Khalil et al. 2017 — Heavy metals in branded and local snacks in Peshawar, Pakistan

This cross-sectional study from Khyber Medical College, Peshawar, measured Pb, Cd, Cr (total), and Cu concentrations in 96 potato- and corn-based snacks sampled from district Peshawar markets, comparing branded products (9 potato brands and 3 corn brands, n=29) against locally produced non-branded snacks (n=67) across four administrative towns. The principal findings were that total chromium exceeded the authors’ cited FAO/WHO “allowed limit” in every sample (branded and local alike) and that lead exceeded permissible limits in the majority of branded snacks and in several non-branded sampling locations; cadmium and copper were within reference ranges across most samples. The study is a snapshot of Peshawar market conditions over a five-month sampling window and is most useful as a regional contextual baseline rather than as a methodologically rigorous occurrence dataset.

Important note on chromium speciation: the analyte reported is total chromium by atomic absorption spectrometry; the paper does not distinguish Cr-VI from total Cr. Regulatory limits and toxicological reference values differ substantially between these two species, so the values on this page are routed to chromium and must not be conflated with Cr-VI occurrence data.

Key numbers

All concentrations in mg/kg (equivalent to ppm; multiply by 1000 for ppb). Values reported as mean ± SD per brand or per sampling location. The paper does not report LOD or LOQ. Where a row has no SD (”.” entry in the source tables), only a single sample of that brand was analyzed.

Branded snacks — potato-based (Table I, 9 brands, n=29 across both branded subtables):

• Pb: range of brand means 0.085–0.423 mg/kg; pooled mean 0.30406 mg/kg (SD 0.128244)
• Cd: range of brand means 0.003–0.046 mg/kg; pooled mean 0.01261 mg/kg (SD 0.010869)
• Cr (total): range of brand means 2.186–2.328 mg/kg; pooled mean 2.21878 mg/kg (SD 0.084287)
• Cu: range of brand means 0.008–0.108 mg/kg; pooled mean 0.06311 mg/kg (SD 0.053741)

Branded snacks — corn-based (Table II, 3 brands):

• Pb: range of brand means 0.240–0.351 mg/kg; pooled mean 0.33655 mg/kg (SD 0.091566)
• Cd: range of brand means 0.007–0.012 mg/kg; pooled mean 0.00800 mg/kg (SD 0.003130)
• Cr (total): range of brand means 2.179–2.254 mg/kg; pooled mean 2.20055 mg/kg (SD 0.076019)
• Cu: range of brand means 0.030–0.082 mg/kg; pooled mean 0.03664 mg/kg (SD 0.025021)

Non-branded (local) snacks — pooled across 7 sampling locations in 4 towns (Table III, n=67):

• Pb: range of location means 0.057–0.415 mg/kg; pooled mean 0.13782 mg/kg (SD 0.142662)
• Cd: range of location means 0.005–0.011 mg/kg; pooled mean 0.00791 mg/kg (SD 0.006037)
• Cr (total): range of location means 2.104–2.237 mg/kg; pooled mean 2.15003 mg/kg (SD 0.082712)
• Cu: range of location means 0.021–0.060 mg/kg; pooled mean 0.04762 mg/kg (SD 0.027572)

Authors’ comparison to FAO/WHO limits (Discussion):

• Pb: branded snacks exceeded the cited permissible level in the majority of samples; non-branded snacks exceeded in samples from Haji Camp (Town 1), Pir Bala Chauk (Town 2), and Hazarkhwani (Town 4).
• Cd: within the authors’ cited normal range across all samples.
• Cr (total): exceeded the cited “allowed limit” in all samples, branded and non-branded alike; authors characterize this as the most alarming finding. The paper does not specify whether the cited limit is for Cr-VI or total Cr, and regulatory limits differ substantially between these species.
• Cu: within normal range, with isolated exceptions.

Branded vs. non-branded summary (Discussion): mean Pb, Cd, Cr, and Cu in branded snacks were 0.314, 0.011, 2.21, and 0.054 mg/kg respectively; mean in non-branded local snacks were 0.149, 0.008, 2.149, and 0.047 mg/kg. Potato-based snacks carried slightly higher concentrations than corn-based snacks for all four metals across both branded and non-branded categories.

Paper-internal discrepancies (worth flagging for downstream synthesis):

• The abstract reports the non-branded Pb range as 0.057–0.324 mg/kg, but Table III shows a location maximum of 0.41533 mg/kg at Haji Camp; this page uses the table value as authoritative.
• The abstract reports the non-branded Cu range as 0.018–0.06 mg/kg, but Table III shows a location minimum of 0.02114 mg/kg at Pir Bala Chauk; this page uses the table value as authoritative.
• The abstract presents the corn-Cr range as “2.254–2.179 mg/kg” with the values transposed; the corrected range (low–high) is 2.179–2.254 mg/kg as confirmed by Table II.
• Sikander/Bilal Town and Haji Camp are both labeled “(Town 1)” in Table III. The seven sampling locations span four administrative towns of Peshawar district; the paper does not resolve the two-locations-per-Town-1 labeling ambiguity.

