Respiratory morbidity in workers exposed to asbestos in the primary manufacture of building materials

Lung function in asbestos-exposed workers, a systematic review and meta-analysis

BACKGROUND

A continuing controversy exists about whether, asbestos exposure is associated with significant lung function impairments when major radiological abnormalities are lacking. We conducted a systematic review and meta-analysis in order to assess whether asbestos exposure is related to impairment of lung function parameters independently of the radiological findings.

METHODS

MEDLINE was searched from its inception up to April 2010. We included studies that assessed lung function parameters in asbestos exposed workers and stratified subjects according to radiological findings. Estimates of VC, FEV1 and FEV1/VC with their dispersion measures were extracted and pooled.

RESULTS

Our meta-analysis with data from 9,921 workers exposed to asbestos demonstrates a statistically significant reduction in VC, FEV1 and FEV1/VC, even in those workers without radiological changes. Less severe lung function impairments are detected if the diagnoses are based on (high resolution) computed tomography rather than the less sensitive X-ray images. The degree of lung function impairment was partly related to the proportion of smokers included in the studies.

CONCLUSIONS

Asbestos exposure is related to restrictive and obstructive lung function impairment. Even in the absence of radiological evidence of parenchymal or pleural diseases there is a trend for functional impairment.

Radiographic outcomes among South African coal miners

OBJECTIVES

This study, the first to document the prevalence of pneumoconiosis among a living South African coal mining cohort, describes dose-response relationships between coal workers' pneumoconiosis and respirable dust exposure, and relationships between pneumoconiosis and both lung function deterioration and respiratory symptoms.

METHODS

A total of 684 current miners and 188 ex-miners from three bituminous-coal mines in Mpumalanga, South Africa, was studied. Chest radiographs were read according to the International Labour Organization (ILO) classification by two experienced readers, one an accredited National Institute for Occupational Safety and Health (NIOSH) "B" reader. Interviews were conducted to assess symptoms, work histories (also obtained from company records), smoking, and other risk factors. Spirometry was performed by trained technicians. Cumulative respirable dust exposure (CDE) estimates were constructed from historical company-collected sampling and researcher-collected personal dust measurements. kappa-Statistics compared the radiographic outcomes predicted by the two readers. An average profusion score was used in the analysis for the outcomes of interest. Because of possible confounding by employment status, most analyses were stratified on current and ex-miner status.

RESULTS

The overall prevalence of pneumoconiosis was low (2%-4%). The degree of agreement between the two readers for profusion was moderate to high (kappa=0.58). A significant association (P<0.001) and trend (P<0.001) was seen for pneumoconiosis with increasing categories of CDE among current miners only. A significant (P<0.0001) additional 58 mg-years/m3 CDE was seen among those with pneumoconiosis compared to those without. CDE contributed to a statistically significant 0.19% and 0.11% greater decline in the percent predicted 1-second forced expiration volume (FEV1) and forced vital capacity (FVC), respectively, among current miners with pneumoconiosis than among those without. Logistic regression models showed no significant relationships between pneumoconiosis and symptoms.

CONCLUSIONS

The overall prevalence of pneumoconiosis, although significantly associated with CDE, was low. The presence of pneumoconiosis is associated with meaningful health effects, including deterioration in lung function. Intervention measures that control exposure are indicated, to reduce these functional effects.

Respiratory symptoms and functional status in workers exposed to silica, asbestos, and coal mine dusts

This study aims to provide further understanding of physiologic and symptomatic changes and radiographic abnormalities due to exposure to silica, asbestos, and coal dusts. Questionnaires and pulmonary function tests were given to 220 silica, 277 asbestos, and 511 coal workers from three different industries in China. Posteroanterior chest radiographs were classified as stages 0, I, II, and III according to degree of parenchymal fibrosis. Significantly poorer pulmonary function and a higher prevalence of dyspnea and chronic cough were observed in workers with pneumoconiosis than those without, irrespective of dust type. Workers with stages II and III silicosis had worse pulmonary function and more common symptoms relative to workers with equivalent coal workers' pneumoconiosis or asbestosis. After adjusting for relevant confounders, reductions in the spirometric parameters and single breath diffusing capacity for carbon monoxide (DLCO) and the occurrence of respiratory symptoms were associated with increasing stage of silicosis, whereas lower DLCO and the occurrence of symptoms were associated with increasing stage of asbestosis and coal workers' pneumoconiosis. The study suggests that despite the differences in degree and pattern due to exposure to different fibrogenic dusts, respiratory impairments of all of the workers are associated with the presence and progression of parenchymal fibrosis and smoking.

Cardiorespiratory responses to incremental exercise in patients with asbestos-related pleural thickening and normal or slightly abnormal lung function

An increasing number of patients with asbestos exposure are being identified with pleural thickening (PT) alone, with little or no impairment in standard tests of lung function despite their frequent complaint of dyspnea. We have employed incremental cardiorespiratory exercise testing to evaluate the types and mechanisms of impairment in 23 such patients. All had normal lung fields on radiographic examinations and normal (group 1, n = 12) or minimally reduced (group 2A slight restriction, n = 5, group 2B, slight obstruction, n = 6), lung function. Excessive ventilation was common in all groups, but especially in group 2B. Abnormal dead space ventilation (VD/VT) was more frequent in groups 2A (4/5) and 2B (4/6) than in group 1 (3/12). It was associated with O2 desaturation in three patients in groups 2A and B. Cardiovascular abnormalities were rare (1/23). Excessive ventilation and dead space provide a basis for the symptom of dyspnea in these patients.

Experiences of a state-sponsored notification and screening program for asbestos workers

Worker notification can involve a broad range of activities including medical screening, personal and mass communications, cohort identification and tracing, and even litigation. The inclusion or exclusion of various supporting activities in a worker notification program may pose significant medical, public health, financial, logistical, and even legal implications for targeted individuals as well as for the agencies involved. This report describes some experiences in a state-sponsored notification and screening program of approximately 4,500 asbestos workers in Minnesota. In this program, a variety of factors led to the decision to provide medical screening to 1,101 workers and 451 spouses. It is anticipated that another 3,400 workers will be notified but not screened. A follow-up survey of notified workers showed overwhelming support for this program. It is estimated that this program will cost more than $650,000 by its completion. The decision to institute medical screening and other support activities should be made with careful consideration of the diverse implications of these activities to the individuals, communities, and agencies involved.

Fissural thickening and exposure to asbestos: occurrence, determinants, and functional impact

The occurrence and determinants of thickened interlobar fissures were assessed in 147 insulators, in order to test the hypothesis that radiographic abnormalities in minor (FMN) and/or major (FMJ) interlobar fissures are associated with restrictive respiratory impairment, which may reflect early parenchymal lung fibrosis. According to the diagnostic criteria developed, definite interlobar thickening was found in 33 (FMN) and in 73 (FMJ) men, and was frequently associated with the presence of classical asbestos pleural disease, though not parenchymal abnormality. Multivariate analyses did not demonstrate any association between either FMN or FMJ and lung function. Such an association, however, was found in the case of the usual asbestos-related pleural change. These findings suggest that fissural thickening seen on chest radiography represents a component of asbestos pleural disease and not asbestosis.