What symbol is used on placards to indicate a toxic substance?

The skull and crossbones symbol is universally recognized as an indicator of toxicity and is specifically used on placards to signal that a substance is toxic. This symbolism effectively communicates the hazard present, as it is a clear and iconic representation of danger related to poisonous materials. It alerts individuals who may come into contact with such substances, emphasizing the need for caution and protective measures when handling or encountering them. The use of this symbol is backed by international regulations and guidelines that govern the transportation and handling of hazardous materials, reinforcing its importance and recognition in addressing toxic hazards.