[Long-term effect of environmental cadmium exposure on human body's mineral metabolic balance].

OBJECTIVE: To investigate the effect of long-term exposure to environmental cadmium on eight mineral element's metabolic balance of human body.

METHODS: To choose a high cadmium area polluted by smelting and mining north of Guangdong province and a cadmium-free area with a similar economic level, and living and eating habit of residents as a contrast from April 2011 to August 2012. Stratified random sampling and clustered sampling method were adopted to choose the non-occupationally cadmium-exposed respondents who have lived in local area for more than 15 years, older than 40 years, having local rice and vegetable as the main dietary source, with simple and relatively stable diet, and without diabetes, kidney disease, thyroid disease, liver disease or other history of chronic disease. This study included 298 respondents, of whom 155 were in cadmium exposure group and 143 in control group. Questionnaires was used to acquire their health status and their morning urine samples were collected. Electrolytically coupled plasma mass spectrometry (ICP-MS) was used to test the concentrations of sodium(Na), magnesium (Mg), phosphorus (P), potassium (K), calcium (Ca), copper (Cu), zinc (Zn) and iodine (I). The Mann-Whitney U test method was used to compare the differences of concentrations of urinary cadmium, Na, Mg, P, K, Ca, Cu, Zn, I, and the ratio of Na to K (Na/K), Ca to P (Ca/P) between exposed group and control group.χ(2) test was used to compare the abnormal rate of urinary cadmium between exposed group and control group. Pearson correlation and multiple regression method were used to investigate the relationship between urinary cadmium levels, gender, age, smoking, passive smoking, and minerals.

RESULTS: The urinary cadmium level P50 (P25-P75) in exposed group was 5.45 (2.62-10.68) μg/g·cr, which was higher than that of the control group, which was 1.69 (1.22-2.36) μg/g·cr (Z=-10.49,P<0.001). The abnormal rate of urinary cadmium was 51.6% (80/155), which was higher than that of the control group (2.8 %(4/143)) (χ(2)= 87.56, P<0.001). The urinary Ca, Cu, Zn, and I level P50 (P25-P75) of exposed group were 173.80 (114.40-251.70), 20.55 (14.95-28.44), 520.23 (390.25-647.15), and 246.94 (203.65-342.97) μg/g·cr, which were higher than those in control group (142.42 (96.87-179.11), 15.44 (12.26-20.98), 430.09 (309.85-568.78) and 213.85 (156.70-281.63) μg/g·cr, respectively) (Z values were-4.33,-5.04,-3.47 and-4.24, all P values <0.001). The urinary P, K level P50 (P25-P75) of exposed group were 582.50 (463.20-742.8), 890.10(666.00-1 305.40) μg/g·cr, which were lower than control group (694.50 (546.20-851.17), 1 098.58(904.53-1 479.18) μg/g·cr) (Z values were-3.36,-4.02, all P values <0.001). on Based the results of Pearson correlation analysis, urinary cadmium was positively correlated with urinary Ca, Cu, Zn, and I, and the correlation coefficients were 0.31, 0.61, 0.38, and 0.25, respectively (all P values <0.05). Based on the results of multiple regression analysis, urinary cadmium levels contributed most to the metabolic balance of urinary Ca, Cu, Zn and I. The standardized regression coefficients were 0.31, 0.59, 0.39, and 0.24, respectively (all P values<0.001).

CONCLUSION: Long-term environmental exposure to cadmium affected the metabolic balance of Ca, Cu, Zn and I in human body.