999

A description of factors affecting hazardous waste workers' use of respiratory protective equipment.

This article describes the first phase of a study that was designed to gain an understanding of hazardous waste workers' attitudes and beliefs about the use of respiratory protective equipment. Exploratory, open-ended interviews were conducted among 28 respirator users at a US Department of Energy facility. Subjects were asked to describe their knowledge, attitudes, and beliefs about their risks to hazards at their worksites and to discuss their use of respiratory protective equipment. A detailed content analysis of the interviews resulted in the generation of a taxonomy of issues and concerns which fell into three general categories: 1) Knowledge, Beliefs, and Attitudes, 2) Physical and Psychological Effects, and 3) External Influences. Knowledge, Beliefs, and Attitudes included Training, Fit Testing, Medical Clearance, Work Exposures, Respirator Use, and Vulnerability to Disease. Physical and Psychological Effects included Somatic/Health Effects, Personal Comfort, Visual Effects, Fatigue, Communication, and Anxiety. External Influences included Structural Environment, Quality and Availability of Equipment, Other PPEs, Co-Worker Influence, Supervisor Influence, and Organizational Culture. The findings from this study have important implications to training and education programs. Effective respiratory protection programs depend on a knowledge of the factors that affect workers' use of equipment. This study suggests that efforts to assure equipment comfort and fit, to assist workers who see and hear less well as a result of their equipment, and to develop strategies to allay worker anxiety when wearing equipment should all be components of a program. An organizational culture that supports and abets the appropriate use of equipment is also a critical element in a successful program.

Adult↗
PubMed1998

The validity of radiographic estimation of total lung capacity in patients with respiratory disease.

STUDY OBJECTIVE: To evaluate the validity of a state-of-the-art computerized planimetry technique for estimation of total lung capacity (TLC) from chest radiographs, when applied to patients with clinical lung disease receiving routine chest radiographs. DESIGN: Retrospective clinical survey. SETTING: An occupational medicine diagnostic clinic. PATIENTS: A convenience sample of 40 subjects with asbestos-related lung disease, 5 patients with nonasbestos-related restrictive defects, 15 subjects with occupational asthma, and 10 subjects with irritant tracheobronchitis. RESULTS: Estimation of TLC using state-of-the-art computerized algorithms demonstrated limited agreement with conventional measures of TLC when applied to patients with occupational lung disease receiving routine chest radiographs. The most pronounced differences occurred in patients with asbestos-related lung disease and restrictive defects, where the radiographic method of measurement significantly overestimated helium dilution TLC by 986 mL (r=0.73, p<0.001) and 1,135 mL (r=0.82, p<0.05), respectively. Good inspiratory effort was associated with significantly increased radiographic TLC relative to helium dilution TLC; however, radiographic features did not fully account for the observed differences between radiographic and helium dilution techniques. CONCLUSIONS: Our findings suggest that this planimetric technique should not be used as a substitute for conventional measures of TLC in clinic populations receiving routine radiographs. The large diagnostic group specific mean differences observed between radiographic and conventional measures of TLC also suggest that this method is of limited utility in clinical evaluation of occupational lung disease.

Adult↗
PubMed1998

A case series of 71 patients referred to a hospital-based occupational and environmental medicine clinic for occupational asthma.

In a ten-year period at the Occupational and Environmental Medicine Program (OEMP) of the University of Washington in Seattle, 71 patients were determined by attending physicians to have work-related asthma. In this cross-sectional descriptive study, we describe these patients. Data were obtained from a database maintained by the OEMP and from chart reviews. We found that the three most common specific agents causing asthma were isocyanates, red cedar, and crabs. At least one pulmonary function study was available for all patients and was positive in 56 patients (79%). Among the 71 asthma cases reported in this article, 18 (25%) were attributed to reactive airways dysfunction syndrome (RADS); 19 (27%) to exacerbation of pre-existing asthma; 27 (38%) to sensitization; and 7 (10%) had undetermined causes. We conclude that occupational asthma presents as a result of diverse exposures in multiple work settings and with an array of characteristics. Prevention efforts need to recognize this diversity.

Adult↗
PubMed1997

The CARET asbestos-exposed cohort: baseline characteristics and comparison to other asbestos-exposed cohorts.

