Disease burden analysis of coal worker pneumoconiosis patients in Jiangsu Province

Introduction

Coal worker’s pneumoconiosis is an occupational interstitial lung disease, which is caused by the deposition of coal mine dust in the lung parenchyma and subsequent tissue reaction (1,2). Coal is one of the most important energy sources in the world, and millions of workers are exposed to coal dust in their professional activities (3). According to literature reports, in China and India alone, workplaces of more than 20 million workers are exposed to coal dust. Although many control measures have been adopted, such as reducing production and on-line monitoring, coal worker’s pneumoconiosis continues to pose a significant public health challenge worldwide (4).

The burden of disease includes economic losses caused by disease, disability, premature death, deterioration of quality of life and loss of life. In 1993, experts from Harvard University proposed a new comprehensive evaluation index—disability-adjusted life years (DALY), which refers to the total healthy life years lost by patients from onset to death, including the year lost due to disability (YLD) and year of life lost (YLL) (5-7). It is used as a supplement of traditional statistical indicators to comprehensively analyze the disease burden in occupational epidemiological research, providing useful information for the reform of occupational health practices and the formulation of health policies, offering professional data support for disease surveillance, health promotion and proactive intervention (8). At present, pneumoconiosis is preventable while incurable. Once the disease occurs, it requires lifelong treatment, which means that patients and their families need to bear the high cost of treatment for a long time. The decline of labor force will cause the loss of social productivity (9). In addition, the state and enterprises also need to provide various guarantees and compensation for pneumoconiosis patients, which has brought a huge economic burden to the society and is not conducive to the development of society. Therefore, it is necessary to analyze the disease burden of patients with coal workers’ pneumoconiosis and explore the related factors, so as to provide reference for the prevention and treatment of coal workers’ pneumoconiosis.

Based on the follow-up data of occupational pneumoconiosis in Jiangsu Province, this study uses DALY and other indicators to calculate the direct and indirect economic losses caused by coal worker’s pneumoconiosis by step-by-step model, human capital method, and discusses the influencing factors of DALY to comprehensively measure the disease burden of coal worker’s pneumoconiosis patients. We present this article in accordance with the STROBE reporting checklist (available at https://jphe.amegroups.com/article/view/10.21037/jphe-24-100/rc).

Methods

Data collection

A retrospective study was conducted from June 2021 to June 2022 to select patients with coal worker’s pneumoconiosis developed from 1981 to 2020 in Jiangsu Province as the study subjects. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). This study underwent ethical review by the Ethics Review Committee of Jiangsu Provincial Center for Disease Control and Prevention (approval No. JSJK2022-B002-01). Individual consent for this retrospective analysis was waived. The age, gender, survival status, stage of pneumoconiosis, disability grade and other information of patients were collected by means of utilizing the combination of the cause of death report and follow-ups through telephone, face-to-face, with enterprises and public security departments. All patients were diagnosed by the occupational disease diagnostic institutions in Jiangsu Province according to the current diagnostic criteria of occupational pneumoconiosis, including GBZ70-2002 Diagnostic Criteria of Pneumoconiosis, GBZ70-2009 Diagnostic Criteria of Pneumoconiosis and GBZ70-2015 Diagnostic Criteria of Occupational Pneumoconiosis. Among them, the classification of disability level is based on GB/T 16180 “Identification of Occupational Injury and Occupational Disease Disability Degree” (10,11).

Calculation of DALY

DALY is a comprehensive measure of the loss of healthy life years due to premature death and disability arising various diseases, including YLD caused by disease disability and YLL caused by premature death. Its calculation is based on the life expectancy data in the 26th level of the family model life table in Western countries. The formula is as follows.

∫x=ax=a+LDCxe−βae−r(x−a)dx[1]

Integrating over the interval a to a+L gives the following formula:

YLLYLD=−DCe−βα(β+γ)2{e−(β+γ)L[1+(β+γ)(L+a)]−[1+(β+γ)α]}[2]

All items in the formula are known values defined in the World Health Organization (WHO) Global Burden of Disease (GBD) study. Among them, D is the disability weight (1 represents death and 0 represents complete health); C is the age weight moderating factor (0.1658); β is the age weight parameter (0.04); γ is the discount rate (0.03); α is the age of onset or death; L is the duration of disability or the time lost due to death. With reference to the disability classification of the global burden of disease and 22 indicative symptoms, the corresponding disability weights of grade 7 to grade 1 pneumoconiosis were 0.25, 0.35, 0.45, 0.55, 0.65, 0.75 and 0.85, respectively according to “Labor Ability Identification: Industrial Injury and Occupational Disease Disability Grade” (GB/T 16180).

