Environmental PM_2.5 Exposure: An Ignored Factor Associated with Blood Cadmium Level in Hemodialysis Patients

Background: The negative impacts of particulate matter with an aerodynamic diameter of 2.5 μm or less (PM_2.5) are well known. Patients undergoing maintenance hemodialysis (HD) have significantly higher blood cadmium levels (BCLs) than healthy individuals. As elemental cadmium can be found in the PM_2.5 particle fraction, we conducted this study to assess the effect of environmental PM_2.5 exposure and other clinical variables on BCLs in maintenance HD patients. Patient and Methods: This cross-sectional study included 754 hD patients who had previously participated in a BCL study. Demographic, hematological, biochemical and dialysis-related data were collected for analysis. For each patient, the mean PM_2.5 concentrations in the living environment during the previous 12 and 24 months were recorded and analyzed. Results: Of all patients, the median BCL of was 0.36 µg/L (range: 0.21, 0.79 µg/L). The mean PM_2.5 concentration was 28.45 ± 3.57 μg/m³ during the 12 months and 29.81 ± 3.47 μg/m³ during the 24 months, respectively. From a multivariate linear regression analysis, log BCL was positively associated with the mean PM_2.5 concentration during the previous 12 and 24 months. In addition, log BCL was positively associated with the number of days with PM_2.5 concentrations above the standard level during the previous 12 and 24 months. Moreover, according to the tertiles of days with a daily mean PM_2.5 concentration above the normal limit in the previous 24 months, patients with the highest exposure days exhibited a significantly higher BCL than those in the other two patient groups. Conclusion: Chronic environmental exposure to PM_2.5 is significantly associated with BCLs in maintenance HD patients, and exposure to PM_2.5-bound cadmium may contribute to the harmful effects on health in this population. Further studies are needed to confirm these observations and to explore the underlying mechanisms.