Objective To investigate the association between the whole blood levels of chromium, lead, cadmium, manganese and erythrocyte-related indicators in people with occupational exposure to chromates.

Methods A total of 170 people exposed to chromates and 123 non-exposed people were selected according to the inclusion and exclusion criteria, and their whole blood samples and basic information were collected. The mass concentrations of chromium, lead, cadmium, and manganese in whole blood were measured by inductively coupled plasma mass spectrometry. The indices of red blood cells (RBC) were analyzed by using an automatic blood cell analyzer. The relationship between blood levels of chromium, lead, cadmium, manganese and erythrocyte related indexes was analyzed using weighted quartile sum (WQS) regression, quartile g-computation, and Bayesian kernel machine regression (BKMR).

Results The chromate exposure group showed significantly higher median blood levels of chromium (2.341.38, 4.59 μg/L vs 1.010.71, 1.94 μg/L) and manganese (14.0811.37, 17.35 μg/L vs 11.9510.07, 14.80 μg/L) than the control group. There were no significant differences in blood levels of lead and cadmium between the two groups. After controlling for confounding factors such as age, sex, education level, body mass index, smoking, and alcohol drinking, the exposure group showed significantly higher red blood cell count (RBC) count, hematocrit (HCT), and coefficient variation of red blood cell volume distribution width (RDW-CV) and significantly lower mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and standard deviation in red cell distribution width(RDW-SD) (all P < 0.001) compared with the control group. The WQS analysis showed that the overall level of heavy metals was positively correlated with RBC count, hemoglobin, hematocrit, mean corpuscular volume, and RDW-CV, with the largest weight coefficient of manganese. Quartile g-computation and BKMR showed that the overall level of the heavy metal mixture was positively correlated with RBC count and RDW-CV, and negatively correlated with MCH and RDW-SD. According to quartile g-computation analysis, chromium was the main metal in the heavy metal mixture which caused an increase in RBC count of workers with chromate exposure. BKMR analysis showed that RBC count increased by 42.3% when the level of the heavy metal mixture rose from the 25th percentile to the 75th percentile.

Conclusion Occupational exposure to chromates may cause the disturbances of various erythrocyte indicators in workers, which may be mainly related to the increase of whole blood manganese and chromium levels.