Introduction and terminology related to food toxicology

3. Toxicology – is the study of the adverse effects of chemicals on
living organisms.
Toxicologists – one who is trained to examine the nature of those
effects (cellular, biochemical, and molecular mechanism of
action) and assess the probability of their occurrence.

4. Food
Toxicology

5. Food toxicology is the study of the nature, properties,
effects and detection of toxic substances in food, and their
disease manifestation in humans.

6.  Toxic – This term relates to poisonous or deadly effects on the body by
inhalation (breathing), ingestion (eating), or absorption, or by direct
contact with a chemical.
 Toxicant - A toxicant (toxic substance) is any chemical that can produce an
adverse biological effect. It may be chemical, physical or biological in form.
Eg. Cyanide (chemical), radiation (physical), and snake venom (biological)

7.  Toxin – toxic substances produced naturally
The term “toxin” usually is used when talking about toxic substances
produced naturally.
A toxin is any poisonous substance of microbial (bacteria or other tiny
plants or animals), vegetable, or synthetic chemical origin that reacts
with specific cellular components to kill cells, alter growth or
development, or kill the organism.
 Toxicity – It describes the degree to which a substance is poisonous or
can cause injury.

9. Toxic effects can be:
 Lethal: resulting in death of individuals
 Sub-lethal: effects not directly resulting death
 Accute effect: sudden and severe exposure and rapid absorption of substance.
Occur over a very short period of time, ususally within 24 hours.
Eg. Cyanide poisoning
 Chronic effect: Characterized by prolong or repeated exposures of a long duration.
Occur over a long periods of time i.e. weeks, months, years
Eg. Lead or mercury poisoning
 Local effect: an adverse health effect occurs at the point/area of contact i.e. skin,
eye etc.
Eg. Strong acids or alkalis

10.  Systemic effect: an adverse health effect that occurs at a location diatant from the
body’s initial point of contact
Eg. Arsenic affects the blood, nervous system, liver, kidneys and skin, Benzene affects
bone marrow
 Cumulative poisons: chemicals that tend to build up in body as a result of numerous
chronic exposures. The effects are not seen until adverse health effects take place.
Eg. Heavy metals
 Synergistic effect: when 2/more hazardous substances are present at same time, the
resulting effect can be greater than the effect predicted based on the effect of
individual substance. Also called as potentiating effect.
Eg. Exposure to alcohol and chlorinated solvents, exposure to smoking and asbestose
simultaneously

11. Dose: Most important factor that influences the toxic effect of a specific
substance
 It is the actual amount of a substance that enters the body
 Dose received may due to acute (short-term) or chronic exposure (long-term)
 The amount of exposure and type of toxin determine the toxic effect
 For each substance, a certain dose produces certain biological effects in the
individual organism.
Response: any biological effect caused by exposure is called as response.
 Typically as the dose of a toxic substance goes up, increase the number of
organisms die or show signs of impaired helath

12.  Xenobiotic: is the general term used for a foreign substance taken in to the body.
 It is derived from the Greek term xeno which means “foreigner”.
 Xenobiotic is a chemical which is found in an organism, but which is not normally
produced or expected to be present in it.
 Xenobiotics may produce beneficial effects (pharmaceuticals) or toxic effects (eg.
Lead)

13. Target organ: an organ which is damaged by xenobiotic or its metabolism.

14.  Selective toxicity: toxicity differences between two species simultaneously
exposed to a toxic substance.
 It implies that a chemical may produce injury to one living being without
harming the other, even though the two may exists together.
 Eg: An insecticide lethal to insects but relatively non-toxic to other animals
Antibiotics are selectively toxic to m.o. but virtually non-toxic to humans
 Sensitivity: People vary widely in their sensitivity to the effect of a chemical.
Many factors determine individual reactions to a chemical i.e. age, sex, diet,
inherited traits, pregnancy, state of health, use of medication, drugs or alcohol
etc.

15. Toxins enter the body by several routes:
 Ingestion:
 To exert a systemic effect, they must be absorbed into circulation.
 Most are absorbed by passive diffusion.
 If not absorbed, they may produce local effects i.e. diarrhea, bleeding,
malabsorption of nutrients
 The GIT, protects the inner body from contaminants (toxins) that have been
ingested

16. Inhalation
The membranes within lungs, protects the inner body
from contaminants that have been inhaled
Transdermal absorption
Skin protects the body from contaminants outside
the body.
Before toxicity develop, a substance must come into
contact with a body surface i.e. skin, mucosa of
digestive or respiratory tract