The Carotene and Retinol Efficacy Trial (CARET) was a double-blind, placebo-controlled trial of the daily administration of 25,000 IU vitamin A and 30 mg beta-carotene for the prevention of lung cancer. Of close to 18,500 participants, more than 4,000 were asbestos-exposed men recruited from shipyard and construction trades at five study centers in the United States. While the primary endpoint of the trial was the incidence of lung cancer, a number of questions about the natural history of asbestos-related disease will also be addressed. The mean age at entry into the trial was 57 years and the mean duration of follow-up on active intervention was 4 years. With the exception of 133 never-smoker pilot participants (3%), all subjects recruited were by intention current (38%) or ex-smokers (58%), with a mean cumulative smoking exposure at entry of 43 pack-years. Mean years from first asbestos exposure were 35, and mean duration of asbestos exposure in a high-risk trade was 19 years. The distribution of radiographic abnormalities was as follows: normal, 34%; parenchymal opacities (ILO profusion score > 1/0) alone, 18%; pleural thickening alone, 27%; both parenchymal opacities and pleural thickening, 21%. The CARET cohort, when compared to previously reported asbestos-exposed cohorts, is characterized by substantial asbestos exposure and high proportion of asbestos-related radiographic findings. The active intervention was halted in 1996, after a mean duration of 40 years. Passive follow-up of the cohort will continue until the year 2000.

Asbestos↗
PubMed1997

Lobe of origin and histologic type of lung cancer associated with asbestos exposure in the Carotene and Retinol Efficacy Trial (CARET).

Lower lobe origin and histologic diagnosis of adenocarcinoma have been described as useful parameters for attributing lung cancer to prior asbestos exposure. To assess whether these characteristics differed between asbestos-exposed individuals and smokers, we evaluated lobe of origin and histologic type of tumors in 78 asbestos-exposed and 214 nonexposed heavy smokers developing lung cancer during the Carotene and Retinol Efficacy Trial (CARET), a prospective cancer chemoprevention trial. Most tumors in both cohorts, regardless of radiographic fibrosis at baseline, originated in upper lobes, representing 67% in asbestos-exposed and 80% in smokers, respectively (adjusted OR for lower lobe = 1.41; 95% CI = 0.69-2.91). Adenocarcinoma represented 32% of lung tumors in the asbestos cohort, and 30% in the smoking cohort (adjusted OR = 0.78; 95% CI = 0.40-1.55), and was inversely associated with radiographic fibrosis (adjusted OR = 0.19; 95% CI = 0.06-0.62). We conclude that neither anatomic site nor histologic cell type of tumors distinguishes effectively between smoking and asbestos as causal factors in development of lung cancer.

Adenocarcinoma↗
PubMed1997

Hazardous materials exposure information service: development, analysis, and medical implications.

The Hazardous Materials Exposure Information Service (HMEIS) was established at the Washington Poison Center (WPC) to rapidly provide information to medical professionals who treat victims of hazardous-materials exposure. Incident description and exposure information is collected from on-site hazardous-materials teams and immediately analyzed by WPC medical toxicologists. Diagnostic and treatment recommendations are provided to prehospital personnel and receiving physicians. Over the first 22 months of operation, 50 calls were received that met HMEIS criteria. Of the 466 individuals exposed, 256 (55%) were transported to a medical facility for treatment. When the WPC was contacted before the decision to transport a patient to a medical facility, 28 of 185 exposure victims (15%) were transported, compared with a transport rate of 81% of exposure victims (66% change; 95% confidence interval [CI], 60% to 72%) in all other concurrent incidents and a historical transport rate of 63% (25% change; 95% CI, 14% to 36%) before the establishment of the HMEIS. These findings, although preliminary and subject to potential confounding, suggest that the HMEIS reduces health care costs through more efficient use of medical resources.

Costs and Cost Analysis↗
PubMed1997

Tuberculosis in health care settings and the estimated benefits of engineering controls and respiratory protection.

Intra-institutional spread of tuberculosis (Tb) has re-emerged as a substantial public and occupational health threat. To characterize the person-hours and lifetime risks of Tb-related morbidity and mortality, we performed a risk assessment for health care workers (HCWs) developing Tb-related morbidity and mortality at varying levels of exposure, engineering controls, and respiratory protection. Under average conditions of exposure, one Tb skin-test conversion is estimated to occur for every 2650 person-hours of work by unprotected workers. With higher exposures, a skin-test conversion for an unprotected worker may occur in as few as 3 person-hours. Use of respiratory protection is estimated to reduce risks by the following proportions: surgical mask, 2.4-fold; disposable dust, fume, mist, or disposable high-efficiency particulate air filtering (HEPA) mask, 17.5-fold; elastomeric HEPA cartridge respirator, 45.5-fold; or powered air-purifying respirator (PAPR), 238-fold. Assuming a lifetime exposure of 250 hours, the risk of a skin-test conversion is estimated to be 9%. We conclude that HCWs are at substantial risk for Tb-related morbidity and mortality, and that administrative controls, engineering controls, and respirators offer substantial benefits in risk reduction.

