The effect of asbestosis on lung cancer risk beyond the dose related effect of asbestos alone

Asbestos-Related lung Cancer: An underappreciated oncological issue

Asbestos, a group of class I (WHO) carcinogenic fibers, is the main cause of mesothelioma. Asbestos inhalation also increases the risk to develop other solid tumours with lung cancer as the most prominent example [91]. The incidence of asbestos-related lung cancer (ARLC) is estimated to be to six times larger than the mesothelioma incidence thereby becoming an important health issue [86]. Although the pivotal role of asbestos in inducing lung cancer is well established, the precise causal relationships between exposures to asbestos, tobacco smoke, radon and 'particulate' (PM2.5) air pollution remain obscure and new knowledge is needed to establish appropriate preventive measures and to tailor existing screening practices[22,61,65]. We hypothesize that a part of the increasing numbers of lung cancer diagnoses in never-smokers can be explained by (historic and current) exposures to asbestos as well as combinations of different forms of air pollution (PM2.5, asbestos and silica).

Lung cancer risk and occupational pulmonary fibrosis: systematic review and meta-analysis

BACKGROUND

Molecular pathways found to be important in pulmonary fibrosis are also involved in cancer pathogenesis, suggesting common pathways in the development of pulmonary fibrosis and lung cancer.

RESEARCH QUESTION

Is pulmonary fibrosis from exposure to occupational carcinogens an independent risk factor for lung cancer?

STUDY DESIGN AND METHODS

A comprehensive search of PubMed, Embase, Web of Science and Cochrane databases with over 100 search terms regarding occupational hazards causing pulmonary fibrosis was conducted. After screening and extraction, quality of evidence and eligibility criteria for meta-analysis were assessed. Meta-analysis was performed using a random-effects model.

RESULTS

52 studies were identified for systematic review. Meta-analysis of subgroups identified silicosis as a risk factor for lung cancer when investigating odds ratios for silicosis in autopsy studies (OR 1.47, 95% CI 1.13-1.90) and for lung cancer mortality in patients with silicosis (OR 3.21, 95% CI 2.67-3.87). Only considering studies with an adjustment for smoking as a confounder identified a significant increase in lung cancer risk (OR 1.58, 95% CI 1.34-1.87). However, due to a lack of studies including cumulative exposure, no adjustments could be included. In a qualitative review, no definitive conclusion could be reached for asbestosis and silicosis as independent risk factors for lung cancer, partly because the studies did not take cumulative exposure into account.

INTERPRETATION

This systematic review confirms the current knowledge regarding asbestosis and silicosis, indicating a higher risk of lung cancer in exposed individuals compared to exposed workers without fibrosis. These individuals should be monitored for lung cancer, especially when asbestosis or silicosis is present.

Expression of microRNAs in leukocytes and serum of asbestosis patients

BACKGROUND

Although asbestos use is banned in many countries, long latency of asbestos-related diseases like pleural plaques or asbestosis mean it is still a public health issue. People suffering from these diseases have a higher risk of developing mesothelioma or lung cancer, which can progress quickly and aggressively. MicroRNAs were suggested as potential biomarkers in several diseases. However, in asbestosis, blood microRNAs are less explored. Since miR-32-5p, miR-143-3p, miR-145-5p, miR-146b-5p, miR-204-5p and miR-451a are involved in fibrotic processes and in cancer, expression of these microRNAs was analyzed in leukocytes and serum of asbestosis patients.

METHODS

MicroRNA expression was analyzed in leukocytes and serum of 36 patients (26 affected by pleural plaques and 10 by asbestosis) and 15 healthy controls by real-time RT-PCR. Additionally, data analyses were performed regarding disease severity based on ILO classification.

