Rahim et al. 2020 — Toxic heavy metals in widely consumed fruits, Pakistan

This primary study measured chromium, cobalt, nickel, cadmium and lead in 11 commonly consumed fruits (apple, apricot, banana, cherry, grapes, guava, lemon, mango, orange, peach and pomegranate) collected from 28 markets across Khyber Pakhtunkhwa (KPK) province in Pakistan, a predominantly mountainous region with limited industrialisation and historically light pesticide use. All concentrations are reported on a dry-weight basis and every fruit×metal mean falls well below the WHO maximum permissible limits the authors cite (Cr 2.3, Co 50, Ni 70, Cd 0.1, Pb 0.3 mg kg⁻¹ DW). The authors attribute the low loadings to the region’s low industrial footprint and frame the dataset as a low-contamination baseline for these fruit commodities.

Key numbers

Mean ± SD in mg kg⁻¹ dry weight (Table 2, p. 64). All means below WHO maximum permissible limits as cited by the authors (Cr 2.3, Co 50, Ni 70, Cd 0.1, Pb 0.3 mg kg⁻¹ DW).

Per-metal extremes (Table 2 / Figures 1–5):

• Cr highest in guava (0.1108) and lemon (0.1063); lowest in apricot and orange (both 0.0069).
• Co highest in banana (0.0833); lowest in lemon (0.0071).
• Ni highest in orange (0.1608); lowest in apricot (0.0086).
• Cd highest in cherry (0.0920) and lemon (0.0783); lowest in apricot (0.0026).
• Pb highest in grapes (0.1072); lowest in apple (0.0052).

Closest approaches to the authors’ cited WHO limits: cherry Cd (0.0920 / 0.1, ~92% of limit), lemon Cd (0.0783, ~78%), grapes Cd (0.0658, ~66%), and grapes Pb (0.1072 / 0.3, ~36%). All other fruit×metal means sit at <40% of the cited limit and most are at <10%.

Dry-weight basis: typical fruit moisture content of ~85–90% implies fresh-weight values are roughly 7–10× lower than the reported DW means.

Methods (brief)

Each of the 11 fruits was purchased at 1 kg per market across 28 fruit markets in Khyber Pakhtunkhwa province (n=308 market-fruit purchases total). Samples were washed with distilled water, sliced with an iron knife, oven-dried at 100°C to constant weight, then crushed with a mortar and pestle. Acid digestion: 2 g dry sample + 50 mL of HNO₃/HClO₄ (4:1) in an Erlenmeyer flask, heated on an electric hot plate at 250°C until the acid mixture evaporated; residue dissolved in distilled water, filtered into a 50 mL volumetric flask and diluted to volume. Analysis by flame atomic absorption spectrophotometry (Perkin Elmer AAS-700) at the Centralized Resource Laboratory, University of Peshawar. Each sample analysed in triplicate; each digest run in duplicate; means and SDs reported. Instrument detection limits (Table 1, in mg L⁻¹ of digest solution): Cr 0.0030, Ni 0.0060, Co 0.0090, Cd 0.0008, Pb 0.0150.

Limitations: no certified reference material is mentioned, no recovery / QC data reported, no inorganic vs total speciation (Cr is total chromium, As/Hg not measured). Sampling reflects a single time-point market survey; seasonal and provenance variability across the 28 markets is not separately characterised.

Implications

Certification: provides a low-contamination dry-weight baseline for 11 fresh-fruit commodities sourced from a low-industry region of Pakistan. Useful as a comparator for category-level fresh-fruit pooling. Values must be converted from dry weight to as-marketed wet weight (typical 7–10× reduction) before comparison with fresh-weight regulatory limits or HMTc per-row standards.

Courses: useful illustration that fruit heavy-metal loadings vary with regional industrial footprint and pesticide use; the authors attribute KPK’s low values to almost-negligible industrialisation and limited pesticide application in the province through 2011.

App: supports a low-contamination prior for fresh apple, peach, apricot, grapes, mango, banana, orange, pomegranate, guava, lemon and cherry sourced from low-industry regions, with the caveat that the data are DW-basis and need conversion before comparison with as-consumed limits.

