Clinical consequences of asbestos-related diffuse pleural thickening: A review

Marked ventilation impairment due to progression of diffuse pleural thickening after cardiac surgery

A 64-year-old Japanese man presented with dyspnea and shortness of breath during exertion. Chest computed tomography revealed bilateral pleural effusion. He was drowsy because of CO₂ storage and died due to ventilatory impairment. His past medical history included a thymectomy and adjuvant radiotherapy with thymoma. He had undergone cardiac surgery and permanent pacemaker implantation. The autopsy examination revealed extensive bilateral pleural adhesions and diffuse visceral pleural thickening. An inspection of multiple lung sections failed to detect any asbestos body formation or mesothelioma. The patient's pleural effusion and diffuse pleural thickening may have exacerbated after cardiac surgery. In this case, the progression and pathophysiology of the pleural thickening could be traced by imaging and an autopsy, and we were able to estimate the factors that exacerbated the pleural thickening and ventilation impairment.

Relations between vital capacity, CO diffusion capacity and computed tomographic findings of former asbestos-exposed patients: a cross-sectional study

BACKGROUND

Asbestos-related lung diseases are one of the leading diagnoses of the recognized occupational diseases in Germany, both in terms of their number and their socio-economic costs. The aim of this study was to determine whether pulmonary function testing (spirometry and CO diffusion measurement (DLCO)) and computed tomography of the thorax (TCT) are relevant for the early detection of asbestos-related pleural and pulmonary fibrosis and the assessment of the functional deficiency.

METHODS

The records of 111 formerly asbestos-exposed workers who had been examined at the Institute for Occupational and Maritime Medicine, Hamburg, Germany, with data on spirometry, DLCO and TCT were reviewed. Workers with substantial comorbidities (cardiac, malignant, silicosis) and/or pulmonary emphysema (pulmonary hyperinflation and/or TCT findings), which, like asbestosis, can lead to a diffusion disorder were excluded. The remaining data of 41 male workers (mean 69.8 years ±6.9) were evaluated. The TCT changes were coded according to the International Classification of High-resolution Computed Tomography for Occupational and Environmental Respiratory Diseases (ICOERD) by radiologists and ICOERD-scores for pleural and pulmonary changes were determined. Correlations (ρ), Cohens κ and accuracy were calculated.

RESULTS

In all 41 males the vital capacity (VC in % of the predicted value (% pred.)) showed only minor limitations (mean 96.5 ± 18.0%). The DLCO (in % pred.) was slightly reduced (mean 76.4 ± 16.6%; median 80.1%); the alveolar volume related value (DLCO/VA) was within reference value (mean 102 ± 22%). In the TCT of 27 workers pleural asbestos-related findings were diagnosed whereof 24 were classified as pulmonary fibrosis (only one case with honey-combing). Statistical analysis provided low correlations of VC (ρ = - 0.12) and moderate correlations of DLCO (- 0.25) with pleural plaque extension. The ICOERD-score for pulmonary fibrosis correlated low with VC (0.10) and moderate with DLCO (- 0.23); DLCO had the highest accuracy with 73.2% and Cohens κ with 0.45. DLCO/VA showed no correlations to the ICOERD-score. The newly developed score, which takes into account the diffuse pleural thickening, shows a moderate correlation with the DLCO (ρ = - 0.35, p < 0.05).

CONCLUSIONS

In formerly asbestos-exposed workers, lung function alterations and TCT findings correlated moderate, but significant using DLCO and ICOERD-score considering parenchymal ligaments, subpleural curvilinear lines, round atelectases and pleural effusion in addition to pleural plaque extension. DLCO also showed highest accuracy in regard to pulmonary findings. However, VC showed only weaker correlations although being well established for early detection. Besides TCT the determination of both lung function parameters (VC and DLCO) is mandatory for the early detection and assessment of functional deficiencies in workers formerly exposed to asbestos.

