BIO 104 5/27/96

Environmental Toxicology
1. Toxicology is the study of adverse systemic effects of 
     chemicals on an organism.
     A. A toxin is any agent that causes acute or chronic
     systemic damage.
          1. Lethal dose of caffeine in 100 cups of coffee
          2. Lethal dose of solanial in 100-400 pounds of 
          potatoes
          3. Lethal dose of oxalic acid in 10-20 pounds of
          spinach
     B. If small amounts of a toxin cause death, then it's a 
     poison.
          1. Dioxins are caused by the break down of plastics
          and pesticides. ("Cancer Alley")
2. How do we draw the line between toxins and poisons?
     A. Acute vs. Chronic toxins
          1. Acute toxins cause systemic damage (or death) due to
          a one-time exposure of relatively short duration to a 
          toxin.  These are relatively easy to test.
               a. Malathion
               b. Vitamin D
          2. Chronic toxins cause systemic damage (or death) due
          to long-term, low-level exposure to a toxin.  These are
          difficult to test.
               a. Mercury
               b. Lead
     B. Human testing
          1. controlled test not (usually) done
          2. data from accidental/intentional poisonings
     C. Animal testing
          1. How much do the results of animal testing tell us?
     D. Legal stuff MCL's and the LD50
          1. MCL: Maximum contaminant level
          2. LD50 stands for lethal dose for 50% of the test 
          population.  If a chemical has an oral LD50 of 50 mg/kg
          or less, it is legally a poison.
               a. The lower the LD50 the more toxic the substance
               b. Dioxins range from .6-200 ug/kg
3. What affects the toxicity of a toxin?
     A. exposure time
     B. How much, how often?
     C. Route of exposure
          1. oral
          2. dermal
          3. Inhalation
     D. Age of person/organism exposed
     *Mercury Poisoning
          Organic                       Inorganic
     -metabolized by bacteria      -if ingested dermally or
                                   inhaled it can be toxic
4. Environmental Contaminations or "Why should you Care"
     A. Direct killing of organisms
          1. Brant geese and diazinon
          2. Utoy Creek catfish
     B. Water Contamination
          1. Do the pesticides I use contaminate the rivers
          everyone uses
     C. Indirect Contamination via food chains
          1. Bioaccumulation is the build-up of a toxin in fatty
          tissues such as the liver and kidneys, and fat around
          the intestines.
          2. Biomagnification is the increase of toxins in body 
          tissues upwards through the food chain.
     
Procedures:
1. What are the environmental preferences of Artemia
     A. Biology of Artemia
     B. 3 tests
          1. Temperature gradient
          2. pH gradient
          3. Control
     C. Experiment Set-up
          1. don't tighten clamps at the beginning: the Artemia 
          must be able to swim freely through the tube
          2. Be careful with the HCL and KOH solutions;  You 
          could possibly burn your eyes out and never be able to
          see again.  By the way, wear those ugly, bulky, fog-up
          way too easy, goggles.  
     D. Calibration of the pipettes
     E. Counting
          1. Don't count dead Artemia
          2. Don't count Artemia cysts
     F. Draw results
2. How tolerant is a brine shrimp (actually those lovable little
     pets we all had as kids:  better known as Sea Monkeys) to 
     environmental stress?
     A. Acute toxicity test
          1. Temperature
          2. Ivialathion (common pesticide)
     B. Experiment set-up
          1. GLA's do this for us.
     C. Counting
          1. count dead Artemia
          2. Do not count cysts and dead juvenile Artemia