Abstract
Exposure to metals poses potential health risks, including insulin resistance (IR), to those exposed to them in excess. Limited studies have examined such risks in occupational workers, including welders, and these have yielded inconsistent results. Thus, we examined the associations between exposure to welding metals and IR in welders. We recruited 78 welders and 75 administrative staff from a shipyard located in northern Taiwan. Personal exposure to heavy metals, including chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu), zinc (Zn), and cadmium (Cd), was monitored through particulate matter with an aerodynamic diameter of less than 2.5 μm (PM2.5) and urine analysis by inductively coupled plasma mass spectrometry (ICP–MS). After each participant fasted overnight, blood samples were collected and analyzed for IR assessment through updated homeostasis model assessment (HOMA2) modeling. Air sampling in the personal breathing zone was performed during a Monday shift prior to the blood and urine sample collection the following morning. The welders’ median personal Cr, Mn, Fe, Ni, Cu, and Zn airborne PM2.5 levels and urinary Cd levels were significantly higher than those of the administrative staff. After adjustment for covariates, logarithmic PM2.5-Mn, PM2.5-Fe, PM2.5-Cu, and PM2.5-Zn levels were positively correlated with logarithmic fasting plasma glucose (P-FGAC) levels (PM2.5-Mn: β = 0.0105, 95% C.I.: 0.0027–0.0183; PM2.5-Fe: β = 0.0127, 95% C.I.: 0.0027–0.0227; PM2.5-Cu: β = 0.0193, 95% C.I.: 0.0032–0.0355; PM2.5-Zn: β = 0.0132, 95% C.I.: 0.0005–0.0260). Logarithmic urinary Zn was positively correlated with logarithmic serum insulin and HOMA2-IR levels and negatively correlated with logarithmic HOMA2-insulin sensitivity (%S; βinsulin = 0.2171, 95% C.I.: 0.0025–0.4318; βIR = 0.2179, 95% C.I.: 0.0027–0.4330; β%S = −0.2180, 95% C.I.: −0.4334 to −0.0026). We observed that glucose homeostasis was disrupted by Mn, Fe, Cu, and Zn exposure through increasing P-FGAC and IR levels in shipyard welders.
Highlights
In vitro models illustrated that metals can catalyze an oxidative stress reaction that leads to decreased insulin gene promoter activity and insulin messenger ribonucleic acid expression in islet β-cells [7]
The hexokinase method was used for analyzing fasting plasma glucose (P-FGAC), glycerol phosphate dehydrogenase method for serum triglycerides (S-TGs), catalase elimination method for serum high density lipoprotein (S-HDL), Jaffe method for creatinine, chemiluminescence method for serum insulin (S-insulin), and high-performance liquid chromatography method for blood glycated hemoglobin (B-HbA1c) levels
After adjusting for the covariates, namely age, smoking status, alcohol intake, regular use of respirator during work, family history of T2DM, body mass indexes (BMIs), and urinary creatinine, we observed that the logarithmized U-Zn was significantly correlated with increased logarithmized S-insulin and HOMA2-insulin resistance (IR) levels and decreased logarithmized HOMA2-%S levels (β%S = −0.2180, 95% C.I.: −0.4334 to −0.0026)
Summary
The deficiencies and excesses of trace elements were implicated in the increasing risk of T2DM through interfering with blood glucose homeostasis [7,8] Essential metals, such as Mn, Fe, Cu, and Zn, are essential for the function of various enzymatic systems of the human body. In vitro models illustrated that metals can catalyze an oxidative stress reaction that leads to decreased insulin gene promoter activity and insulin messenger ribonucleic acid (mRNA) expression in islet β-cells [7] Both essential and toxic metals are unambiguously present in the environment, and pollution sources could result in various metal profiles [14,15]. The evaluation of heavy metals in the workplace and their associations with IR are essential measures of sustainable development in enterprises. This study (1) quantified personal exposure to metals in particulate matter with an aerodynamic diameter of less than 2.5 μm (PM2.5 ) in welding fumes (2) evaluated the IR of welders and administrative staff and (3) identified associations between exposure to metals from welding fumes and IR in welders and administrative staff
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