RESULTS

MicroRNA miR-146b-5p was significantly down-regulated in leukocytes of patients suffering from pleural plaques with a large effect indicated by η²_p = 0.150 and Cohen's f = 0.42, a value of difference of 0.725 and a 95% confidence interval of 0.070-1.381. In patients suffering from asbestosis miR-146b-5p was not significantly regulated. However, data analyses considering disease severity only, revealed that miR-146b-5p was significantly down-regulated in leukocytes of mildly diseased patients compared to controls with a large effect indicated by η²_p = 0.178 and Cohen's f = 0.465, a value of difference of 0.848 and a 95% confidence interval of 0.097-1.599. Receiver operating characteristic (ROC) curve and an area under the ROC curve value of 0.757 for miR-146b-5p indicated acceptable discrimination ability between patients suffering from pleural plaques and healthy controls. Less microRNAs were detectable in serum than in leukocytes, showing no significant expression differences in all participants of this study. Moreover, miR-145-5p was regulated significantly differently in leukocytes and serum. An R² value of 0.004 for miR-145-5p indicated no correlation in microRNA expression between leukocytes and serum.

CONCLUSION

Leukocytes seem more suitable than serum for microRNA analyses regarding disease and potentially cancer risk assessment of patients suffering from asbestos-related pleural plaques or asbestosis. Long-term studies may reveal whether down-regulation of miR-146b-5p in leukocytes might be an early indicator for an increased cancer risk.

Comorbidities and Causes of Death of Patients With Asbestosis

OBJECTIVE

Comorbidities are common and affect the prognosis of patients with interstitial lung diseases, but few previous studies have investigated patients with asbestosis.

METHODS

We collected comorbidities and death causes of 116 patients with asbestosis treated in Oulu University Hospital. Causes of death were confirmed by autopsy in 68% of the cases.

RESULTS

The most common comorbidities of asbestosis patients were pleural plaques (96%) and coronary artery disease (CAD; 67%). The prevalence of rheumatoid arthritis was 8.6%. The most common underlying causes of death were asbestosis (36%), CAD (24%), and lung cancer (LC) (10%). CAD and LC were associated with shorter survival in adjusted analyses.

CONCLUSIONS

Patients with asbestosis have multiple comorbidities. Prevention and treatment of CAD and LC may influence the prognosis of asbestosis patients.

Pleural plaques and risk of lung cancer in workers formerly occupationally exposed to asbestos: extension of follow-up

BACKGROUND

Occupational asbestos exposure is associated with pleural plaques (PP), a benign disease often seen as a marker of past exposure to asbestos and lung cancer. The association between these two diseases has not been formally proved, the aim of this study was to evaluate this association in the asbestos-related disease cohort (ARDCO) cohort.

METHODS

ARDCO is a French multicentric cohort including workers formerly occupationally exposed to asbestos from 2003 to 2005. CT scan was performed to diagnose PP with double reading and lung cancer (incidence and mortality) was followed through health insurance data and death certificates. Cox models were used to estimate the association between PP and lung cancer adjusting for occupational asbestos exposure (represented by cumulative exposure index, time since first exposure and time since last exposure) and smoking status.

RESULTS

A total of 176 cases (of 5050 subjects) and 88 deaths (of 4938 subjects) of lung cancer were recorded. Smoking status was identified as an effect modifier. Lung cancer incidence and mortality were significantly associated with PP only in non-smokers, respectively, HR=3.13 (95% CI 1.04 to 9.35) and HR=16.83 (95% CI 1.87 to 151.24) after adjustment for age, occupational asbestos exposure and smoking status.

CONCLUSIONS

ARDCO study was the first to study this association considering equal asbestos exposure, and more specifically, our study is the first to test smoking as an effect modifier, so comparison with scientific literature is difficult. Our results seem to consolidate the hypothesis that PP may be an independent risk factor for lung cancer but they must be interpreted with caution.

Military exposures and lung cancer in United States veterans

Lung cancer screening begins at age 50, with yearly low dose computed tomography (LDCT) scans until age 80, for patients determined to be high risk due to tobacco smoking. Veterans serving from World War II to the Gulf War are now at the age where LDCT is recommended. This recommendation from the United States Preventative Service Task Force includes patients who have a 20-pack year tobacco history and currently smoke or quit within the last 15 years. This recommendation does not consider additional risk factors such as exposures to lung carcinogens. We discuss unique operational and occupational exposures encountered while serving in the armed forces, which may potentially increase the risk of lung cancers in the Veteran population. The additional risk of lung cancer due to military exposure history is unclear and more work is needed to identify and quantify risk at an individual level. Increasing awareness at the provider level regarding the carcinogenic exposures encountered may allow a larger population of Veterans, not meeting traditional LDCT criteria, to benefit from lung cancer screening.

