Sarker et al. 2022 — Heavy metals in Bangladesh food webs: systematic review (ESPR)
This systematic review in Environmental Science and Pollution Research is the first comprehensive synthesis of heavy metal contamination, multi-trophic transfer, and associated health risks in Bangladesh’s food webs. The authors surveyed rice, vegetables, fruits, fish, meat, dairy, and water matrices, concluding that heavy metals in most food categories in Bangladesh exceed WHO/FAO maximum tolerable limits (MTLs), primarily due to poor management of industrial effluents, contaminated irrigation water, improper use of metal-containing pesticides and fertilizers, and weak regulatory enforcement. The review specifically notes that arsenic in Bangladesh is a well-documented crisis (groundwater-derived), and that Pb in mango and Cd in tomatoes exceeded WHO/FAO limits in a national survey of 30 agroecological zones. Tilapia was found to contain arsenic at 1.486 mg/kg, higher than other fish species studied, posing chronic toxicity risks in communities relying on cheap freshwater fish.
Key numbers
From cited primary studies reviewed:
- Tilapia arsenic: 1.486 mg/kg (above safety limits), highest among rahu, tilapia, and pangas species studied
- Lead in mango: above WHO/FAO MTL (exact value from Shaheen et al. 2016)
- Cadmium in tomato: above WHO/FAO MTL (exact value from Shaheen et al. 2016)
- Bangladesh rice, vegetables, fish: “higher than acceptable limits set by WHO/FAO” — specific concentrations distributed across cited primary studies not directly reported in the extracted text
Heavy metals identified as predominant contaminants in Bangladesh ecosystems: As, Pb, Cd, Cr, and Zn in agricultural land, foodstuffs, suburban soil, and waterways.
Multi-trophic transfer was identified as a significant but understudied pathway: heavy metals accumulate progressively from soil to plant to herbivore to higher trophic levels, but quantitative data on the full chain were lacking at time of review.
Methods (brief)
Systematic review (but no PRISMA protocol stated); comprehensive literature bank from Google Scholar, PubMed, Science Direct, Scopas, ResearchGate, Springer, and official websites. No specific timeline exclusion. Published in ESPR vol. 29 (2022), received July 2021, accepted October 2021. Evidence tier A: peer-reviewed in a major Springer environmental journal, systematic methodology, focused geographic scope with strong primary-study base. Key limitation: all concentration data are secondary; primary values must be traced to the cited studies for HMT&C use. The focus on Bangladesh limits direct transferability to other jurisdictions.
Implications
Certification: Documents that Bangladeshi-origin food commodities (rice, vegetables, freshwater fish, dairy) carry elevated heavy metal risk versus WHO/FAO limits, due to systemic irrigation and industrial contamination. Bangladesh origin is a red flag for Pb, Cd, As, and Cr in ingredient sourcing screening. Relevant for ingredient origin audits.
Courses: Valuable case study for supply-chain contamination module showing how industrial effluent management failures propagate through entire national food systems. Multi-trophic transfer concept is important for seafood module (freshwater fish in contaminated river systems).
App: Qualitative risk flag: Bangladeshi-origin rice, vegetables, and freshwater fish should receive elevated risk rating. Tilapia arsenic datum (1.486 mg/kg) is a concrete upper-bound reference for aquaculture fish.