pg 1-5

​​Personal care products pg. 39

E.g cleanser, conditioners, make-up, sunscreen

What is oxybenzone and how is it released into the environment

  • Oxybenzone is found in numerous sunscreen products as it protects the skin against UV lights. It is photo-toxic, meaning its adverse effects increase by light

  • It is released into the environment by swimmers that apply the sunscreen to their body. Also by wastewater discharge
     

What are the effects of oxybenzone on planulae

  • There are large concentrations of oxybenzone in the US Virgin Island and Maui, Hawaii

  • Coral Planulae exhibited a reduction in ciliary movement and morphology

  • Median LC50 after 8hr exposure in light was 3.1 mg/L

  • Hawaii banned sunscreens containing oxybenzone to protect marine ecosystems

 

Toxins

What are toxins?

  • A toxicant that is produced by a living organisms

  • All toxins are toxicants, but not all toxicants are toxins

  • Known for medicinal and harmful properties

  • E.g streptomycin -> aminoglycoside antibiotic derived from soil bacteria

  • E.g aspirin -> synthetic nonsteroidal anti-inflammatory replaced a well-known salicylic acid from the bark of the willow tree

They classified

  • Microbial toxins -> produced by microorganisms

  • Mycotoxins -> produced by fungi

  • Algal toxins -> produced by algae

  • Plant toxins -> produced by plants

  • Animal toxins -> produced by animals   

Microbial toxins

What is microbial toxins?

  • Microbial toxins are toxic substances produce by microorganism

  • Have high molecular weight and antigenic properties (means that they can stimulate the immune response on exposure)

  • E.g botulinus toxin, tetanus toxin
     

How are microbial toxins classified?

  1. Exotoxins: If they are produced and secreted

  2. Endotoxin: if produced and remain in bacterium

 

 

What is Bt toxins and how are they used in agriculture?

  • Bacillus thuringiensis called crystal proteins or cry proteins, produces endotoxin that is used as a insecticide

  • Cry toxins bind to the insect midgut and disrupts the cell membrane in sensitive lepidoptera species
     

Mycotoxins

  • Produced as secondary metabolites(substance formed for metabolism) by fungi
     

  • What is aflatoxin B1 and why is it a potent carcinogen?

    • Aflatoxin B1 is a metabolite produced by molds of Aspergillus flavus. Found in improperly stored food produces like grains. Targets the liver organ.

 

  • Describe some examples of algal toxins.

    • ASP (amnesic shellfish poisoning) -> due to several diatom species -> from contaminated mussels -> domoic acid

    • NSP (Neurotoxic shellfish poisoning) -> due to dinoflagellate -> found in filter feeders (oysters) -> brevetoxin

    • DSP (Diarrhetic shellfish poisoning) ->  due to dinoflagellate -> found in mussels, clams -> okadaic acid

    • CFP (Ciguatera fish poisoning)->  due to dinoflagellate -> tainted reef fishes -> ciguatera toxin
       

  • Explain what happens upon dermal exposure to sap from giant hogweed.

    • Burns blisters and scarring due to phototoxic furanocoumarins. They react with DNA when exposed to radiation, which causes cell death and skin blistering.
       

  • What is the difference between an animal that is venomous versus one that is poisonous?

    • An animal can be passively poisonous and/or actively venomous. Used for either offense or defense

    • Either:

      • create own venom

      • accumulate poisonous metabolites from their environments

 

  • What are the main components in bee venom and what does each component do?

    • Apamin : Small peptide that crosses blood- brain barrier, affecting nervous system

    • Melittin peptide : Allows the venom to be inserted into membranes/phospholipid bilayers

    • Mast cell degranulating peptide : neurotoxin and inhibits K+ channels

    • Hyaluronidase : breaks down hyaluronic acid in tissues and spreads the been venom through the tissue.

 

  • What is Saxitoxin and what do they do?

Saxitoxin is an algal toxin that caused human and sea bird death by inhibiting neuron function and suppressing nerve impluse. Produced by the dinoflagellate Alexandrium, it contaminated shellfish and fish.

