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D H Wegman

Publications and source records attributed to D H Wegman.

At least 37 records · Page 2Linked to original sources
PubMed1997

A strategy to reduce healthy worker effect in a cross-sectional study of asthma and metalworking fluids.

This report describes the reanalysis of a cross-sectional study of asthma in a large cohort of autoworkers with exposure to metalworking fluids (MWF). There is strong evidence from case reports, clinical studies, and medical surveillance data that exposure to MWF can cause asthma, yet no association was found in the original analysis. The central hypothesis of the reanalysis was that the absence of an association between asthma and MWF exposure was the result of bias caused by the self-selection of asthmatics out of exposed jobs. We addressed the potential job transfer bias by redefining exposure and disease status at the time of asthma onset, rather than at the time of the health survey. This permitted us to treat the cross-sectional study as if it were a historical cohort study, despite the fact that the population was a biased sample of the full cohort. This approach resulted in a significantly elevated incidence rate ratio of 3.2 (95% CI: 1.2-8.3) for synthetic MWF estimated in a Cox proportional hazards model. Although the cross-sectional design makes it impossible to document or control for differential selection out of the workforce, the approach described here provides a strategy for reducing the healthy-worker effect due to job transfer bias in cross-sectional studies.

Adult↗
PubMed1996

Machining operations and associated machining fluid exposures: issues for health and safety intervention in manufacturing.

The outline for a workshop discussion of intervention research in manufacturing industry is presented. The example used is the control of machining fluid exposures, a widespread exposure that is associated with risk of cancer, pulmonary disease, dermatitis, and several types of accident-related injuries. Relevant technical considerations for conducting intervention research include the selection of machining fluid for different machining purposes, the management of fluids in use, and the selection and maintenance of environmental controls. Equally important are nontechnical considerations including the need for creating labor-management health and safety committees, the use of administrative rules on job performance for both workers and management, and training on the role of individuals from either group in exposure control. Clarity concerning the objectives for an intervention study and plans for clear means to evaluate study outcomes is critical. Important study variables will include site selection, plant size, plant demographics, the involvement of workers in the study, a willing management, and concern for susceptible workers.

Accidents, Occupational↗
PubMed1995

Healthy worker effect in a longitudinal study of one-second forced expiratory volume (FEV1) and chronic exposure to granite dust.

BACKGROUND: Low level effects of granite dust on one-second forced expiratory volume (FEV1) are estimated in 618 Vermont granite workers followed for 5 years with annual pulmonary function tests. Reduced pulmonary function has already been reported for the subset of subjects lost to follow-up (dropouts) suggesting possible bias in analyses based only on survivors. METHOD: Healthy worker selection bias is directly assessed by comparing the dose-response associations between survivors who remained in the study for the full 5-year observation period and the dropouts. RESULTS: The 353 survivors had an FEV1 of 96% of predicted at baseline and were losing FEV1 at an average rate of 44 ml/yr. No association was found in this group between the rate of FEV1 decline and lifetime dust exposure. However, the 265 workers with incomplete follow-up, 'dropouts', had a lower FEV1 at baseline (94%) and were losing FEV1 at an average rate of 69 ml/yr. The dose-response parameter in this group was estimated to be 4 ml/yr loss per mg/m3-year and was statistically significant. CONCLUSIONS: These results provide an illustration of bias due to the healthy worker effect and an example of the failure to detect a true work-related health effect in a study based only on a 'survivor' population.

Adult↗
PubMed1994

Hearing loss.

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Hearing Loss, Noise-Induced↗
PubMed1994

A case-control study of cancer mortality at a transformer-assembly facility.

To address earlier reports of excess cancer mortality associated with employment at a large transformer manufacturing plant, each plant operation was rated for seven exposures: Pyranol (a mixture of polychlorinated biphenyls and trichlorobenzene), trichloroethylene, benzene, mixed solvents, asbestos, synthetic resins, and machining fluids. Site-specific cancer deaths among active or retired employees were cases; controls were selected from deaths (primarily cardiovascular deaths) presumed to be unassociated with any of the study exposures. Using job records, we then computed person-years of exposure for each subject. All subjects were white males. The only unequivocal association was that of resin systems with lung cancer (odds ratio = 2.2 at 16.6 years of exposure, P = 0.001, in a multiple logistic regression including asbestos, age, year of death, and year of hire). Certain other odds ratios appeared larger, but no other association was so robust and remained as distinct after considering the multiplicity of comparisons. Study power was very limited for most associations, and several biases may have affected our results. Nevertheless, further investigation of synthetic resin systems of the type used in the study plant appears warranted.

