Which natural ingredient led to the largest recall of herbal supplements in 2015 after it was found to contain dangerous levels of a neurotoxin?

In the natural products industry, product recalls can sometimes stem from unexpected interactions with nature itself. This trivia question explores one of the most significant natural product recalls in recent history, where a seemingly harmless ingredient led to widespread health concerns. Test your knowledge about how the natural world sometimes reminds us of its power even in carefully formulated products.

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Blue-green algae (Spirulina) contaminated with microcystin
Echinacea root harvested from drought-affected regions
Turmeric powder with excessive natural lead content
Ginseng extract containing naturally occurring arsenic compounds