Economic loss calculation

In this study, the sum of medical expenses, one-time disability subsidy, disability allowance, funeral subsidy, living and nursing expenses, dependent relatives’ pension and food subsidy of patients with coal worker’s pneumoconiosis caused by disease was taken as the direct economic loss of patients.

This study uses the human capital method to calculate the indirect economic burden, including the loss of social productivity, the transportation cost of accompanying family members, the training cost of new employees to fill roles, and the loss of social productivity of accompanying family members and so on. The loss of social productivity uses the human capital method to calculate the economic loss caused by DALY. That is, based on the per capita gross domestic product (GDP) of the region in that year and with DALY as an indicator, the specific calculation formula is as follows: indirect economic burden of coal worker’s pneumoconiosis patients = DALY × per capita GDP × productivity weight.

The determination of productivity weight is based on that the productivity varies across different ages. In this study, the productivity weights of different age groups were assigned according to Barnum method (12), in which the weights of 15–44 years old and 45–59 years old were 0.75 and 0.80 respectively, and the productivity weights of people over 60 years old were 0.10.

Statistical analysis

Excel 2022 is used to set up a database and cleanse the data. The distribution of different age, sex, stage, and disability grade of patients with coal worker’s pneumoconiosis was statistically described by SPSS 26.0. Continuous variables are represented by mean ± standard deviation and compared using analysis of variance. Classification variables are expressed as percentages and used χ² test or Fisher’s exact probability method. Multiple linear regression method was used to analyze the influencing factors of DALY, and P<0.05 was considered to be statistically significant.

Results

Basic information

A total of 5,020 cases of coal worker’s pneumoconiosis were reported in Jiangsu Province from 1981 to 2020, including 4,964 male patients (98.88%) and 56 female patients (1.12%). Among them, 3,055 (60.86%) survived and 1,965 (39.14%) died. The minimum age of diagnosis was 23.50 years, the maximum was 83.89 years, and the mean age of diagnosis was (54.77±11.39) years. Of the 5,020 patients, 3,686 (73.43%) were in stage I, 1,123 (22.37%) in stage II, and 211 (4.20%) in stage III. According to the disability rating, the number of people with disabilities in grade 6 was the largest, with 1,364 (27.17%), and the number of people in grade I was the lowest, numbering 86 (1.71%), as shown in Table 1.

DALY loss in coal workers’ pneumoconiosis

The total DALY loss of 5,020 patients with coal workers’ pneumoconiosis was 39,710.48 person-years, and the per capita loss was 7.91 person-years. With the increase of onset age, the per capita DALY showed a decreasing trend (Figure 1). Among them, the YLD loss was 34,173.01 person-years (86.06%), and the per capita YLD loss was 6.81 person-years. YLD losses were mainly concentrated in the 35–65 years age group, with a cumulative loss of 23,722.30 person-years, accounting for 59.74% of the total YLD losses. The YLL loss was 5,537.47 person-years (13.94%), and the per capita YLL loss was 2.79 person-years, as shown in Table 2.

Figure 1 Distribution of DALY loss per capita at different age groups of onset. DALY, disability-adjusted life years.

Influencing factors of DALY

Multiple linear regression analysis was performed, with the DALY loss of pneumoconiosis patients as the dependent variable, and indexes that may affect the DALY loss, such as disability grade (weight value of disability), age of diagnosis, age of exposure to dust, grade of pneumoconiosis (Stage I =1, Stage II =2, Stage III =3), gender (male =1, female =2) and survival status (survival =1, death =2), as independent variables, to reveal that disability grade, age of diagnosis, Survival status, grade of pneumoconiosis and gender are main factors of DALY loss (P<0.05) (Table 3).

