Rahim et al. 2020 — Toxic heavy metals in widely consumed fruits, Pakistan
This primary study measured Cr, Co, Ni, Cd, and Pb 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. All concentrations were reported on a dry weight basis and were substantially below WHO maximum permissible limits. The authors attribute the low values to limited industrialization and minimal pesticide use in this predominantly mountainous region of Pakistan. This dataset provides a useful low-contamination baseline for these fruit types.
Key numbers
Concentrations in mg/kg dry weight (DW). WHO limits: Cr = 2.3, Co = 50, Ni = 70, Cd = 0.1, Pb = 0.3 mg/kg DW.
| Fruit | Cr (mg/kg DW) | Ni (mg/kg DW) | Cd (mg/kg DW) | Pb (mg/kg DW) |
|---|---|---|---|---|
| Apple | 0.0417 | 0.0106 | 0.0065 | 0.0052 |
| Apricot | 0.0069 | 0.0086 | 0.0026 | 0.0073 |
| Banana | 0.0508 | 0.1092 | 0.0088 | 0.0941 |
| Cherry | 0.0281 | 0.0170 | 0.0920 | 0.0934 |
| Grapes | 0.0805 | 0.0711 | 0.0658 | 0.1072 |
| Guava | 0.1108 | 0.0109 | 0.0333 | 0.0117 |
| Lemon | 0.1063 | 0.0729 | 0.0783 | 0.0692 |
| Mango | 0.0805 | 0.0609 | 0.0099 | 0.0905 |
| Orange | 0.0069 | 0.1608 | 0.0106 | 0.0392 |
| Peach | 0.0641 | 0.0399 | 0.0507 | 0.0738 |
| Pomegranate | 0.0750 | 0.0538 | 0.0083 | 0.0830 |
| WHO limit | 2.3 | 70 | 0.1 | 0.3 |
Co concentrations: range 0.0071–0.0833 mg/kg DW (all well below WHO limit of 50 mg/kg). Highest Co in banana (0.0833), lowest in lemon (0.0071). All five metals were below WHO limits across all 11 fruits.
Notable: cherry Cd = 0.092 and grapes Cd = 0.066 mg/kg DW approach the WHO limit of 0.1; grapes Pb = 0.107 mg/kg DW approaches the WHO limit of 0.3.
Dry weight basis: fresh weight values would be substantially lower (typical fruit moisture content ~85–90%).
Methods (brief)
FAAS (Perkin Elmer AAS-700). Acid digestion: 2 g dry sample + 50 mL HNO3/HClO4 (4:1), heated at 250°C, filtered into 50 mL volumetric flask. Samples oven-dried at 100°C to constant weight before digestion. Triplicate samples; duplicate runs per solution. Analysis at Centralized Resource Laboratory, University of Peshawar, Pakistan. No certified reference materials mentioned; LODs reported (Cr: 0.003, Ni: 0.006, Co: 0.009, Cd: 0.0008, Pb: 0.015 mg/L). All values on dry weight basis.
Implications
Certification: Values are very low relative to WHO limits and likely representative of minimally industrialized regions. Cd in cherry (0.092 mg/kg DW) and grapes (0.066 mg/kg DW) are the closest to the WHO limit; convert to wet weight (~10x lower) for comparison with fresh-weight regulatory limits.
Courses: Useful illustration that heavy metal accumulation in fruits is strongly geography- and industry-dependent; KPK data stand in notable contrast to more industrialized or arsenic-groundwater-impacted regions.
App: Supports low-risk designation for orchard fruits (apple, peach, apricot, grapes) from low-industrial regions of Pakistan. Note dry-weight basis requires conversion before comparison with fresh-weight standards.