How are signal words for toxicity assigned?

• A. Based on the lowest measured toxicity among routes
• B. Based on the highest measured toxicity among a single route
• C. Based on the highest measured toxicity, whether oral, dermal or inhalation
• D. Based on exposure duration only

Answer: (C)

Signal words on a pesticide label reflect the worst acute toxicity outcome among the potential routes of exposure. To assign them, you compare oral, dermal, and inhalation toxicity data. The label uses the signal word corresponding to the most severe result seen across those routes. In other words, you take the highest level of toxicity measured (the most hazardous route) and assign the label’s warning accordingly. This approach ensures the warning matches the greatest risk a person might face, whether from swallowing, skin contact, or inhaling the product. Exposure duration doesn’t determine the signal word. If one route is more toxic than the others, that route drives the signal word; if all routes show only low toxicity, a milder signal word is used.