Humans↗
PubMed1997

The protective effect of beta-carotene and retinol on ventilatory function in an asbestos-exposed cohort.

The association between serum beta-carotene or retinol concentration and level of ventilatory function was investigated in a population of asbestos-exposed men with a high rate of current and former cigarette smoking. The study population consisted of 816 subjects enrolled in the pilot component of the Carotene and Retinol Efficacy Trial (CARET), a placebo-controlled trial of supplemental beta-carotene and retinyl palmitate for the chemoprevention of lung cancer. Data available for analysis included baseline questionnaire, spirometry, chest X-ray, food frequency questionnaire, and serum beta-carotene and retinol concentrations. Serum beta-carotene concentration was associated with FEV1 (p < 0.05) and FVC (p < 0.05), with an approximately 100-ml increase over predicted values associated with raising the serum concentration from the 25th to the 75th percentile of the distribution in the study population (absolute difference = 155 ng/ml), even after adjustment for the confounding effects of asbestos exposure and cigarette smoking. Raising the serum retinol concentration from the 25th to the 75th percentile (absolute difference = 211 ng/ml) was associated with an approximately 70 ml increase in FVC (p < 0.05) over the predicted value. These results provide support for the hypothesis that beta-carotene and retinol have a protective effect on loss of ventilatory function.

Aged↗
PubMed1996

Risk factors for lung cancer and for intervention effects in CARET, the Beta-Carotene and Retinol Efficacy Trial.

BACKGROUND: Evidence has accumulated from observational studies that people eating more fruits and vegetables, which are rich in beta-carotene (a violet to yellow plant pigment that acts as an antioxidant and can be converted to vitamin A by enzymes in the intestinal wall and liver) and retinol (an alcohol chemical form of vitamin A), and people having higher serum beta-carotene concentrations had lower rates of lung cancer. The Beta-Carotene and Retinol Efficacy Trial (CARET) tested the combination of 30 mg beta-carotene and 25,000 IU retinyl palmitate (vitamin A) taken daily against placebo in 18314 men and women at high risk of developing lung cancer. The CARET intervention was stopped 21 months early because of clear evidence of no benefit and substantial evidence of possible harm; there were 28% more lung cancers and 17% more deaths in the active intervention group (active = the daily combination of 30 mg beta-carotene and 25,000 IU retinyl palmitate). Promptly after the January 18, 1996, announcement that the CARET active intervention had been stopped, we published preliminary findings from CARET regarding cancer, heart disease, and total mortality. PURPOSE: We present for the first time results based on the pre-specified analytic method, details about risk factors for lung cancer, and analyses of subgroups and of factors that possibly influence response to the intervention. METHODS: CARET was a randomized, double-blinded, placebo-controlled chemoprevention trial, initiated with a pilot phase and then expanded 10-fold at six study centers. Cigarette smoking history and status and alcohol intake were assessed through participant self-report. Serum was collected from the participants at base line and periodically after randomization and was analyzed for beta-carotene concentration. An Endpoints Review Committee evaluated endpoint reports, including pathologic review of tissue specimens. The primary analysis is a stratified logrank test for intervention arm differences in lung cancer incidence, with weighting linearly to hypothesized full effect at 24 months after randomization. Relative risks (RRs) were estimated by use of Cox regression models; tests were performed for quantitative and qualitative interactions between the intervention and smoking status or alcohol intake. O'Brien-Fleming boundaries were used for stopping criteria at interim analyses. Statistical significance was set at the .05 alpha value, and all P values were derived from two-sided statistical tests. RESULTS: According to CARET's pre-specified analysis, there was an RR of 1.36 (95% confidence interval [CI] = 1.07-1.73; P = .01) for weighted lung cancer incidence for the active intervention group compared with the placebo group, and RR = 1.59 (95% CI = 1.13-2.23; P = .01) for weighted lung cancer mortality. All subgroups, except former smokers, had a point estimate of RR of 1.10 or greater for lung cancer. There are suggestions of associations of the excess lung cancer incidence with the highest quartile of alcohol intake (RR = 1.99; 95% CI = 1.28-3.09; test for heterogeneity of RR among quartiles of alcohol intake has P = .01, unadjusted for multiple comparisons) and with large-cell histology (RR = 1.89; 95% CI = 1.09-3.26; test for heterogeneity among histologic categories has P = .35), but not with base-line serum beta-carotene concentrations. CONCLUSIONS: CARET participants receiving the combination of beta-carotene and vitamin A had no chemopreventive benefit and had excess lung cancer incidence and mortality. The results are highly consistent with those found for beta-carotene in the Alpha-Tocopherol Beta-Carotene Cancer Prevention Study in 29133 male smokers in Finland.