Clinical study of asbestos-related lung cancer diagnosed by asbestos medical examination

AIM

People with occupational exposure to asbestos demonstrate a high incidence of lung cancer. Asbestos medical examination for those at risk was implemented as a national policy in Japan. This study aimed to characterize patients with asbestos-related lung cancer who were diagnosed by these examinations.

METHODS

We retrospectively investigated 120 individuals exposed to asbestos who were examined from 2008 to 2016 at our institution. Clinical data, including CT findings and time-related exposure variables, were evaluated. Each asbestos-related change was assigned 1 point if present, and the scores were compared between patients with and without asbestos-related lung cancer using the Mann-Whitney U test and Fisher's exact test.

RESULTS

Five patients were diagnosed with lung cancer, and four underwent surgical treatment. At the time of writing, three of four operated patients were alive without recurrence, with a similar prognosis to patients with lung cancer unrelated to asbestos. Average scores for asbestos-related findings on CT Scan were 1.8 (9/5) for patients with lung cancer and 0.79 (91/115) for those without lung cancer.

CONCLUSION

Patients with lung cancer had significantly more asbestos-related changes on CT scan than those without lung cancer. Concurrent calcified plaque and interstitial changes might be a predictor of lung cancer incidence. Although further investigation with a larger study group is needed, regular medical examination and CT scan every 6 months might contribute to the early detection of lung cancer with asbestos-related changes on CT.

The Secretory Response of Rat Peritoneal Mast Cells on Exposure to Mineral Fibers

BACKGROUND

Exposure to mineral fibers is of substantial relevance to human health. A key event in exposure is the interaction with inflammatory cells and the subsequent generation of pro-inflammatory factors. Mast cells (MCs) have been shown to interact with titanium oxide (TiO₂) and asbestos fibers. In this study, we compared the response of rat peritoneal MCs challenged with the asbestos crocidolite and nanowires of TiO₂ to that induced by wollastonite employed as a control fiber.

METHODS

Rat peritoneal MCs (RPMCs), isolated from peritoneal lavage, were incubated in the presence of mineral fibers. The quantities of secreted enzymes were evaluated together with the activity of fiber-associated enzymes. The ultrastructural morphology of fiber-interacting RPMCs was analyzed with electron microscopy.

RESULTS

Asbestos and TiO₂ stimulate MC secretion. Secreted enzymes bind to fibers and exhibit higher activity. TiO₂ and wollastonite bind and improve enzyme activity, but to a lesser degree than crocidolite.

CONCLUSIONS

(1) Mineral fibers are able to stimulate the mast cell secretory process by both active (during membrane interaction) and/or passive (during membrane penetration) interaction; (2) fibers can be found to be associated with secreted enzymes-this process appears to create long-lasting pro-inflammatory environments and may represent the active contribution of MCs in maintaining the inflammatory process; (3) MCs and their enzymes should be considered as a therapeutic target in the pathogenesis of asbestos-induced lung inflammation; and (4) MCs can contribute to the inflammatory effect associated with selected engineered nanomaterials, such as TiO₂ nanoparticles.

Chest physician-reported, work-related, long-latency respiratory disease in Great Britain

Much of the current burden of long-latency respiratory disease (LLRD) in Great Britain is attributed to historical asbestos exposure. However, continuing exposure to other agents, notably silica, also contributes to disease burden. The aim of this study was to investigate the incidence of work-related LLRD reported by chest physicians in Great Britain, including variations by age, gender, occupation and suspected agent.LLRD incidence and incidence rate ratios by occupation were estimated (1996-2014). Mesothelioma cases by occupation were compared with proportional mortality ratios.Cases were predominantly in men (95%) and 92% of all cases were attributed to asbestos. Annual average incidence rates (males) per 100 000 were: benign pleural disease, 7.1 (95% CI 6.0-8.2); mesothelioma, 5.4 (4.8-6.0); pneumoconiosis, 1.9 (1.7-2.2); lung cancer, 0.8 (0.6-1.0); chronic obstructive pulmonary disease (COPD), 0.3 (0.2-0.4). Occupations with a particularly high incidence of LLRD were miners and quarrymen (COPD), plumbers and gas fitters (asbestosis), and shipyard and dock workers (all other categories). There was a clear concordance between cases of SWORD mesothelioma and proportional mortality ratios by occupation.Occupationally caused LLRD continues to contribute to a significant disease burden. Many cases are attributable to past exposure to agents such as asbestos and silica, but the potential for occupational exposures persists.