Economic losses

Direct economic loss

• Medical expenses: medical expenses include the cost of diagnosis and treatment, hospitalization services and drugs, etc. The number of days of hospitalization and annual hospitalization expenses shall be replaced by the relevant data of pneumoconiosis patients of middling coal workers in occupational disease prevention and control hospitals in Jiangsu Province in 2021. The average annual medical cost of coal worker’s pneumoconiosis patients was 9,462.95 yuan per person in 2021. According to the life expectancy, the average survival time of 5,020 coal worker’s pneumoconiosis patients was 29.45 years. The medical cost of 5,020 coal worker’s pneumoconiosis patients was 1,398,993,065.05 yuan, with an average loss of 278,683.88 yuan per patient.
• Food (Meal) allowance during hospitalization: according to the data, the standard of food subsidy for general staff in Jiangsu Province was 20 yuan per person per day for business trips, the average hospitalization days was 12.14 per person per year, and the average survival time of 5,020 coal worker’s pneumoconiosis patients was 29.45 years. Thus, the food subsidy for patients with coal worker’s pneumoconiosis during hospitalization was 35,895,309.20 yuan in total.
• Disability allowance: according to the Regulation on Work-Related Injury Insurance (13), disabled coal worker’s pneumoconiosis patients with grade 6 and above are eligible to receive disability allowance before retirement. In this study, the retirement age was 60 for males and 55 for females. The average monthly salary of employees in Jiangsu Province in 2021 was 9,822.33 yuan (14), and 2,382 of the 5,020 coal worker’s pneumoconiosis patients were entitled to disability allowance, with a cumulative subsidy of 2,145,404,673.21 yuan, as shown in Table S1.
• One-time disability subsidy: according to the Regulation on Work-Related Injury Insurance, for employee with work-related disability assessed as having class 1 to class 7 disability, one-time disability subsidy shall be paid from the work-related injury insurance fund in accordance with the level of disability. A subsidy of 873,863,233.11 yuan was required according to the economic standard of 2021, as shown in Table S2.
• Living care fee: according to the regulations on Work-Related Injury Insurance, 50%, 40% and 30% of the average monthly salary of workers in the pooling region in the preceding year will be paid as fees for living care based on the disability grade of coal worker’s pneumoconiosis patients. In 2020, the average annual salary per capita for in-service employees in Jiangsu Province was 106,034 yuan (15), with a total of 74 cases having a disability level of four or above. According to the compensation standard, a compensation of 1,475,648,457.43 yuan is required for living care expenses, as shown in Table S3.
• Funeral allowance: according to the regulations on Work-Related Injury Insurance, the funeral subsidy is 6 months’ average monthly salary of the employees in the pooling region in the preceding year. The average annual salary of employees in Jiangsu Province in 2020 was 106,034 yuan (15). Therefore, 1,654 first-to-fourth-grade disabled workers and 202 deceased patients requires a total subsidy of 98,399,552.00 yuan.
• Bereavement payments for dependent family members: according to the Regulations on Work-Related Injury Insurance, in the case of a work-related death of an employee, the bereavement payments for dependent family members shall be made at a certain percentage of the employee’s wage to each of the family members of the employee that, before the employee’s death, was dependent on the employee for primary source of income and that has no work capability. According to the standard of retirement, the average annual salary of employees in Jiangsu Province in 2021 was 117,868 yuan. With 116 men having an average of 54.75 years, and 1 female died during the period of suspension from pay at the age of 54.35 years old, the required bereavement payment was 71,858,226.20 yuan.
• Direct economic loss analysis: the direct economic loss caused by 5,020 cases of coal worker’s pneumoconiosis was 6,100,062,516.20 yuan, and the per capita direct economic loss was 1,215,151.90 yuan, with the disability allowance accounting for highest proportion of 35.17%, as shown in Table S4.

