Kurniawati et al. 2021 — Heavy metals in Jakarta staple foods by neutron activation analysis
This study reports cobalt (Co), chromium (Cr), mercury (Hg), and zinc (Zn) concentrations in 14 staple food commodities purchased from five traditional markets across the five administrative regions of Jakarta, Indonesia, using neutron activation analysis (NAA). The metals measured are primarily micronutrients or trace contaminants rather than the four priority heavy metals (Pb, Cd, iAs, MeHg), but the Hg data are relevant: several commodities exceeded Indonesia’s SNI 7387:2009 maximum permissible limit (MPL) of 0.03–0.5 mg/kg for Hg, with crackers recording the highest Hg concentration (0.25 mg/kg wet weight). Health risk index (HRI) calculations showed that rice, the dominant staple in the Indonesian diet, drove the highest HRI for Hg (2.1, indicating risk) owing to its high daily consumption rate (240 g/person/day), even though its Hg concentration (0.15 mg/kg) is modest relative to other matrices. All other food categories and metals had HRI values below 1.
Key numbers
Concentration ranges across all commodities (wet weight, mg/kg):
- Co: 0.01 (papaya) to 0.15 (crackers) mg/kg
- Cr: 0.02 (egg) to 0.49 (meat) mg/kg
- tHg: 0.02 (papaya) to 0.25 (crackers) mg/kg
- Zn: 1.87 (papaya) to 46.2 (soybean) mg/kg
Selected commodity values (wet basis, mg/kg):
- Rice: Cr 0.10, Zn 22.1, Co 0.09, tHg 0.15
- Soybean: Cr 0.26, Zn 46.2, Co 0.14, tHg 0.22
- Spinach: Cr 0.10, Zn 10.1, Co 0.10, tHg 0.07
- Mackerel: Cr 0.16, Zn 9.62, Co 0.04, tHg 0.18
- Crackers: Cr 0.37, Zn 5.11, Co 0.15, tHg 0.25 (highest Hg of any sample)
Health risk index (HRI) highlights:
- Rice Hg HRI = 2.1 (above safe threshold of 1.0), driven by high rice consumption rate 240 g/day
- All other food-metal combinations: HRI < 1
- Consumption rates used: rice 240 g/day; tempeh 22 g/day; egg 18.6 g/day; water spinach 11.9 g/day
Indonesia SNI 7387:2009 MPL for Hg: 0.03–0.5 mg/kg. Several commodities (rice, crackers, mackerel, egg, chicken) fell within or above this range.
Methods (brief)
Analytical method: neutron activation analysis (NAA) using the G.A. Siwabessy multipurpose reactor at Serpong, Indonesia; thermal neutron flux 10¹³ n·cm⁻²·s⁻¹. Samples counted by HPGe gamma spectrometer (CANBERRA) after one-month decay. No speciation performed; all metals reported as total. Method validation against NIST 1567a Wheat Flour and NIST 8414 Bovine Muscle Powder, with recovery 103–104% and CV 4.06–8.42%. HRI calculated using Indonesian population consumption data (SUSENAS 2012). Key limitation: NAA measures Co, Cr, Hg, Zn only; Pb, Cd, and iAs — the metals of greatest concern for food safety regulation — were not measured in this study.
Implications
Certification: Mercury data for Indonesian staple foods; rice Hg HRI > 1 in this study is at odds with the general consensus that rice Hg is low risk globally. Contextualizes regional variation in HMT&C assessments; direct utility limited because Pb and Cd were not measured.
Courses: Useful case study for illustrating how high-volume staple consumption (rice as daily staple at 240 g/day in Indonesia) amplifies HRI even when per-gram concentrations appear modest. Also illustrates NAA as an alternative to ICP-MS in low-resource settings.
App: tHg data in rice and vegetables for Indonesian market context. Rice tHg 0.15 mg/kg wet weight. Soybean tHg 0.22 mg/kg.