Fundamental Concepts of Toxicology

A set of key vocabulary flashcards covering fundamental terms, dose-response metrics, branches, effects, and control measures in toxicology.

Toxicology

The science that studies the adverse or poisonous effects of chemicals on living organisms.

Toxicant

A toxic substance produced or released as a result of human (anthropogenic) activities.

Toxin

A poisonous substance produced naturally by living organisms such as plants, animals, fungi, or bacteria.

Toxoid

A toxin rendered non-toxic but still able to stimulate protective antibody formation; used in vaccines.

Xenobiotic

Any foreign chemical substance found within an organism that is not normally produced by or expected to be present in it.

Endogenous Substance

A chemical naturally produced within an organism; normally kept within specific concentration ranges (e.g., blood calcium).

Dose

The mass of chemical received by an organism, usually expressed in mg per kg of body weight.

Acute Effect

A short-term toxic response that appears rapidly after a single or brief exposure.

Chronic Effect

A toxic response that develops after a long latency period or prolonged, repeated exposure.

Hazard Identification

The process of determining whether exposure to a substance can cause increased adverse health effects.

Dose-Response Evaluation

Quantitative analysis that relates contaminant dose to incidence or severity of adverse effects in a population.

NOEL (No Observed Effect Level)

The highest tested dose at which no measurable effects are observed.

NOAEL (No Observed Adverse Effect Level)

The highest dose at which no harmful or adverse effects are detected.

LD50

The dose that is lethal to 50 % of a test population; a common measure of acute toxicity, expressed in mg/kg.

LC50

The concentration of a chemical in air or water that kills 50 % of a test population within a specified time.

ED50

The dose that produces a desired (effective) response in 50 % of a population.

TD50

The dose that produces a specific toxic, irreversible effect in 50 % of a population.

Therapeutic Index (TI)

Ratio of LD50 to ED50; indicates relative drug safety (higher TI = safer).

Margin of Safety (MOS)

Difference between LD5 and ED95; a conservative indicator of safety for most sensitive individuals.

Mechanistic Toxicology

Branch that investigates cellular, biochemical, and molecular mechanisms by which chemicals cause toxicity.

Descriptive Toxicology

Field that performs toxicity testing to provide data for safety evaluation and regulatory requirements.

Regulatory Toxicology

Discipline that determines whether chemicals pose acceptable risks for intended use and sets exposure limits.

Forensic Toxicology

Application of toxicology and analytical chemistry to medicolegal investigations of poisoning and drug use.

Clinical Toxicology

Study and treatment of diseases uniquely associated with toxic substances in humans.

Environmental Toxicology

Study of chemical pollutants' impacts on non-human organisms and ecosystems.

Ecotoxicology

Specialized area focusing on toxic effects on population and ecosystem dynamics.

Developmental Toxicology

Study of adverse effects on developing organisms from pre-conception to puberty (includes teratology).

Reproductive Toxicology

Study of chemical-induced adverse effects on male or female reproductive systems.

Graded Response

A continuous, measurable change in a single organism in relation to varying doses (e.g., enzyme inhibition).

Quantal Response

All-or-none outcome in a population (e.g., alive vs. dead) used to plot distribution of responses to dose.

Carcinogen

A substance capable of causing cancer in humans or animals.

Teratogen

An agent that causes malformations or birth defects during embryonic or fetal development.

Mutagen

A chemical or physical agent that induces genetic mutations or chromosomal damage.

Allergic Reaction (Chemical Allergy)

Immunologically mediated adverse response after prior sensitization to a chemical or related compound.

Idiosyncratic Reaction

Genetically determined abnormal reactivity, showing extreme sensitivity or insensitivity to a chemical.

Additive Effect

Combined effect of two chemicals equals the sum of their separate effects (1 + 1 = 2).

Synergistic Effect

Combined effect of two chemicals is greater than the sum of their individual effects (1 + 1 > 2).

Potentiation

A non-toxic chemical enhances the toxic effect of another chemical (0 + 1 > 1).

Antagonism

One chemical decreases or counteracts the effect of another, reducing overall toxicity.

Functional Antagonism

Two chemicals produce opposite physiological effects on the same function, balancing each other.

Chemical Antagonism (Inactivation)

Direct chemical reaction between two substances forming a less toxic product.

Dispositional Antagonism

Altered absorption, distribution, metabolism, or excretion lowers concentration of a toxicant at target organs.

Receptor Antagonism

Two chemicals compete for the same receptor, diminishing the overall biological response.

Bioaccumulation

Build-up of substances in an organism when intake exceeds metabolic elimination or excretion.

Detoxification

Biotransformation of chemicals into less harmful forms, often facilitating elimination.

Immunocompetence

The immune system’s ability to recognize and respond to diverse foreign substances.

Autoimmunity

Pathological condition where the immune system attacks the body’s own tissues as foreign.

Placebo Effect

A positive health response arising from belief in a treatment rather than the treatment’s pharmacology.

Threshold Limit Value (TLV)

Airborne concentration under which nearly all workers can be exposed daily without adverse effects.

Engineering Controls

Physical workplace modifications (e.g., substitution, isolation, ventilation) designed to remove or reduce hazards.

Administrative Controls

Policies or work-practice changes (e.g., rotation, scheduling, training) that limit exposure to hazards.

Personal Protective Equipment (PPE)

Wearable gear that creates a barrier between workers and hazards when other controls are inadequate.