Lung cancer and mesothelioma risks in a prospective cohort of workers with asbestos-related lung or pleural diseases

BACKGROUND

Asbestos causes mesothelioma and lung cancer. In the European Union, asbestos was banned in 2005, but it is still in use in many other countries. The aim of this study was to estimate the lung cancer and mesothelioma incidence risk of men with benign asbestos-related lung or pleural diseases.

METHODS

Between 2008 and 2018, 2439 male participants of a German surveillance program for asbestos workers were included in the cohort. All participants had a recognized occupational asbestos-related disease of the pleura or lung. We estimated the mesothelioma and lung cancer risks by calculating standardized incidence ratios (SIR) with corresponding 95% confidence intervals (95% CI).

RESULTS

We observed 64 incident lung cancer and 40 mesothelioma cases in the cohort. An SIR of 17.60 (95% CI: 12.57-23.96) was estimated for mesothelioma and 1.27 (95% CI: 0.98-1.62) for lung cancer. The presence of pleural plaques was associated with a strongly increased risk (SIR: 13.14; 95% CI: 8.51-19.40) for mesothelioma, but not for lung cancer (SIR: 1.05; 95% CI: 0.76-1.41). The highest lung-cancer risk (SIR: 2.56; 95% CI 1.10-5.04) was revealed for cohort members with less than 40 years since first asbestos exposure. Lung cancer risks by duration of asbestos exposure did not show a consistent time trend, but for time since last exposure a trend for mesothelioma was seen.

CONCLUSIONS

Compared to the general population, we demonstrated an association between benign asbestos-related lung or pleural disease and mesothelioma risk in workers with a history of occupational asbestos exposure. Because lung-cancer risk is dominated by smoking habits, a possible effect of asbestos exposure may have been masked. Efforts should be made to ban production and use of asbestos worldwide and to establish safe handling rules of legacy asbestos.

Comparison of Asbestos Victim Relief Available Outside of Conventional Occupational Compensation Schemes

The asbestos victim relief schemes were introduced to resolve the issue of victims of asbestos-related diseases not receiving compensation through conventional legal orders. This article seeks to derive the differences and commonalities of various asbestos victim relief schemes available outside of the conventional occupational compensation system along with a systematic understanding and to propose plans for improvement through a comparative study. After the degree of asbestos exposure, the population, and the period of implementation were corrected, the recognized claims of the total of conventional occupational compensation schemes and the asbestos victim relief schemes could be ranked in the order of South Korea (KOR) (1867, total), France (FRA) (1571), Japan (JPN) (966), KOR (847, asbestosis grade 2,3 excluded), the United Kingdom (GBR) (670), and the Netherlands (NLD) (95). The average amount of compensation per person, in the case of mesothelioma, was higher in the order of FRA (4.60 times), KOR (1.46 times), GBR (1.03 times), and NLD (0.73 times) of the median income per year. The differences between countries were largely caused by the purpose of institutional design and influenced by the level of qualification, the existence of an expiration date, type of disease, type of benefit, level of judgment criteria, the existence of a procedure for appeals, and recognition rate (GBR: 102%, FRA: 84%, NLD: 81%, JPN: 76%, KOR: 73%, and BEL: 54%). Based on this analysis, suggestions could be made regarding the expansion of disease types, benefit types, and the overall review of judgment criteria.

Mesothelin (MSLN) methylation and soluble mesothelin-related protein levels in a Chinese asbestos-exposed population

OBJECTIVES

This study investigated the mesothelin (MSLN) methylation and its relationship with soluble mesothelin-related protein (SMRP) levels in participants stratified by asbestos exposure scenarios and benign asbestos-related diseases (ARDs).

