1. What is environmental toxicology ?
‘ecotoxicology’
Definition: ‘study of impacts of pollutants on the
structure and function of ecosystems’
manmade poisonous chemicals and their effect on the environment
does not include the study of naturally occurring toxins, for example cholera toxin, or brevitoxin

2. Environmental toxicology is a new discipline that grew out of studies on the environmental fate and transport of pesticides in the 1940s and 1950s
The discipline ‘toxicology’ is as old as medicine – many toxic plant chemicals are used as therapeutic agents in medicine.
The term ‘ecotoxicology’ appeared in the literature in 1969
Field was pioneered by Rachel Carson

3. Environmental toxicology is highly interdisciplinary field

4. Definition : XENOBIOTIC
a chemical that is foreign to the biosphere i.e. is not produced by a natural biological or abiotic source
Also called anthropogenic, man-made, synthetic, pollutant, contaminant, recalcitrant, persistent, and toxicant
Distinguishes between quantity and scale – Gordon Gribble e.g. studied the natural occurrence of organohallogens (chlorbenzoates in fungi) – this is different from large scale chemical processes for the production of PCBs
BTEX is an acronym for benzene, toluene, ethylbenzene, and xzylene – natural ??

5. Environmental toxicology depends on
Lab work
Effects of toxicants on biochemistry and physiology
Field work
Field observations of reproduction and survival in polluted vs. non-polluted sites
Modeling of fate and transport of toxicants in the environment i.e. exposure and risk assessment
Static models : short term modeling of ecosystems
Strategic models : model of a specific aspect of a
system
Testable models : model makes predictions that can
be tested in the field or laboratory

6. Purpose/function of environmental toxicology is to
Identify the mode / site of action of a xenobiotic
FATE and TRANSPORT / interaction of a xenobiotic with the biosphere (including specific organisms) after it is released / pollution occurs
identify the effect the xenoboitic has on an ecosystems / higher level organisation e.g. loss of fertility of Alligators in Lake Apopca
Introduction of
xenobiotic
Ecosystem
effect
site of
action
biotransformation
physiology
behavior
community
parameters
biochemistry
population
dynamics

7. Parameters of xenobiotic interaction with the ecosystem
Physiology, Behavior
Chromosome damage
Lesions, Necrosis
Tumors
Teratogenic effects
Behavior, Mortality
Community structure
Diversity
Energy transfer
Stability
Succession
Chemical parameters
DNA
RNA
Receptors
Key enzymes
Biochemical integrity
Introduction of
xenobiotic
Ecosystem
effect
Stress proteins
Metabolic indicators
Acetylcholinesterase inhibition
Adenyl energy charge
Metallothionen production
Immuno suppression
enzyme induction
Glutathione S Transferase
Mixed Functional Oxidases
Hydrolases
DNA repair mechanisms
Population density
Productivity
Mating success
Fecundity
Genetic alterations
Competitive alterations

8. Biotic environmental fate
The interaction of a xenobiotic at the site of action in an organism is often ‘molecular happenstance’ i.e. xenobiotic mimic compounds which are naturally found in species that they affect – hormone mimics
Bioaccumulation
The storage of a compound in fatty tissue of an animal
Result of food chain / trophic levels
Biotransformation
Metabolic processes, mainly by environmental bacteria, that alter the structure and toxicity of a compound
Biodegradation
Breakdown of a xenobiotic to CO2 and water

9. Biotic mode of action (Receptors)
Chemicals that interfere with biochemical receptor sites
Signaling
proteins in membranes
Replication
Protein synthesis
Chemicals that damage biochemical or molecular targets
DNA damage
Strange breakage
Chromosome abnormalities
Cancer
Non-genotoxic effects such as immunosuppression

10. Physiological and behavioral effects
Standard tool for assessing toxicological effects on populations
Tissue lesions
Tumors
Reproductive success
Population success
Population age structure – xenobiotics often exert a stronger effect on juveniles => a shift in age structure might indicate that a population is not doing well, because it is affected by a xenobiotic
Shift in bacterial communities – contamination reduces bacterial diversity; bacterial numbers often increase because the contaminant is food for some while it is toxic for others

11. Community effects Ecosystem effects Species diversity Abundance
Distribution
Ecosystem effects
Productivity
Trophic level structure
Stability