Bisphenol-A Question #1 by nur18009


									         Announcements                            Bisphenol-A Question #1
 • Final exam structure details               • How long does it take to breakdown?
                                                – In river water it takes about 5 days
                                                – In the body it reacts with a sugar and is
                                                  ultimately removed within 3 days

   Bisphenol-A Question #2                        Bisphenol-A Question #3
• How much are we exposed to?                 • Does exposure change based on
  – CDC study says average concentration is     lifestyle issues (drinking soda, etc.)?
    under 50 ng / (kg day)                      – From CDC study
  – Because it is rapidly metabolized, this        • Mexican Americans have lower levels that
    means low-level exposure is likely               others
    continuous                                     • Women have higher levels than men
                                                   • Lower income people have higher levels
                                                   • Children have higher levels than adolescents
                                                     who have higher levels than adults
        Bisphenol-A Question #4                             Bisphenol-A Question #5
   • Does anything increase risk?                        • What is meant by “being exposed”?
      – To release bisphenol-A from polycarbonate          – The most likely method of exposure is
        requires a reaction called hydrolysis                through swallowing it after it has leached
        (essentially adds back the water from                into food or liquids.
        polymerization and breaks up the bond.)            – Touching polycarbonate materials is NOT a
                                                             route for exposure.
      – Heating and exposure to basic solutions
                                                           – It’s probable that the primary source of
        increases hydrolysis                                 bisphenol-A is the resins that coat food

        Bisphenol-A Question #6
                                                            Bisphenol-A Question #7
• How does it work as an estrogen mimic?
                                                         • How do we know about human effects?
  – Basic mechanism is that it binds with receptors
                                                           – In addition to whole animal studies on rats,
    that influence calcium ion movement into or out of
                                                             studies can be done on cell lines -
    cells.                                                   including human cells.
                                                           – Looking at data from previous study, points
                                                             to a challenge, effects don’t always
                                                             increase with greater amounts.
                                                           – Suggests low dose exposure may be more
                                                             worrisome (but proves nothing.)
   Bisphenol-A Question #8                               Risk - benefit analysis
 • Are there alternatives?                         • Should we regulate polymers that
   – Polycarbonate has many favorable properties     contain bisphenol A to remove them
      • High strength
                                                     from consumer products?
      • Scratch resistant                          •
      • Lightweight
   – It’s possible to make other polymers with
     similar properties (likely more expensive).   •
   – Coatings on cans need to be able to
     withstand sterilization procedures - so
     alternatives are harder to find, perhaps.

 The fate of disposed plastics                         What factors matter most?
• Plastics comprise about 11% of the               • Think of advantages of each - paper or
  garbage - by volume - in the US.                   plastic
• Paper vs. plastic.                               • Think of disadvantages of each
• What is the best way to bring home               •
  your groceries?
• Note figure 9.12 (weight and volume of
  100 bags: 17 lbs & 1219 in3 vs. 122 lbs
  and 8085 in3)
         Recycling plastic                                 Collection
• The process for recycling plastics         • About 7500 cities have curbside
  requires several steps.                      collection
• Collection                                 • About 12,000 additional cities have
• Sorting                                      collection centers.
• Processing                                 • Most of the collection co-mingles the
• Creation and sale of new products            plastics with other recyclable materials
                                               which requires additional handling

             Processing                              Closing the triangle
• Separation is often based on density         • One of the most important steps in any
• In Milwaukee they use a machine that           recycling is the product that results.
  jostles the co-mingled materials and the     • If nobody purchases a product made from
  plastics end up on the top for the most        recycled materials, the materials won’t be
  part.                                          recycled any longer.
• Can also use floating techniques.            • A key challenge for plastic because it
                                                 tends to degrade through the processing
                                                 in must undergo.

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