A popular spice used in Asian cooking has been blamed for rising lead levels across the continent's southeast.
Turmeric laced with lead chromate - a yellow pigment - has been linked to elevated blood lead levels among Bangladeshis in a new study at Stanford University.
And there are fears contaminated turmeric is being traded worldwide.
"People are unknowingly consuming something that could cause major health issues," said lead author Jenna Forsyth.
"We know adulterated turmeric is a source of lead exposure, and we have to do something about it."
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Bangladesh is one of the top sources in the world for turmeric, but many spice manufacturers are unaware of the dangers lead poses, the researchers say.
They detected the exact same type of lead that's used to colour turmeric in locals' bloodstreams, confirming the link previous research had only hinted at.
Stanford researchers said locals told them the adding of lead chromate dated back to the 1980s, when a "massive flood left turmeric crops wet and relatively dull in colour".
"Demand for bright yellow curry led turmeric processors to add lead chromate - an industrial yellow pigment commonly used to color toys and furniture - to their product. The practice continued as a cheap, fast way to produce a desirable color."
The problem is there is no safe level of lead when it comes to consumption.
"It's a neurotoxin in its totality," said senior author Stephen Luby. "We cannot console ourselves proposing that if the contamination were down to such and such level, it would have been safe."
Lead consumption interferes with children's brain development and increases the risk of brain and heart disease in adults.
A number of turmeric brands have been recalled in Western countries in recent years after authorities detected high levels of lead. While these robust systems protect consumers outside of southeast Asia, the researchers warn some could be slipping through the net.
"The current system of periodic food safety checks may catch only a fraction of the adulterated turmeric being traded worldwide," the researchers said.
The research was published in journal Environmental Science & Technology.
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