METHODS

The presence of benign ARDs was confirmed through chest X-ray and the asbestos exposure history was obtained using a standardized questionnaire in this study, including 262 participants. Sera SMRP were measured using MESOMARK, and MSLN methylation in genomic DNA extracted from whole blood was detected by real-time methylation-specific PCR. Covariates were compared with SMRP concentrations using correlation analysis and the potential covariates affecting SMRP were determined by multiple linear regression analysis, and the distribution of methylation status was analyzed by Chi-square test.

RESULTS

There was a trend toward elevation of SMRP values in healthy individuals exposed to asbestos as compared with those without asbestos exposure. The highest median level of SMRP was 1.3 nM in subjects with asbestosis, followed by cases with pleura plaque and asbestosis (1.2 nM), pleura plaque (0.9 nM), healthy subjects with occupational exposure (0.9 nM), non-occupational exposure (0.8 nM), and mixed exposure (0.8 nM). Within asbestosis cases, those with higher profusion scores had higher SMRP values than those with lower profusion scores (1.6 vs. 0.8 nM). Based on multi-regression analysis, the trend toward elevation of SMRP remained significant in subjects with occupational exposure or in those with asbestosis, as compared with healthy subjects without exposure (p < 0.01), although body mass index had an effect on SMRP (p < 0.0001). Regardless of the differences in SMRP levels among these subgroups, MSLN methylation ranged from 80.5 to 92.5 %, with no significant difference. The elevated level of SMRP in asbestosis with higher profusion scores could not be attributed to low MSLN methylation status.

CONCLUSIONS

Our findings suggest that the elevation of SMRP is related to asbestos exposure and benign ARDs especially for cases with high profusion scores, which is independent of MSLN methylation.

Mortality among sheet metal workers participating in a respiratory screening program

BACKGROUND

The Sheet Metal Occupational Health Institute Trust (SMOHIT) established a screening program in 1985 to examine the health hazards of the sheet metal industry in the U.S. and Canada.

METHODS

17,345 individuals with over 20 years in the trade and who participated in the program were followed for causes of death between 1986 and 2010. Both SMRs and Cox proportional hazards models investigated predictors of death due to lung cancer, mesothelioma, and chronic obstructive pulmonary disease (COPD).

RESULTS

Significant excess mortality was seen for mesothelioma and asbestosis. Controlling for smoking, a strong trend for increasing lung cancer risk with increasing chest x-ray profusion >0/0 was observed. With an profusion score <1/0, FEV1 /FVC <80% was associated with lung cancer risk. COPD risk increased with increasing profusion score.

CONCLUSIONS

This study demonstrates asbestos-related diseases among workers with largely indirect exposures and an increased lung cancer risk with low ILO scores.

Mortality of older construction and craft workers employed at department of energy (DOE) nuclear sites: follow-up through 2011

BACKGROUND

The Building Trades National Medical Screening Program (BTMed) was established in 1996 to provide occupational medicine screening examinations for construction workers who have worked at US Department of Energy nuclear sites. Workers participating in BTMed between 1998 and 2011 were followed to determine their vital status and mortality experience through December 31, 2011.

METHODS

The cohort includes 18,803 BTMed participants and 2,801 deaths. Cause-specific Standardized Mortality Ratios (SMRs) were calculated based on US death rates.

RESULTS

Mortality was elevated for all causes, all cancers, cancers of the trachea, bronchus, and lung and lymphatic and hematopoietic system, mesothelioma, COPD, and asbestosis.

CONCLUSIONS

Construction workers employed at DOE sites have a significantly increased risk for occupational illnesses. Risks are associated with employment during all time periods covered including after 1980. The cancer risks closely match the cancers identified for DOE compensation from radiation exposures. Continued medical surveillance is important.

