Iqbal et al. 2023 — Heavy metals in poultry feed and poultry products from Rawalpindi/Islamabad farms

This Saudi Journal of Medical and Pharmaceutical Sciences article reports concentrations of Pb, Cd, Cr, Hg, and Fe in solid feed, water, liver, breast muscle, thigh muscle, egg albumen, egg yolk, and whole eggs from six poultry farms in Rawalpindi and Islamabad, Pakistan. Mercury was not detected in any sample; lead was present in feed and most tissues with farm-level values often above WHO permissible limits; iron in liver and chromium in feed and certain tissues were similarly elevated. Liver accumulated the highest Fe and Cd concentrations among the tissues.

Key numbers

• Sampling: 6 layer-breed chicken farms; total 40 samples analyzed for 5 heavy metals: 6 solid feed + 6 liquid feed (water) + composite liver, breast muscle, thigh muscle from same farms + separate egg albumen and egg yolk (Materials and Methods, p. 490).
• Heavy metals in feed (mean across 6 farms, ppm = mg/kg): Cr 2.36; Fe 20.31; Pb 2.605; Cd ND; Hg ND. WHO permissible limits cited in Table 1: Cr 0.1; Pb 0.05; Hg/Fe/Cd not specified for feed (p. 491).
• Per-farm feed values (Table 1, ppm): Farm A feed Cr 0.65, Pb 2.32; Farm B Cr 0.61, Pb 1.22; Farm C Cr 0.84, Pb 1.08; Farm D Cr 0.61, Pb 0.93; Farm E Cr 10.20, Pb 8.87 (outlier); Farm F Cr 1.27, Pb 1.21 (p. 491).
• Liver (Table 1, ppm; Hg ND): Cd 0.09-0.39 (mean 0.1666); Cr 0.30-1.10 (mean 0.6083); Fe 181.51-676.84 (mean 451.9783); Pb 0.54-8.42 (mean 2.9083). WHO MPL listed: Cd 0.05; Cr 0.5; Pb 0.1 (p. 491).
• Breast muscle (ppm; Cd ND, Hg ND): Cr 0.32-1.28 (mean 0.6683); Fe 22.16-33.96 (mean 26.895); Pb 0.41-6.95 (mean 2.655). WHO MPL: Cr 1.0; Pb 0.1 (p. 491).
• Thigh muscle (ppm; Cd ND, Hg ND): Cr 0.20-0.66 (mean 0.32); Fe 37.80-55.46 (mean 44.4116); Pb 0-5.98 (mean 1.655) (p. 491).
• Egg albumen (ppm; Cd ND, Hg ND): Cr ND-0.94 (mean 0.4775, computed excluding ND row); Fe 3.73-15.52 (mean 7.04); Pb 0.46-7.40 (mean 2.322) (p. 491). Note: Farm D albumen was not analyzed (n=5).
• Egg yolk (ppm; Cd ND, Hg ND): Cr 0.57-4.63 (mean 1.57); Fe 53.12-75.18 (mean 62.416); Pb 4.64-8.21 (mean 6.634) (p. 491). Note: Farm D yolk was not analyzed (n=5).
• Whole egg (ppm; Cd ND, Hg ND): Cr 0.82-5.09 (mean 1.952); Fe 59.64-83.43 (mean 69.456); Pb 6.34-15.01 (mean 8.956). WHO permissible limits cited in Table 1 (Ref 14) for whole egg: Cd 0.06-0.07; Cr 0.05; Fe 44.0; Pb 0.43 — all study means exceed Cr, Fe, and Pb limits (p. 492).
• Farm E showed outlier feed values driving exceedances (Cr 10.20 ppm, Pb 8.87 ppm); Farm F whole-egg Pb reached 15.01 ppm (Table 2, p. 492).
• Comparison with prior poultry studies (Table 5, p. 495, ppm, columns = Reported / Sample under study): feed Cr 1.93 / 2.36 (study slightly higher); feed Pb 7.9-32.6 / 2.605 (study below the prior range); liver Cd 0.62 / 0.16 (study lower); liver Cr 0.10 / 0.60 (study higher); liver Pb 0.26 / 2.908 (study higher); liver Fe 54 / 451.9 (study much higher); egg albumen Cr 0.09 / 0.47, Pb 0.13 / 2.32 (study higher on both); egg yolk Cr 1.57, Pb 6.63, Fe 1.27 / 62.41 (Fe study much higher).

