Overview
Kukusamude and colleagues measured chromium (Cr), Mn, Co, nickel (Ni), Cu, Zn, arsenic (As), and cadmium (Cd) in 55 Thai local rice samples representing four regional rice varieties. The study reports total metal concentrations by rice variety, then uses Thai rice-consumption and body-weight inputs to calculate estimated weekly intake, hazard quotients, hazard index, and lifetime cancer-risk outputs. The occurrence table reports total arsenic; inorganic arsenic appears only as a source-estimated risk input based on a 70% conversion factor from total arsenic.
Key numbers
| Finding | Source-reported value |
|---|---|
| Sample count | 55 Thai local rice samples |
| Rice varieties | Khaowong Kalasin sticky rice (n=15), Pka Am Pun rice (n=9), Jek Chuey Sao Hai rice (n=5), Leb Nok rice (n=26) |
| Mean chromium (Cr) by variety | 0.033, 0.052, 0.073, and 0.054 mg kg-1 for Khaowong Kalasin, Pka Am Pun, Jek Chuey Sao Hai, and Leb Nok rice, respectively |
| Mean Mn by variety | 16.24, 28.33, 13.12, and 15.52 mg kg-1 |
| Mean Co by variety | 0.022, 0.052, 0.025, and 0.018 mg kg-1 |
| Mean nickel (Ni) by variety | 0.26, 1.26, 0.12, and 0.22 mg kg-1 |
| Mean Cu by variety | 1.51, 3.34, 1.55, and 2.76 mg kg-1 |
| Mean Zn by variety | 25.18, 25.47, 19.53, and 25.31 mg kg-1 |
| Mean total As by variety | 0.16, 0.19, 0.11, and 0.24 mg kg-1 |
| Mean cadmium (Cd) by variety | 0.024, 0.021, 0.006, and 0.009 mg kg-1 |
| Total arsenic (As) ranges | 0.067-0.254, 0.077-0.283, 0.081-0.135, and 0.166-0.402 mg kg-1 by the same variety order |
| cadmium (Cd) ranges | 0.003-0.092, 0.006-0.055, 0.002-0.010, and 0.003-0.029 mg kg-1 by the same variety order |
| LOD and LOQ ranges | LOD 0.09-35.75 μg kg-1; LOQ 0.023-42 μg kg-1 |
| Method recoveries | 80.3-101.4%; repeatability less than 3%; intermediate precision less than 10% |
| Source-estimated inorganic arsenic (As) | The paper states that total As was converted to inorganic As using a 70% conversion factor; approximately 11.5% of Leb Nok rice samples were found above the 0.2 mg kg-1 maximum level used by the authors |
| Estimated weekly intake outputs | Table 2 reports As EWI values of 0.82/0.88, 5.43/5.81, 3.15/3.36, and 6.86/7.34 μg kg-1 BW for male/female consumers by the same variety order |
| Hazard index | 0.74, 5.65, 2.97, and 5.37 for Khaowong Kalasin, Pka Am Pun, Jek Chuey Sao Hai, and Leb Nok rice |
| 90th-percentile HQ exceptions above 1 | Mn in Pka Am Pun rice was 1.46; As in Pka Am Pun, Jek Chuey Sao Hai, and Leb Nok rice was 4.34, 2.09, and 4.43 |
| Conclusion-reported mean HQ exceptions | Mn in Pka Am Pun rice (HQ=1.27) and As in Pka Am Pun rice (HQ=2.79), Jek Chuey Sao Hai rice (HQ=1.65), and Leb Nok rice (HQ=3.58) |
| Lifetime cancer probability range | Maximum probabilities over lifetime rice consumption ranged from 5:10,000 chance to 3:1,000 chance |
The four-value concentration rows follow the Table 1 variety order: Khaowong Kalasin sticky rice, Pka Am Pun rice, Jek Chuey Sao Hai rice, and Leb Nok rice. Arsenic occurrence values are total As. The source-estimated inorganic arsenic entries are retained as risk-model outputs and not treated as measured arsenic speciation.
Methods (brief)
The authors collected 55 paddy rice samples from Kalasin, Surin, Saraburi, and Phatthalung provinces in Thailand. Samples were sun-dried after cultivation; polished and unpolished rice samples were pulverized, microwave digested from 0.8 g powdered rice aliquots, reconstituted in 2% HNO3, and analyzed in triplicate by Agilent 7900 ICP-MS. The method used NIST rice flour SRM 1568b and spiked real samples for validation. Probabilistic health-risk assessment used Thai rice-consumption rates, Thai body weights, reference doses, and Monte Carlo simulation with 100,000 iterations.
Implications
This source contributes Thai-market rice-grain occurrence data for Cr, Mn, Co, Ni, Cu, Zn, total As, and Cd, with separate rice-variety means and standard deviations suitable for downstream rice-pool consideration. Its arsenic speciation evidence is limited: total arsenic was measured directly, while inorganic arsenic was estimated from total arsenic for risk calculations using a conversion factor. The paper is most useful for rice-bulk-grain occurrence context, Thai-market stratification, and source-level notes about polished, unpolished, and sticky rice forms.
Update history
The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git.
| Commit | Date | Change | Description |
|---|---|---|---|
| b01ec52c31 | 2026-08-04 | major | 1 section added |
| 3171d069e3 | 2026-08-02 | major | 1 section added |
| 90a2f9a38e | 2026-07-30 | major | 1 section added and 1 removed; narrative text revised |
| eaa8eeeedf | 2026-07-27 | major | 1 section added and 1 removed |
| 50de6ab217 | 2026-07-27 | minor | Narrative text revised |