Retrospective exposure assessment to airborne asbestos among power industry workers

Health Effects of Occupational and Environmental Exposures to Nuclear Power Plants: A Meta-Analysis and Meta-Regression

PURPOSE OF REVIEW

Numerous epidemiological studies have shown increased health risks among workers and residents living near nuclear power plants exposed to radiation levels meeting regulatory dose limits. This study aimed to evaluate the association between radiation exposure and disease risks among these populations exposed to radiation levels meeting the current regulatory dose limits.

RECENT FINDINGS

We searched four databases (Cochrane Library, PubMed, ScienceDirect, and Web of Science) for studies published before August 2023, screened eligible studies (inclusion and exclusion criteria based on population, exposure, comparator, and outcome framework), and collected data on exposure indicators and disease risks. We applied random-effects models of meta-analysis to estimate the pooled effects and meta-regression to assess the dose-response relationship (radiation dose rate for workers and distance for residents). We identified 47 studies, 13 with worker and 34 with resident samples, covering 175 nuclear power plants from 17 countries, encompassing samples of 480,623 workers and 7,530,886 residents. Workers had a significantly lower risk for all-cancer and a significantly higher risk for mesothelioma. Residents had significantly higher risks for all-cancer, thyroid cancer, and leukemia. Notably, children under 5 years old showed the highest risk for all-cancer. Our meta-regression showed a significantly positive dose-response relationship between cumulative dose of radiation exposure and risk for circulatory disease among workers. Our findings demonstrated higher risks for mesothelioma for workers and all-cancer, thyroid cancer, and leukemia for residents exposed to low-dose radiation from nuclear power plants. Some included studies did not adjust for cancer risk confounders, which could overestimate the association between radiation exposure and cancer risk and increase the risk of bias.

Artificial intelligence-based diagnosis of asbestosis: analysis of a database with applicants for asbestosis state aid

OBJECTIVES

In many countries, workers who developed asbestosis due to their occupation are eligible for government support. Based on the results of clinical examination, a team of pulmonologists determine the eligibility of patients to these programs. In this Dutch cohort study, we aim to demonstrate the potential role of an artificial intelligence (AI)-based system for automated, standardized, and cost-effective evaluation of applications for asbestosis patients.

METHODS

A dataset of n = 523 suspected asbestosis cases/applications from across the Netherlands was retrospectively collected. Each case/application was reviewed, and based on the criteria, a panel of three pulmonologists would determine eligibility for government support. An AI system is proposed, which uses thoracic CT images as input, and predicts the assessment of the clinical panel. Alongside imaging, we evaluated the added value of lung function parameters.

RESULTS

The proposed AI algorithm reached an AUC of 0.87 (p < 0.001) in the prediction of accepted versus rejected applications. Diffusion capacity (DLCO) also showed comparable predictive value (AUC = 0.85, p < 0.001), with little correlation between the two parameters (r-squared = 0.22, p < 0.001). The combination of the imaging AI score and DLCO achieved superior performance (AUC = 0.95, p < 0.001). Interobserver variability between pulmonologists on the panel was estimated at alpha = 0.65 (Krippendorff's alpha).

CONCLUSION

We developed an AI system to support the clinical decision-making process for the application to the government support for asbestosis. A multicenter prospective validation study is currently ongoing to examine the added value and reliability of this system alongside the clinic panel.

KEY POINTS

• Artificial intelligence can detect imaging patterns of asbestosis in CT scans in a cohort of patients applying for state aid. • Combining the AI prediction with the diffusing lung function parameter reaches the highest diagnostic performance. • Specific cases with fibrosis but no asbestosis were correctly classified, suggesting robustness of the AI system, which is currently under prospective validation.

Retrospective Exposure Assessment Methods Used in Occupational Human Health Risk Assessment: A Systematic Review

As part of the assessment and management of chemical risk and occupational hygiene, retrospective exposure assessment (REA) to chemical agents can be defined as the estimate of exposure associated with a person's work history. The fundamental problem underlying the reconstruction of the exposure is that of transforming this type of information in quantitative terms to obtain an accurate estimate. REA can follow various approaches, some of which are technically complicated and both time and resource consuming. The aim of this systematic review is to present the techniques mainly used for occupational REA. In order to carry out this evaluation, a systematic review of the scientific literature was conducted. Forty-four studies were identified (published from 2010 to date) and analyzed. In exposure reconstruction studies, quantitative approaches should be preferable, especially when estimates will be used in the context of health impact assessment or epidemiology, although it is important to stress how, ideally, the experimental data available for the considered scenario should be used whenever possible as the main starting information base for further processing. To date, there is no single approach capable of providing an accurate estimate of exposure for each reasonably foreseeable condition and situation and the best approach generally depends on the level of information available for the specific case. The use of a combination of different reconstruction techniques can, therefore, represent a powerful tool for weighting and integrating data obtained through qualitative and quantitative approaches, in order to obtain the best possible estimate.

