The results of our study show a consistent trend with previous research, indicating that exposure to dust is positively associated with an increased risk of dyslipidemia in workers. Existing literature has reported a close relationship between air pollution and increased cardiovascular disease (CVD) and CVD-related mortality rates. Dyslipidemia is an important cause of CVD and is closely connected to particulate matter (PM) in the dust. The American Heart Association (AHA) reported in 2004 that PM made a certain contribution to cardiovascular morbidity and mortality rates in the United States and other countries. A study analyzing the relationship between the daily death rate and fine particles from different sources in six US cities showed that every 10µg/m3 increase in PM from coal sources could increase the daily death rate by 1.1%.
A cross-sectional analysis(MCGUINN, LA, et al., 2019)of 6,587 patients demonstrated that exposure to particulate matter of 1 unit increase resulted in a 2% increase in serum total lipid levels. In a study by Ryan P. Shanley et al. using the NHANES database(SHANLEY, R P, et al., 2016), people who were chronically exposed to PM10 in dust had a 2.42% increase in triglyceride levels (95% CI: 1.09–3.76). However, a cohort study conducted in China(MAO, S, et al., 2020) showed that higher levels of PM1 exposure were associated with adverse changes in blood lipid levels, mainly demonstrated as elevation in total cholesterol (TC) (95% CI: 0.11%-0.31%) and low-density lipoprotein cholesterol (LDL-C) (95% CI: 0.61%-0.90%), as well as reduction in triglycerides (TG) (95% CI: 2.43%-2.93%) and high-density lipoprotein cholesterol (HDL-C) (95% CI: 0.35%-0.59%). Another longitudinal study(ZHANG, K, et al., 2021) in Shijiazhuang, China, showed a positive association between exposure to PM2.5 and PM10 and elevation in triglycerides, total cholesterol, and low-density lipoprotein cholesterol. In our study, exposure to dust significantly increased triglyceride or cholesterol levels in coal miners. Due to the differences in these results, we adjusted for a number of potential influencing factors such as Sex, Age, BMI or blood pressure in our multiple regression model and performed further stratified analysis.
Previous studies(PAN, L, et al., 2016) have demonstrated that the incidence of dyslipidemia differs by gender, with men being more prone to developing the condition than women. Our stratified analysis according to sex showed that this risk was also significant in men, possibly due to the presence of poor habits such as smoking and drinking in male workers. Additionally, because female workers were underrepresented in our study, future large-scale prospective studies may be necessary to further explore the relationship between dust exposure and the risk of dyslipidemia in female workers.
Age is a major risk factor for dyslipidemia, as multiple studies have shown positive correlations between age and TC, LDL-C, and TG concentrations, with HDL-C negatively correlated. Elderly individuals may therefore lack awareness of normal blood lipid levels and timely screening and prevention(LIU, X, et al., 2018; GOH, V H, et al., 2007; STEVENSON, J C, et al., 1993). We adjusted for age in our regression model for this reason. Dyslipidemia is characterized by high blood fat content, and is closely related to obesity, insulin resistance, and pro-inflammatory lipid factors(VEKIC, J, et al., 2019). BMI has been found to be positively correlated with dyslipidemia in Chinese adults, with both general and abdominal obesity being significant risk factors(CAO, L, et al., 2021). Hypertension and hyperlipidemia often co-occur, and the incidence of dyslipidemia has been found to be highest among workers with 6–10 years or more of duration of work(LIU, J, et al., 2016). Our study found that with increasing length of service and exposure to polluted dust, the risk of developing dyslipidemia increased, with saturation after 22 years. Other published reports support these findings(DA-SILVA, C, et al., 2019).
Our study has several strengths, including a large sample size and the adjustment of potential confounding factors in our analysis. However, limitations should be noted. Firstly, our study did not investigate potential lifestyle factors that may influence dyslipidemia, and this may have impacted our conclusions. Secondly, our study was cross-sectional and although animal experiments supported a potential causal relationship, the animals were exposed to silica rather than coal dust, which is a main component of interest. Finally, the limited representation of female workers in our study warrants future large-scale investigation to improve understanding of the impact of dust exposure on women's risk of dyslipidemia.