Lead in turmeric threatens public health in Bangladesh

Turmeric is widely used in Bangladeshi cooking, but a new study suggests adulteration of the spice with lead is common and a major public health threat.

The researchers – whose work is published in the journal Environmental Research – found evidence of turmeric adulteration in seven of nine districts that produce the spice, with some samples exceeding the national limit for lead by up to 500 times.

The driver for the adulteration seems to be a desire by Bangladeshi consumers for bright yellow turmeric, which ‘polishers’ – who process the spice into its final form before it goes on sale – achieve by adding lead chromate to dried turmeric root.

“Farmers stated that merchants are able to sell otherwise poor-quality roots and increase their profits by asking polishers to adulterate with yellow pigments,” write the scientists, headed by Jenna Forsyth from Stanford University in the US.

The polishers are tough to be unaware of the toxic effects of lead chromate, they add. The pigment is associated with neurotoxic effects, particular in young people whose brains are still developing. Lead poisoning has been linked to brain damage, mental retardation, behavioural problems, nerve damage, and possibly Alzheimer’s disease, Parkinson’s disease, and schizophrenia.

The scientists initiated the study to explore whether some environmental issue such as soil contamination or lead piping was behind data showing high levels of lead in the blood of people in some areas Bangladesh, but are now sure that turmeric adulteration is playing a major role.

“People are unknowingly consuming something that could cause major health issues,” said Forsyth, a postdoctoral scholar at the Stanford Woods Institute for the Environment. “We know adulterated turmeric is a source of lead exposure, and we have to do something about it.”

Spices are among the top five most commonly adulterated food types because they are expensive commodities that are processed prior to sale, according to the scientists.

The investigation relied on samples of turmeric, pigments, dust, and soil as well as interviews with people who produce, sell, distribute and consume the spice. The sampling was carried out in nine turmeric-producing districts as well as two control districts with little production.

Another recent study, published in Environmental Science & Technology, was able to use lead isotopes to fingerprint lead chromate-adulterated turmeric as the most likely culprit by matching it to isotopes in people’s blood.

The researchers now plan to focus on shifting consumer behaviours away from eating contaminated turmeric and reducing incentives for the practice, according to a Stanford University press release.

They recommend alternative and more effective drying technologies for turmeric processing, and also say import inspectors around the world should screen turmeric with X-ray devices that can detect lead and other chemicals.

Image credit: stevepb via Pixabay