Addition of Lead Chromate to Turmeric Represents Health Risk in Bangladesh

Reviewed: Forsyth JE, Weaver KL, Maher K, Saiful Islam M, Raqib R, Rahman M, Fendorf S, Luby SP. Sources of blood lead exposure in rural Bangladesh. Environ Sci Technol. 2019;53(19):11429-11436.

Forsyth JE, Nurunnahar S, Sahiful Islam S, Baker M, Yeasmin D, Saiful Islam M, Rahman M, Fendorf S, Ardoin NM, Winch PJ, Luby SP. Turmeric means “yellow” in Bengali: Lead chromate pigments added to turmeric threaten public health across Bangaldesh. Environ Res. 2019;179:108722.

Keywords: Adulteration, Curcuma longa, ICP-MS, lead chromate

Studies on blood lead concentrations show that 54-78% of children in Bangladesh have elevated levels (>5-10 µg/dL),^1,2 compared to 3% in the United States.³ Among the possible sources of lead intake is turmeric (Curcuma longa, Zingiberaceae) based on the use of lead chromate as a coloring agent added during polishing of turmeric roots. Lead chromate and other colorants are used to make poor-quality roots visually more appealing. Such artificially colored roots can be sold at a higher price driven by consumer preferences for colorful yellow curries.

Blood samples were taken from 430 pregnant women and lead concentrations were determined by inductive coupled plasma — mass spectrometry (ICP–MS). A subset of the samples was further subjected to lead (Pb) isotope analysis in order to determine the origin of the lead. Blood lead isotope composition was compared with the isotope composition of lead from ash, clay, food can solder, and turmeric, all of which are known as possible sources of exposure to lead. Ash and clay are ingested by women practicing geophagy, the habit of eating various types of soil materials. Clay samples consisted primarily of a type of tablet specifically formulated for pregnant women, which is consumed like a lozenge.⁴

Samples of turmeric (41) sold as loose or packaged powder, or whole roots were obtained from four major retailer markets in Bangladesh. Some of the turmeric was knowingly processed using pigments. In addition, three samples of the yellow pigment used to polish the turmeric were collected. Lead content in these 41 turmeric samples ranged from 0.1–1152 µg/g, with pigment-processed samples having higher lead concentrations than regular turmeric.

Using a scatter plot showing the ²⁰⁷Pb/²⁰⁴Pb ratio as a function of the ²⁰⁶Pb/²⁰⁴Pb ratio, the ash, clay, can solder, and turmeric samples could be distinguished. Blood samples clustered with the turmeric materials, suggesting that the elevated blood concentrations in pregnant women are due to ingestion of lead-contaminated turmeric.⁴

In a subsequent paper,⁵ the authors investigated the reasons for polishing the turmeric roots with lead chromate. One of the reasons is to “hide” imperfections of the root, such as a partly rotten surface, using the colorants. Another reason is the importance of the color as part of the cooking tradition. According to the authors, “yellow curries and sauces made with turmeric were described as integral to Bangladeshi cuisine. Serving dull-colored foods would not only reflect poorly on the cook's abilities, but would also go against cultural norms.”

Comment: The two papers paint a disturbing picture of the turmeric trade in Bangladesh. Ingestion of lead is correlated with a number of health risks, in particular damage to the brain. Awareness of the pigment-processing is low in rural areas, and many people cannot afford the branded products, which are generally devoid of yellow colorants. The authors suggest increased financial resources for food inspectors, and more efforts to instruct the population in Bangladesh about the risks of ingesting polished turmeric. Also discussed is the use of an affordable, non-toxic yellow pigment as an alternative to lead chromate.

The extent of lead-contaminated turmeric being sold in other countries is not well-known. Analysis of lead in 32 turmeric samples purchased from mainstream grocery stores, specialty stores, and ethnic markets in the Boston area showed that two samples had excessive levels (34.78 and 99.50 µg/g) of lead,⁶ and in 2016, the US FDA issues an import alert on turmeric, allowing detention of shipments from certain importers, mainly from Bangladesh and India. Since testing for expected contaminants is required as part of the dietary supplement cGMP regulations, it is expected that manufacturers of turmeric dietary supplements will perform the necessary testing to prevent lead-contaminated turmeric to reach the market.

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