Overview
The foundational investigation of lead chromate adulteration in Bangladesh’s turmeric supply chain, combining analytical chemistry (n=524 samples) with 152 semi-structured interviews across the entire production and distribution chain. This study mapped the mechanism by which PbCrO4-based industrial yellow pigments enter the food supply: polishers add yellow pigment to dried turmeric roots during the polishing process to enhance color and compensate for poor-quality roots, driven by consumer preference for bright yellow turmeric and demand from Dhaka wholesalers.
Key numbers
Turmeric samples: 340 total (140 from 9 major turmeric-producing districts, 200 from Dhaka and Munshiganj). 11% of samples from producing districts exceeded Bangladesh’s national limit of 2.5 µg/g Pb, versus 26% in Dhaka and Munshiganj.
Maximum Pb in turmeric: polished bulbs had highest concentrations across all districts. Loose powder max 690 µg/g (producing districts) to 1,152 µg/g (Dhaka/Munshiganj). Packaged powdered turmeric exceeded national limit in 2 samples.
Yellow pigment samples (n=7 from polishing mills, 6 from color merchants): median Pb 20,024 µg/g, maximum 115,500 µg/g. Five of 7 polishing-mill pigments were PbCrO4-based (2-10% Pb by weight). Pb:Cr molar ratio average 1.26 for high-Pb samples.
Polishing dust: median 25.4 µg/g, maximum 21,166 µg/g. Floor dust: median 20.5 µg/g, maximum 66,060 µg/g.
Soil around polishing mills: maximum 4,257 µg/g Pb at 3m distance; 32% of soil samples exceeded California residential soil Pb limit of 80 µg/g.
Physical evidence of yellow pigment adulteration found in 7 of 9 major turmeric-producing districts. 23 of 43 machine-polishers and all 3 manual polishers showed physical evidence.
Interviews (n=152): practice began more than 30 years ago (1970-1990). Catalyzed by 1988 flooding that damaged turmeric crop quality. None of the polishers were aware that the yellow pigments contained Pb.
Methods (brief)
Analytical: ICP-MS (Thermo Scientific XSERIES 2, Stanford Environmental Measurements Facility) for turmeric samples; XRF (Spectro XEPOS HE) for pigments, dust, soil. LOD: ICP-MS not explicitly stated; XRF adequate for high-concentration pigment samples. Microwave digestion in HNO3. Repeat measurements reproducible within 6%.
Qualitative: snowball sampling, 2-3 individuals per district across production/distribution chain. Semi-structured interviews in Bengali, translated, coded inductively and deductively.
Implications
Certification: this study documents the mechanism of contamination in detail sufficient to design supply-chain testing protocols. Polishing is the critical control point. XRF screening at polishing mills or at import is the recommended intervention.
Courses: the qualitative data (Table 2 interview quotes) is exceptional teaching material. Polishers do not know the pigments contain Pb. Consumers cannot detect adulteration by visual inspection. Inspectors lack resources. The market failure is multi-layered.
App: turmeric sourced from Bangladesh, particularly from Dhaka wholesale markets and producing districts in the North and Northwest, carries the highest adulteration risk.
Wiki pages updated on ingest
Update history
The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.
| Commit | Date | Change | Description |
|---|---|---|---|
| a8052bb | 2026-08-09 | major | 6 sections added; narrative text revised |