Bhattacharya and Deka 2024 — Metals in traditional rice beers of Assam tribes

Bhattacharya and Deka measured concentrations of eleven metals (Cd, Co, Cr, Cu, Fe, Pb, Mn, Ni, K, Na, Zn) in four traditional alcoholic rice beers prepared by indigenous Rabha and Sonowal Kachari communities of Assam, India, by atomic absorption spectroscopy. Concentrations of cadmium (0.002–0.008 mg/L), chromium (0–0.012 mg/L), cobalt (0–0.008 mg/L), nickel (0.024–0.094 mg/L), and lead (0.09–0.19 mg/L) were below the WHO drinking-water guideline values applied as the comparator throughout the paper, while iron (1.09–1.56 mg/L) and manganese (1.67–2.53 mg/L) ranged above the WHO drinking-water guideline for those analytes. Total target hazard quotient (ΣTHQ) was below 1 for all four beers and highest for the Pati Rabha sticky-rice beer (0.351). The paper concludes the beers can be marked as safe relative to WHO drinking-water permissible limits despite the Fe and Mn exceedances noted in its own discussion.

Key numbers

All concentrations in mg/L as reported by the authors (Table 1 reports total metal-content load per beer in µg/mL; 1 µg/mL = 1 mg/L). Method: atomic absorption spectroscopy after wet acid digestion. Comparator throughout: WHO drinking-water guideline values, applied by the authors to alcoholic beverages rather than to drinking water.

Concentration ranges across the four beers (abstract; Results and Discussion p. 202):

• Cd: 0.002–0.008 mg/L
• Co: 0–0.008 mg/L
• Cr (total): 0–0.012 mg/L
• Cu: 0.092–0.121 mg/L
• Fe: 1.09–1.56 mg/L
• Pb: 0.09–0.19 mg/L
• Mn: 1.67–2.53 mg/L
• Ni: 0.024–0.094 mg/L
• K: 175.8–290.8 mg/L
• Na: 9.7–25.8 mg/L
• Zn: 0.639–1.678 mg/L

Per-beer values back-calculated from the EDI table (Table 2; EDI = C × 250 mL / 60 kg; values verified to match the abstract ranges):

• Pati Rabha sticky-rice beer (n metals quantified = 9; Co and Cr below estimated limit): Cd 0.008, Pb 0.130, Ni 0.094, Cu 0.190, Fe 1.130, Mn 2.530, Zn 0.716 mg/L.
• Koch Rabha sticky-rice beer (n=11): Cd 0.005, Co 0.008, Cr 0.012, Pb 0.190, Ni 0.024, Cu 0.119, Fe 1.210, Mn 1.670, Zn 0.639 mg/L.
• Rangdani Rabha “Janga” (n=11; Goalpara district): Cd 0.002, Co 0.001, Cr 0.002, Pb 0.090, Ni 0.046, Cu 0.121, Fe 1.560, Mn 1.850, Zn 0.954 mg/L.
• Sonowal Kachari “Rohi” (n=10; Dibrugarh district; Co below estimated limit): Cd 0.003, Cr 0.012, Pb 0.161, Ni 0.064, Cu 0.092, Fe 1.090, Mn 2.100, Zn 1.678 mg/L.

Statistical summary (Table 1) — per-beer metal-content total (µg/mL): Pati Rabha 254.998 (population mean 28.33, SD 71.23); Koch Rabha 256.297 (mean 23.30, SD 67.00); Rangdani Rabha 321.226 (mean 29.20, SD 83.04); Sonowal Kachari 191.299 (mean 19.13, SD 52.30). The high SDs reflect the dominance of K and Na in the totals.

Estimated daily intake (EDI; Table 2; assumes 250 mL/day intake, 60 kg adult body weight) ranges across the four beers (µg/kg bw/day): Cd 0.0083–0.033 (versus the authors’ cited tolerable EDI of 1 µg/kg bw/day); Cr 0–0.05 (versus 2.2 µg/kg bw/day); Pb 0.375–0.79; Ni 0.039–0.39; Fe 4.54–6.50; Mn 6.96–10.54; Zn 2.66–6.99.

Total target hazard quotient (Table 5; ΣTHQ): Pati Rabha 0.351 (highest); Koch Rabha 0.269; Sonowal Kachari 0.270; Rangdani Rabha 0.220. All ΣTHQ values are below 1, the threshold the authors apply for non-carcinogenic concern. Per-metal Cd THQ was 0.033 in the Pati Rabha beer (highest of the four). Cobalt THQ in Koch Rabha beer was 0.110, which is the highest single-metal THQ reported in the study; the authors do not flag this in the discussion.

Evidence Fitness

This source provides occurrence values for a four-beer convenience sample drawn from named indigenous communities in four districts of Assam, with no within-beer replication structure reported and no LOD/LOQ values disclosed. It can support discovery, contextual evidence on metal occurrence in traditional non-commercial rice beers of north-eastern India, and a methodology anchor (AAS with HNO3/H2O2 digestion) for that product category. It is not large enough or structured enough to support pooled-percentile work on the fermented-beverages-non-tea-based row. Reported public evidence label: Context only.

Methods (brief)

Sample collection: rice-beer samples obtained from named indigenous-community brewers in Goalpara, Baksa, Bongaigaon, and Dibrugarh districts of Assam state, India. Sample preparation: degassing by ultrasonic bath for 30 min; 20 mL aliquot digested with 2 mL conc. HNO3 + 2 mL H2O2 in a digestion tube. Quantification: atomic absorption spectroscopy. Statistical analysis: Duncan test and one-way ANOVA at p ≤ 0.05 using SPSS version 24 (SPSS Inc., Chicago). Limitations explicitly visible in the source: (i) the AAS instrument vendor/model and the operating mode (flame vs graphite furnace) are not specified; (ii) no LOD or LOQ values are reported; (iii) no certified reference material recoveries or quality-assurance figures are disclosed; (iv) replication structure within each beer type is not described — Table 1 reports a single “metal content total” per beer and standard deviations computed across the metals within a beer rather than across replicates of the same metal; (v) chromium is quantified as total Cr with no hexavalent speciation; (vi) arsenic and mercury were not measured.

