Objective: To investigate the characteristics of urinary cadmium of the non-occupational-cadmium-exposed population in non-cadmium contaminated rural area in China.
Methods: Randomly selected non-occupational cadmium exposed population 2548 people (male 1290, female 1258) with each gender and age groups, questionnaire surveyed and collected random urine. Urinary cadmium and urinary creatinine (Cr) concentration were tested, excluding urinary Cr < 0.3 g/L and > 3 g/L. Analyze the impact factors of urinary cadmium and calculated 95% quantile (P95) of urinary cadmium after correction by urinary Cr.
Results: Urinary cadmium increased with age and showed an upward trend. The urinary cadmium of the population of ≥ 30 years old was significantly higher than that of < 30 years old, women significantly higher than male, and smokers significantly higher than non-smokers (P < 0.01). Generalized linear model for multivariate analysis showed that smoking, age and gender are still significantly affected on urinary cadmium after adjusting for other factors (P < 0.01), regression equation: urinary cadmium (Cr corrected) = 0.854 + 0.325 x smoking + 0.111 x age--0.305 x gender (F = 367.69, P < 0.01). However, the multiple correlation coefficient of regression equation R2 = 0.0350, which is only 3.50% available in urinary cadmium variations can be explained by gender, age, and smoking. According to gender, smoking and < 30 and ≥ 30 years of age, analysis the upper limit of cadmium in urine, the 95% upper limit of urinary cadmium of ≥ 30 year-old female smokers (13.47 μg/g Cr) was significantly higher than other populations (< 6.0 μg/g Cr), the 95% upper limit of urinary cadmium of ≥ 30 year-old female and ≥ 30 year-old male smokers exceeded the urinary cadmium limits (5 μg/g Cr) of the occupational cadmium poisoning diagnostic criteria in China (GB Z17-2002).
Conclusion: The urinary cadmium reference value of non-occupational-cadmium-exposed populations is < 6.0 μg/g Cr in the three non-cadmium contaminated rural area in China, but for smoking women over 30 year-old it needs more research to explore.