Molecular basis of asbestos-induced lung disease

Asbestos causes asbestosis and malignancies by molecular mechanisms that are not fully understood. The modes of action underlying asbestosis, lung cancer, and mesothelioma appear to differ depending on the fiber type, lung clearance, and genetics. After reviewing the key pathologic changes following asbestos exposure, we examine recently identified pathogenic pathways, with a focus on oxidative stress. Alveolar epithelial cell apoptosis, which is an important early event in asbestosis, is mediated by mitochondria- and p53-regulated death pathways and may be modulated by the endoplasmic reticulum. We review mitochondrial DNA (mtDNA)-damage and -repair mechanisms, focusing on 8-oxoguanine DNA glycosylase, as well as cross talk between reactive oxygen species production, mtDNA damage, p53, OGG1, and mitochondrial aconitase. These new insights into the molecular basis of asbestos-induced lung diseases may foster the development of novel therapeutic targets for managing degenerative diseases (e.g., asbestosis and idiopathic pulmonary fibrosis), tumors, and aging, for which effective management is lacking.

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.

Familial aggregation of malignant mesothelioma in former workers and residents of Wittenoom, Western Australia

Clustering of cases of malignant mesothelioma within families has often been observed, but disentangling genetic and exposure effects has not been done. Former workers and residents exposed to crocidolite at Wittenoom, Western Australia, where many families shared exposure to asbestos, have had high rates of mesothelioma. Our study aimed to estimate the additional risk of mesothelioma in relatives, after allowance for common exposure to crocidolite. More than 11,000 former asbestos workers and residents from Wittenoom have been followed up in cancer and death registries. Levels of exposure for all members of the Wittenoom cohorts have been estimated previously. Relationships between family members of all mesothelioma cases were established from questionnaires, birth and death certificates. Expected numbers of cases of mesothelioma were estimated by fitting a Weibull survival model to all data, based on time from first asbestos exposure, duration and intensity of exposure and age. For each family group, the earliest case was considered the index case. Predicted risk was estimated for each subject from the time of diagnosis of the index case. Familial risk ratios were estimated by dividing observed cases by the sum of risks of all same degree relatives of index cases. There were 369 family groups with at least one case of mesothelioma and a further 25 cases of mesothelioma among relatives in the same families, with 12.9 expected. The risk ratio for blood relatives was 1.9 (95% confidence interval [CI] = 1.3-2.9, p = 0.002). These findings suggest an important, but not large, genetic component in mesothelioma, similar to many other cancers.

Asbestos-related cancer risk in patients with asbestosis or pleural plaques

INTRODUCTION

The relationships between benign asbestos-related diseases (asbestosis and pleural plaques) and thoracic cancers are still debated. The aim of this paper was to review the epidemiological data relevant to this issue.

CURRENT KNOWLEDGE

Published studies show a significant relationship between occupational exposure to asbestos and lung cancer risk, even in the absence of abnormalities consistent with asbestosis on the postero-anterior chest x-ray. For a given cumulative asbestos exposure, the presence of radiographic evidence of asbestosis is associated with an increased risk of lung cancer. Among asbestos-exposed individuals, those having radiographic evidence of pleural plaques are at increased risk for lung cancer and pleural mesothelioma, compared to the general population. However, there is no evidence that pleural plaque confers an increased risk of lung cancer or pleural mesothelioma within a population of individuals having the same cumulative asbestos exposure.

PERSPECTIVES

The studies identified for this review relied only on chest radiograph data. Studies involving accurate evaluations of asbestos exposure and computed tomography of the chest are needed.

CONCLUSION

Currently available data indicate that patient follow-up modalities should be dictated solely by the estimated cumulative asbestos exposure and not by the existence of pleural plaques.

