Overview
Rittirong and Saenboonruang quantified aluminium and seven heavy metals in Thai cooked-rice samples prepared with different cooking utensils and water chemistries. The study found high aluminum (Al) and Zn relative to the other measured elements, but no strong indication that the tested utensils substantially increased metal concentrations compared with raw rice. The health-risk calculations identified lead (Pb), arsenic (As), Al, and cadmium (Cd) as the dominant contributors.
Key numbers
| Finding | Source-reported value |
|---|---|
| Metals | Al, Cr, Fe, Cu, Zn, As, Cd, Pb |
| Raw rice aluminum (Al) | 76.50 mg/kg |
| Cooked rice aluminum (Al) | 76.83 mg/kg |
| Raw rice Zn | 22.86 mg/kg |
| Cooked rice Zn | 22.43 mg/kg |
| Relative order | Al > Zn > Fe > Pb approximately Cu > Cr > As approximately Cd |
| Utensil conditions | New Al cooker, used Al cooker, Teflon-coated Al cooker, stainless steel cooker, glass beaker |
| Water conditions | Tap water, de-ionized water, acidic water, basic water |
| Weekly intake from 0.3 kg rice/day | Al 181.07 mg/kg-week; Pb 4.85 mg/kg-week as reported by authors |
| Source PTWI comparators for 60 kg person | Al 120 mg/kg-week; Pb 1.5 mg/kg-week |
| Hazard index | 9.18, with Pb 3.19, As 2.67, and Al 1.51 as largest contributors |
| Total cancer risk | 2.45 x 10^-2, with Pb 1.0 x 10^-2 and Cd 1.2 x 10^-2 as largest contributors |
Methods (brief)
The authors purchased three brands of white rice from a local grocery store in Thailand. Rice was cooked with five utensil types and four water conditions, dried, ground, digested with nitric acid, and analyzed by ICP-MS. The study used t-tests at p < 0.05 to compare cooked and raw rice conditions and calculated non-carcinogenic and carcinogenic risk metrics.
Arsenic is reported as total/unspecified arsenic. The basis is dried cooked-rice material after preparation, not wet ready-to-eat rice.
Implications
For rice pages, this is direct Thailand-market occurrence evidence for cooked rice. For cookware pages, the study suggests tested utensil conditions did not substantially change metal concentrations in rice relative to raw grain under the tested design.
For standards work, cooked-rice values must be kept on the study’s dried cooked-rice basis unless a later contribution log converts to as-consumed wet rice.
Related evidence
- Rice
- Rice (white, brown, wild — bulk grain)
- Metal utensils
- Metal and alloy cookware (cast iron, stainless steel, aluminum)
- Nonstick-coated cookware
- Aluminum
- Lead
- Cadmium
- Arsenic, Total
- Chromium
Update history
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