1 Introduction

Coal Workers’ Pneumoconiosis (CWP) is a systemic disease characterized by the diffuse fibrosis of lung tissues, which is mainly caused by the long-term inhalation of mineral dust during occupational activities like coal mining (Qi et al. 2021). To reduce the occurrence of pneumoconiosis, strict exposure limits have been set, and personal protective equipment such as masks, goggles, and protective clothing have been implemented. Currently, the allowable exposure limit for respirable coal mine dust (RCMD) in China is 2.5 mg/m3, and with the upgrading of occupational protection measures, such as the use of masks, the incidence of pneumoconiosis in China has decreased in recent years (Decision of the ministry of emergency management on amending the coal mine safety regulations 2022). Despite a more than 50% reduction in the incidence rate of pneumoconiosis compared to 2012, there were still 11,809 new cases of occupational pneumoconiosis in China in 2021 (The National Health Commission released the 2021 2022). Pneumoconiosis is a chronic disease that can only be 100% cured through lung transplantation (Hall et al. 2019). Patients with pneumoconiosis may experience weakened lung function, decreased immunity, and are susceptible to respiratory infections (Bell and Mazurek 2020). Due to the prolonged and debilitating nature of the disease, patients are prone to negative emotions such as anxiety, fear, pessimism, and depression (Morrison et al. 2017). Miners are a high-risk group for pneumoconiosis, facing various work-related pressures and the risk of occupational disease. The resulting psychological problems not only affect the individual's quality of life but also pose a hidden danger to workplace safety. Therefore, timely identification of the psychological status of miners at different stages of their career and corresponding interventions can prevent adverse events, improve their quality of life, and enhance their well-being.

To assess the psychological state of patients, commonly used tools in China include the Self-rating Anxiety Scale (SAS) (Cheng et al. 2017), Self-rating Depression Scale (SDS) (Smith et al. 2018), and Depression Anxiety Stress Scale-21 (DASS-21) (Jiang et al. 2018).

Content validity is typically assessed through expert reviews, which serve as an indication of the accuracy of the measured content or topic (Hayes and Preacher 2010). In general, content validity is established based on experts' comments, with I-CVI representing the number of experts who score 4 or 5 for the importance of the research divided by the total number of experts, and S-CVI representing the number of items with a score of 4 or 5 divided by the total number of items (Egger-Rainer 2018). In this study, both I-CVI and S-CVI exceeded 0.7, indicating that the Chinese CCEI has strong content validity.

4.2 Coal miners mental disorder

Miners working underground are all male. The results of the comparison among active miners, CWP patients, and retired miners show that the highest detection rate of psychological problems in active miners is 35.8%, mainly focusing on the dimensions of DEP, FFA, and SOM. The main reasons for the high prevalence of psychological issues in active miners are likely due to the harsh operating environment underground and the pressure from work management. These findings are consistent with the research reported by Ailing Fu et al. (2022). The second is the detection rate of psychological disorders in CWP patients, which is 21%, mainly focusing on the dimensions of PHO and SOM. According to the national policy (Shi et al. 2020), once pneumoconiosis is diagnosed, patients can enjoy free medical treatment, which largely eliminates patients’ concerns. But pneumoconiosis will have the symptoms of respiratory disorder and hypoxia. For those suffering from pneumoconiosis, they are worried that they will not get timely help, especially when they live alone, which will cause fear to patients. It is worth noting that the detection rate of psychological problems in retired miners without pneumoconiosis is only 13.6%, which is lower than the incidence of psychological problems in the general elderly. It shows that the quality of life of retired miners is quite satisfactory after retiring from their posts. On the one hand, they are out of the high-risk occupational environment, and can freely spend their time while receiving monthly pensions. Compared with the stress during work, it is a state from bitter to sweet. This study suggests that miners have different psychological problems at different career stages. Coal operators should pay attention to the psychological problems of miners and formulate targeted psychological intervention measures to improve the mental health and quality of life of miners.

5 Conclusions

The dimensions as well as the questionnaire in this study enjoy sound internal consistency and good structural validity and reliability. It thus can be used as one of the measurement tools to assess the phobia indexes of coal miners at different periods of their working and retirement life. Though this study is based on coal miners, it is expected the Chinese CCEI can be applied to other types of patients in the future, for whom it is critical to assess psychological problems in a short period of time.

It should be noted that this study has some limitations. The limitations may include: (1) Although the sample size is relatively considerable, the study focuses on the population of only one city, which may have potential environmental impacts. (2) The questionnaires involved in this study are all men, and whether it can be applied to the female population still needs to be further explored.