Comparative Interpretation of CT and Standard Radiography of the Pleura

Many diseases affect the pleural space in both adults and children, including common diseases such as pneumonia, cancer and heart failure. Pleural effusion is the most common manifestation of pleural disease, and it is often a secondary effect of another disease process.

Imaging plays a crucial role in the management of pleural disease. Chest radiography often remains the first examination in the assessment of these patients. Depending on the clinical context, the optimal imaging technique for further evaluation might be computed tomography (CT), ultrasound (US), or magnetic resonance (MR).

Natural carcinogenic fiber and pleural plaques assessment in a general population: A cross-sectional study

Natural carcinogenic fibers are asbestos and asbestiform fibers present as a natural component of soils or rocks. These fibers are released into the environment resulting in exposure of the general population. Environmental contamination by fibers are those cases occurred in: rural regions of Turkey, in Mediterranean countries and in other sites of the world, including northern Europe, USA and China. Fluoro-edenite(FE) is a natural mineral species first isolated in Biancavilla, Sicily. The fibers are similar in size and morphology to some amphibolic asbestos fibers, whose inhalation can cause chronic inflammation and cancer. The aim of the current study is to assess the presence and features of pleural plaques (PPs) in Biancavilla's general population exposed to FE through a retrospective cross-sectional study. All High-Resolution Computed Tomography (HRCT) chest scans carried out between June 2009 and June 2015 in Biancavilla municipality hospital site (exposed subjects) were reviewed. The exposed groups were 1:1 subjects, matched according to age and sex distributions, with unexposed subjects (n.1.240) randomly selected among HRCT chest scans carried out in a Hospital 30km away from Biancavilla. Subjects from Biancavilla with PPs were significantly more numerous than the control group ones (218 vs 38). Average age of either group was >60 years; the age of exposed subjects was significantly (p=0.0312) lesser than the unexposed group. In exposed subjects, in most PPs thickness ranged between 2 and 4.9cm(38%, n=83); while in unexposed ones PPs thickness was less than 2cm (55%, n=21). As to the size of PPs in exposed subjects, in most cases it ranged between 1cm and 24% of chest wall (53%, n=116); while in unexposed ones the size of PPs was lesser than 1cm (23%, n=58). Among exposed subjects, 36 cases (17%) PPs were detected with calcification, whereas in unexposed ones only three (8%) presented calcification. 137 lung parenchymal abnormalities were observed in exposed group; whereas, 12 lung parenchymal involvement were registered in unexposed subjects. The RR for PPs is 6,74 CI 95% (4,47-9,58) p<0,0001 in the exposed population. These findings, suggested the urge to extend the screening on the possible involvement of the respiratory tract to all Biancavilla's population, particularly in those aged more than 30. Besides, it seems essential to start indoor monitoring Biancavilla's municipality.

Exercise training to improve exercise capacity and quality of life in people with non-malignant dust-related respiratory diseases

BACKGROUND

Non-malignant dust-related respiratory diseases, such as asbestosis and silicosis, are similar to other chronic respiratory diseases and may be characterised by breathlessness, reduced exercise capacity and reduced health-related quality of life. Some non-malignant dust-related respiratory diseases are a global health issue and very few treatment options, including pharmacological, are available. Therefore, examining the role of exercise training is particularly important to determine whether exercise training is an effective treatment option in non-malignant dust-related respiratory diseases.

OBJECTIVES

To assess the effects of exercise training for people with non-malignant dust-related respiratory diseases compared with control, placebo or another non-exercise intervention on exercise capacity, health-related quality of life and levels of physical activity.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE/PubMed, EMBASE, CINAHL, PEDro and AMED (all searched from inception until February 2015), national and international clinical trial registries, reference lists of relevant papers and we contacted experts in the field for identification of suitable studies.