[What are the tools for post-occupational follow-up, how should they be performed and what are their performance, limits and benefit/risk ratio? Chest X-Ray and CT scan]

Chest radiography and computed tomography (CT) are the two radiological techniques used for the follow-up of people exposed to asbestos. Since the last conference of consensus (1999), the scientific literature has primarily covered high-resolution CT and high-resolution volume CT (HR-VCT). We consider in turn the contribution of digital thoracic radiography, recommendations for the performance of HR-VCT to ensure the quality of examination while controlling the delivered radiation dose, and the need to refer to the "CT atlas of benign diseases related to asbestos exposure", published by a group of French experts in 2007, for interpretation. The results of the published studies concerning radiography or CT are then reviewed. We note the great interobserver variability in the recognition of pleural plaques and asbestosis, indicating the need for adequate training of radiologists, and the importance of defining standardized, quantified criteria for CT abnormalities. The very low agreement between thoracic and general radiologists must be taken into account. The reading of CT scans in cases of occupational exposure to asbestos should be entrusted to thoracic radiologists or to general radiologists having validated specific training. A double interpretation of CT could be considered in medicosocial requests. CT is more sensitive than chest radiography in the detection of bronchial carcinoma but generates a great number of false positive results (96 to 99%). No scientific data are available to assess the role of imaging by either CT or chest radiography in the early detection of mesothelioma.

Proteomic detection of cancer in asbestosis patients using SELDI-TOF discovered serum protein biomarkers

OBJECTIVES

To identify biomarkers for cancer in asbestosis patients.

METHODS

SELDI-TOF and CART were used to identify serum biomarker profiles in 35 asbestosis patients who subsequently developed cancer and 35 did not develop cancer.

RESULTS

Three polypeptide peaks (5707.01, 6598.10, and 20,780.70 Da) could predict the development of cancer with 87% sensitivity and 70% specificity. The first two peaks were identified as KIF18A and KIF5A, respectively, and are part of the Kinesin Superfamily of proteins.

CONCLUSIONS

We identified two Kinesin proteins that can be potentially used as blood biomarkers to identify asbestosis patients at risk of developing lung cancer.

Occupational toxicology of asbestos-related malignancies

INTRODUCTION

Asbestos is banned in most Western countries but related malignancies are still of clinical concern because of their long latencies. This review identifies and addresses some controversial occupational and clinical aspects of asbestos-related malignancies.

METHODS

Papers published in English from 1980 to 2009 were retrieved from PubMed. A total of 307 original articles were identified and 159 were included.

ASSESSMENT OF EXPOSURE

The retrospective assessment of exposure is usually performed by using questionnaires and job exposure matrices and by careful collection of medical history. In this way crucial information about manufacturing processes and specific jobs can be obtained. In addition, fibers and asbestos bodies are counted in lung tissue, broncho-alveolar lavage, and sputum, but different techniques and interlaboratory variability hamper the interpretation of reported measurements. SCREENING FOR MALIGNANCIES: The effectiveness of low-dose chest CT screening in exposed workers is debatable. Several biomarkers have also been considered to screen individuals at risk for lung cancer and mesothelioma but reliable signatures are still missing. ATTRIBUTION OF LUNG CANCER: Exposures correlating with lung cancer are high and in the same range where asbestosis occurs. However, the unresolved question is whether the presence of fibrosis is a requirement for the attribution of lung cancer to asbestos. The etiology of lung cancer is difficult to define in cases of low-level asbestos exposure and concurrent smoking habits. MESOTHELIOMA: The diagnosis of malignant mesothelioma may also be difficult, because of procedures in sampling, fixation, and processing, and uses of immunohistochemical probes.

CONCLUSIONS

Assessment of exposure is crucial and requires accurate medical and occupational histories. Quantitative analysis of asbestos body burden is better performed in digested lung tissues by counting asbestos bodies by light microscopy and/or uncoated fibers by transmission electron microscopy. The benefits of screenings for asbestos-related malignancies are equivocal. The attribution of lung cancer to asbestos exposure is difficult in a clinical setting because of the need to assess asbestos body burden and the fact that virtually all these patients are also tobacco smokers or former smokers. Given the premise that asbestosis is necessary to causally link lung cancer to asbestos, it follows that the assessment of both lung fibrosis and asbestos body burden is necessary.

Smoking and the Asian American workforce in the National Latino and Asian American Study

BACKGROUND

Smoking among the Asian American workforce has not been extensively researched. This study examines smoking prevalence among a nationally representative sample of Asian Americans with an emphasis on occupational classification.