Adult↗
PubMed1994

The real-time dust exposures of sodium borate workers: examination of exposure variability.

As part of an epidemiologic study of acute respiratory irritation, an assessment of the short term (TWA-0.25 hr) and daily (TWA-6 hr) dust and boron exposures of workers in a sodium borate production facility was undertaken. A real-time continuous aerosol monitor was used in an active mode with an in-line filter to collect a TWA-6 gravimetric sample with a datalogger to store the continuous aerosol measurements. Over 430 person-days of personal exposure measurements were made, resulting in more than 10,000 15-minute average (TWA-0.25) dust concentration measurements. The arithmetic mean total dust concentrations for the 13 job groups exposed to sodium borate dust ranged from 0.29 to 18.95 mg/m3. The geometric standard deviation of the TWA-6 total dust exposures within the sodium borate exposed job groups had a median of 2.78. The geometric standard deviation of the TWA-0.25 total dust exposures had a median of 3.97. In most jobs the "within-day" variability accounted for over 50% of the total variability in exposure levels. In jobs with constant exposure to sodium borate, the second most important source of exposure variability was attributable to "between worker" differences. Where there was only intermittent exposure, the second most important source of exposure variability was "within-worker" variability. The implications of these findings for control strategies are discussed. Based on boron measurements, a substantial portion of a total dust air sample is nonborate material such as cigarette smoke, vehicle exhaust, ambient dust, or hydration mass. Thus, even in an environment where sodium borate is being packaged, total dust measurements are an overestimate of the actual borate exposure level.

Air Pollutants, Occupational↗
PubMed1994

Cotton dust exposure, across-shift drop in FEV1, and five-year change in lung function.

To evaluate chronic loss of lung function in cotton dust-exposed workers, a 5-yr follow-up study was performed in Shanghai, China from 1981 to 1986. Workers at a nearby silk thread manufacturing mill were used as a control population. There were 384 cotton textile workers restudied from an original group of 446, and 403 silk workers restudied from the original 468. The presence of byssinosis among retested cotton workers at the time of first survey was 7.3%. The prevalence of byssinosis was 9.7% at the initial survey among those lost to follow-up. No byssinosis was found among control subjects. The mean annual decline in FEV1 was 39.5 ml among cotton workers and 30.6 ml for silk workers (p < 0.05). The greatest annual decrements were found among smoking cotton workers, but nonsmoking cotton workers also lost lung function at a faster rate than silk nonsmokers (annual loss = 33.3 ml versus 24.4 ml, respectively). Autoregressive modeling revealed that after adjustments for age, sex, height, and smoking, cotton dust exposure was significantly associated with decline in FEV1. Moreover, across-shift drop of 5% or more at the time of first survey was predictive of 5-yr decline in FEV1. Cotton workers who had an acute response (5% or greater drop in FEV1 at the time of first survey) suffered a 57.0 ml/yr FEV1 drop compared with a 35.1-ml drop among cotton workers with less acute response at baseline (p < 0.01). Silk workers with or without 5% across-shift drops had similar annual rates of decline (-33.8 ml and -36.1 ml, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Acute and chronic respiratory effects of sodium borate particulate exposures.

This study examined work-related chronic abnormality in pulmonary function and work-related acute irritant symptoms associated with exposure to borate dust in mining and processing operations. Chronic effects were examined by pulmonary function at the beginning and end of a 7-year interval. Time-specific estimates of sodium borate particulate exposures were used to estimate cumulative exposure during the study interval. Change in pulmonary function over the 7 years was found unrelated to the estimate of cumulative exposure during that interval. Exposure-response associations also were examined with respect to short-term peak exposures and incidence of five symptoms of acute respiratory irritation. Hourly measures of health outcome and continuous measures of particulate exposure were made on each subject throughout the day. Whenever a subject reported one of the irritant symptoms, a symptom intensity score was also recorded along with the approximate time of onset. The findings indicated that exposure-response relationships were present for each of the specific symptoms at several symptom intensity levels. The associations were present when exposure was estimated by both day-long and short-term (15-min) time-weighted average exposures. Associations persisted after taking account of smoking, age, and the presence of a common cold. No significant difference in response rate was found between workers exposed to different types of sodium borate dusts.