SELECTION CRITERIA

We included only randomised controlled trials (RCTs) that compared exercise training of at least four weeks duration with no exercise training, placebo or another non-exercise intervention.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. Two review authors independently assessed study eligibility and risk of bias, and extracted data. We employed the GRADE approach to assess the overall quality of evidence for each outcome and to interpret findings. We synthesized study results using a random-effects model based on the assessment of heterogeneity. We conducted subgroup analyses on participants with dust-related interstitial lung diseases (ILDs) and participants with asbestos related pleural disease (ARPD).

MAIN RESULTS

Two RCTs including a combined total of 40 participants (35 from one study and five from a second study) met the inclusion criteria. Twenty-one participants were randomised to the exercise training group and 19 participants were randomised to the control group. The included studies evaluated the effects of exercise training compared to a control group of no exercise training in people with dust-related ILDs and ARPD. The exercise training programme in both studies was in an outpatient setting for an eight-week period. The risk of bias was low in both studies. There were no reported adverse events of exercise training. Following exercise training, six-minute walk distance (6MWD) increased with a mean difference (MD) of 53.81 metres (m) (95% CI 34.36 to 73.26 m). Improvements were also seen in the domains of health-related quality of life: Chronic Respiratory Disease Questionnaire (CRQ) Dyspnoea domain (MD 2.58, 95% CI 0.72 to 4.44); CRQ Fatigue domain (MD 1.00, 95% CI 0.11 to 1.89); CRQ Emotional Function domain (MD 2.61, 95% CI 0.74 to 4.49); and CRQ Mastery domain (MD 1.51, 95% CI 0.29 to 2.72). Improvements in exercise capacity and health-related quality of life were also evident six months following the intervention period: 6MWD (MD 52.68 m, 95% CI 27.43 to 77.93 m); CRQ Dyspnoea domain (MD 3.03, 95% CI 1.41 to 4.66); CRQ Emotional Function domain (MD 5.57, 95% CI 2.34 to 8.81); and CRQ Mastery domain (MD 2.66, 95% CI 1.08 to 4.23). Exercise training did not result in improvements in the Modified Medical Research Council (MMRC) dyspnoea scale immediately following exercise training or six months following exercise training. The improvements following exercise training were similar in a subgroup of participants with dust-related ILDs and in a subgroup of participants with ARPD compared to the control group, with no statistically significant differences in treatment effects between the subgroups.

AUTHORS' CONCLUSIONS

The evidence examining exercise training in people with non-malignant dust-related respiratory diseases is of very low quality. This is due to imprecision in the results from the small number of trials and the small number of participants, the indirectness of evidence due to a paucity of information on disease severity and the data from one study being from a subgroup of participants, and inconsistency from high heterogeneity in some results. Therefore, although the review findings indicate that an exercise training programme is effective in improving exercise capacity and health-related quality of life in the short-term and at six months follow-up, we remain unsure of these findings due to the very low quality evidence. Larger, high quality trials are needed to determine the strength of these findings.

Asbestos in Asia

Asbestos is a global killer. Despite lessons learned in the developed world on the use of asbestos and its hazardous pulmonary consequences, its use continues to increase in Asia. Although some countries such as Japan, Korea and Singapore have curtailed the use of this mineral, there are numerous countries in Asia that continue to mine, import and use this fibre, particularly China, which is one of the largest consumers in the world. Numerous factors ranging from political and economic to the lack of understanding of asbestos and the management of asbestos-related lung disease are keys to this observed trend. Awareness of these factors combined with early intervention may prevent the predicted Asian 'tsunami' of asbestos diseases.

Systematic review of pleural plaques and lung function

Context

US EPA proposed a Reference Concentration for Libby amphibole asbestos based on the premise that pleural plaques are adverse and cause lung function deficits.