Indirect economic loss

• Loss of social productivity: the per capita GDP of Jiangsu Province was 137,039 yuan in 2021 (14). The cumulative DALY loss of 5,020 patients with coal worker’s pneumoconiosis was 39,710.47. Combined with the weight of productivity, the loss of social productivity caused by coal workers’ pneumoconiosis was 3,460,764,268.70 yuan, as shown in Table S5.
• Transportation expenses of accompanying family members and loss of social productivity: the average standard of transportation expenses for Chinese residents was 2,000 yuan per person per year (16), the average survival time of 5,020 coal worker’s pneumoconiosis patients was 29.45 years, and the average annual hospitalization days was 12.14 days per person. The per capita GDP in Jiangsu Province was 137,039 yuan in 2021 (14), and the productivity weight was calculated as 0.5 of the total population. Assuming that each inpatient needs one family member to accompany them, the transportation cost was 9,834,331.29 yuan, and the loss of social productivity was 336,921,731.33 yuan.
• Training fees for new employees to fill roles: according to the provisions of The State Council’s “Decision on Vigorously Promoting the Reform and Development of Vocational Education” (17), general enterprises pay for the education and training expenses in accordance with 1.5% of the total salary of employees, and thus the training fees for new employees of enterprises are 1,768.02 yuan/person. It has been shown that 3,416 people develop the disease before the statutory retirement age, the training fee for new workers to fill roles would be 6,039,556.32 yuan.
• Indirect economic loss analysis: the indirect economic loss caused by coal workers’ pneumoconiosis totaled 3,813,559,887.64 yuan, and the per capita loss was 759,673.28 yuan. Among them, the loss of social productivity accounted for the highest proportion (90.75%), followed by the loss of social productivity of accompanying family members (8.83%), as shown in Table S6.

Total economic loss of coal worker’s pneumoconiosis patients

To sum up, the total economic loss caused by 5,020 patients with coal worker’s pneumoconiosis was 9,913,622,403.85 yuan, with a per capita loss of 1,974,825.18 yuan, of which the direct economic loss was 6,100,062,516.21 yuan (61.53%) and the indirect economic loss accounted for 3,813,559,887.64 yuan (38.47%), as shown in Table S7.

Discussion

Coal worker’s pneumoconiosis is one of the most serious occupational diseases in China (18). In recent years, China has adopted a number of measures such as action on prevention and control of pneumoconiosis (19), effectively improving the workplace environment. However, due to the delayed onset of coal worker’s pneumoconiosis and the irreversibility of fibrosis, those who work in a lower dust concentration or leave the dust environment may still suffer from coal worker’s pneumoconiosis. At present, extensive attention has been paid to the early diagnosis, treatment and preventive measures of coal worker’s pneumoconiosis, but there is still a lack of high-quality clinical research (9). Therefore, analyzing the burden of patients with coal worker’s pneumoconiosis from the point of view of health economics is of great significance to reduce the occurrence of coal worker’s pneumoconiosis, lighten the economic burden of patients and the social burden.

In this study, DALY was used as a comprehensive index to measure the disease burden, enabling a quantitatively analysis of that of coal workers’ pneumoconiosis patients. A total of 5,020 cases of coal worker’s pneumoconiosis were reported in Jiangsu Province. The cumulative loss of DALY was 39,710.48 person-years, with a per capita loss of 7.91 person-years, which was much lower than the per capita DALY of silicosis patients (9.04 person-years) (20). The possible reasons are related to the nature and concentration of dust that exposed to workers and the intensity of physical labor. The DALY loss of coal worker’s pneumoconiosis is mainly due to YLD, with a cumulative loss of 34,173.01 person-years (86.06%) and a per capita YLD of 6.81 person-years. The YLL loss is 5,537.47 person-years (13.94%), and the per capita YLL loss is 2.79 person-years. The loss of YLD in coal workers’ pneumoconiosis in Jiangsu Province was predominant, and mainly concentrated between 35 and 65 years old, with a cumulative loss of 23,722.30 (59.74%) person-years. The results of multiple linear regression analysis showed that the main factors affecting DALY were disability grade, diagnosis age, pneumoconiosis stage, survival status and sex. The higher the disability grade and the younger the diagnosis age, the greater the DALY loss and the more serious the disease burden.

