BIOL354 – Environmental Toxicology I Spring 2012
Lecture 2: Contaminants from Source to Receptor to Impact
- Contaminant Fate studies: Investigates the origins, concentrations, partitioning & persistence.
o E.g. Total [SSRI] with increasing distances (Highest @ point of release, dilutes as it travels, &
accumulates meters downstream) (Searching for  that induce side effects)
- Contaminant Effect studies: Evaluates biotic & abiotic consequences of contaminant exposures.
o E.g. Mating behavior & egg production of Japanese medaka (Already @ the  for negative effects to
occur, monitors different effects compare to a normal control group).
- Contaminant movement:
o Environment: Abiotic simple diffusion
o Organisms: Biotic bio-concentrated (water uptake) or bio-accumulated (water & food uptake).
(Higher  in the organism relative to the environment)
Food chain: Bio-magnification in higher organisms (especially PCBs & dioxins).
Accumulates more in adipose tissues than muscle tissues.
Lipophilic drugs do not accumulate (except for synthetic estrogen, which can bind to
a variety of receptors)
- Toxicity Event: Generate contaminants, release, & transport them into a biotic receptor (protein, tissue, or
organism) through up-take. Biotic receptor is exposed @ a sufficient [contaminant] & duration, resulting in
an adverse biological response.
- Toxicants enters the environment from 2 sources:
o Direct point source discharges: Sewage water discharge, & industrial super-stack. The bigger source,
easier to measure & regulate.
o Indirect non-point source discharges: Agricultural & urban runoff, automobile exhaust &
UNTREATED discharges down the road drainages (extremely toxic). The smaller source, much harder
to regulate & [contaminant] cannot be measured.
- Exposure Routes:
o Oral: Dosage of toxicants administered to the organism through the mouth or diet.
Dose: weight of toxicant/weight of organism (1 ppm = 1 mg Kg ).
Rotovap (lab): Uniformly dose food for oral administration.
o Injection: Dose administrated directly into the bloodstream through intravenous, subcutaneous, or
intra-peritoneal methods (skips the digestive tract).
o Topical/Surface: Toxicants applied on to the skin (e.g. dermal antibiotics etc. in patches).
Amphibians are highly sensitive to environmental toxicants.
o Respiratory: Inhalation of certain concentration of toxic air via lungs or gills.
Left lung bigger than right lung, higher rate of lung disease @ right lung (less SA).
Concentration: weight of toxicant/volume of air or water (1 ppm = 1 mg L ).
- Bioassay: Determine toxicant effects (if the chemical is toxic & how toxic it is relative to others).
o Sufficient exposure time at a given range of doses/concentrations.
o Sufficient doses/concentrations within a given period of exposure.
- Toxicity responses (@ molecular, biochemical, individual, species or community levels)
o Based on degree of response:
Lethal: Response is death (results reveal less information).
Sub-lethal: Response/changes other than death (3 organizational levels).
o Biochemical: Enzyme inhibition;
o Hormonal: Cortisol level changes u