Are the knowledge of non-malignant asbestos-related diseases and lung function impairment differentially associated with psychological well-being? A cross-sectional study in formerly asbestos-exposed workers in Germany

OBJECTIVES

The knowledge of past asbestos exposure may lead to chronic psychological strain. In addition, the information about an increased cancer risk can place a psychological burden on individuals triggering mental health symptoms of depression or anxiety. This applies in particular to individuals with non-malignant asbestos-related disease (ARD) such as lung fibrosis and pleural thickening with or without lung function impairment. ARDs with or without lung function impairment may develop even years after exposure cessation. Therefore, the aim of the present study was to test for our cohort whether non-malignant ARD and lung function impairment have differential effects on mental health and psychological strain.

DESIGN

Cross-sectional study.

PARTICIPANTS AND SETTING

Overall, 612 male participants (mean age=66.2 years, SD=9.5) attending a surveillance programme for ARDs received routine examinations including lung function testing (24% refused to fill in the psychological questionnaire) at a German university hospital study centre from August 2008 to August 2013.

OUTCOME MEASURES

Using multiple hierarchical regression analysis, ARD diagnosis and lung function impairment were used to predict psychological health as measured with validated questionnaires for depression and anxiety. Psychological strain was operationalised by intrusive thoughts and specific fear of cancer.

RESULTS

The strongest predictor for mental health was obstructive functional impairment (eg, anxiety: β=0.22, p<0.001). Psychological strain was predicted by the presence of a non-malignant ARD (eg, intrusive thoughts: β=0.17, p=0.003).

CONCLUSIONS

The presence of mental health symptoms is associated with ventilation disturbances, whereas the knowledge of an already initiated morphological change-caused by asbestos exposure-is primarily associated with psychological strain. Specifically, the affected individuals are more prone to intrusive thoughts and specific fear of asbestos-related cancer. As an implication, physicians should be sensitised about possible consequences of risk communication and functional impairment to counteract excessive fear or anxiety.

Investigating the association between occupational exposure to asbestos and ovarian carcinoma: results from a pilot study in Germany

Background

The aim of this pilot study was to assess the feasibility of a large-scale epidemiologic investigation elucidating the quantitative association between occupational exposure to asbestos and ovarian cancer in former German asbestos workers.

Methods

Between December 2017 and May 2018, a random sample of one thousand insured woman registered at the health service of a German trade association as formerly occupationally exposed to asbestos were invited to participate in a pilot study. Participation included a phone interview using a standardised questionnaire. The feasibility of the project was evaluated using a priori defined criteria. They included response, number of cases, eligibility of the questionnaire data for exact estimation of asbestos fibre-years, and availability of relevant medical documentation (imaging procedures, medical reports, and histologic materials).

Results

The response (17%) was clearly below the intended number of 60%. With six tumour suspects, of which two could be confirmed by medical documents, the number of cases was within the expected range of two to eleven cases. Exact asbestos fibre-year estimations could be performed for 29% of all interviewees, but only for one suspected case. Medical documentation could be collected for only few participants, while no histology reports could be obtained for all cases. Thus, only the feasibility criterion of the expected number of cases was fulfilled.

Conclusion

The results of the pilot study indicate that the planned project is feasible only to a very limited extent. For further planning of the study, measures to improve recruitment of participants are necessary.

Occupational exposure to respirable dust from the coal-fired power generation process: sources, concentration, and health risk assessment

To investigate the contamination levels of respirable dust released in the work environment and the induced workers' health risk at a coal-fired power plant, we collected 405 dust samples from different dusty workstations by personal sampling during the coal-fired power generation process. Then, an inhalation risk assessment model from the USEPA was combined with the Monte Carlo simulation method to quantitatively evaluate the health risk caused by dust inhalation. Of 10 workstations researched, the dust concentration in the most workstations exceeded the prescribed occupational exposure limit. Workers engaged in ash removal suffered the highest health risk at 4.08 × 10^-6 ± 2.85 × 10^-6 (95% CI), closely followed by those involved in other job categories. The results can contribute to the formulation of targeted dust prevention measures and implementation of risk management for the coal-fired power sector.

Lung function not affected by asbestos exposure in workers with normal Computed Tomography scan

BACKGROUND

It has been suggested that asbestos exposure affects lung function, even in the absence of asbestos-related pulmonary interstitial or pleural changes or emphysema.