Methods (brief)

Six layer-breed chicken samples from each of six farms in Rawalpindi/Islamabad. Birds slaughtered with sterilized knife; liver, breast muscle, thigh muscle separated and frozen. Solid feed dried in hot-air oven at 105 °C to constant weight. Liver and muscle composite-sampled per farm, ground to powder, sieved through 0.25 mm mesh. Eggs separated into albumen and yolk by plastic bottle method and dried. Sample digestion: 15 mL HNO3:HClO4 (4:1) at 80 °C for 2 h to colorless solution; filtered; diluted to 25 mL; refrigerated until analysis. Analytical method: inductively coupled plasma optical emission spectrometry (ICP-OES, iCAP 6500 Thermo Scientific, UK). Speciation: total metals only - no As speciation, no Cr-VI speciation (so Cr reported here is total Cr, not Cr-VI). Hg reported by ICP-OES which is not the most sensitive Hg method; “Hg not detected” therefore reflects ICP-OES detection capability, not necessarily absence at lower levels. LOD/LOQ values are not stated in the paper, which is a methodological limitation; the authors’ Limitations paragraph on p. 495 acknowledges non-availability of reference limits for each sample type but does not specifically address LOD/LOQ. Limitations stated: small farm count; no national reference limits for each sample type; no isotopic tracing of feed→tissue absorption.

Implications

• Certification (HMTc): Contributes Pb, Cd, total Cr, and Fe occurrence data for Pakistani retail-adjacent poultry tissues (liver, breast, thigh) and eggs. Liver Cd (0.09-0.39 ppm) and Pb (0.54-8.42 ppm) data are most relevant to organ-meat threshold work; whole-egg Pb (6.34-15.01 ppm) is unusually high and reflects a single-region small-sample-size study. Not yet a load-bearing source for HMTc standards work given n=6 farms and Pakistan-specific scope; reads as occurrence-context rather than threshold anchor.
• Courses: Teachable case for supply-chain QA on how heavy-metal contamination travels feed → tissue → egg in a developing-market poultry system; pairs with FDA / EFSA poultry occurrence data for cross-jurisdictional contrast.
• App: Contributes Pb, Cd, Cr (total), tHg, Fe rows to Poultry, Eggs, and Organ Meats (Kidney and Liver) (liver specifically).

Wiki pages this source may touch

• Lead
• Cadmium
• Chromium
• Mercury, Total
• Iron
• Poultry
• Chicken
• Eggs
• Organ Meats (Kidney and Liver)
• Meat and Poultry

Verification notes

• The matrices tokens used here — poultry-feed, chicken, liver, breast-muscle, thigh-muscle, eggs — are bare strings; chicken and eggs are common matrices vocabulary, but poultry-feed, liver, breast-muscle, and thigh-muscle are not in the standard matrices snapshot. Used here as descriptive bare strings because no closer terms exist; flagging for Karen’s review per Part 10 if the matrices vocabulary is closed in the future.
• Cr reported is total Cr by ICP-OES; Cr-VI speciation was NOT performed. Per Part 14 the wiki must keep total Cr distinct from Cr-VI; this source contributes only to total Cr.
• Hg “not detected” by ICP-OES; LOD not reported. Whether Hg was truly absent or below ICP-OES sensitivity cannot be inferred from the paper.
• Composite sampling: although text states “33 liver, 33 breast, 33 thigh samples collected”, the analysis was composited to one value per farm (n=6 per tissue type). The reported per-farm means in Table 1 reflect those composites, not individual-bird measurements.
• 2026-05-29 merge-enhance: prior revision misattributed the WHO whole-egg permissible limits (Cd 0.06-0.07, Cr 0.05, Fe 44.0, Pb 0.43 ppm) to egg albumen; Table 1 of the source places the “Ref: (14)” attribution row between yolk and whole-egg rows, indicating these MPLs apply to whole egg only — corrected. Prior revision also reported egg-yolk minimum values (Cr 0.21, Fe 41.22, Pb 0.49) that match the thigh-muscle minima rather than the yolk column in Table 1; corrected to the actual yolk minima (Cr 0.57 from BY, Fe 53.12 from CY, Pb 4.64 from CY). Means and maxima were unchanged and remain verified. products: populated with poultry-product and eggs-product to clear the routing-malformed advisory; the prior empty products: [] predated the 2026-05-17 Phase 1 frontmatter-discipline rule.
• 2026-05-29 audit-application: fresh-context Agent subagent (verdict REVISE) flagged the Table 5 comparison sentence as misframed — prior wording claimed the study’s feed Pb (2.605 ppm) was “within ranges (7.9-32.6 feed)” when in fact 2.605 is below the 7.9-32.6 prior range; rewritten as tissue-by-tissue Reported / Sample-under-study pairs that preserve direction. Also tightened the LOD/LOQ attribution to reflect what the Limitations paragraph (p. 495) actually says (non-availability of reference limits, not LOD/LOQ specifically). Matrices verification note expanded to flag all four non-standard tokens (poultry-feed, liver, breast-muscle, thigh-muscle) rather than just poultry-feed.

Page history

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