PRINCIPLES OF TOXICOLOGY
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Transcript PRINCIPLES OF TOXICOLOGY
PRINCIPLES OF TOXICOLOGY
...a discussion of the fundamental
means by which toxicological
properties are determined.
DEFINITIONS
Toxicology
Science
that studies the harmful or toxic
properties of substances
TOXICITY vs HAZARD
[an important distinction]
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
Hazard
The
probability that the concentration will
occur at that site in the body
Toxicity vs. Hazard
Two chemicals can possess the same
degree of toxicity, but present different
degrees of hazard.
Ex.
Odorless and non-irritating vs. pungent
odor
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
TOXICOLOGY IS MULTIDISCIPLINARY
CHEMISTRY
BIOCHEMISTRY
PHYSIOLOGY
PATHOLOGY
IMMUNOLOGY
PHYSICS
ENGINEERING
STATISTICS
ROUTES OF EXPOSURE
Inhalation
Ingestion
Skin contact
Injection
EFFECTS OF EXPOSURE
ACUTE - a “one-time” event
rapid
absorption of material
exposure sudden & severe
critical period for death/survival
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]
Route of Exposure
inhalation
ingestion
skin absorption
Type of Contact
acute
chronic
Number of Agents
Other Aspects
TYPES OF TOXIC EFFECT
mortality
pathological change
growth rate change
physiological injury
biochemical change
behavioral effects
reproductive system
damage
mutagenic, etc.
Toxic Effect by Target Organ
irritant
asphyxiant
anesthetic
hepatotoxic
nephrotoxic
neurotoxic
pulmonary
Factors Influencing Intensity
of Toxic Action
route of entry
rate of exposure
age of host
prior exposure
environment
host factors
gender, genetics
other factors
Dose-Response Relationship
Correlation between the amount of
exposure and the resulting effect
Lethal Dose/Lethal Concentration
LD50 - Dose required to kill 50% of
population
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
descriptive
retrospective (conventional)
prospective (cutting edge)
Sources of Toxicological
Information
Material Safety Data Sheet
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