Toxic substances are chemicals or compounds that can cause harm to living organisms, including humans, animals, and plants, when they are absorbed or ingested in sufficient quantities. These substances can lead to various adverse effects, ranging from mild irritation to severe health problems, including poisoning, organ damage, or even death. Toxic substances can be found in many forms, including heavy metals, pesticides, industrial chemicals, and certain natural compounds. Their impact often depends on factors such as dose, exposure duration, and individual susceptibility.