What are sources of thallium?

• A. Water contamination
• B. Rodenticide and insecticides (banned in US) - very toxic and cumulative
• C. Cosmetics
• D. Food coloring

Answer: (B)

Thallium exposure is classically tied to thallium-containing pesticides, especially rodenticides and insecticides. These formulations used thallium salts because they are highly toxic to pests, but the same properties make them dangerous to humans and animals. Thallium behaves as a cumulative toxin—it’s absorbed readily and tends to persist in tissues, so repeated or prolonged exposure builds up in the body and leads to lasting effects. In the United States, these pesticides have been banned due to their high toxicity, which is why this source is highlighted in questions about thallium exposure. While water contamination, cosmetics, or historic food-coloring uses can contribute to exposure in some contexts, the most classic and well-recognized source in toxicology discussions is thallium in rodenticides and insecticides.