Overview
Hao and colleagues measured total arsenic (tAs), inorganic arsenic (iAs), lead (Pb), cadmium (Cd), chromium (Cr), and total mercury (Hg) in 220 rice samples from Xiangtan County, Hunan Province, China, a multi-mining county with rice cultivation. The paper is routeable as rice-bulk-grain occurrence evidence because Table 2 reports rice concentrations directly; mining and soil context should be treated as source-attribution context rather than product concentration data. The rice occurrence finding is dominated by Cd, tAs, and iAs, with iAs kept separate from tAs and total Hg kept separate from methylmercury.
Key numbers
Table 2 reports concentration characteristics for rice (N=220):
| Element/species | Mean ± SD, mg·kg−1 | Range, mg·kg−1 | Limited value, mg·kg−1 | PEL | CV | Skewness | Probability distribution |
|---|---|---|---|---|---|---|---|
| total arsenic (tAs) | 0.34±0.20 | [0.125,1.84] | 0.2 | 99.1% | 167.9% | 4.26 | Lognormal |
| inorganic arsenic (iAs) | 0.15±0.09 | [0.045,0.83] | 0.2 | 22.7% | 168.5% | 3.39 | Lognormal |
| lead (Pb) | 0.08±0.15 | [0.001,1.02] | 0.2 | 10.5% | 53.8% | 3.72 | Lognormal |
| cadmium (Cd) | 0.48±0.50 | [0.001,2.73] | 0.2 | 72.7% | 96.2% | 2.38 | Lognormal |
| chromium (Cr) | 0.6±1.56 | [0.001,12.38] | 1 | 10.0% | 38.4% | 5.18 | Lognormal |
| total mercury (tHg) | 0.0023±0.0020 | [0.0001,0.0106] | 0.02 | 0.0% | 117.7% | 1.91 | Normal |
Additional source-reported values:
- The source states that the iAs/tAs ratio in the study was 44.1%.
- Method detection limits were tAs 0.01 mg·kg−1, iAs 0.02 mg·kg−1, Hg 0.003 mg·kg−1, Pb 0.02 mg·kg−1, Cd 0.002 mg·kg−1, and Cr 0.05 mg·kg−1.
- Table 1 reports bioaccessibility inputs from related studies: iAs 39.90±8.30% with range [8.63,68.5], Pb 23.94±11.00% with range [7.58,48.34], Cd 35.25±20.06% with range [6.67,87.50], and Cr 9.87±5.66% with range [3.26,32.04].
- The source reports probability of non-carcinogenic risk exceeding 1 via rice consumption as 72% for adults and 78% for children. It reports probability of carcinogenic risk as 100%.
- Table 4 reports total HI/TCR point estimates and uncertainty values: adult HI point estimate 2.74, P5 0.67, P50 1.43, P95 5.50; child HI point estimate 2.86, P5 0.43, P50 1.49, P95 6.21; adult TCR point estimate 5.2E-03, P5 7.4E-04, P50 2.8E-03, P95 2.1E-02; child TCR point estimate 5.4E-03, P5 5.5E-04, P50 2.9E-03, P95 2.3E-02.
Methods (brief)
The authors collected rice from 220 sampling sites in Xiangtan County, with five subsamples per site mixed into one sample. Rice was dried to less than 13% moisture, threshed to brown rice, ground, and homogenized. Total Pb, Cd, and Cr were measured after HNO3-HClO4 digestion by ICP-MS; total arsenic (As) used HNO3-HClO4 wet digestion and AFS; Hg used microwave digestion and AFS; and iAs was extracted with 0.15 mol/L HNO3 and quantified by LC-AFS. Quality control used national rice reference material GBW10043, one reference material per 10 samples, and triplicate analyses with RSD less than 5%. The study also used a bioaccessibility-adjusted health-risk model, Monte Carlo simulation with 10,000 iterations, sensitivity analysis, and ArcGIS spatial mapping.
Implications
This source contributes China-market rice occurrence evidence for tAs, iAs, Cd, Pb, Cr, and total Hg, with arsenic speciation resolved and the product matrix tied to brown rice from a multi-mining county. It is useful for rice geographic-variance and supply-chain-context work, especially because the paper links rice concentrations to mining-area spatial patterns. It should not be silently pooled into a United States rice benchmark without an explicit cross-market rationale, and its total Hg result should not be treated as methylmercury.
Related evidence
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