Wiki pages updated on ingest

• chromium
• cobalt
• nickel
• cadmium
• lead
• apple
• banana
• grapes
• guava
• mango
• oranges
• peach
• fresh-fruit

Verification notes

Merge-enhanced 2026-05-19 from the 2026-05-14 revision against the source PDF (Journal of Physical Science 31(2):61–73, 2020; DOI 10.21315/jps2020.31.2.5). Changes:

• raw_handle standardised from the generic manual-fetch-kimi to MFK_analysis-of-toxic-heavy-metal-content-of-the-most-.
• raw_path corrected from a truncated filename (...Most Widely Used Fru.pdf) to the full filename under raw/Manual Fetch Kimi /01_Fruits_and_Fruit_Products/01_Fruits_and_Fruit_Products/.
• metals extended from [Cr, Ni, Cd, Pb] to [Cr, Co, Ni, Cd, Pb]: cobalt is one of the five analytes the paper measures and reports in Table 2, omitted in the prior revision.
• ingredients revised: [[ingredients/orange]] corrected to the existing slug [[ingredients/oranges]]; [[ingredients/lemon]] removed (no current taxonomy slug — paper-level coverage retained in body); apricot, cherry and pomegranate not declared in frontmatter (no current taxonomy slugs — paper-level coverage retained in body).
• matrices simplified from [fresh-fruit, fruit-flesh, dry-weight] to [fresh-fruit]: dry-weight is a reporting basis, not a matrix; fruit-flesh was not supported by the paper’s preparation (whole sliced fruit, no peel removal described).
• sample_population rewritten to make the 11×28 = 308 design and the triplicate / duplicate-run structure explicit.
• ## Key numbers: body table now includes the Co column (previously only summarised in prose) and reports Mean ± SD as in Table 2 (prior revision reported means only). All other numerical values cross-checked against Table 2 and unchanged.
• Per-metal extremes block added, lifted directly from the source’s Figures 1–5 commentary.
• ## Methods (brief) expanded with the 11×28 market design, sample mass, acid ratio, and the detection-limit table values; recovery/CRM limitation called out explicitly.
• Frontmatter updated advanced to 2026-05-19.

Existing cite_key, doi, license, evidence_tier, near_duplicates, sample_n and products preserved as in the prior revision.

Post-ingest audit (fresh-context subagent, 2026-05-19): verdict REVISE.

• Check 5 ⚠️ on the Courses bullet phrase “arsenic-groundwater regions” — verified against §3 Discussion (p. 64): the paper attributes low KPK values to “almost negligible industrialisation” and “negligible” pesticide application through 2011 only; it does not invoke arsenic-groundwater context. Applied: Courses bullet rewritten to track the paper’s own attribution.
• Check 5 ⚠️ on the Certification bullet phrase “HMTc per-row standards” — audit itself rated this on the allowed side of the Part 2 boundary (contributes occurrence data, does not propose a threshold value). No change applied; leaving the phrase as written.
• Check 1 ⚠️ on sample_n: 308 as a wiki-side derivation — verified: §2.1 (p. 63) states each fruit was purchased from 28 markets at 1 kg, and §1 / Table 2 enumerate the 11 fruit varieties. The total 11 × 28 = 308 is an explicit consequence of the stated design and is preserved in sample_population. No change applied.
• Check 1 ⚠️ on closest-approach ratios (cherry Cd ~92%, lemon Cd ~78%, grapes Cd ~66%, grapes Pb ~36%) — verified: each ratio is arithmetic on the source’s Table 2 means and the source’s own cited WHO limits (Cr 2.3, Co 50, Ni 70, Cd 0.1, Pb 0.3 mg kg⁻¹ DW). The paper’s own §3 framing is qualitative (“much lower”); the wiki adds the quantitative ratios from the same source values. No change applied; ratios retained as useful for downstream pooling.
• Checks 2, 3, 4 returned clean.

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.