Adult↗
PubMed1994

Pulmonary function among cotton textile workers. A study of variability in symptom reporting, across-shift drop in FEV1, and longitudinal change.

Longitudinal variability in respiratory responses, including symptom reporting and across-shift change in ventilatory function, were examined in relation to long-term loss of ventilatory function in a group of 447 cotton textile workers in Shanghai, China. The study used a standardized respiratory questionnaire and standardized spirometric testing before and after a work shift on the first day of the workweek. Prediction equations for FEV1 were generated from a group of silk textile workers from the same city. Environmental samples included both vertical elutriated cotton dust and endotoxin levels. There was considerable variability in symptom reporting between the baseline and 5-year follow-up survey for all symptoms. However, subjects who consistently reported symptoms had a significantly accelerated 5-year loss in FEV1 compared with those who never reported symptoms. Subjects with symptoms of chest tightness or dyspnea at one survey lost FEV1 at a rate intermediate between the never or both groups. Moreover, subjects with an across-shift change in FEV1 of more than 5 percent at both surveys had the greatest loss in FEV1 over 5 years (-267 ml) when compared with one-time responders (-224 ml), and nonresponders (-180 ml), though the differences were not significant. Workers with chest tightness and chronic bronchitis in both surveys were overrepresented in the high dust and endotoxin areas. Our results indicate that even with substantial survey-to-survey variability in responses, there is important information contained in both questionnaires and across-shift spirometry. Among cotton workers, consistent responders to either symptom questionnaire or across-shift FEV1 decrements of > or = 5 percent appear to be at increased risk for lung function impairment.

Adult↗
PubMed1993

Cotton dust and gram-negative bacterial endotoxin correlations in two cotton textile mills.

Exposure to cotton dust is known to cause both acute and chronic respiratory illness. A specific pattern of symptoms called byssinosis is well described to occur among workers in the cotton processing (e.g., yarn preparation) industry. Recent studies have implicated Gram-negative bacterial endotoxin as one of the agents responsible for acute, and possibly chronic, respiratory illness. Laboratory experiments using a model cardroom have found poor correlations between airborne dust and associated endotoxin. This study reports the results of vertical elutriated dust and endotoxin levels in 11 work areas of 2 cotton textile mills in 1986 in Shanghai, China. The overall correlation between dust and endotoxin was strong, rs = 0.66 and 0.79 (p < 0.0001) for mills 1 and 2, respectively. The dust-endotoxin correlation was relatively poor in early yarn preparation in the workshops and improved in the later preparation areas. Our findings suggest that in these mill settings, dust and endotoxin levels may be well correlated in most work areas. Therefore, dust may be a useful index for monitoring populations employed in the cotton textile industry throughout the world. Additional field studies need to be performed which consider the various determinants of dust and endotoxin levels.

Air Pollutants, Occupational↗
PubMed1993

Application of an event marker in the occupational epidemiologic study of acute irritant symptoms.

Field studies of occupational exposure to airborne irritants have predominantly relied on symptom surveys of study participants. As part of a new approach to the study of acute irritant symptoms, subjects exposed to sodium borate dusts recorded their symptom responses at hourly interviews as well as instantaneously on an electronic device called an event marker. Overall, the unprompted marks indicated fewer irritant events than the interviews. Marks were more frequent in the presence of more than one type of symptom and also appeared to reflect more severe symptoms. A proportion of the marked events occurred in time intervals when no symptoms were recalled during the interview. The exposure-response relations were similar regardless of whether they were based on the interview reports or the electronically marked symptoms. The event marker provided a means to examine the time of onset of the acute symptom event. It also made it possible to examine directly the timing profiles of symptom response in relation to changes in exposure levels in a field setting. Despite some inconsistencies, the finding suggests that the event marker may provide an alternative to frequent interviews of exposed workers to obtain irritant symptom responses for exposure-response modeling.

Acute Disease↗
PubMed1992

Measuring exposure for the epidemiologic study of acute effects.

