Toxicology Cheat Sheet

The core ideas of Toxicology distilled into a single, scannable reference — perfect for review or quick lookup.

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Quick Reference

Dose-Response Relationship

The fundamental principle in toxicology describing how the magnitude of a biological effect changes with varying amounts of exposure to a substance. The relationship is typically represented as a sigmoidal curve and is used to determine safe exposure levels, therapeutic windows, and lethal doses.

LD50 (Median Lethal Dose)

The dose of a substance required to kill 50% of a test population under specified conditions. It is one of the most widely used indices for comparing the acute toxicity of different substances, with lower LD50 values indicating greater toxicity.

Toxicokinetics (ADME)

The study of how a toxic substance is absorbed, distributed, metabolized, and excreted (ADME) by the body. Toxicokinetics determines the concentration of the toxicant at the target organ over time and is critical for understanding why the same dose can produce different effects in different individuals or species.

Mechanism of Toxicity

The specific molecular, biochemical, or cellular process by which a toxicant produces its adverse effect. Understanding the mechanism allows toxicologists to predict toxicity, develop antidotes, and design safer chemicals.

Risk Assessment

A systematic process for evaluating the probability and severity of adverse health effects from exposure to a hazardous substance. It involves four steps: hazard identification, dose-response assessment, exposure assessment, and risk characterization.

Bioaccumulation and Biomagnification

Bioaccumulation is the progressive buildup of a substance in an organism over time because it is absorbed faster than it is eliminated. Biomagnification is the increase in concentration of a substance at each successive trophic level in a food chain.

Threshold Dose and NOAEL

The threshold dose is the minimum amount of a substance required to produce a detectable adverse effect. The No Observed Adverse Effect Level (NOAEL) is the highest dose at which no statistically significant adverse effect is observed in toxicity studies, and is used as a starting point for setting safe exposure limits.

Antidotes and Treatment of Poisoning

An antidote is a substance that counteracts the effects of a specific poison or class of poisons, either by neutralizing the toxicant directly, blocking its mechanism of action, or enhancing its elimination. Effective treatment often includes decontamination, supportive care, and specific antidotal therapy.

Xenobiotic Metabolism

The biochemical modification of foreign substances (xenobiotics) by the body, primarily occurring in the liver through Phase I reactions (oxidation, reduction, hydrolysis via cytochrome P450 enzymes) and Phase II reactions (conjugation with glucuronic acid, sulfate, glutathione, or amino acids) to make them more water-soluble for excretion.

Teratogenicity

The capacity of a substance to cause structural or functional abnormalities in a developing embryo or fetus when the mother is exposed during pregnancy. Teratogenic effects depend on the timing, duration, and dose of exposure during critical developmental windows.

Key Terms at a Glance

Acute Toxicity:Adverse effects occurring within a short time (usually 24 hours) after a single exposure or multiple exposures to a substance.

Antidote:A substance that counteracts or neutralizes the effects of a poison or toxin.

Bioactivation:The metabolic conversion of a substance into a more toxic or reactive form.

Bioaccumulation:The progressive buildup of a substance in an organism's tissues over time.

Biomagnification:The increasing concentration of a persistent substance at higher levels of a food chain.

Carcinogen:An agent capable of causing cancer by inducing genetic mutations or promoting uncontrolled cell growth.

Chelation:The use of chemical agents to bind and remove heavy metals from the body.

Chronic Toxicity:Adverse effects resulting from repeated or long-term exposure to a substance over weeks, months, or years.

Cytochrome P450:A superfamily of heme-containing enzymes responsible for the oxidative metabolism of most xenobiotics, primarily located in the liver.

Dose-Response Curve:A graphical representation of the relationship between the dose of a substance and the magnitude of the biological response.

Ecotoxicology:The study of the effects of toxic substances on ecosystems, including organisms, populations, and communities.

Genotoxicity:The ability of a substance to damage DNA, potentially leading to mutations and cancer.

Glutathione:A tripeptide antioxidant critical for detoxifying reactive metabolites and protecting cells from oxidative damage.

Half-Life:The time required for the concentration of a substance in the body to decrease by half through metabolism and excretion.

Hepatotoxicity:Toxicity directed at the liver, the primary organ of xenobiotic metabolism.

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