The Hazard Quotient methodology uses an exposure-duration of 53.88 years (intake from age 15 to life expectancy 68.88 years), MDI 250 mL/day, body weight 60 kg, and EPA oral reference doses (RfD, mg/kg/day) listed in Table 4: Cu 4×10⁻², Cd 1×10⁻³, Ni 2×10⁻³, Fe 7×10⁻¹, Zn 3×10⁻¹, Pb 1.5, Mn 1.4×10⁻¹, Cr 1.5, Co 3×10⁻⁴. The Pb RfD of 1.5 mg/kg/day printed in Table 4 is anomalously large compared to current US EPA IRIS treatment of Pb (which uses BLL-based modeling rather than a single oral RfD); the authors do not source this value to a specific EPA document and the resulting low Pb THQ values are dominated by this divisor.

Implications

• Certification: contributes occurrence data on traditional non-commercial rice beers from Assam to the evidence base for fermented-beverages-non-tea-based. The Pb range (0.09–0.19 mg/L = 90–190 µg/L) and Cd range (2–8 µg/L) sit well above the Codex/EU drinking-water-style baselines that the authors compare against, but neither analyte exceeds the food-contact-acidic-beverage caps that govern HMTc work on this row. Sample size is insufficient to inform pooled percentile selection.
• Courses: useful as a teaching case for the limits of “within WHO drinking-water guidelines” framing when applied to fermented food products, and for the conflation in the discussion between the authors’ own observation that Fe exceeded the WHO drinking-water value in Rangdani Rabha beer and the abstract-level conclusion that all samples are safe.
• App: contributes Pb, Cd, Ni, Cr (total), Co, Cu, Fe, Mn, and Zn occurrence points for rice-substrate fermented beverages.

Provenance notes

Open-access article distributed under CC BY 4.0 (license declaration at the foot of page 1). Accessed via the Manual Fetch Discovery autopilot. The PDF was published online 31 December 2023 (Asian J. Chem. Vol. 36 No. 1, formal issue dating 2024); the cite-key uses 2024 to align with the formal journal-volume year per the convention used in akhmetsadykova2013-camel-milk-lab-lead. The raw-handle preserves the discover-skill filename which used the online-publication year 2023.

Evidence tier set to B rather than A. The journal is peer-reviewed (Asian Journal of Chemistry, indexed; ISSN-bearing) but the paper has multiple methodological transparency gaps (no LOD/LOQ, no CRM recovery, no replication structure, no instrument specification, an anomalous RfD for Pb that drives the THQ conclusion). A-tier on the HMI scale requires both peer review and methodological transparency sufficient for independent re-derivation of the headline values; this paper does not clear that bar.

Wiki pages this source may touch

• lead
• cadmium
• chromium
• nickel
• cobalt
• copper
• iron
• manganese
• zinc
• rice
• fermented-beverages-non-tea-based

Verification notes

The paper exhibits an internal framing tension between its abstract-level safety claim (“all the samples can be marked as safe as the metal concentrations are within the permissible limits of WHO”) and its own Results-section statement that “Iron contamination is highest in Rangdani Rabha beer, which is above the WHO permissible limit,” followed by a note that manganese also exceeds permissible limits “in all alcoholic beverages.” This page reports both claims as the authors stated them and does not adjudicate which framing is correct, per Part 2 of CLAUDE.md (the wiki reports what the literature supports, not what is convenient).

No brand names appear in the paper or on this page. The community and beer-style names recorded here (Pati Rabha, Koch Rabha, Rangdani Rabha, Sonowal Kachari, “Janga”, “Rohi”) are ethnographic identifiers of indigenous brewing traditions in named geographic districts, not commercial brand names; Part 12 brand-firewall does not apply. Method-vendor references (SPSS Inc., Chicago) are reproduced under the methods-vendor exception.

Chromium is total Cr (no hexavalent speciation in the source); the frontmatter uses Cr, not Cr-VI, accordingly. Arsenic and mercury were not measured, so iAs, tAs, MeHg, and tHg are absent from the metals list.

The per-beer concentrations in this page are back-calculated from the EDI table (Table 2) using the authors’ formula C = EDI × W / V with W = 60 kg and V = 250 mL, then cross-checked against the abstract ranges. The Average Daily Dose values printed in Table 3 are numerically identical to the EDI values in Table 2 and inherit the same back-calculation. Figure 1 (”% of metals in traditional rice beers”) shows the same per-beer concentrations rendered as a stacked bar with axis values that match the back-calculated concentrations after unit scaling, providing a third independent check.

Table 2 prints the cadmium EDI for Rangdani Rabha as “0.0083” while Table 3 prints the same row as “0.008”; the underlying concentration is the same (≈ 0.002 mg/L). Table 2 prints the cadmium EDI for Sonowal Kachari as “0.0125” and Table 3 prints it as “0.012”. These are display-precision differences in the source, not data inconsistencies.

The authors’ choice of EPA oral RfD for Pb (1.5 mg/kg/day, Table 4) is not consistent with current US EPA IRIS practice for lead, which has withdrawn a single oral RfD in favor of BLL-based assessment. The low per-metal Pb THQ values (0.000–0.001) in Table 5 are driven by this divisor and should not be read as the principal HMI-relevant finding for Pb; the concentration data (0.09–0.19 mg/L) are the primary contribution and are reported above without reliance on the THQ framing.

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.