METHODS

Cross-sectional data come from the National Latino and Asian American Study. Multivariate logistic regression analyses were used to determine smoking prevalence by occupation, gender, and nativity, among 1,528 participants self-identifying as in the labor force.

RESULTS

Blue collar workers reported the highest smoking prevalence (32%) followed by unemployed (19%), other (17%), service (14%), and white collar (10%). Among both employed males and females, blue collar workers had the highest prevalence (45% and 18%, respectively). By nativity, smoking was highest among blue collar workers for immigrants (25%) and highest among the unemployed for U.S. born (16%). Blue collar employment was significantly associated with being a current smoker (OR = 2.52; 95% CI: 1.23-5.16; P < 0.05) controlling for demographics (e.g., age, gender, ethnic group, nativity, etc.).

CONCLUSIONS

Findings reveal that smoking differs by occupation among Asian Americans. Future research should examine factors explaining differences while considering gender and nativity.

Mortality among sheet metal workers participating in a medical screening program

BACKGROUND

The Sheet Metal Occupational Health Institute Trust (SMOHIT) was formed in 1985 to examine the health hazards of the sheet metal industry in the U.S. and Canada through an asbestos disease screening program. A study of mortality patterns among screening program participants was undertaken.

METHODS

A cohort of 17,345 individuals with 20 or more years in the trade and who participated in the asbestos disease screening program were followed for vital status and causes of death between 1986 and 2004. Data from the screening program included chest X-ray results by International Labour Office (ILO) criteria and smoking history. Standardized mortality ratios (SMRs) by cause were generated using U.S. death rates and Cox proportional hazards models were used to investigate lung cancer risk relative to chest X-ray changes while controlling for smoking.

RESULTS

A significantly reduced SMR of 0.83 (95% CI = 0.80-0.85) was observed for all causes combined. Statistically significant excess mortality was observed for pleural cancers, mesothelioma, and asbestosis in the SMR analyses. Both lung cancer and COPD SMRs increased consistently and strongly with increasing ILO profusion score. In Cox models, which controlled for smoking, increased lung cancer risk was observed among workers with ILO scores of 0/1 (RR = 1.17, 95% CI = 0.89-1.54), with a strong trend for increasing lung cancer risk with increasing ILO profusion score >0/0.

CONCLUSIONS

Sheet metal workers are at increased risk for asbestos-related diseases. This study contributes to the literature demonstrating asbestos-related diseases among workers with largely indirect exposures and supports an increased lung cancer risk among workers with low ILO profusion scores.

Renal, vascular and cardiac fibrosis in rats exposed to passive smoking and industrial dust fibre amosite

Passive smoking is an independent risk factor for cardiovascular diseases. Industrial fibrous dust, e.g. the asbestos group member, amosite, causes lung cancer and fibrosis. No data are available on renal involvement after inhalational exposure to these environmental pollutants or of their combination, or on cardiovascular and renal toxicity after exposure to amosite. Male Wistar rats were randomized into four groups (n= 6): control and amosite group received initially two intratracheal instillations of saline and amosite solution, respectively. Smoking group was subjected to standardized daily exposure to tobacco smoke for 2 hrs in a concentration resembling human passive smoking. Combined group was exposed to both amosite and cigarette smoke. All rats were killed after 6 months. Rats exposed to either amosite or passive smoking developed significant glomerulosclerosis and tubulointerstitial fibrosis. Combination of both exposures had additive effects. Histomorphological changes preceded the clinical manifestation of kidney damage. In both groups with single exposures, marked perivascular and interstitial cardiac fibrosis was detected. The additive effect in the heart was less pronounced than in the kidney, apparent particularly in changes of vascular structure. Advanced oxidation protein products, the plasma marker of the myeloperoxidase reaction in activated monocytes/macrophages, were increased in all exposed groups, whereas the inflammatory cytokines did not differ between the groups. In rats, passive smoking or amosite instillation leads to renal, vascular and cardiac fibrosis potentially mediated via increased myeloperoxidase reaction. Combination of both pollutants shows additive effects. Our data should be confirmed in subjects exposed to these environmental pollutants, in particular if combined.