According to the American Thoracic Society, occupational exposure to risk factors accounts for 10–20% of the causes of COPD. In areas with poorly regulated work environments, occupational exposure to risk factors may contribute far more to COPD than this. Among the 908 COPD patients, 258 patients had a history of exposure to occupational risk factors, accounting for 28.4% of the causes of COPD, which was higher than the results of the American Thoracic Society study.
4.1 Occupational exposure is generally associated with COPD
Industrial bronchitis became known as early as 1966 [10]. With the exception of smoking, occupational exposures to respiratory risk factors are generally higher than non-occupational exposures. Thus, as with other chronic occupational diseases, the age of onset of COPD due to occupational exposure is lower than that of non-occupational exposure. Thus, the prevalence of COPD in people exposed to gases, fumes and vapours is twice as high in people under 40 years of age as in the general population. In this age group, non-occupational COPD is relatively rare, except for conditions with a significant genetic component, such as alpha-1 antitrypsin deficiency [11]. Recently, a large epidemiological study in China showed [12] that the prevalence of COPD in men aged 20–49 years was 16.4% in men and 7.4% in women. This study found that 100% of COPD patients under 40 years of age had a history of occupational exposure, and 90.0% of patients under 50 years of age had occupational exposure. The disease latency (16.22 ± 9.24) in patients in the non-exposed group is about twice that of the non-exposed group (7.99 ± 4.50), so the age of onset of patients with occupational COPD may be lower than that of ordinary COPD patients. The education level of patients in the exposure group was generally low, accounting for 81.8% of the patients with primary school education or below, and the FEV 1% pred value was low, which was consistent with the conclusions of previous studies. There is an indirect correlation between education level and COPD, and education level determines an individual's socioeconomic status, lifestyle, living environment, and awareness of health knowledge. People with low education level, poor living conditions, less knowledge of health care, and therefore more exposure to risk factors and lower lung function values.
4.2 Occupational exposure correlates with clinical symptoms in patients with COPD
There are differences in clinical, radiological, and physiologic manifestations between COPD secondary to smoking and COPD in never-smokers [13]. Exposure to inorganic dusts such as coal dust and silica, organic dusts such as wood dust and cotton, irritating gases and fumes such as welding and paint have been shown to increase respiratory symptoms and worsen lung function in patients[14]. The COPDGene study suggests that exposure to occupational-related risk factors increases symptoms such as chronic cough, sputum production, and persistent wheezing, leading to decreased lung function, and increases the risk of COPD GOLD class II ~ IV [15]. Studies have also confirmed that biofuel smoke can induce bronchial mucosal goblet cell metaplasia, excessive mucus secretion, cause an increase in eosinophils and neutrophils, lead to more obvious airway inflammation, dyspnea and other symptoms are more obvious than those exposed to tobacco smoke groups, and clinical symptoms are more severe. In this study, it can be found that the proportion of respiratory symptoms such as cough and sputum in the VGDF contact group is higher than that in the non-exposed group, and the airflow restriction, mMRC score, comprehensive assessment and other scale scores of patients in the exposed group are higher than those in the non-exposed group.
The study found that COPD was associated with exposure to occupational risk factors and cumulative exposure. Trupin [16] found that occupational exposures were associated with a significantly increased risk of COPD regardless of smoking: 1.6 (1.1–2.5) for high exposures and 1.4 (1.1–1.9) for moderate exposures (95% CI). Möhner [17] surveyed 1421 quartz processing workers and showed that every average exposure to quartz dust of 1mg/m3 years led to a reduction of FEV1/FVC by 2.75% (P < 0.001) and a 1.81-fold increase in the risk of COPD. A meta-analysis also showed that persistent dust particle exposure was associated with accelerated lung function decline and the risk of COPD, with a 1.6 mL decrease in lung function FEV1 per 1 mg/year ·cm3 per person smoked and a 7 percent increased risk of COPD. In this study, the relationship between exposure to occupational risk factors and respiratory symptoms, the degree of illness, and the number of acute exacerbations in COPD patients in the past year found that the exposure level of occupational risk factors was the influencing factor. As the level of exposure to occupational risk factors in patients with COPD increases, so does the proportion of respiratory symptoms; Taking the cumulative exposure of occupational risk factors as the independent variable, FEV1% of COPD patients was used as the dependent variable for linear regression analysis, and the linear regression results showed that the cumulative exposure of occupational risk factors was linearly negatively correlated with FEV1, and the higher the cumulative exposure of occupational risk factors, the worse the patient's lung function.
3 Strengths And Limitations Of Research Research
The National Institute for Occupational Safety and Health has developed a job expose matrix (JEM) for assessing COPD to assess the risk of COPD by the level of occupational exposure to occupational disease hazards [18–19]. The results of DONY et al [20] showed that there was a clear correlation between the determination of COPD and JEM assessment as COPD by measuring lung function. In this study, the assessment of occupational exposure was relatively rough, as self-reported exposures based on individual items were susceptible to recall bias or subjective influence, as opposed to the Job Exposure Matrix (JEM), which is considered the "gold standard". However, previous studies in the general population have shown that self-reported exposures can accurately identify associations between occupation and disease compared to complex assessments such as work exposure matrices [21]. As an example, in two cohort studies of adult asthma, self-reported exposure to occupational risk factors was sensitive to exposure defined by JEM [22]. In addition, some studies have found that an increase in respiratory symptoms is associated with self-reported exposure to occupational risk factors [23]. As an example, a study of patients with COPD showed that prior exposure to occupational risk factors was associated with increased symptoms at 1 year [24] follow-up.
The patients in this study were surveyed in a third-class public hospital in a province and city in China, which is a developing country, so the occupational exposure rate in this study is higher than that of COPD patients reported in other studies. These differences can be due to various methodological reasons. For example, while we included jobs where the exposure time accumulated for more than one year, other studies determined to include only jobs with the longest holding time [24]. Therefore, the definition of exposure to occupational risk factors in this study may be responsible for the increased exposure to occupational risk factors in this study. In addition, this study is a clinical epidemiological study of a large sample of COPD, a retrospective investigation of COPD cases by means of a questionnaire, therefore, it depends heavily on the patient's memory. This is a common problem in occupational health research, especially those with cross-sectional designs. The study was a retrospective survey and did not have complete clinical data, particularly lung function and smoking volume, which prevented a detailed discussion of the role of smoking as a confounding factor.