cours Toxicologie

1. TOXICOLOGY
B. Sc. THIRD YEAR
PAPER – i

2. INTRODUCTION TO TOXICOLOGY - Outline
• What is Toxicology
• Scope
• Basic divisions of toxicology
• Goals
• Concepts - Types of Toxicants

3.  Toxicology Formerly The Science of Poisons
Now
The science that deals with the adverse effects of chemicals on living organisms
and assesses the probability of their occurrence
 Toxicology term derived from
Toxicon – arrow (poison)
logos – study
 Scientifically speaking, toxicology is the quantitative and qualitative study of the
adverse or toxic effects of chemicals and other anthropogenic materials or
xenobiotic on organisms.
 Toxicology is the youngest science of poisons

4. Definition of toxicology
• The study of the adverse effects of a toxicant on living organisms.
Adverse effects may be
• any change from an organism’s normal state
• dependent upon the concentration of active compound at the target site for a
sufficient time.
• Toxicant
• any agent capable of producing a deleterious response in a biological system
• Living organism
• a „sac of water” with target sites, storage depots and enzymes

5.  Toxicology is both
Science , like medicine and
An art, like practise
• It is one of the several multi disciplinary fields of environmental sciences where many
disciplines are common with other fields
• It is concern with the study of concentrations, transport, distribution , transformation
and the ultimate fate of toxins and chemicals in the environment.
• It is essential to understand the chemical reactions (eg. Hydrolysis, oxidation,
photolysis), physical (eg. Molecular structure, solubility, volatility and sorption) and
biological (eg. Biotransformation, accumulation, biomagnification) factors that affect
environmental concentration of chemicals in order to assess how toxic agents act in
environment and how environment act and try to neutralize these agents and impact
on living beings.
• Environmental toxicology: The study of the effects of pollutants on organisms,
populations, ecosystems, and the biosphere.
SCOPE OF TOXICOLOGY

6. Environmental toxicology is a multidisciplinary science involving many widely
diverse areas of study such as
• chemistry, the characterization of toxins;
• pharmacology, the mode of entry and distribution of toxins in the body;
• biochemistry, the metabolism and interaction of toxins with cell components;
• physiology, the effect of toxins on body organs;
• .biology, the effect of toxins on the environment;
• .genetics, the effect toxins can have on the reproductive system and on future generations by
altering genetic codes;
• epidemiology, the effect on the population as a whole of chronic exposure to small quantities of
suspected agents;
• law, regulation of the use or release into the environment of toxic substances; and
• economics, evaluation of the environmental cost vs. benefit ofeconomic development and the
determination of trade-offs among economy, health, and the environment.

7. BASIC DIVISIONS OF TOXICOLOGY
On the basis of toxic effects of the chemical,
toxicity is subdivided into
• Acute effects – related to short term exposure of few hours, days
or weeks to a chemical . They are much severe in nature
• Chronic effects – ingestion of smaller quantities over a
prolonged period of time leading to toxic concentrations or long term
exposures

8. DEFINITIONS
• TOXIC SUBSTANCE- is the one which demonstrate the potential to induce cancer,
body injury or long term disease
• TOXIN – can be of plant, microbial or animal origin or a synthetic substance
• TOXICITY – is a relative term commonly used to compare one chemical’s potential
with another.
• Toxicity of a substance is capacity to cause injury to a living organism
• Toxicity is thus, a relative term which is a function of the concentration of the
chemical and duration of exposure
• TOXICITY TESTS - are performed to evaluate the adverse effects of a chemical o
living organism under standardised conditions .
• TOXICANT - is an agent that can produce an adverse response in the biological
system, seriously damaging its structure and function or even, death.

9. ENTRY OF TOXICANTS
• NON- POINT SOURCES – such as agricultural runoff,
contaminated ground water, urban discharges etc.
• POINT SOURCES- such as effluent discharge from
manufacturing plants, hazardous waste disposal sites,
municipal waste treatment plants etc.

10. TOXINS
• Naturally occurring toxicants originate from animal, plant or mineral
sources
• Animal toxins- such as venoms
• Plant toxins – such as opium, atropine, reserpine, quinine, picrotoxin etc.
• Crude plant extracts used in veterinary medicine
• Large number of antibiotics come from microorganisms as mycotoxins
• Many heavy metals such as lead, cadmium, zinc, mercury etc.
• Radioactive substances as hazards
• All Pollutants

11. • Toxins – biological compounds (Ricin, botulism)
• Carcinogens - may induce cancer or increase its incidence and can
affect any cells or tissues (benzene, vinyl chloride, benzo(a)pyrene )
• Mutagen - may induce hereditary genetic defects or increase their
incidence and effect on the germ cells (gonads). (radiation,
nitrosoamines)
• Teratogens - may induce non-hereditary congenital malformations or
increase their incidence and effect on the growing fetus (rubella,
thalidomide, PCBs, Dioxins)
• Endocrine disruptor – hormone mimic (PBDE, BPA)
CHEMICALS: Major Types of Toxicity

12. FACTORS THAT INFLUENCE TOXICITY
EXPOSURE
ACUTE
SUB CHRONIC
CHRONIC
DOSE
RESPONSE