Transcript PRINCIPLES OF TOXICOLOGY

PRINCIPLES OF TOXICOLOGY
...a discussion of the fundamental
means by which toxicological
properties are determined.
DEFINITIONS
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Toxicology
 Science
that studies the harmful or toxic
properties of substances
TOXICITY vs HAZARD
[an important distinction]
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Toxicity
 The
ability of a substance to have an
adverse effect on the health or well-being of
a human
– The toxicity of a chemical depends on the
degree of exposure and absorption
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Hazard
 The
probability that the concentration will
occur at that site in the body
Toxicity vs. Hazard
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Two chemicals can possess the same
degree of toxicity, but present different
degrees of hazard.
 Ex.
Odorless and non-irritating vs. pungent
odor
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The chemical with warning properties
may present a lesser degree of hazard.
TOXICOLOGY
Early interest was in “how to poison”
 In 1800’s, tests to identify poisons were
developed (i.e., forensic medicine)
 Only in 20th century has toxicology been
applied to defining safe work conditions
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TOXICOLOGY IS MULTIDISCIPLINARY
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CHEMISTRY
BIOCHEMISTRY
PHYSIOLOGY
PATHOLOGY
IMMUNOLOGY
PHYSICS
ENGINEERING
STATISTICS
ROUTES OF EXPOSURE
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Inhalation
Ingestion
Skin contact
Injection
EFFECTS OF EXPOSURE
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ACUTE - a “one-time” event
 rapid
absorption of material
 exposure sudden & severe
 critical period for death/survival
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CHRONIC - small doses over long time
 rate
of intake > rate of elimination
 material remains in tissue; injures
Comparison of Chemical Exposures
[Industrial vs Non-Industrial]
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Route of Exposure
inhalation
ingestion
skin absorption
Type of Contact
acute
chronic
Number of Agents
Other Aspects
TYPES OF TOXIC EFFECT
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mortality
pathological change
growth rate change
physiological injury
biochemical change
behavioral effects
reproductive system
damage
mutagenic, etc.
Toxic Effect by Target Organ
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irritant
asphyxiant
anesthetic
hepatotoxic
nephrotoxic
neurotoxic
pulmonary
Factors Influencing Intensity
of Toxic Action
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route of entry
rate of exposure
age of host
prior exposure
environment
host factors
gender, genetics
other factors
Dose-Response Relationship
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Correlation between the amount of
exposure and the resulting effect
Lethal Dose/Lethal Concentration
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LD50 - Dose required to kill 50% of
population
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LC50 – Concentration required to kill
50% of population
How is toxicological data obtained?
animal toxicological studies
 accidental human overexposures
 controlled exposures of human
volunteers
 epidemiological studies
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descriptive
retrospective (conventional)
prospective (cutting edge)
Sources of Toxicological
Information
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Material Safety Data Sheet
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Identity
 Hazardous Ingredients/Identify Information
 Physical/Chemical Characteristics
 Fire and Explosion Hazard Data
 Reactivity Data
 Health Hazard Data
 Precautions for Safe Handling and Use
 Control Measures
Information Resources
http://msds.ehs.cornell.edu/msdssrch.asp
 http://hazard.com/msds/index.php
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