Objective

We conducted a systematic review to evaluate whether there is an association between pleural plaques and lung function and ascertain whether results were dependent on the method used to identify plaques.

Methods

Using the PubMed database, we identified studies that evaluated pleural plaques and lung function. We assessed each study for quality, then integrated evidence and assessed associations based on the Bradford Hill guidelines. We also compared the results of HRCT studies to those of X-ray studies.

Results

We identified 16 HRCT and 36 X-ray studies. We rated six HRCT and 16 X-ray studies as higher quality based on a risk-of-bias analysis. Half of the higher quality studies reported small but statistically significant mean lung function decrements associated with plaques. None of the differences were clinically significant. Many studies had limitations, such as inappropriate controls and/or insufficient adjustment for confounders. There was little consistency in the direction of effect for the most commonly reported measurements. X-ray results were more variable than HRCT results. Pleural plaques were not associated with changes in lung function over time in longitudinal studies.

Conclusion

The weight of evidence indicates that pleural plaques do not impact lung function. Observed associations are most likely due to unidentified abnormalities or other factors.

Lung Function Profiles among Individuals with Nonmalignant Asbestos-related Disorders

Background

Inhalation of asbestos fibers can lead to adverse health effects on the lungs. This study describes lung function profiles among individuals with nonmalignant asbestos-related disorders (ARDs).

Methods

The study population was from the Workers' Compensation (Dust Diseases) Board of New South Wales, Sydney, Australia. Lung function measurements were conducted in males with asbestosis (n = 26), diffuse pleural thickening (DPT; n = 129), asbestosis and DPT (n = 14), pleural plaques only (n = 160) and also apparently healthy individuals with a history of asbestos exposure (n = 248). Standardized spirometric and single-breath diffusing capacity for carbon monoxide (DL_CO) measurements were used.

Results

Mean age [standard deviation (SD)] was 66.7 (10.3) years for all participants. Current and ex-smokers among all participants comprised about 9.0% and 54.8%, respectively. Median pack-years (SD) of smoking for ex- and current-smokers were 22.7 (19.9). Overall 222 participants (38.6%) and 139 participants (24.2%) had forced expiratory volume in 1 second (FEV₁) and forced vital capacity (FVC) measurements < 80% predicted, and 217 participants (37.7%) had FEV₁/FVC results < 70%. A total of 249 individuals (43.8%) had DLco values < 80% predicted and only 75 (13.2%) had DLco/VA results < 80% predicted. A total of 147 participants (25.6%) had peak expiratory flow (PEF) measurements < 80% predicted. The presence of ARDs lowered the lung function measurements compared to those of healthy individuals exposed to asbestos.

Conclusion

Lung function measurement differs in individuals with different ARDs. Monitoring of lung function among asbestos-exposed populations is a simple means of facilitating earlier interventions.

Awareness of Asbestos and Action Plans for Its Exposure can Help Lives Exposed to Asbestos

Despite the fact that asbestos is a known carcinogen to humans, it is still used in industrialized countries, especially Asian countries. The global incidence of asbestos-related diseases (ARDs) due to the past use of asbestos, continues to increase, although many countries have adopted a total ban on asbestos use. The implementation of effective strategies to eliminate ARDs is therefore an important challenge in Asia, where asbestos is still mined and consumed. Collaborative efforts and strategies at the local and international levels are vital, in the pursuit toward the elimination of ARDs in this region.

Asbestos and the lung in the 21st century: an update

The asbestos-related disorders (ARDs) are currently of significant occupational and public health concern. Asbestos usage has been banned in most developed countries, but asbestos is still used in many developing countries and the number of cases of ARDs worldwide is rising. Many countries are now experiencing an epidemic of ARDs that is the legacy of occupational exposure in the 1960s-1980s because of the long latency period between asbestos exposure and manifestation of disease. It is likely that asbestos-related mortality and morbidity will continue to increase. Although the most feared complications of asbestos inhalation are the malignant conditions such as mesothelioma and lung cancer, asbestos inhalation more frequently results in benign conditions such as pleural plaques, diffuse pleural thickening, and asbestosis (pulmonary fibrosis due to asbestos exposure). Over recent years, there have been changes in the epidemiology of mesothelioma, in clinical management of ARDs and developments in new techniques for early detection of malignancy. This review provides an update on the respiratory manifestations of asbestos exposure and also considers advances in screening methods that may affect future management in the workplace.