This report explores the importance of characterizing short-term (peak) exposures for successful epidemiologic study of acute reversible effects. By selecting upper respiratory tract irritation, which is time-limited, reversible, and not critically affected by host factor sensitivities, the illustrated approach (directed at an acute respiratory irritant) provides insights on issues important in the general study of acute effects. The fundamental concern in a study of acute irritant effects is that such events occur in response to abrupt increases in exposure. This calls for a closer examination of how to distinguish bursts, or peaks, of exposure from continuous exposures measured simply as time weighted averages. Three parameters of peak exposures are discussed: duration, magnitude, and frequency. The importance of duration is illustrated by contrasting exposure patterns relevant for the study of acute vs. chronic health effects. The minimum magnitude of a peak relevant to the study of a specific physiologic response requires knowledge of the threshold below which no detectable response occurs. For any identified threshold level, only exposures exceeding that level are defined as relevant peaks for an exposure-response analysis. Finally, the issue of frequency, the minimum length of time between successive exposures necessary for the subject to return to baseline risk, is explored. A study of respiratory irritation associated with sodium borates is used to illustrate these issues.

Acute Disease↗
PubMed1992

Dose related acute irritant symptom responses to occupational exposure to sodium borate dusts.

A repeated measurement design was employed in the study of acute symptoms of eye and respiratory tract irritation resulting from occupational exposure to sodium borate dusts. The symptom assessment of the 79 exposed and 27 unexposed subjects comprised interviews before the shift began and then at regular hourly intervals for the next six hours of the shift, four days in a row. Exposures were monitored concurrently with a personal real time aerosol monitor. Two different exposure profiles, a daily average and short term (15 minute) average, were used in the analysis. Exposure-response relations were evaluated by linking incidence rates for each symptom with categories of exposure. Acute incidence rates for nasal, eye, and throat irritation, and coughing and breathlessness were found to be associated with increased exposure levels of both exposure indices. Steeper exposure-response slopes were seen when short term exposure concentrations were used. Results from multivariate logistic regression analysis suggest that current smokers tended to be less sensitive to the exposure to airborne sodium borate dust. There was no indication that anhydrous sodium borate was more potent than the other sodium borates in this work environment.

Adult↗
PubMed1992

The potential impact of epidemiology on the prevention of occupational disease.

This presentation reviews occupational epidemiology as a foundation for workplace disease prevention activities. By examining descriptive, etiologic and intervention occupational epidemiology studies, a range of opportunities are illustrated where epidemiology has played, or could play a principal role in guiding preventive efforts. Descriptive studies presented include ones based on vital records, on epidemic investigations, cross-sectional surveys, and surveillance. Etiologic studies review the largely successful development of knowledge for lung cancer and asbestos exposure for pulmonary effects of isocyanate exposures. However, attention is also directed to the need for etiologic studies of work environment risks for both cardiovascular and musculoskeletal disease. Finally importance is placed on the too infrequent epidemiologic studies of intervention. Historical examples of control of large risks from nickel cancers and silicosis are balanced with more recent examples of successes at reducing smaller risks of cardiovascular disease and oil acne. Throughout, emphasis is placed on the importance of reintegrating the academic discipline of epidemiology into the application of study findings to prevention of workplace risks.

Causality↗
PubMed1991

An epidemiologic approach to the study of acute reversible health effects in the workplace.

We present an epidemiologic approach for the study of the irritant effects of sodium borate exposure that can be used to study acute reversible health effects more generally. Acute irritant responses, such as symptoms of nasal irritation or cough, are subjective. They may, however, be accompanied by transient airway obstruction, which can be objectively measured by a change in peak expiratory flow (PEF) or forced expiratory volume in one second (FEV1). Because these physiologic responses are reversible and follow short-term peaks of exposure, they cannot be studied effectively using conventional epidemiologic methods of design and analysis. The proposed study design is a short-term prospective cohort study with frequently repeated measures of health effects and simultaneous measures of exposure. Because each subject passes through periods of high and low short-term exposure, the study has the form of a crossover design. This design permits each acute response to be linked to the corresponding short-term average exposure, providing the data necessary for dose-response analyses within subject. We present the results of the sodium borate study to illustrate the analysis of such data.

Acute Disease↗