An increase in DALY usually means a higher incidence of disability and a longer course of illness, which can lead to increased medical expenses and loss of social productivity, thereby increasing the economic burden on families and society. This study used the step-by-step model method and the human capital method to calculate the economic losses caused by coal workers’ pneumoconiosis (21,22). According to the economic data of Jiangsu Province in 2021, the total economic loss caused by 5,020 coal worker’s pneumoconiosis patients was 9.91362 billion yuan, and the per capita loss was about 1.97 million yuan. The direct economic loss was about 6.10006 billion yuan (61.53%), and the indirect economic loss was about 3.81356 billion yuan (38.47%). This result is slightly different from the previous foreign research results (23,24), and the main reasons for the difference may be the large gap in GDP and per capita wage among different regions, and the different investigation methods and evaluation indicators included in the research. Among the direct economic losses, disability allowance (35.17%), living and nursing expenses (24.19%) and medical expenses (22.93%) accounted for the highest proportion. The medical expenses need to be borne jointly by the patient’s family and the state, and the disability allowance and living and nursing expenses also need to be borne by the state, indicating that coal worker’s pneumoconiosis has brought serious economic losses to the country and the patient’s family. In terms of indirect economic losses, the social productivity losses of the patients and accompanying family members were 90.75% and 8.83% respectively, resulting in a serious shortage of social labor force and limiting social development. It also brings serious economic burden to the patients’ families. Indirect economic loss is more hidden than direct economic loss. It is easy to ignore the decline of social productivity and invisible economic loss, making it necessary to improve the awareness of indirect economic loss. In addition, with the development of social economy, the economic loss caused by coal worker’s pneumoconiosis is expected to further increase. Therefore, to prevent the occurrence of new cases of coal worker’s pneumoconiosis is the key to reducing economic loss and disease burden. The relevant departments should attach importance to the prevention and control of the occupational disease, strictly abide by the occupational health system, and take appropriate health protection, such as equipping workers with effective personal protective equipment; Strengthen the publicity of occupational disease self-protection knowledge and improve the workers’ self-protection awareness; strengthen health monitoring, so as to achieve early detection, early diagnosis and early treatment, and ensure the personal safety and health of employees.

There are still some shortcomings in this study. First of all, this study uses wages or medical expenses in recent years to replace the economic level of previous years, so the calculated cumulative economic loss may be higher than the actual economic loss. Secondly, when using the human capital method to calculate indirect economic losses, the average wages of employees in Jiangsu Province are used as the wage level of workers, and there may be differences between them. Finally, when calculating the medical cost, the patients with comorbid and non-comorbid coal workers’ pneumoconiosis are not separately calculated, so the calculated medical cost is different from the actual medical cost.

Conclusions

To sum up, according to the economic data of Jiangsu Province in 2021, each coal workers’ pneumoconiosis patient will cause an economic loss of about 1.97 million yuan and 7.91 healthy life years. It demonstrates that the economic loss caused by coal worker’s pneumoconiosis is severe, posing great threat to economic development. In addition, disability grade, age of diagnosis, stage of pneumoconiosis, survival and sex were the main influencing factors of DALY. Therefore, dust control, health monitoring and prevention of new cases of coal worker’s pneumoconiosis are the key points to reduce the burden of coal worker’s pneumoconiosis.

Acknowledgments

Thanks to Professor Chunhui Ni and Professor Tingting Yu from Nanjing Medical University for their support of this study.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://jphe.amegroups.com/article/view/10.21037/jphe-24-100/rc

Data Sharing Statement: Available at https://jphe.amegroups.com/article/view/10.21037/jphe-24-100/dss

Peer Review File: Available at https://jphe.amegroups.com/article/view/10.21037/jphe-24-100/prf

