Study of cadmium exposure level in rural residents in soil polluted areas and environmental correlation

Objective To comprehensively evaluate cadmium (Cd) exposure levels among rural residents, and to explore the association of environmental Cd exposure with internal human Cd exposure in residents.

Methods Soil and crop samples were collected from typical soil Cd pollution areas and clean areas without soil Cd pollution. Morning urine samples were collected from local adult permanent residents, and a complete dietary survey was also conducted. Inductively coupled plasma mass spectrometry was used to measure Cd contents in environmental and biological samples. The relationship between environmental Cd exposure and Cd body burden was explored through correlation analysis, path analysis, and generalized linear regression analysis.

Results The Cd exposure level in contaminated areas was significantly higher than that in clean areas. The median Cd levels in soil, rice and vegetables from contaminated areas and clean areas were 0.50 mg/kg vs. 0.49 mg/kg, 0.23 mg/kg vs. 0.02 mg/kg, and 0.03 mg/kg vs. 0.02 mg/kg, respectively. The participants in polluted areas had a significantly higher average dietary Cd intake per day median, 2.59 μg/kg body weight (BW) vs. 0.19 μg/kg BW and a significantly higher urinary Cd content median, 4.27 μg/g creatine (Cr) vs. 1.34 μg/g Cr than those in the clean areas. Cd levels in soil, rice, vegetables and dietary Cd intake were all significantly positively correlated with urinary Cd content, with the correlation coefficients being 0.36, 0.78, 0.61 and 0.69, respectively (all P < 0.05). The path analysis showed that the Cd content in rice Cd was the main determinant of the urinary Cd level. The generalized linear regression analysis showed that for every 1 μg/kg BW increase in average daily dietary Cd intake, the urinary Cd level increased by 0.69 μg/g Cr; and for every 1 μg/kg BW increase in average daily Cd intake from rice, the urinary Cd level increased by 0.68 μg/g Cr.

Conclusion There is a positive exposure-response relationship between environmental Cd exposure and Cd body burden. Controlling rice-related Cd intake is the primary way to reduce Cd exposure in the populations.