Toxic substances are materials that can cause harm to living organisms, including humans, animals, and plants. These substances can be found in various forms, such as chemicals, heavy metals, and biological agents. Exposure to toxic substances can occur through inhalation, ingestion, or skin contact, leading to health issues ranging from mild irritation to severe illness or even death. Common examples of toxic substances include lead, mercury, and certain pesticides. These materials can enter the environment through industrial processes, waste disposal, or agricultural practices. Understanding the risks associated with toxic substances is essential for protecting public health and the environment.