EESA10H3 Lecture Notes - Lecture 9: Teratology, Reproductive Toxicity, Rodent
5 Jul 2018
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LECTURE #9 TOXICOLOGY
-Toxicology: human health ecotoxicology = env. System health, not just humans
Introduction to Fate and Transport
-Key definition
oTransport: movements of contaminants within or between env. Media
Eg. Transport is the things that can move the pollutant (eg. Soil, water)
call it transport within the environmental compartment and between
them
oFate: physical, chemical, or biological transformations of contaminants
Physical-Chemical Properties
-Fate and transport of chemicals affected by their physical-chemical properties (eg. If
something is volatile, you want just the air for its conc.)
-How harmful a substance is depends on physical-chemical properties of the substance
-Volatility (higher vapour pressure = easier to evaporate, typically VOCs)
-EN
-Polarity
-Solubility (eg. Water soluble toxins, fat soluble toxins[non-polar]; lipophilic
tendency, metal are soluble in water so look for them in fats)
-Oxidation state (eg. Zero valent = less bio available = less toxic)
-Molecular weight
oEg. bioremediation look for
biological organisms that can
break down organic chemicals
naturally
If H-C are large = have
molecular weight = doesn’t
fit into the microbial cell =
cannot be broken
complicates the ability to
naturally break it down
-Everything is related in the env.
partitioning between air and water (eg.
Some will go from air to water, water to
air etc.)
-If chemical is lipophilic look for it in the tissues of living org (eg. Fatty fish, seals etc.)
-If chemical has tendency to absorb on organic carbon, it has tendcy to accumulate on
sediments, soil etc. everything will go where physical-chemical properties are directing
them will partition into specific env. Compartment, result in equilibirum
-Consequences of lipophilic tendency
oBio concentration: movement into fatty tissues of organisms
oBioaccumulation: building up over time in individual organisms]
oBio-magnification: building up over time, across the levels in a food chain
Physical-chemical properties
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-Generally, higher molecular weight chemicals are
oLipophilic and more persistent (are hard to breakdown) heavy molecules
If lipophilic, these lipophilic chemicals can pass through the plasma
membrane bilayer of cells (that are also non-polar)
oLess volatile and less water soluble
-Persistence in environment
oQuantified as a half-life in air, water, or soil
oAffected by env. Conditions cannot control env. conditions
Introduction to Toxicology
-Toxicology: the science of the effects of toxic substances and of their fate and transport
in the body (eg. Study what’s in the living org. and what’s in the env)
-Study of poisons
-the science which studies toxic substances or poisons, that are substances which cause
alteration or perturbation in the function of an organisms leading to harmful effects
-4 main terms: receptor, exposure, dose, and response
Receptor
-Organisms receiving exposure or dose (eg. Human) person that receives the chemical
-The human envelope: the boundary that spearates the interior of the body from the
exterior environment
oEssentially separates the inside from the outside
-Age, general health (eg. ill, the generally healthy, genetic makeup (don’t want genetic
makeup to interfere w/ results; someone will be more susceptible than others)
o(have to define all of these)
Exposure
-Contact w/ the human envelope
-Routes of exposure
oIngested (often greatest course of chemical exposure, 85%)
oInhaled (air pollution, particles, volatiles)
oAbsorbed through the skin
Dimethyl mercury extremely toxic in US, researcher working with it
managed to go have it go through his glove, into his skin, and he died
within hours
-Frequency of exposure
-Exposure assessment
oGoal is to quantify
exposure (find out the
DOSE)
oMethods draw on
understanding of both:
Environmental
science (fate and
transport of
toxicants in env)
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Toxicology (fate and
transport of toxicants
in the body)
-Completing the conceptual model of
exposure
oIt begins with exposure and
concludes with
toxicokinetics and effects in
the body
oExposure = goes in through
those pathways
oThen: our body recognize the chemical (eg. proteins) absorb it (but not all is
absorbed not all are affecting receptors) those that affect the receptors are
biologically effective dose (bioavailability factors goes from 0 to 1)
oIf the absorbed dose = biological effective dose, what is the bioavailabiliy factor?
1 (100%)
0 ( nothing stays in the receptor)
closer to 1 = more dangerous, closer to 0 excreted, broken down etc
otoxicokinetics from BED to change on the tissues (potential effect)
concerned with what is happening with the body, before measurable illness
eg. things change in a
molecular level, but no
detectable change if
significant change, then have
health effects
Quantifying exposure
-translating event of exposure into a dose
of estimate
-Tools for area monitoring and personal
monitoring
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