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Occurrence and Risk Evaluation of Trace Metals in Infant Nutrition Sources in Rural and Urban Multan, Pakistan

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Overview

Mumtaz and colleagues measured trace metals in infant nutrition sources from rural and urban Multan, Pakistan and evaluated non-carcinogenic and carcinogenic risk. The study covers two matrices — breast milk from lactating mothers and commercial infant formula collected from local pharmacies and supermarkets — and reports Pb, Cd, Ni, Zn, and Fe concentration summaries and risk indices stratified by rural versus urban dwelling. Concentrations are reported on a liquid basis (mg/L). It should be kept market-specific to Pakistan.

Key numbers

  • Target analytes are Zn, Fe, Ni, Pb, and Cd, quantified by ICP-MS in mg/L.
  • Table 1 reports ICP-MS LODs and LOQs (Pb LOD 0.01 mg/L, Cd LOD 0.005 mg/L) and CRM recoveries (Pb 97.9%, Cd 99.7% against NIST SRM 1643f).
  • Table 2 summarizes mean concentrations by area. Rural mean Pb 0.0044 ± 0.0057 mg/L vs urban 0.0082 ± 0.0064 mg/L; urban Cd 0.0016 ± 0.0012 mg/L. Urban samples had higher Pb and Cd; rural samples had higher Zn (0.275 ± 0.161 mg/L) and Fe (0.873 ± 0.292 mg/L).
  • Table 3 statistical comparison: Pb p = 0.018 (Cohen’s d = −0.612, medium); Cd p = 0.0157 (d = −0.628, medium).
  • Table 7 risk thresholds: cumulative HI 2.30 ± 2.70 (rural, 54.8% exceeding 1) vs 4.18 ± 3.13 (urban, 90.6% exceeding 1), p = 0.0128. Cumulative TCR 0.00161 (rural) vs 0.00205 (urban); both regions exceed the 10⁻⁴ TCR threshold.
  • Table 8 effect sizes: Cd d = 1.05 (large); TCRCd d = 0.88 (large); HI d = 0.72 (medium); Pb d = 0.65 (medium).

Methods (brief)

Cross-sectional sampling of 62 breast milk samples from lactating mothers plus infant formula samples from all major available brands across rural and urban Multan. Sample powders homogenized, dried 48 h at 60 °C, digested in nitric/perchloric acid (USEPA 1996 protocol), diluted to 25 mL, filtered through 0.45 µm cellulose nitrate membranes. Quantification by PerkinElmer NexION 2000B ICP-MS, calibrated against NIST SRM 1643f (Trace Elements in Water) and NIST SRM 1577c (Bovine Liver), with Rh and Bi internal standards for drift correction. Risk indices (EDI, THQ, HI, TCR) computed per USEPA RAGS Vol. I (2011). Statistics in R 4.5.2 with t-tests, Cohen’s d, correlation, and PCA. Results are total element concentrations and should retain rural/urban strata.

Implications

Contributes Pakistan-market occurrence data for Pb, Cd, Ni, Zn, and Fe in infant formula and breast milk, with rural-urban stratification and aggregate risk indices. Geographic scope is limited to Multan; do not pool with US- or EU-market data without explicit geographic-variance handling.

Useful for course material on rural-urban exposure disparities in infant nutrition matrices in South Asia.

App-relevant only after per-brand or per-product-form extraction, which this paper does not provide (values are aggregated at rural/urban level only).

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