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Stanford researcher finds lead in South Asian turmeric and jumpstarts a bigger movement

Researchers part of the King Center initiative focused on lead poisoning have shown that turmeric is a key contributor to heightened blood-lead levels.
spice market
Spices on display in a market | Credit: Nazlican Boztas

Jenna Forsyth had a hunch. Pregnant women in rural Bangladesh were showing higher-than-expected levels of lead in their blood—and nobody knew why. Lead, a devastating neurotoxin that is especially harmful to children’s cognitive development, costs the country an estimated $6 billion a year in lost GDP. 

Likely culprits for lead contamination included rice, pesticides, food cans, and even clay fragments that expectant mothers chew on to alleviate nausea. Forsyth had another idea, based on a small study of Bangladeshi children that she had read: turmeric, the yellow-hued spice found in curries and other South Asian foods and prized worldwide as a health supplement.

Forsyth, then a Stanford doctoral student in environment and resources, thought there might be something to the turmeric theory. With the encouragement of Stephen Luby, her adviser and a Stanford professor of medicine, she ran with her suspicion—even as lead experts repeatedly voiced their doubts. They pulled together a team of Stanford experts and, with financial support from the Stanford King Center on Global Development, set out to solve the problem of lead exposure in rural Bangladesh.

Five years later, Forsyth’s doggedness is paying off.

jenna forsyth
Jenna Forsyth

In a pair of peer-reviewed studies, published last fall in Environmental Research and Environmental Science & Technology, Forsyth and her collaborators show that turmeric is a key contributor to lead levels in the blood of rural Bangladeshis and that the problem arises when some processors, unaware of the health risks, add a color-enhancing industrial pigment to make their product more attractive to buyers. Their findings followed earlier research confirming that lead levels in pregnant women in Bangladesh were elevated.

As news of Stanford’s discoveries spread, the response was swift. Bangladesh’s prime minister vowed to control imports of the added pigment, lead chromate. The country’s food safety officials began issuing fines to wholesalers and distributed 50,000 posters that were designed with the Stanford team’s input and sought to educate the public about lead risk in turmeric.

Outside of Bangladesh, Forsyth connected with public health representatives from around the world who had evidence that adulterated spices were responsible for higher-than-expected lead levels among South and Central Asians living at home and abroad. Anxious consumers contacted Forsyth directly and flocked to a Reddit discussion. Small U.S. spice purveyors sought her input on ways to make the turmeric supply chain more transparent.

Now there are early signs that heightened public awareness—and government action—about turmeric are having an impact at points of sale. Turmeric samples collected by research partners in Bangladesh before her studies became public had found that nearly 50 percent contained higher than expected levels of lead—16 percent of those had exceedingly high levels. A few months later, in early 2020, fresh turmeric samples tested for lead showed a precipitous drop: only 5 percent contained above-normal amount of lead and, of those, 1 percent had concentrations that were off the charts.

Forsyth cautions that the sample results are preliminary and that plans for additional testing are on hold due to the COVID-19 pandemic. It is possible, she says, that the decrease will not hold up over time. Still, she is optimistic that awareness will lead to changes that are meaningful and permanent.

“The problem of adulterated spices, especially in lower and middle-income countries, has been going on for so long,” says Forsyth, who is now a postdoctoral fellow at Stanford’s Woods Institute for the Environment. “Now we have proof that links lead in spices to lead levels in humans. People can’t sweep this under the rug anymore.”

An ‘enormously bad actor’

The real-world impacts may just be beginning. Forsyth is now part of an expanded initiative at the King Center to design market innovations to reduce lead exposure more broadly in Bangladesh and possibly beyond. This includes not only turmeric, but also another major source of poisoning: recycled lead acid batteries, which are increasingly used to power rickshaws and solar panels in Bangladesh and are cheaper alternatives to brand new ones. Much of the country’s battery recycling happens informally and under incredibly unsafe conditions.

When Forsyth and her team sampled 70 children living near an abandoned recycled battery site, every one of them had exorbitant levels of lead in their blood, according to Forsyth. “We don’t have evidence of any battery recyclers operating safely in Bangladesh,” she says. Exposure can be short-lived and still have dangerous, long-term effects.

The lead initiative has attracted top Stanford scholars from across multiple disciplines—including medicine, environmental science, engineering, business, law, and design thinking—as well as officials from leading NGOs, government officials, and other researchers in Bangladesh. With support from the King Center, the team is working on, among other solutions, easier ways to detect adulterated turmeric and cheaper alternatives to processing the spice so it better retains its bright yellow color.

The problem they are trying to address is global, but it is most damaging to lower income countries, where 90 percent of children with elevated blood levels live. The metal irreversibly damages the brain and permanently lowers IQ. It also increases the risk of heart disease and strokes and has been associated with depression, panic disorders, and difficulty with mood regulation.

“Lead is just an enormously bad actor,” says Luby, who is a faculty affiliate at the King Center. The global economy, he says, loses an estimated $1 trillion a year from lead’s cognitive impacts alone.

Practical solutions, global impacts

In Bangladesh, lead-contaminated turmeric appeared after a 1988 flood damaged crops and led to a sustained increase in imports from India. To compete, Bangladeshi processors began adding lead chromate, which cheap and easy to do and ensured a brilliant yellow product in years with heavy rains.

“The color of turmeric powder is not necessarily indicative of its quality, but consumers don’t always know this,” says Forsyth. With help from Scott Fendorf, a Stanford professor and a King Center faculty affiliate, and his researchers at the Department of Earth System Science, she was able to match blood lead levels to turmeric using isotope analysis.

One solution to consumers’ misconception, then, is to educate them about turmeric quality and the dangers of lead chromate. A team led by Stanford Professor of Bioengineering Manu Prakash is also developing low-cost technology that relies on density separation and centrifugation to identify lead chromate, which is invisible to the human eye. Using just a handheld device, health officials could better spot adulterated turmeric across the supply chain.

But a fix also requires helping suppliers through incentive-compatible approaches. Jeff Wood, a Stanford lecturer in mechanical engineering, will soon be working with undergraduate students to adapt a low-cost root dehydrator that previous students developed to improve large-scale chili pepper processing in India. Imagine mini solar greenhouses, but with advanced features including water thermal storage.

Wood says that, if successful, the concept would preserve turmeric’s color and quality. Processing would also take less time and be less labor-intensive. “We think we can improve turmeric processing in ways that are culturally sensitive, efficient, and inexpensive,” says Wood, who teaches a course that allows undergraduate seniors to work on real-world problems.

Erica Plambeck, a professor at the Graduate School of Business, is pulling together a team of students to develop supply-chain innovations both for turmeric processing and battery recycling. Among other steps, they are working to educate rickshaw owners and other users about the benefits of longer-lasting, higher-quality batteries. They also see an opportunity to raise awareness within Bangladesh’s powerful garment manufacturing industry about the impact that lead poisoning can have on workers, through turmeric consumption or proximity to battery recycling centers.

If successful, the lead initiative’s multi-pronged approach could extend across South Asia and to other developing regions experiencing especially high concentrations of lead contamination. Since 2011, there have been nine turmeric recalls worldwide targeting spice exports from Bangladesh and India. Batteries of all kinds, meanwhile, account for 80 percent of lead used globally.

“We are confident,” says Luby, “that we can solve these problems through incentive-compatible approaches that benefit not only Bangladesh, but also the world.”