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); Fe 3.73-15.52 (mean 7.04); Pb 0.46-7.40 (mean 2.322). WHO MPL: Cd 0.06-0.07; Cr 0.05; Fe 44.0; Pb 0.43 (p. 491-492).
- Egg yolk (ppm; Cd ND, Hg ND): Cr 0.21-4.63 (mean 1.57); Fe 41.22-75.18 (mean 62.416); Pb 0.49-8.21 (mean 6.634) (p. 491).
- 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) (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 Pakistan poultry studies (Table 5, p. 495, ppm): the present study’s feed Pb (2.605 ppm), liver Pb (2.9083 ppm), and whole-egg/yolk Pb (6.63 ppm) are within ranges (7.9-32.6 feed; 0.26-2.32 albumen) but Cr in feed (2.36 ppm) is higher than the cited 1.93 ppm reference.
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 - this is a methodological limitation per author acknowledgements (p. 495). 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 (liver specifically).
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Verification notes
- “poultry-feed” matrix is not in the standard matrices vocabulary; flagging for Karen’s review per Part 10. Used here as a bare-string matrix because no closer term exists.
- 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.
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