toxic

Toxic is an adjective describing something capable of causing harm to living organisms. The word derives from Latin toxicus, via Old French toxique, itself rooted in Greek toxikon, meaning poison for an arrow.

In toxicology, the science that studies adverse effects of substances, toxicity is characterized by the relationship between dose and harm. The maxim "the dose makes the poison" expresses that a substance can be harmless at low exposure but harmful at higher exposure. Toxicity depends on dose, duration of exposure, route (inhalation, ingestion, dermal contact), and the organism’s genetics and health. Toxic effects can be acute (short-term) or chronic (long-term) and may target particular organs or systems. Substances may also be toxic to humans, animals, or ecosystems, and symptoms range from irritation to organ damage or death. Substances may also be toxic only to certain species or individuals.

Common toxic substances include heavy metals such as lead and mercury, organic solvents, pesticides, and natural toxins produced by organisms (for example, botulinum toxin). Some substances are classified as toxic or highly toxic by regulatory bodies, with hazard statements that reflect potential risk at certain exposure levels. Toxicity can be chemical, biological (toxins produced by organisms), or environmental, including pollutants that disrupt ecosystems.

Assessment and regulation: toxicology uses experimental data and observational studies to identify hazards, estimate dose–response relationships, and characterize risk. Laboratory tests may include in vitro assays, animal studies, and computational models. Regulatory frameworks use parameters like LD50 or LC50, along with exposure limits, to set safety standards and permissible exposure limits.

In popular usage, toxic describes people, relationships, or environments perceived as harmful, abusive, or dangerous. While figurative, such use reflects genuine concerns about ongoing exposure to harmful influences.