I'm a little surprised at the initial confusion about the source of lead, or perhaps it's the way the article has been written. As someone who grew up in India, our school textbooks in the 90s had a list of common food adulterants, and turmeric adulteration with lead chromate was common knowledge to middle schoolers. I recall the curriculum included how to detect adulteration with simple at home tests. After turmeric, the next suspect probably would be yellow lentils.

EDIT: actually the next suspect should be red chillis, adulterated with lead oxide.

On an aside, food adulteration used to be such a common social menace in India in the 70s & 80s, such that it was a common theme in the backdrop of Bollywood films, with the hero taking on local mafia bosses who also dabble in food adulteration. India did a mediocre job controlling the rampant food adulteration, with the last major case I recall being an outbreak of Epidemic Dropsy in 1998 due to contamination of mustard oil. There's been cases every once in a while, though I suspect in those cases it is inadvertent contamination with Argemone plants growing in mustard fields.