Methods (brief)

Cross-sectional design; convenient sampling from seven retail locations spanning four administrative towns of Peshawar district (Sikander and Bilal Town, Haji Camp, Pir Bala Chauk, Mathra Bazar, Raufabad, Hazarkhwani, Pando Chauk). Sample size calculated as n = (1.96)² × (0.25)² / (0.05)² ≈ 96, with S = maximum standard deviation 0.25 taken from a previous study and d = 5% margin of error. Analysis performed at the Public Health Laboratory, Khyber Medical College, Peshawar. Sample preparation: 2 g sample weight subjected to wet acid digestion with perchloric acid and nitric acid (HClO₄:HNO₃ in a 1:3 ratio; 5 mL HClO₄ + 15 mL HNO₃ in a volumetric flask) on a hot plate for approximately 2 hours until white fumes appeared and the volume reduced to roughly 10 mL; digestion repeated to ensure completeness; diluted to 100 mL with de-ionised water; filtered through Whatman No. 40 filter paper. Quantitation by atomic absorption spectrometer; the paper does not specify make, model, or wavelength settings, nor does it distinguish flame vs graphite furnace AAS for any individual analyte. Statistical reporting limited to per-brand and per-location means with standard deviations; no LOD, LOQ, recovery, or certified reference material reported. No speciation: Cr is total Cr, not Cr-VI; arsenic and mercury were not measured.

Significant methodological limitations relevant to downstream use:

• No LOD/LOQ reported, so detection-rate inference is impossible and “below limit” samples cannot be distinguished from “not measured” samples.
• Total Cr only; the paper compares against unspecified FAO/WHO limits without resolving whether those limits are Cr-VI or total Cr, which materially affects exceedance interpretation.
• Convenient sampling limits generalisability even within Peshawar district.
• No inter-laboratory validation; no reference materials documented.
• Sampling window (December 2016 to April 2017) is short and does not capture seasonal variation in raw-material sourcing.
• Single-sample brands (no SD) in Tables I and II contribute disproportionately to the pooled SDs.

Implications

Certification: chromium values from this paper are total Cr and do not contribute to Cr-VI-specific occurrence work; route them to chromium only. The Pb data, expressed in mg/kg, are roughly an order of magnitude higher than the low-ppb literature from higher-income markets and are most usefully read as a regional contextual baseline reflecting Pakistani supply-chain conditions (soil contamination, processing inputs, packaging) rather than as a globally representative occurrence dataset. The single-market design and absence of LOD/LOQ limit the data’s standalone weight in any pooled distribution.

Courses: useful case study illustrating that branded labelling does not by itself guarantee lower heavy-metal burden than locally produced equivalents in the same market: in this dataset branded snacks carried higher mean Pb, Cd, Cr, and Cu than non-branded ones. The paper’s framing of contamination pathways (soil uptake in raw vegetables, frying oil, spices, storage containers) is a clean entry point for teaching multi-pathway snack-food contamination.

App: for the ingredient-risk estimator, the relevant signal is that potato- and corn-based snacks sourced from Pakistan/KPK markets carry elevated Pb and elevated total Cr relative to higher-income-country baselines. The values should not be used as global category baselines given the single-market design; they belong in a geographic-variance annotation rather than the central percentile distribution.

Microbiome: not addressed.

Verification notes

• Merge-enhance ingest 2026-05-20 from the original 2026-05-13 page (pre-2026-05-14 schema): re-read the PDF end-to-end and reconciled all numerical values against Tables I, II, and III.
• Frontmatter changes: added Cu to metals: (the paper measures four metals — the prior version omitted Cu); changed [[ingredients/potato]] to the correct slug [[ingredients/potato-chips]] (the prior slug is not in the taxonomy and the measured form is the fried chip, not the raw tuber); removed [[products/root-tuber-vegetables]] (the paper measures finished snack products, not whole root vegetables; root-tuber-vegetables is for raw produce); replaced matrices: [snack, potato-chip, corn-chip] with matrices: [snacks, potato-chips, corn-chips, processed-foods]; added near_duplicates: [].
• Numerical reconciliation against Tables I/II/III: pooled means and SDs now use the exact table values (e.g., potato Pb mean 0.30406 with SD 0.128244, rather than the previous rounded 0.304/0.128); the prior version’s non-branded Cu range “0.018–0.060” used the abstract value, which conflicts with Table III’s location minimum 0.02114; this page now uses Table III as authoritative and notes the abstract/table mismatch explicitly under “Paper-internal discrepancies.”
• Documented three further paper-internal discrepancies (non-branded Pb abstract vs. Table III, transposed corn-Cr abstract range, two-locations-labeled-Town-1 ambiguity) so downstream synthesis is not blindsided by them.
• Removed the legacy ## Wiki pages updated on ingest heading per current source-page schema; relevant page targets are routed via frontmatter and the routing audit.
• Strict Part 12 brand firewall: the paper names 9 potato brands and 3 corn brands by trade name in Tables I and II. None of those brand names appear on this page; per-brand values are aggregated as ranges of brand means and pooled SDs only. Brand-by-brand attribution belongs in the private brand-intelligence build (Part 26), not here.
• Chromium speciation: paper measures total Cr only; metals frontmatter uses Cr (not Cr-VI) per Part 14, and the chromium-speciation caveat is surfaced in the lede, Key numbers, Methods, and Implications.
• Cu added to metals: because the paper measures Pb/Cd/Cr/Cu, but Cu is reported as low across both branded and non-branded samples and does not bind any HMTc analyte (Cu is not in the HMTc 10-analyte vocabulary); it is included for fidelity to the source and routes to copper only.

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.