Forsyth et al. 2024 — Turmeric lead chromate adulteration across South Asia
The first systematic assessment of lead chromate adulteration in turmeric across four South Asian countries representing more than 80% of global turmeric production and 1.7 billion people. Turmeric samples were collected from 23 major cities in India, Pakistan, Sri Lanka, and Nepal between December 2020 and March 2021, analyzed by XRF and ICP-MS for lead and chromium concentrations, with Pb:Cr molar ratios used to distinguish lead chromate adulteration from environmental contamination.
Key numbers
Total samples: 356 (180 dried turmeric roots, 176 turmeric powder).
14% of samples (n=51) had detectable Pb above 2 µg/g (LOD). 7% (n=24) exceeded the Indian standard of 10 µg/g.
Pb exceeded 10 µg/g in seven cities: Patna (max 2,274 µg/g), Guwahati (max 127 µg/g), Chennai (max 11 µg/g) in India; Karachi (max 2,935 µg/g), Islamabad (max 22 µg/g), Peshawar (max 1,051 µg/g) in Pakistan; Kathmandu (max 82 µg/g) in Nepal.
Lead concentrations exceeded 1,000 µg/g in Patna (Bihar, India) and Karachi and Peshawar (Pakistan).
Samples with Pb >18 µg/g had Pb:Cr molar ratios near 1:1 (average 0.92, SD 0.30), confirming lead chromate (PbCrO4) as the source. Samples with Pb ≤15 µg/g had lower Pb:Cr ratios (average 0.44, SD 0.30), consistent with natural environmental contamination.
By turmeric type (Table 2): polished roots (n=143) max 2,935 µg/g, 9% above 100 µg/g; loose powder (n=90) max 1,665 µg/g, 4% above 100 µg/g; unpolished roots (n=37) max 18 µg/g.
Modeled child BLL increases (Table 3): Patna (Bihar) children estimated BLL increase 345-790 µg/L from turmeric alone. Karachi: 173-396 µg/L. Peshawar: 55-125 µg/L. These exceed the CDC Blood Lead Reference Value of 35 µg/L by 10-fold or more.
Curcumin content averaged 1.45% (SD 0.67), below the 2% minimum set by the Food Safety Standards Authority of India, suggesting the low curcumin content (and associated pale color) incentivizes adulteration.
Methods (brief)
Analytical: XRF (Olympus Delta DCC-4000, LOD 2 µg/g for Pb in powdered spices) for all samples from India, Nepal, Sri Lanka. ICP-MS (Eurofins, Delhi, LOD 0.01 µg/g) for subset above XRF LOD. Pakistan samples analyzed by ICP-OES (LOD 0.5 µg/g) at National Textiles University’s accredited laboratory because samples could not be shipped to India. Pb:Cr molar ratio calculated from molecular masses (Pb 207.2, Cr 51.9961 g/mol); ratio near 1:1 indicates PbCrO4.
Sampling: mystery shopping protocol at largest wholesale and largest retail bazaar in each city. At least 50g of each unique turmeric type from at least two vendors. Loose powder, packaged powder, polished roots, and unpolished roots collected.
BLL modeling: two approaches (linear calculation from Glasgow Duplicate Diet Study + AALM v3.0 EPA model), assuming 42.9% bioaccesibility of Pb in turmeric, household consumption data from national surveys.
Implications
Certification: turmeric and turmeric-containing products require Pb screening at ingredient intake. Polished roots and loose powder are highest risk. The 500× exceedance of regulatory limits in some cities means that even trace inclusion of adulterated turmeric in a formulation can push finished-product Pb above certification thresholds.
Courses: demonstrates non-agricultural contamination mechanism (deliberate adulteration with industrial pigment PbCrO4) distinct from soil-uptake or bioaccumulation pathways. The Pb:Cr molar ratio method is a teachable diagnostic for distinguishing adulteration from environmental contamination.
App: turmeric as an ingredient carries a sourcing-dependent Pb risk that cannot be resolved by typical agricultural mitigation. Origin region and supplier specification are the primary levers.