Anticarcinogenic Agents↗
PubMed1996

Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease.

BACKGROUND: Lung cancer and cardiovascular disease are major causes of death in the United States. It has been proposed that carotenoids and retinoids are agents that may prevent these disorders. METHODS: We conducted a multicenter, randomized, double-blind, placebo-controlled primary prevention trial -- the Beta Carotene and Retinol Efficacy Trial -- involving a total of 18,314 smokers, former smokers, and workers exposed to asbestos. The effects of a combination of 30 mg of beta carotene per day and 25,000 IU of retinol (vitamin A) in the form of retinyl palmitate per day on the primary end point, the incidence of lung cancer, were compared with those of placebo. RESULTS: A total of 388 new cases of lung cancer were diagnosed during the 73,135 person-years of follow-up (mean length of follow-up, 4.0 years). The active-treatment group had a relative risk of lung cancer of 1.28 (95 percent confidence interval, 1.04 to 1.57; P=0.02), as compared with the placebo group. There were no statistically significant differences in the risks of other types of cancer. In the active-treatment group, the relative risk of death from any cause was 1.17 (95 percent confidence interval, 1.03 to 1.33); of death from lung cancer, 1.46 (95 percent confidence interval, 1.07 to 2.00); and of death from cardiovascular disease, 1.26 (95 percent confidence interval, 0.99 to 1.61). On the basis of these findings, the randomized trial was stopped 21 months earlier than planned; follow-up will continue for another 5 years. CONCLUSIONS: After an average of four years of supplementation, the combination of beta carotene and vitamin A had no benefit and may have had an adverse effect on the incidence of lung cancer and on the risk of death from lung cancer, cardiovascular disease, and any cause in smokers and workers exposed to asbestos.

Aged↗
PubMed1996

Investigating clandestine drug laboratories: adverse medical effects in law enforcement personnel.

A retrospective cohort study was conducted among an international group of 46 law enforcement chemists and 13 Washington State clandestine drug laboratory investigation team members with more than 2,800 combined investigations. Each participant completed a questionnaire concerning previous drug laboratory investigations and adverse health effects during response activities. Methamphetamine laboratories accounted for 81-97% of all responses. Total illness incident rates varied between 0.75-3.4% of responses. Most exposures were through inhalation, and many occurred in the years prior to use of personal protective equipment. Symptoms were primarily those of headache and respiratory, mucous membrane, and skin irritation. Most illness episodes occurred during the processing phase of laboratory responses, and none occurred during the entry phase. A majority of illness episodes occurred in laboratories with leak/spills, fire/explosion, or uncontrolled reactions. Responding to an active laboratory was associated with a 7 to 15-fold risk of becoming ill as compared with setup, in-transit, or former (equipment removed) laboratory responses. No other laboratories characteristics were consistently associated with a significantly elevated relative risk of adverse health effects.

Accidents, Occupational↗
PubMed1996

Longitudinal pattern of reported respiratory symptoms and accelerated ventilatory loss in asbestos-exposed workers.

Studies investigating the relation between respiratory symptoms and change in ventilatory function have been limited by use of reported symptoms at a single point in time. To assess the relation between the longitudinal pattern of reported cough, phlegm, wheeze, and dyspnea and ventilatory loss, we prospectively investigated changes in FVC and FEV1 associated with development, resolution, or persistence of these symptoms over a 3- to 5-year period in 446 asbestos-exposed workers. Longitudinally reported symptoms changed frequently, with 52 to 61% of subjects reporting a specific symptom noting resolution or development of that symptom during follow-up. Initially reported symptoms were not predictive of accelerated loss of FVC or FEV1. In contrast, development of any new respiratory symptom, and to a lesser extent persistence of symptoms during follow-up, were associated with significantly greater ventilatory losses compared with asymptomatic individuals, ranging from 28 mL/yr in FEV1 for newly developed dyspnea, to 67 mL/yr in FVC for developed wheeze (p < 0.01). We conclude that development or persistence of respiratory symptoms over time, rather than the presence of symptoms per se, is predictive of future ventilatory loss. Recognition of interval changes in symptom reporting during surveillance of asbestos-exposed workers may effectively identify groups at risk for progressive ventilatory impairment.

Aged↗