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A research team from Central South University and Beihang University conducted a study in the Hunan Province, the heartland of China’s non-ferrous mining area, and found that urinary cadmium levels (UCLs) were higher in people living near mining areas than in those living in other places.
In a paper published in the journal Frontiers of Environmental Science & Engineering, the scientists explain that cadmium is mainly absorbed by the human body from the external environment through contact, drinking, or inhalation and is metabolized slowly. After entering the body, Cd can be absorbed into the liver or kidneys, causing damage to kidney function. Cd may also lead to cancer.
The research group used statistical models to analyze the UCLs of 211 people residing near mining operations and the corresponding characteristics of nine groundwater samples in such areas.
Previous studies have pointed out that the two primary sources of Cd exposure in the general population are diet and smoking. However, these studies did not integrate the relationship between the UCL and environmental exposure to Cd.
Conducting this analysis in the Hunan Province is particularly important because, in addition to being a hotspot for non-ferrous mining, smelting and machinery manufacturing, it is also famously regarded as the home of fish and rice, cultivating over 4000 hectares of the cereal.
Previous studies also found that there are uncontrolled emissions and releases of waste gas, wastewater, and sludge from various industries in the area, all of which are prominent sources of cadmium. Such contaminants cause a decrease in surface vegetation, thereby accelerating the infiltration of surface water and increasing groundwater Cd pollution.
According to the new study, the UCLs of residents along the riverbank were relatively high.
The paper notes that groundwater Cd concentration ranged from 0.02 to 1.15 μg/L, aligning with class III of the national standard; the range of UCL of nearby residents was 0.37–36.60 μg/L, exceeding the national guideline of 0–2.5 μg/L. Groundwater Cd levels were positively correlated with the UCL (P < 0.001, correlation coefficient 95 % CI = 9.68, R2 = 0.06).
“There is an extremely significant positive correlation between groundwater and urine Cd in people residing near heavy metal industries,” the group noted in a media statement. “With an increase in total Cd of 1000 μg/L groundwater, the concentration of Cd in urine will increase by 11.01 μg/L. In addition, sociological characteristics, such as smoking status and education level, also affect UCL. All results indicate that local governments should strengthen the prevention and abatement of groundwater Cd pollution.”
The team also pointed out that this study is the first to systematically evaluate the relationship between groundwater Cd and UCL using internal and external environmental exposure data.
“Notably, the concentration of Cd in groundwater contributes more significantly to the UCL than do sociological characteristics,” the researchers said. “The relevant departments should strengthen the control and remediation of groundwater Cd and guide the population to prevent Cd pollution.”
