Which of these statements about signal words is TRUE?

The statement that signal words signify relative acute toxicity levels to humans is accurate because signal words are specifically designed to communicate the potential hazards associated with a pesticide. These words, such as "Caution," "Warning," and "Danger," help users and handlers to quickly assess the degree of toxicity and the appropriate safety measures to take. This classification of toxicity is especially important as it provides essential information about how dangerous a pesticide could be if misused or if exposure occurs, thereby helping to protect public health and the environment.

Signal words are not related to the effectiveness of a pesticide; their primary function is to convey toxicity information. Additionally, while signal words are typically found on hazardous pesticides, they are not exclusive to this group. Some pesticides might not have signal words depending on their toxicity profile. Finally, while signal words are commonly required for most pesticide labeling, there are exceptions based on specific regulatory frameworks and pesticide formulations, meaning that they are not mandatory for all pesticides universally.