Asbestos-related pleuropulmonary diseases: benign and malignant

Asbestos is known for its desirable properties of thermal and heat resistance along with excellent strength and durability. It was widely used in many industries since the late 19th century, until its adverse effects on health were recognized. The occurrence of pleuropulmonary changes from exposure to asbestos often has a latency period of 20 to 30 years. The use of asbestos has been banned, regulated, and minimized in many countries, but in several developing countries, the use of asbestos in industries is still a common practice. In this article, the benign and malignant clinical manifestations of asbestos exposure are discussed.

Asbestos-related pleural disease

PURPOSE OF REVIEW

Asbestos exposure is the cause of significant pleural disease - both benign and malignant. Although there is increased awareness, individuals continue to be exposed, and we will continue to see its sequelae for years to come because of the delay between exposure and disease manifestation. Asbestos-related pleural disease includes pleural plaques, diffuse pleural thickening, benign asbestos-related pleural effusions (BAPEs), and malignant pleural mesothelioma (MPM).

RECENT FINDINGS

Several recent studies are highlighted throughout this review, including a comparative analysis of diagnostic imaging modalities for identifying and characterizing pleural plaques, the effect of pleural plaques on lung volumes and flows, and how pain is a relatively common feature in patients with pleural plaques. Advances in the treatment of MPM are limited, but a recent publication highlights the increased morbidity associated with surgical debulking procedures and questions the benefit of these procedures.

SUMMARY

Asbestos-related pleural disease will continue to present a significant burden of illness. Recent publications have suggested potential treatment benefit and point to areas that would require further investigation.

[Follow-up of subjects occupationally exposed to asbestos: MRI and PET scans]

MRI and PET scans are not normally used for screening and follow-up of patients following occupational exposure to asbestos. These examinations usually complement the investigation of a parenchymal mass, an effusion or pleural thickening. PET and MRI have an excellent ability to define a parenchymal lesion as malignant (cancer versus rounded atelectasis) or a pleural lesion (mesothelioma versus plaque). MRI distinguishes perfectly the involvement of sub-pleural fat by bronchial carcinoma or mesothelioma. MRI, taking account of its lack of irradiation, could be regarded as suitable for potentially repeated examinations following initial screeing by CT scan. A comparative study of multidetector scanner versus MRI, including diffusion MRI could be, nevertheless, interesting. PET cannot be proposed for the follow up or for screening on account of the irradiation induced and the difficulty of access. Pleural plaques do not take up FDG. There is no specific study of asbestos related fibrosis and there is discordance between studies of other types of pulmonary fibrosis.

Descriptive analysis of the respiratory health status of persons exposed to Libby amphibole asbestos

OBJECTIVE

Describe respiratory health and quality of life in persons exposed to Libby amphibole asbestos (LAA) contaminated vermiculite.

DESIGN

Cross-sectional descriptive.

SETTING

Asbestos-related disease clinic in Libby, Montana USA.

PARTICIPANTS

329 individuals exposed to LAA; mostly men, married, between 50 and 69 years; two-thirds lived in the surrounding county; one-third lived elsewhere in the state and USA.

PRIMARY OUTCOME MEASURES

Chest radiograph (CXR), pulmonary function data and the St George Respiratory Questionnaire (SGRQ).

