Overview
Bolan and colleagues compared total arsenic, operational arsenic fractions, EXAFS species, and gastric-phase bioaccessibility in selected rice grains and complementary medicines. The rice samples were deliberately high-arsenic materials grown with arsenic-contaminated or arsenic-spiked irrigation water, so they are not a general-market rice baseline. The complementary-medicine set included herbal and ayurvedic medicines; the ayurvedic products had higher total and bioaccessible arsenic than the herbal products.
Key numbers
All concentration ranges below are reported by the source in mg kg-1 unless otherwise stated. The accepted-manuscript text layer does not expose clean per-sample values from the figures, so this page records only ranges and equations stated in the text.
| Matrix | Arsenic result | Source-reported value |
|---|---|---|
| Rice grains | Total As range | 0.456-1.095 mg kg-1 |
| Complementary medicines | Total As range | 0-36.71 mg kg-1 |
| Complementary medicines | Average comparison | Ayurvedic medicines averaged 8.8 times higher As than herbal medicines |
| Rice grains | Bioaccessibility as % of total As | 23.16%-32.34% |
| Herbal medicines | Bioaccessible As concentration | 1.00-4.07 mg kg-1 |
| Ayurvedic medicines | Bioaccessible As concentration | 8.77-13.37 mg kg-1 |
| Ayurvedic medicines | Bioaccessibility as % of total As | 36.63%-79.11% |
| Herbal medicines | Bioaccessibility as % of total As | 35.34%-48.48% |
The rice samples were high-arsenic research materials: the paper states they were grown with arsenic-contaminated irrigation water, including arsenic supplied as Na2HAsO4.7H2O.
Speciation/fractionation findings:
- Soluble arsenic contributed less than
5%of total arsenic in rice grains and less than19%of total arsenic in complementary medicines. - Organic-bound fractions dominated in rice grains and herbal medicines, while inorganic fractions dominated in ayurvedic medicines.
- The TFA extraction indicated that the majority of arsenic in rice grain was present as organic species.
- EXAFS on selected high-arsenic ayurvedic medicines indicated mineral arsenic compounds including orpiment (arsenic trisulphide), realgar (arsenic disulphide), and arsenolite (arsenic trioxide).
Bioaccessibility/speciation regressions for complementary medicines:
| Relationship | Equation |
|---|---|
| Soluble arsenic (As) to bioaccessible As | y = 5.875x1 + 0.570 (R2 = 0.881) |
| Soluble + carbonate arsenic (As) to bioaccessible As | y = 1.8215x2 + 0.2769 (R2 = 0.8871) |
| Measured vs predicted bioaccessibility in Fig. 4 | y = 0.8808x + 0.7613 (R2 = 0.8912) |
For the paper’s daily-intake calculation, rice consumption was assumed to be 0.5 kg d wt d-1 for a 60 kg adult; medicine dose was derived from the product instructions. The source states that the estimated daily intake values based on total arsenic were above the selected safety guideline in all rice-grain samples, while bioaccessible-arsenic intake was below the guideline except for one rice sample with total arsenic (As) 1.095 µg g-1. The source-estimated maximum total As concentration in rice grain without exceeding its PTWI-based limit was 0.30 µg g-1. Complementary-medicine daily intake estimates were below the source’s selected safety guideline because of the low daily dose, even when products had high concentration values.
Methods (brief)
Rice grains came from research grain collections in Bangladesh, Korea, and India. Herbal and ayurvedic medicines were purchased in 2014 from Indian and Chinese shops; four additional medicines were later sourced for regression testing. Total arsenic was measured after digesting 0.5 g of ground material (<0.2 mm) with 5 ml aqua regia (1:3 HNO3 : HCl) using USEPA Method 3051H, followed by ICP-MS with internal standardisation and external calibration. CRM/QA materials included Montana Soil SRM 271 and Rowe Scientific NCS-DC73349.
Operational arsenic fractions were measured by a Tessier-style sequential fractionation into soluble, carbonate-bound, oxide-bound, organic-bound, and residual fractions. Rice-grain arsenic species were also checked by TFA extraction. Selected high-As ayurvedic medicines were analyzed by EXAFS at the Pohang Accelerator Laboratory 7D XAFS beamline with linear-combination fitting to arsenic reference spectra. Gastric-phase bioaccessibility used 0.4 M glycine adjusted to pH 1.5, with 1 g of <250 µm sample at 1:100 solid:solution ratio for 1 hour at 37oC, followed by 0.45 µm filtration and arsenic analysis.
Implications
This source should be treated as targeted arsenic exposure and bioaccessibility context, not as a clean market baseline for rice. It is useful for showing that high-arsenic irrigation can produce rice-grain total As well above the paper’s intake benchmark, and that the bioaccessible fraction may be substantially lower than total As for these organic-dominated rice samples. For complementary medicines, the source separates herbal from ayurvedic products and shows that ayurvedic formulations can carry mineral inorganic arsenic species while still producing low daily intake estimates when label-dose amounts are small.
Related evidence
- Rice (white, brown, wild — bulk grain)
- Dietary Supplements
- Ingredient class — botanicals/herbs/traditional formulas
- Rice
- Herbal botanicals
- Arsenic, Total
- Arsenic, Inorganic
Update history
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