Lead polished turmeric widespread, blameable for raised blood-lead level

Muhammad Zahir Hassan Nabil

Lead chromate, a toxic, industrial pigment, is being added to turmeric to enhance its brightness, suggests new evidence from an icddr,b study with collaborators from Stanford university.

Yellow, lead chromate polished turmeric (left); unpolished turmeric (right) Photo: Musa Baker / icddr,b

While turmeric is an essential spice in South Asian cuisine, lead contamination resulting from lead chromate-polished dazzling yellow turmeric inflicts irreversible damage to the brain. It can thereby have a permanent impact on IQ or intelligence level of the consumers, notes the study conducted in nine major turmeric producing districts in Bangladesh.

“Dhaka and Munshiganj topped the chart for the highest level of lead-adulterated turmeric, with lead concentration at 1,152 μg per gram of turmeric,” mentions Professor Stephen P. Luby, professor of medicine at Stanford University and senior author of the study published in Environmental Research.

Lead levels reported in this new study have exceeded the countrywide reported limits by nearly 500 times, which is also 2 to 10 times higher than the maximum concentrations reported in other similar studies.

“Unlike other metals, there is no safe consumption limit for lead; even small doses are toxic to the brain,” clarifies Prof Luby. We cannot console ourselves proposing that if the contamination were down to such and such level, it would have been safe, he adds.

There is no purpose for lead in the body. It only causes harm. It can specifically impact children’s developing brains; reducing intelligence and reducing earning potential throughout one’s life. It also causes many diseases in adults including heart disease.

Lead consumption can permanently impair the brain and lower IQ. Photo: GMB Akash / icddr,b

Lead chromate is commonly applied during the “polishing” process that removes the skin from turmeric roots, especially to color low-quality turmeric to make it appear to be of high quality.  These findings are based on over 500 samples of turmeric, pigments, dust, and soil and over 150 interviews across the turmeric supply chain, reports Dr Mahbubur Rahman, co-author of the study and project coordinator at icddr,b Environmental Interventions Unit. Soil samples from polishing mills contained a maximum of 4,257 μg lead per gram of soil.

Therefore, to avoid being cheated into buying low-quality adulterated turmeric, we encourage consumers and businesses to buy only unpolished root, with its protective skin on. Consumers could grind unpolished root at home or watch their turmeric-provider grind it.  Some packaged turmeric powder contains lead, unbeknownst to its manufacturer, because the manufacturer is buying polished root turmeric. 

Customers have no idea what damage lead-polished turmeric can cause. Photo: GMB Akash / icddr,b

“We encourage consumers to purchase unpolished, dried turmeric roots instead of turmeric powder. In choosing the roots, select those without obvious yellow color in order to avoid the potential lifelong damage from lead chromate,” comments Ms Jenna Forsyth, first author of the study and a doctoral researcher at Emmett Interdisciplinary Program in Environment and Resources at Stanford University.

According to reports from turmeric wholesalers, such practice has been in place for more than 30 years, sometime between the 1970s and the 1990s. Dhaka’s major wholesale market, the largest hub for this spice, was found to be selling most of the adulterated dried turmeric roots. This market would be a good place for the government and other food safety organizations to regularly monitor for lead-adulterated turmeric to prevent its sale and consumption.

Customers’ demand for dazzling yellow turmeric to brighten up curries is one of the main reasons behind this adulteration, notes the study. The authors suggest immediate intervention around this matter, especially conveying the harmful effects of lead adulteration to everyone along the supply-and-demand chain, especially the customers and wholesalers.

If customers and businesses clearly understand the devastating health impact of lead-chromate-polished turmeric so buy only unpolished turmeric roots, that would eliminate the need for polishing with lead chromate.


Elevated Blood Lead Level in Pregnant Women: Turmeric to blame?

Last July, the Stanford researchers and icddr,b researchers have raised the alarm about presence of higher level of lead blood samples from pregnant women in rural Bangladesh.

Elevated blood lead level during pregnancy is a serious public health concern. Photo: Shehzad Noorani / icddr,b

New evidence of persistent turmeric adulteration, coupled with findings from a second study conducted by the same team convinced the researchers that adulterated turmeric is the main cause of higher lead levels in pregnant women’s blood who live in rural Bangladesh.

Published in Environmental Science and Technology, the second study used delicate laboratory techniques to measure ratios of lead isotopes – variants of the same element, in order to track fingerprints of elevated blood lead level and environmental source. Although lead as an element may be found in different sources, tracking one of its unique isotopes can reveal a precise signature that the researchers analysed to find the most likely suspected source.

“Lead isotopes from turmeric matched most precisely with the blood lead specimens,” says Ms Forsyth.

Graphic Source: Authors / Study

Earlier the researchers highlighted that elevated blood lead level during pregnancy threatens mothers and their developing foetus as well as the newborn. Lead deposits in the mothers’ bodies are released in blood and subsequently into breast milk, according to CDC. It interferes with children’s brain development and increases the risk of heart and brain disease in adults.

With the recent confirmation, the researchers suggest expanding the investigation to nearby South Asian regions where turmeric is consumed regularly.

Support for these studies came from Stanford University’s Woods Institute, Stanford’s Center for South Asia, Stanford’s Emmett Interdisciplinary Program in Environment and Resources, the United States Agency for International Development (USAID), and the Bill and Melinda Gates Foundation (Grant OPPGD759 to the University of California, Berkeley).