Associations of long-term cadmium exposure with peripheral white blood cell subtype counts and indices in residents of cadmium-polluted areas.

Background: Experimental evidence suggests that exposure to cadmium (Cd) could affect immune cells in vivo and in vitro. However, the associations of long-term Cd exposure with white blood cell (WBC) subtype counts and hemogram-derived indices have been rarely investigated. Therefore, we evaluated these relationships in residents of cadmium-polluted areas.

Methods: This cross-sectional study included 431 participants aged 45-75 years without occupational exposure histories from Cd-contaminated areas of southern China. We detected WBC, neutrophil, lymphocyte, and monocyte counts using routine blood tests and calculated neutrophil-lymphocyte ratio (NLR), systemic inflammation response index (SIRI), and lymphocyte-monocyte ratio (LMR). Urinary Cd (U-Cd) was measured with inductively coupled plasma mass spectrometry and adjusted for creatinine. To evaluate the associations of U-Cd with peripheral WBC subtype counts and indices, we performed multivariate linear regression, logistic regression and subgroup analyses using U-Cd categorized into quartiles.

Results: In models adjusted for all potential confounders, U-Cd was negatively associated with WBC, neutrophil, and monocyte counts in Q2, compared with Q1 of U-Cd (p < 0.05). A similar relationship was observed between U-Cd and NLR and SIRI, whereas the corresponding association for LMR was positive (p < 0.05). In subgroup analyses, U-Cd was negatively associated with neutrophil count, except for never smokers, after full adjustment.

Conclusions: U-Cd was negatively associated with WBC count, neutrophil count, monocyte count, NLR, and SIRI, and positively associated with LMR. Therefore, neutrophil count could be a potential indicator of long-term Cd exposure-associated immunosuppressive effect.