METHODS

We analyzed associations between well-known asbestos-related risk factors, such as individual cumulative asbestos exposure, and key lung function parameters in formerly asbestos-exposed power industry workers (N = 207) with normal CT scans. For this, we excluded participants with emphysema, fibrosis, pleural changes, or any combination of these.

RESULTS

The lung function parameters of FVC, FEV1, DLCO/VA, and airway resistance were significantly associated with the burden of smoking, BMI and years since end of exposure (only DLCO/VA). However, they were not affected by factors directly related to amount (eg, cumulative exposure) or duration of asbestos exposure.

CONCLUSIONS

Our results confirm the well-known correlation between lung function, smoking habits, and BMI. However, we found no significant association between lung function and asbestos exposure.

Exposure to airborne asbestos in thermal power plants in Mongolia

BACKGROUND

Coal-fired thermal power plants (TPPs) in Mongolia use various types of asbestos-containing materials (ACMs) in thermal insulation of piping systems, furnaces, and other products.

OBJECTIVE

To investigate the occupational exposure of insulation workers to airborne asbestos in Mongolian power plants.

METHODS

Forty-seven air samples were collected from four power plants in Mongolia during the progress of insulation work. The samples were analyzed by phase contrast microscopy (PCM) and transmission electron microscopy (TEM).

RESULTS

The average phase contrast microscopy equivalent (PCME) asbestos fiber concentration was 0·93 f/cm(3). Sixteen of the 41 personal and one of the area samples exceeded the United States Occupational Safety and Health Administration (US OSHA) short-term exposure limit of 1·0 f/cm(3). If it is assumed that the short-term samples collected are representative of full-shift exposure, then the exposures are approximately 10 times higher than the US OSHA 8-hour permissible exposure limit of 0·1 f/cm(3).

CONCLUSION

Power plant insulation workers are exposed to airborne asbestos at concentrations that exceed the US OSHA Permissible Exposure Limit. Action to mitigate the risks should be taken in Mongolia.

Mesothelioma in Mongolia: case report

BACKGROUND

More than 80% of cases of mesothelioma worldwide have a history of asbestos exposure. In Mongolia, workers in coal burning thermal power plants (TPP) have widely utilized asbestos as an insulation material.

METHODS

We describe the case of a 47-year-old woman diagnosed with a malignant pleural mesothelioma. She worked in a TPP in Ulaanbaatar, Mongolia for 28 years.

RESULTS

A computer tomography (CT) scan showed a circumferential ring around her left lung, and tissues' samples had a biphasic variant of mesothelioma with epithelioid and sarcomatoid components.

DISCUSSION

This is the first reported case of mesothelioma in Mongolia. We expect additional cases of mesothelioma, as well as other asbestos related diseases, will be identified in the future. In order to properly track asbestos related diseases in the country, we recommend the creation of an asbestos related disease registry.

Radiological surveillance of formerly asbestos-exposed power industry workers: rates and risk factors of benign changes on chest X-ray and MDCT

BACKGROUND

To determine the prevalence of asbestos-related changes on chest X-ray (CXR) and low-dose multidetector-row CT (MDCT) of the thorax in a cohort of formerly asbestos-exposed power industry workers and to assess the importance of common risk factors associated with specific radiological changes.

METHODS

To assess the influence of selected risk factors (age, time since first exposure, exposure duration, cumulative exposure and pack years) on typical asbestos-related radiographic changes, we employed multiple logistic regression and receiver operating characteristic (ROC) analysis.

RESULTS

On CXR, pleural changes and asbestosis were strongly associated with age, years since first exposure and exposure duration. The MDCT results showed an association between asbestosis and age and between plaques and exposure duration, years since first exposure and cumulative exposure. Parenchymal changes on CXR and MDCT, and diffuse pleural thickening on CXR were both associated with smoking. Using a cut-off of 55 years for age, 17 years for exposure duration and 28 years for latency, benign radiological changes in the cohort with CXR could be predicted with a sensitivity of 82.0% for all of the three variables and a specificity of 47.4%, 39.0% and 40.6%, respectively.

CONCLUSIONS

Participants aged 55 years and older and those with an asbestos exposure of at least 17 years or 28 years since first exposure should be seen as having an increased risk of abnormal radiological findings. For implementing a more focused approach the routine use of low-dose MDCT rather than CXR at least for initial examinations would be justified.

Is it useful to combine sputum cytology and low-dose spiral computed tomography for early detection of lung cancer in formerly asbestos-exposed power industry workers?

Background

Low-dose spiral computed tomography (LDSCT) in comparison to conventional chest X-ray proved to be a highly sensitive method of diagnosing early stage lung cancer. However, centrally located early stage lung tumours remain a diagnostic challenge. We determined the practicability and efficacy of early detection of lung cancer when combining LDSCT and sputum cytology.

