Toxin
Overview
Toxin (독소; 毒素) is a collective term for toxic substances produced by living organisms that exert harmful effects on other organisms. In the narrow sense, it refers to toxins produced by bacteria, fungi, plants, animals, and other organisms; in modern usage, however, it is used as a broad concept that also includes harmful substances artificially accumulated in the environment, such as heavy metals, pesticides, microplastics, and endocrine disruptors. The human body has a detoxification system that metabolizes and excretes toxins, centered on the liver, kidneys, and lymphatic system, but chronic excessive exposure causes various diseases.
Main Content
Definition and Etymology
The term "toxin" was established in 1888 when German bacteriologist Friedrich Loeffler described harmful substances produced by the diphtheria bacterium. Its etymology is the Greek "toxikon" (poison smeared on arrows). Toxins are classified according to chemical structure and mechanism of action, and are broadly divided into protein toxins and non-protein toxins.
Classification of Biological Toxins
- Bacterial toxins: Exotoxins and endotoxins. Exotoxins are proteins secreted by Gram-positive bacteria, with tetanus, diphtheria, and botulinum toxins as representative examples, and are fatal even in extremely small amounts. Endotoxins are lipopolysaccharides (LPS) in the outer membrane of Gram-negative bacteria and, when excessively released, cause sepsis and systemic inflammation.
- Fungal toxins (mycotoxins): Aflatoxin, ochratoxin, and others are produced by molds growing on grains, and have strong hepatotoxicity and carcinogenicity.
- Plant toxins: Ricin (castor bean), solanine (potato sprouts), cyanogenic compounds (apricot kernels, cassava), etc.
- Animal toxins: Venoms of snakes, scorpions, and spiders; tetrodotoxin in pufferfish; toxins of jellyfish and shellfish; ecologically, these evolved as means of defense against predators and hunting.
Environmental Toxins
Since industrialization, exposure to artificial toxins has increased rapidly. Representative examples include heavy metals (lead, mercury, cadmium, arsenic), pesticide residues, dioxins, polychlorinated biphenyls (PCBs), microplastics, and endocrine disruptors (bisphenol A, phthalates). These substances exhibit the characteristic of increasing in concentration toward higher levels of the food chain through bioaccumulation and biomagnification.
The Body's Detoxification Mechanisms
The liver converts fat-soluble toxins into water-soluble metabolites through the cytochrome P450 enzyme system, and then through phase II reactions (glucuronic acid, sulfate, and glutathione conjugation) makes them into an excretable form. The kidneys excrete toxins in urine, and bile and the intestines send them out in feces. The antioxidant enzyme system (glutathione, SOD, catalase) neutralizes reactive oxygen species generated during metabolic processes.
Exposure Routes and Health Effects
The main exposure routes are the respiratory tract (air, smoking), digestive tract (food, water), and skin contact. Acute poisoning causes vomiting, convulsions, and respiratory paralysis; chronic exposure is associated with liver damage, neurotoxicity, endocrine disruption, immune dysfunction, and increased risk of cancer. In particular, fetuses and infants have high susceptibility to toxins and require caution.
Recent Trends
In 2024–2025, the "detox" industry grew rapidly while controversy over lack of evidence also grew. Microbiome research is shedding light on the effects of gut microbiota on toxin metabolism and excretion, and research results have been published showing that certain gut strains promote heavy metal excretion. As microplastics have been detected in the bloodstream and major organs, regulatory discussions are expanding, centered on the EU. In addition, as blood- and urine-based biomonitoring technologies advance, personalized detoxification and nutritional therapies are drawing attention, while academia and regulatory agencies are strengthening warnings against exaggerated advertisements for detox products. Furthermore, toxin detection sensors and AI-based toxicity prediction models are being introduced in drug development and food safety fields.
Related Topics
- [[Heavy metals]]
- [[Microplastics]]
- [[Detox]]
- [[Microbiome]]
- [[Endocrine disruptors]]
- [[Liver]]