RESULTS

Exposure categories included vermiculite workers=7.6%; family/household contact of vermiculite worker=32%; and environmental exposure only=60%. Of the participants, 55% had only pleural abnormalities; 5.4% had only interstitial abnormalities; nearly 21% had both abnormalities and 18% had no lung abnormality on chest x-ray. Mean forced vital capacity (FVC) 95.3% (SD=18.7); forced expiratory volume (FEV(1)) mean 87% (SD=20.2); ratio of FEV1(1)/FVC 95.5% (SD=12.0); and diffusing capacity (DLCO) of 83% (SD=21.7) of the percent predicted. The mean total SGRQ (38.5; SD=22.1) indicated a lower quality of life than healthy persons and persons with other chronic conditions. SGRQ subscale means were Symptoms 52.1 (SD=24.9), activity 49.4 (SD=26.9) and impacts 27.5 (SD=21.9). Participants with normal CXR differed significantly from those with both interstitial and pleural abnormalities on total, activity and impacts scores. For activity alone, subjects with normal CXR differed significantly from those with pleural disease; no differences were found for those with interstitial disease. Significant findings were found for smoking history across all pulmonary measures, and for exposure status, radiographic findings, age and gender for select pulmonary parameters. Subjects with any smoking history had significantly worse average total and subscale scores on the SGRQ.

CONCLUSIONS

Of 329 persons exposed to LAA, the majority (182) had pleural abnormalities identified on CXR. SGRQ scores for persons with abnormalities (pleural, interstitial or both) (269) differed significantly from those with a normal CXR.

Erionite in road gravel associated with interstitial and pleural changes--an occupational hazard in western United States

OBJECTIVE

To determine the rate of chest radiographic abnormalities among residents of North Dakota potentially exposed to road gravel containing the fibrous mineral erionite.

METHODS

Participants (n = 34) completed a questionnaire, chest radiograph, and high resolution computed tomography scan to assess the rate of interstitial and pleural changes consistent with fibrous mineral exposure.

RESULTS

Interstitial, pleural, or both changes typically associated with asbestos exposure were observed by high resolution computed tomography in seven (21%) individuals. The primary exposure pathway for six of these was from gravel pits, road maintenance, or both. Three participants (8.8%) demonstrated bilateral localized pleural changes with calcification; two of these also had accompanying interstitial changes. All three reported extensive work in gravel pits, road maintenance, or both.

CONCLUSIONS

These results indicate that occupational exposure to erionite contained within road gravel in the United States represents a potential health hazard.

CLINICAL SIGNIFICANCE

This study identifies chest radiographic changes among residents of North Dakota occupationally exposed to road gravel containing erionite. Public health officials and physicians in affected areas should be aware of the potential health effects of erionite exposure. Precautionary measures should be taken to limit occupational exposure to gravel containing erionite.

Role of mutagenicity in asbestos fiber-induced carcinogenicity and other diseases

The cellular and molecular mechanisms of how asbestos fibers induce cancers and other diseases are not well understood. Both serpentine and amphibole asbestos fibers have been shown to induce oxidative stress, inflammatory responses, cellular toxicity and tissue injuries, genetic changes, and epigenetic alterations in target cells in vitro and tissues in vivo. Most of these mechanisms are believe to be shared by both fiber-induced cancers and noncancerous diseases. This article summarizes the findings from existing literature with a focus on genetic changes, specifically, mutagenicity of asbestos fibers. Thus far, experimental evidence suggesting the involvement of mutagenesis in asbestos carcinogenicity is more convincing than asbestos-induced fibrotic diseases. The potential contributions of mutagenicity to asbestos-induced diseases, with an emphasis on carcinogenicity, are reviewed from five aspects: (1) whether there is a mutagenic mode of action (MOA) in fiber-induced carcinogenesis; (2) mutagenicity/carcinogenicity at low dose; (3) biological activities that contribute to mutagenicity and impact of target tissue/cell type; (4) health endpoints with or without mutagenicity as a key event; and finally, (5) determinant factors of toxicity in mutagenicity. At the end of this review, a consensus statement of what is known, what is believed to be factual but requires confirmation, and existing data gaps, as well as future research needs and directions, is provided.

