Poisons

Poison refers to any substance that can cause injury, illness, or death when introduced into the body or when environmental exposure exceeds safe levels. Toxicology is the science that studies how poisons act, how exposure occurs, and how poisoning can be treated. A foundational idea is the dose–response relationship: the severity of harm depends on the amount of substance and the route of exposure, encapsulated in the saying that “the dose makes the poison.”

Poisons arise from natural sources such as plants, animals, and minerals, or from synthetic sources including industrial chemicals and pharmaceuticals. They can be organic or inorganic and may act through a variety of mechanisms, such as enzyme inhibition, disruption of cellular respiration, interference with signaling pathways, or oxidative damage. Common routes of exposure include ingestion, inhalation, dermal contact, and injection. Some toxic substances can accumulate in the body and cause delayed or chronic effects, especially heavy metals and persistent organic pollutants.

Well-known examples include cyanide, which inhibits cellular respiration; carbon monoxide, which reduces oxygen delivery; arsenic, which disrupts energy metabolism; lead and mercury, which affect nervous system function; and botulinum toxin, which blocks nerve signaling. Everyday materials, pharmaceuticals, pesticides, and industrial chemicals can be poisonous in sufficient doses or for sensitive individuals.

Prevention focuses on safe storage and handling, clear labeling, and adherence to safety guidelines. Poison control centers provide guidance during exposure incidents. Treatment depends on the substance and exposure level and may involve removal of the poison, activated charcoal in some cases, supportive care, and, when available, specific antidotes.