Dose Effect and Confounding Factors in Toxicology

These flashcards cover the fundamental principles of toxicology, including dose-response relationships, factors affecting toxicity, biological barriers, endocrine disruption, and risk assessment methodologies.

Paracelsus (1493-1541)

The individual who stated that all substances are poisons and that the right dose differentiates a poison from a remedy.

Risk Formula

$$\text{Hazard} \times \text{Exposure} = \text{Risk}$$

Dose-Response

One of the three principles of toxicology describing the relationship between the amount of an agent and the resulting biological effect.

Acute Exposure

A short-term exposure to a substance.

Chronic Exposure

A long-term exposure to a substance.

ADME

An acronym representing the processes of Absorption, Distribution, Metabolism, and Excretion.

Exposure Dose

The dose of a toxin present in the environment.

Absorbed Dose

The proportion of the exposure dose that actually enters the living organism.

Target Organ Dose

The amount of toxicant that reaches the specific site where adverse effects occur; also called the biologically effective dose.

Threshold Dose

The dose at which a toxic effect is first observed.

LD50

A statistically derived dose that is lethal to $50\%$ of a test population, typically expressed in $mg/kg$.

NOAEL

An acronym for No Observed Adverse Effect Level.

Half Life

A measurement of time useful in biomonitoring that indicates how long it takes for half of a substance to be eliminated or transformed.

Monotonic Curve

A dose-response curve where the slope never reverses from positive to negative or vice versa.

Strateum corneum

A natural barrier in the skin containing keratin which reduces the ability of the skin to absorb toxicants.

Blood Brain Barrier

A barrier that prevents proteins and other large molecules from entering brain cells effectively.

Endocrine Disrupting Chemical (EDC)

An exogenous substance that causes adverse health effects by causing changes in the endocrine system.

Bisphenol A (BPA)

An endocrine disruptor used in polycarbonate plastics and epoxy resins with reported concerns for its effects on the brain and behavior in fetuses and infants.

Atrazine

A herbicide that can alter the sex of frogs and is suspected of impacting humans, currently banned in the EU but used in the US.

ABC/MDR Transporters

Transporters located on specialized organs that act as natural barriers to toxin absorption.

Alcohol Dehydrogenase

An enzyme lower in females than males, resulting in a reduced ability to detoxify alcohol.

G6PD Deficiency

An X-linked genetic condition where reduced enzyme levels lead to increased oxidative damage of hemoglobin and susceptibility to drug-induced hemolytic anemias.

Gilbert’s Syndrome

A condition characterized by reduced gluconyl transferase, leading to a reduced ability to conjugate bilirubin.

Bioaccumulation

The lifelong exposure to and accumulation of range of toxins in an organism.

Biomagnification

The increase in concentration of a toxin (such as DDT) in tissues as it moves through trophic levels, from producers to tertiary consumers.

Bay Theory

A theory predicting that an epoxide located in the bay region of a Polynuclear Aromatic Hydrocarbon (PAH) will be highly reactive and mutagenic.

Biomarker of Exposure

A chemical, its metabolite, or an interaction product measured in biological fluid to reflect an individual's internal dose.

Biomarker of Effect

A measurable biochemical, physiological, or behavioral change associated with exposure to a toxin.

Precautionary Principle

The principle stating that precautionary measures should be taken when an activity raises threats of harm, even if cause-and-effect relationships are not fully established scientifically.

Risk Characterisation

The final step of risk assessment that brings together hazard ID, dose-response assessment, and exposure assessment to make recommendations.