Bolan et al. 2017 - arsenic speciation and bioaccessibility in rice and complementary medicines

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.

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 than 19% 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:

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 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.

Wiki pages this source may touch

• rice-bulk-grain
• dietary-supplements
• supplements-botanicals-herbs
• rice
• herbal-botanicals
• arsenic-total
• arsenic-inorganic

Verification notes

• Identity checks before writing found no existing source page for DOI 10.1016/j.chemosphere.2017.04.126, raw handle MFK_bolan2017, title text, or cite key bolan2017-rice-complementary-medicines-arsenic.
• All Key numbers were rechecked against /tmp/hmi-seaweed-027.txt, extracted with pdftotext -layout. Figure axis text was not used for per-sample values because the extracted text layer does not expose clean numeric bars; only text-stated ranges and equations are transcribed.
• Units are preserved as mg kg-1, µg g-1, µg day-1, and kg d wt d-1 exactly as the source reports them; no unit conversion was performed.
• Speciation check: total arsenic is recorded as tAs. Inorganic arsenic is included because the source explicitly reports inorganic fractions dominating ayurvedic medicines and EXAFS-identified arsenic minerals; no numeric iAs concentration is inferred from the figures.
• Brand firewall: the page does not reproduce manufacturer/brand names or attach values to product labels. Traditional formulation names are not tabulated as brand-ranked values; category-level herbal versus ayurvedic results are used for the occurrence summary.
• Source-scope caution: rice samples were grown under arsenic-contaminated/spiked irrigation conditions and are not representative general-market rice samples.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.