Toxicology

Toxicology is the science concerned with the adverse effects of chemical substances on living organisms, including the detection, understanding, and prediction of harm. It analyzes how dose, route of exposure, and duration influence outcomes, and it integrates toxicokinetics (absorption, distribution, metabolism, excretion) with toxicodynamics (mechanisms of action).

Subfields address different contexts: chemical toxicology, environmental toxicology, forensic toxicology, clinical toxicology, occupational toxicology, and ecotoxicology, as well as regulatory toxicology that informs safety standards and policy. Methods combine in vivo animal studies, in vitro cellular assays, and analytical chemistry, with increasing use of biomarkers, high-throughput screening, and computational (in silico) models. The 3Rs—replacement, reduction, refinement—guide ethical methods and the development of alternatives.

Risk assessment comprises hazard identification, dose–response assessment, exposure assessment, and risk characterization to estimate the likelihood and severity of adverse effects and to guide regulatory decisions and product safety.

Historically, toxicology arose from Paracelsus’ dictum that the dose makes the poison and evolved through pharmacology, industrial hygiene, and modern safety testing. Traditional measures like LD50 have given way to more comprehensive endpoints, such as carcinogenicity, teratogenicity, mutagenicity, and organ-specific toxicity.

Applications span drug development, environmental protection, occupational health, consumer safety, and poison control. Common exposure routes include inhalation, ingestion, and dermal contact. Understanding toxicology supports public health by informing monitoring, regulation, and risk communication.