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, and Cu concentrations in 96 potato- and corn-based snacks from district Peshawar markets, comparing branded products (9 potato brands, 3 corn brands, n=29) against locally produced non-branded snacks (n=67). The principal finding was that Cr exceeded permissible limits in all samples, both branded and local, by a large margin; mean total Cr in branded snacks was 2.21 mg/kg against FAO/WHO thresholds. Lead was also elevated above permissible limits in the majority of branded snacks and in samples from three of four market towns for local snacks. Cadmium and copper were within acceptable ranges across most samples. The study provides a snapshot of Peshawar market conditions at one point in time and is primarily useful for geographic context and for the observation that branded products did not carry lower contamination than local ones for these analytes.
Key numbers
Note: the study reports Cr as total chromium by AAS; the analyte is not speciated to Cr-VI. All values are in mg/kg unless noted. Evidence tier B because the study is published in a regional medical journal with limited methodological transparency (LOD/LOQ not reported, convenient sampling).
Branded snacks — Potato-based (Table I):
- Pb: range across brands 0.085–0.423 mg/kg; overall mean 0.304 mg/kg (SD 0.128)
- Cd: range 0.003–0.046 mg/kg; overall mean 0.013 mg/kg (SD 0.011)
- Cr (total): range 2.186–2.328 mg/kg; overall mean 2.219 mg/kg (SD 0.084)
- Cu: range 0.008–0.108 mg/kg; overall mean 0.063 mg/kg (SD 0.054)
Branded snacks — Corn-based (Table II):
- Pb: range 0.240–0.351 mg/kg; overall mean 0.337 mg/kg (SD 0.092)
- Cd: range 0.007–0.012 mg/kg; overall mean 0.008 mg/kg (SD 0.003)
- Cr (total): range 2.179–2.254 mg/kg; overall mean 2.201 mg/kg (SD 0.076)
- Cu: range 0.030–0.082 mg/kg; overall mean 0.037 mg/kg (SD 0.025)
Non-branded (local) snacks — all types pooled (Table III, by market location):
- Pb: range across locations 0.057–0.415 mg/kg; overall mean 0.138 mg/kg (SD 0.143)
- Cd: range 0.005–0.012 mg/kg; overall mean 0.008 mg/kg (SD 0.006)
- Cr (total): range 2.104–2.237 mg/kg; overall mean 2.150 mg/kg (SD 0.083)
- Cu: range 0.018–0.060 mg/kg; overall mean 0.048 mg/kg (SD 0.028)
Authors’ comparison to FAO/WHO limits:
- Pb: FAO/WHO limit for food not specified beyond “permissible level”; branded snacks exceeded this in majority of samples; local snacks exceeded in samples from Haji Camp, Pir Bala Chauk, and Hazarkhwani locations.
- Cd: within normal range across all samples.
- Cr (total): exceeded “allowed limits” in all samples; authors characterize this as alarming. Note: the study does not distinguish total Cr from Cr-VI; regulatory limits differ significantly between these two forms.
- Cu: within normal range, with isolated exceptions.
Branded vs. local comparison (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 local snacks were 0.149, 0.008, 2.149, and 0.047 mg/kg. Potato snacks showed slightly higher concentrations than corn snacks for all four metals across both branded and local categories.
Methods (brief)
Cross-sectional design; convenient sampling from four administrative towns of Peshawar district (Sikander/Bilal Town, Haji Camp, Pir Bala Chauk/Mathra Bazar, Raufabad, Hazarkhwani, Pando Chauk). Sample size calculated using formula n = (1.96)² × (0.25)² / (0.05)² = 96. All samples analyzed at the Public Health Laboratory, Khyber Medical College Peshawar. Sample preparation: acid digestion with HClO4/HNO3 (1:3, 5 mL and 15 mL) for 2 hours until white fumes; repeated to ensure complete digestion; diluted to 100 mL with deionized water; filtered through Whatman No. 40. Detection by Atomic Absorption Spectrometer (make/model not specified). LOD and LOQ not reported. Statistical summary reported as mean and SD per brand or market location.
Significant limitations: no speciation of Cr (total Cr ≠ Cr-VI for regulatory comparison purposes); no LOD/LOQ reported, making detection-rate inference impossible; convenient sampling limits generalizability; no inter-laboratory validation; sampling period only 5 months from a single district.
Implications
Certification: This study’s chromium data cannot be used for HMT&C Cr-VI standards because the analyte is total Cr. The Pb data are in mg/kg and are higher than the low-ppb literature from higher-income-country markets, consistent with industrial and soil contamination in the Peshawar region. The data are most useful as a regional contextual baseline for supply-chain origin risk assessment rather than as direct standards inputs.
Courses: Useful case study illustrating that branded labeling does not guarantee lower heavy metal burden relative to locally produced snacks, and that Pb and Cr contamination pathways in snack manufacturing (soil uptake in raw vegetables, processing oil, spices, packaging) are common to both branded and artisanal producers.
App: The potato and corn chip ingredient entries can note that regional origin (Pakistan/KPK) is associated with elevated Pb and total Cr relative to higher-income markets; app should not use these values as global baseline given the single-market study design.
Microbiome: Not addressed.