Topic: Fate of Contaminants

  • What are the elements of a toxicity event?

    • Generation

    • Release

    • Movement to receptor

    • Exposure at high contaminate and time

    • A response

 

  • What is the difference between point and non-point source?

    • Point source: toxicant comes from direct sources (sewage discharge)

    • Non-point source: toxicant comes from indirect source: pesticides

 

  • Describe what is meant by “accidental release”, “intentional release”, “deliberate
    application”, and “urban runoff” when describing contaminant sources.

    • Contaminate sources:

    • Accidental release of contaminates like from nuclear accidents, oil spills, forest fires

    • Intentional release through disposal of waste that is deliberate, from btoh direct and indirect sources (landfills and mines)

    • Deliberate application like pesticides applied directly to the land (leach in soil, surface water or ground water become contaminates)

    • Urban storm runoff where contaminates from the first wet weather overflows pipes and into rivers

 

  • Give some examples of how contaminants may enter the atmosphere. How about land
    or groundwater entry?

    • atmosphere entry from land or surface water through volatile means (easily evaporates and moves between land and atmosphere) 

      • Volatile organic compounds (VOC) beneze, naphthalene

    • Land and groundwater entry through leaching into soils/groundwater, intentional pollution(pesticides, fertilizers), combustion that create volatile compounds, leaking of storage tanks
       

  • What are the fates of contaminates

    1. Water solubility

    2. Hydrophobicity

    3. Vapour pressure

    4. Environmental half life

 

  • Define water solubility?

    • Sw: the maximum amount of substance that can dissolve in water at equilibrium
       

  • What is KOW and how is it measured (i.e. describe the steps to determine KOW and
    include the equation for the calculation). Note, you will not be asked to calculate KOW
    directly, but should be able to apply knowledge of KOW values.

    • KOW is the (octanol-water partition) coefficient and measures a compounds hydrophobicity

      • The ratio of concentration of octanol to water

 

  • Determining KOW :

    1. Dissolve compound in equal volumes of octanol and distilled water

    2. Measure concentration of chemical in water and octanol and compare the concentrations

    3. Calculate Kow ->

 

KOW = concentration of chemical in octanol ÷ concentration of chemical in water
 

  1. Predicts the partition between water and lipids.

  • Higher  value = higher affinity for lipids, lipophilic/hydrophobic

  • lower value = affinity for water, hydrophilic/lipophobic

     

  • What is the Henry’s law coefficient? What is the equation?

    • Henry's law (H) coefficient: the ratio of vapour pressure to water solubility

    • Kaw - air-water partition coefficent between a liquid and gas

      • Higher value = gas escapes from water to air (more volatile)

      • Lower value = gas has high solubility and stay in the liquid

 

H= concentration of chemical in AIR ÷ concentration of chemical in WATER

 

  • What impacts environmental half-life?

    • Environmental half life depends on conditions and chemicals

    • If the organic compound has:

      • Double bonds or oxygen containing functional groups -> More susceptible to attack

        • Less persistent from breakdown by enzymes and light

      • Hydrogen replaced by halogens -> increases persistence

 

  • What are the processes that contribute to the loss of contaminants in the environment?

    • Process for Loss of contaminants due to:

      1. Hydrolysis, oxidation, photolysis

      2. Radioactive decay

      3. Complexation

      4. Burial in sediments

      5. Dilution in ocean/atmosphere

 

  • What is the fate of inorganic pollutants?

    • Inorganic pollutants will end up in the ocean, some remains in solution, or deposited insediments
       

  • Describe some examples of environmental factors that may impact the loss of
    contaminants in the environment.

    • Environmental factors for Loss of contaminants:

      1. Temp., light, pH, redox potential

      2. Ionic composition of water

      3. Microbial activity

      4. Dissolved organic carbon

      5. Sedimentation rates

      6. Others, depending on what contaminant and where
          

  • What is long-range transport mean with respect to environmental contaminants?

    • Long-rang transport -> where contaminants travel from their origin via air or water