[rolandog]

In addition to lead chromate, in some instances metanil yellow is also used. It can also be potentially neurotoxic and hepatotoxic [1].

I found a spice producer's site that contained some instructions of how to determine if it's adulterated [2]:

Metanil Test: To test for the presence of metanil yellow, place a pinch of turmeric powder in a test tube, add a few drops of strong hydrochloric acid, and violently shake it.

If the solution becomes pink, this indicates the existence of metanil. Consuming turmeric powder that is high in metanil will make you feel nauseated, create stomach problems, and cause food poisoning.

Lead Chromate Test: To test the presence of lead chromate in turmeric powder, mix a teaspoon of turmeric powder with water. It will instantly leach streaks of water-soluble colour into the solution, indicating the presence of lead chromate.

[1]: https://en.wikipedia.org/wiki/Metanil_Yellow

[2]: https://www.vasantmasala.com/blog/how-to-check-adulteration-...