Heavy Metal Contamination in Rice-Producing Soils of Hunan Province, China and Potential Health Risks

Heavy metal contamination of soils resulting from mining and smelting is causing major concern due to the potential risk involved. This study was designed to investigate the heavy metal (Cu, Zn, Pb and Cd) concentrations in soils and food crops and estimate the potential health risks of metals to humans via consumption of polluted food crops grown at four villages around the Dabaoshan mine, South China. The heavy metal concentrations in paddy and garden soils exceeded the maximum allowable concentrations for Chinese agricultural soil. The paddy soil at Fandong village was heavily contaminated with Cu (703 mg kg(-1)), Zn (1100 mg kg(-1)), Pb (386 mg kg(-1)) and Cd (5.5 mg kg(-1)). Rice tended to accumulated higher Cd and Pb concentration in grain parts. The concentrations of Cd, Pb and Zn in vegetables exceeded the maximum permissible concentration in China. Taro grown at the four sampled villages accumulated high concentrations of Zn, Pb and Cd. Bio-accumulation factors for heavy metals in different vegetables showed a trend in the order: Cd>Zn>Cu>Pb. Bio-accumulation factors of heavy metals were significantly higher for leafy than for non-leafy vegetable. The target hazard quotient (THQ) of rice at four sites varied from 0.66-0.89 for Cu, 0.48-0.60 for Zn, 1.43-1.99 for Pb, and 2.61-6.25 for Cd. Estimated daily intake (EDI) and THQs for Cd and Pb of rice and vegetables exceeded the FAO/WHO permissible limit. Heavy metal contamination of food crops grown around the mine posed a great health risk to the local population through consumption of rice and vegetables.

The effect of underweight and obesity on mortality has not been well characterized in Asian populations. To examine the relationship between body mass index (BMI) and mortality in Chinese adults. A prospective cohort study in a nationally representative sample of 169,871 Chinese men and women aged 40 years or older. Data on body weight and covariables were obtained at a baseline examination in 1991 using a standard protocol. Follow-up evaluation was conducted in 1999-2000, with a response rate of 93.4% (n = 158,666). Body mass index and all-cause mortality. After excluding those participants with missing body weight or height values, 154,736 adults were included in the analysis. After adjustment for age, sex, cigarette smoking, alcohol consumption, physical activity, education, geographic region (north vs south), and urbanization (urban vs rural), a U-shaped association between BMI and all-cause mortality was observed (P<.001). Using those participants with a BMI of 24.0 to 24.9 as the reference group, the relative risks of all-cause mortality across categories of BMI were 1.65 (95% confidence interval [CI], 1.54-1.77) for BMI less than 18.5, 1.31 (95% CI, 1.22-1.41) for BMI 18.5 to 19.9, 1.20 (95% CI, 1.11-1.29) for BMI 20.0 to 20.9, 1.12 (95% CI, 1.04-1.21) for BMI 21.0 to 21.9, 1.11 (95% CI, 1.03-1.20) for BMI 22.0 to 22.9, 1.09 (95% CI, 1.01-1.19) for BMI 23.0 to 23.9, 1.00 (95% CI, 0.92-1.08) for BMI 25.0 to 26.9, 1.15 (95% CI, 1.06-1.24) for BMI 27.0 to 29.9, and 1.29 (95% CI, 1.16-1.42) for BMI 30.0 or more. The U-shaped association existed even after excluding participants who were current or former smokers, heavy alcohol drinkers, or who had prevalent chronic illness at the baseline examination, or who died during the first 3 years of follow-up. A similar association was observed between BMI and mortality from cardiovascular disease, cancer, and other causes. Our results indicate that both underweight and obesity were associated with increased mortality in the Chinese adult population. Furthermore, our findings support the use of a single common recommendation for defining overweight and obesity among all racial and ethnic groups.

Food safety is a major concern for the Chinese public. This study collected 465 published papers on heavy metal pollution rates (the ratio of the samples exceeding the Grade II limits for Chinese soils, the Soil Environmental Quality Standard-1995) in farmland soil throughout China. The results showed that Cd had the highest pollution rate of 7.75%, followed by Hg, Cu, Ni and Zn, Pb and Cr had the lowest pollution rates at lower than 1%. The total pollution rate in Chinese farmland soil was 10.18%, mainly from Cd, Hg, Cu, and Ni. The human activities of mining and smelting, industry, irrigation by sewage, urban development, and fertilizer application released certain amounts of heavy metals into soil, which resulted in the farmland soil being polluted. Considering the spatial variations of grain production, about 13.86% of grain production was affected due to the heavy metal pollution in farmland soil. These results many provide valuable information for agricultural soil management and protection in China.