Breath analysis in asbestos-related disorders: a review of the literature and potential future applications

Asbestos usage was very common worldwide in the last century and continues in several countries today. Several diseases occur due to asbestos exposure, including malignant tumours such as malignant mesothelioma of the pleura and lung cancer, which have a very poor prognosis. Asbestos inhalation may also result in more benign conditions such as asbestosis (or pulmonary fibrosis due to asbestos), pleural plaques and pleural thickening. It is predicted that asbestos-associated mortality and morbidity will continue to increase, but methods for diagnosing asbestos-related disease are currently invasive and unsuitable for an increasingly elderly population. New non-invasive methods such as analysis of exhaled breath biomarkers e.g. exhaled nitric oxide (F(E)NO), exhaled breath condensate or of exhaled volatile organic compounds could potentially be extremely useful in these conditions. This article reviews the current literature on this topic and suggests areas for their application in the future.

Hypoventilation syndromes

A wide variety of mechanisms can lead to the hypoventilation associated with various medical disorders, including derangements in central ventilatory control, mechanical impediments to breathing, and abnormalities in gas exchange leading to increased dead space ventilation. The pathogenesis of hypercapnia in obesity hypoventilation syndrome remains somewhat obscure, although in many patients comorbid obstructive sleep apnea appears to play an important role. Hypoventilation in neurologic or neuromuscular disorders is primarily explained by weakness of respiratory muscles, although some central nervous system diseases may affect control of breathing. In other chest wall disorders, obstructive airways disease, and cystic fibrosis, much of the pathogenesis is explained by mechanical impediments to breathing, but an element of increased dead space ventilation also often occurs. Central alveolar hypoventilation syndrome involves a genetically determined defect in central respiratory control. Treatment in all of these disorders involves coordinated management of the primary disorder (when possible) and, increasingly, the use of noninvasive positive pressure ventilation.

Refractory ceramic fiber (RCF) toxicity and epidemiology: a review

This paper provides a review of the relevant literature on refractory ceramic fibers (RCFs), summarizing relevant data and information on the manufacture, processing, applications, potential occupational exposure, toxicology, epidemiology, risk analysis, and risk management. RCFs are amorphous fibers used for high-temperature insulation applications. RCFs are less durable/biopersistent than amphibole asbestos, but more durable/biopersistent than many other synthetic vitreous fibers (SVFs). Moreover, as produced/used, some RCFs are respirable. Toxicology studies with rodents using various exposure methods have shown that RCFs can cause fibrosis, lung cancer, and mesothelioma. Interpretation of these animal studies is difficult for various reasons (e.g., overload in chronic inhalation bioassays). Epidemiological studies of occupationally exposed cohorts in Europe and the United States have demonstrated measurable effects (e.g., mild respiratory symptoms and pleural plaques) but no disease (i.e., no interstitial fibrosis, no excess lung cancer, and no mesothelioma) to date. The RCF industry, working cooperatively with various government agencies in the United States, has developed a comprehensive product stewardship program (PSP) to identify and control risks associated with occupational exposure. One provision of the PSP is the adoption of a voluntary recommended exposure guideline (REG) of 0.5 fibers/milliliter (f/ml). Selected on the basis of prudence and demonstrated feasibility, compliance with the REG should reduce risks to levels between 0.073/1000 and 1.2/1000, based on extrapolations from chronic animal inhalation studies.

Asbestos-related occupational lung diseases in NSW, Australia and potential exposure of the general population

Asbestos is a fibrous silicate which is recognized as causing a variety of lung disorders including malignant mesothelioma of the pleura, lung cancer and asbestosis. Asbestos use has been banned in most developed countries but exposure still occurs under strict regulation in occupational settings and also occasionally in domestic settings. Although the hazards of asbestos are well known in developed countries, awareness of its adverse health effects is less in other parts of the world, particularly when exposure occurs in non-occupational settings. Experience of asbestos use and its adverse heath effects in developed countries such as Australia have resulted in development of expertise in the diagnosis and treatment of asbestos-related diseases as well as in screening and this can be used to help developing countries facing the issue of asbestos exposure.