Methods

Of a cohort of 4446 formerly asbestos exposed power industry workers, we examined a subgroup of 187 (4.2%) high risk participants for lung cancer at least once with both LDSCT and sputum cytology. After the examination period the participants were followed-up for more than three years.

Results

The examinations resulted in the diagnosis of lung cancer in 12 participants (6.4%). Six were in clinical stage I. We found 10 non-small cell lung carcinomas and one small cell lung carcinoma. Sputum specimens showed suspicious pathological findings in seven cases and in 11 cases the results of LDSCT indicated malignancies. The overall sensitivity and specificity of sputum cytology was 58.0% and 98% with positive (PPV) and negative (NPV) predictive values of 70% and 97%. For LDSCT we calculated the sensitivity and specificity of 92% and 97%. The PPV and NPV were 65% and 99% respectively.

Conclusions

Our results confirmed that in surveillance programmes a combination of sputum cytology and LDSCT is well feasible and accepted by the participants. Sputum examination alone is not effective enough for the detection of lung cancer, especially at early stage. Even in well- defined risk groups highly exposed to asbestos, we cannot recommend the use of combined LDSCT and sputum cytology examinations as long as no survival benefit has been proved for the combination of both methods. For ensuring low rates of false-positive and false-negative results, programme planners must closely cooperate with experienced medical practitioners and pathologists in a well-functioning interdisciplinary network.

Changes of mesothelin and osteopontin levels over time in formerly asbestos-exposed power industry workers

PURPOSE

In patients developing malignant pleural mesothelioma (MPM) or lung cancer, using effective tumour markers is the quickest way to ensure early diagnosis and improve survival time. The aim of our study was to assess the influence of age and asbestos exposure on the blood levels of the proposed tumour markers, mesothelin and osteopontin, and to determine the change of these markers over time.

METHODS

We analysed 3,329 blood samples of 2,262 participants including 1,894 formerly asbestos-exposed power industry workers, a mixed group of 266 participants with an unknown history of asbestos exposure and a group of 102 non-asbestos-exposed controls. Marker concentrations were determined using commercial ELISA kits.

RESULTS

While age had a strong influence on marker levels, there was no association between exposure duration or benign asbestos-related disease and marker levels. In order to assess the maximum increase that can be expected to occur in asbestos-exposed workers those with an at least 10 % increase were selected (n = 290 for mesothelin and n = 81 for osteopontin). The 95th percentile of the annual change was 0.402 nmol/l for mesothelin and 334 ng/ml for osteopontin. In two patients with MPM and five with lung cancer, we could obtain more than one marker result before the diagnosis was made. Both MPM patients showed a steep increase of mesothelin levels.

CONCLUSIONS

Fixed cut-off values for deciding between intensive clinical work-up and continued surveillance appeared inadequate for the evaluated markers. While general conclusions cannot be drawn, we can say that the results of the two patients would be consistent with a mesothelin increase between 6 and 18 months before clinical symptoms developed.

Retrospective exposure assessment in a chemical research and development facility

The objective of this exposure assessment was to reconstruct cumulative historical exposures for workers who have been exposed to multiple chemicals and chemical groups to better understand a cluster of brain cancers within a research and development lab. Chemicals of interest, including acrylates, bis-chloromethyl ether (BCME), chloromethyl methyl ether (CMME), isothiazolones and nitrosoamines, were selected on the basis of the plausibility of penetrating the blood-brain barrier and the uniqueness of the chemical's biological activity. In a complicated exposure setting such as a chemical R&D facility, multiple exposure estimation methods were needed. First, similarly exposure groups (SEGs) were created for these materials based on department group, time period of the department's existence and function associated with job titles. A probabilistic framework for assessing exposures was developed using Bayesian analysis of historical monitoring data, mathematical exposure modeling and professional judgments of current and former industrial hygienists at the facility were used to reconstruct the exposure history for acrylates, BCME and CMME for each SEG over the time period of interest. Since sufficient measurement data for isothiazolones and nitrosoamines were not available, the exposure histories for each SEG for these chemicals were estimated. This was done using objective formaldehyde levels and subjective employee interviews. The interviews assessed workplace determinants of exposure as distinct surrogates for estimating inhalation and dermal exposures. The exposure assessments by these methods were compared against each other to estimate the potential for exposure misclassification. A job exposure matrix (JEM) was constructed that contained the exposures obtained from above multiple approaches for each of these chemical groups for each SEG for each year of interest. The combination of methods used in this work is a unique and potentially helpful framework that can be used in analogous workplace settings involving multiple exposures with incomplete objective measurement information.