Funding: This study mainly received funding from the Jiangsu Provincial Science and Technology Plan Special Fund (Social Development Key R&D Plan) Project (No. BE2022803).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jphe.amegroups.com/article/view/10.21037/jphe-24-100/coif). B.Z. serves as the Editor-in-Chief of Journal of Public Health and Emergency from January 2017 to December 2026. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). This study underwent ethical review by the Ethics Review Committee of Jiangsu Provincial Center for Disease Control and Prevention (approval No. JSJK2022-B002-01). Individual consent for this retrospective analysis was waived.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Zosky GR, Hoy RF, Silverstone EJ, et al. Coal workers’ pneumoconiosis: an Australian perspective. Med J Aust 2016;204:414-8. [Crossref] [PubMed]
2. Druzhinin VG, Baranova ED, Matskova LV, et al. Sputum Microbiota in Coal Workers Diagnosed with Pneumoconiosis as Revealed by 16S rRNA Gene Sequencing. Life (Basel) 2022;12:830. [Crossref] [PubMed]
3. Devnath L, Luo S, Summons P, et al. Deep Ensemble Learning for the Automatic Detection of Pneumoconiosis in Coal Worker’s Chest X-ray Radiography. J Clin Med 2022;11:5342. [Crossref] [PubMed]
4. Wang D, Liang R, Yang M, et al. Incidence and disease burden of coal workers’ pneumoconiosis worldwide, 1990-2019: evidence from the Global Burden of Disease Study 2019. Eur Respir J 2021;58:2101669. [Crossref] [PubMed]
5. Murray CJ. Quantifying the burden of disease: the technical basis for disability-adjusted life years. Bull World Health Organ 1994;72:429-45. [PubMed]
6. Murray CJ, Lopez AD, Jamison DT. The global burden of disease in 1990: summary results, sensitivity analysis and future directions. Bull World Health Organ 1994;72:495-509. [PubMed]
7. The global burden of cancer attributable to risk factors, 2010-19: a systematic analysis for the Global Burden of Disease Study 2019. Lancet 2022;400:563-91. [Crossref] [PubMed]
8. Health effects of dietary risks in 195 countries, 1990-2017: a systematic analysis for the Global Burden of Disease Study 2017. Lancet 2019;393:1958-72. [Crossref] [PubMed]
9. Qi XM, Luo Y, Song MY, et al. Pneumoconiosis: current status and future prospects. Chin Med J (Engl) 2021;134:898-907. [Crossref] [PubMed]
10. The General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China, and the National Standardization Administration of China Labor capacity assessment: Occupational injury and disability level of employees: GB/T 16180-2006. Beijing: China Standards Publishing House; 2006.
11. The General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China, and the National Standardization Administration of China Labor capacity assessment: Occupational injury and disability level of employees: GB/T 16180-2014. Beijing: China Standards Publishing House; 2014.
12. Barnum H. Evaluating healthy days of life gained from health projects. Soc Sci Med 1987;24:833-41. [Crossref] [PubMed]
13. The State Council of the People’s Republic of China. Regulations on Work Injury Insurance, Order No. 375 Safety and Health 2003.
14. Jiangsu Provincial Bureau of Statistics. 2021 Jiangsu Statistical Yearbook. Beijing: China Statistical Publishing House; 2022.
15. Jiangsu Provincial Bureau of Statistics. 2020 Jiangsu Statistical Yearbook. Beijing: China Statistical Publishing House; 2021.
16. Cui F. Research on the Epidemic Law, Disease Prediction, and Prevention and Control Benefits of Coal Workers’ Pneumoconiosis in Huaibei Mining Group. North China University of Technology; 2016.
17. Decision of the State Council on Vigorously Promoting the Reform and Development of Vocational Education. The State Council Communique of the People’s Republic of China 2002.
18. Li Y, Xian W, Xu H, et al. Time trends and future prediction of coal worker’s pneumoconiosis in opencast coal mine in China based on the APC model. BMC Public Health 2018;18:1010. [Crossref] [PubMed]
19. Wang H, Ye Q, Zhang H, et al. Prevention and Treatment of Pneumoconiosis in the Context of Healthy China 2030. China CDC Wkly 2023;5:927-32. [Crossref] [PubMed]
20. Zheng J, He L, Chen L, et al. Estimation of years of health life loss in 290 hospitalized patients with pneumoconiosis in Sichuan Province. Modern Preventive Medicine 2020;47:2720-3+43.
21. Liang YX, Wong O, Fu H, et al. The economic burden of pneumoconiosis in China. Occup Environ Med 2003;60:383-4. [Crossref] [PubMed]
22. Shen F, Liu H, Yuan J, et al. Cost-Effectiveness of Coal Workers’ Pneumoconiosis Prevention Based on Its Predicted Incidence within the Datong Coal Mine Group in China. PLoS One 2015;10:e0130958. [Crossref] [PubMed]
23. Leigh JP, Robbins JA. Occupational disease and workers’ compensation: coverage, costs, and consequences. Milbank Q 2004;82:689-721. [Crossref] [PubMed]
24. Leigh JP. Economic burden of occupational injury and illness in the United States. Milbank Q 2011;89:728-72. [Crossref] [PubMed]