Accumulation of blood chromium and cobalt in the participants with metal objects: findings from the 2015 to 2018 National Health and Nutrition Examination Survey (NHANES)

Background Chromium (Cr) and cobalt (Co) are the essential elements for producing metal implants, but might have potential health issues. The research on the correlation between metal implants and blood Cr and Co on a large population is still limited. Methods National Health and Nutrition Examination Survey (NHANES) is a program of studies designed to assess the health status of Americans began in the early 1960s. The study was based on the NHANES database from two data collection years (2015–2016 and 2017–2018). The exposure variable of this study was whether the participants had metal objects in the body or not. The outcome variables were blood concentrations of Cr and Co. Age, body mass index, sex, race/ethnicity, income to poverty ratio, tap water behavior, shellfish/fish/tuna/salmon eating habits, level of education, smoking behavior, marital status, blood hemoglobin, and data collection years were included as confounding variables. Results A total of 4412 participants, aged 40 years or older, were included in this analysis, consisting of the without metal objects group ( n = 3150) and the metal objects group ( n = 1262). Metal objects was positively correlated to the accumulation of blood Cr (β = 0.072, 95% CI: 0.043–0.102, p < 0.001) and blood Co (β = 0.079, 95% CI: 0.049–0.109, p < 0.001). However, the positive correlation of metal objects with blood Cr was only presented in women (β = 0.112, 95% CI: 0.074–0.151, p < 0.001), but not in men. Meanwhile, the positive relationship between metal objects and blood Cr/Co was not observed in the Asian subgroup. Conclusions Blood Cr and Co concentrations were statistically higher in people with metal objects, but with race and sex differences. Level of Evidence Level IV, cross-sectional study