Re: question

[Sam McClintock <scmcclintock@ipass.net>]

  cc: Susan
  
  Susan Snow wrote:
  
  > Can anyone answer the following question for a friend of mine?
  >
  > Is there any possibility that mercury could be produced as a by-product
  > of the PVC plastic production process, including incineration?
  >
  > Susan Snow
  
  Short answer:  Normally no, but it is slightly possible to have a problem.
  
  You cannot produce mercury (Hg) in the sense that most people think of,
  e.g. you have several compounds in a tank that are NOT Hg and Hg is formed
  by their reaction. Hg is not formed by simple chemical reactions.
  
  However, Hg can work its way into any manufacturing process as a trace
  contaminant, e.g. something that was not intentionally made or placed their
  but because it was impossible to remove all traces of Hg from the process.
  You can find Hg as a trace contaminant in many things, more commonly
  pigmentation that may go into PVC production (though not a lot).  It might
  help in understanding the process in that one of the white pigments, one of
  the more common colors, comes from the processes of refining titanium ore,
  rutile, just stuff you dig out of the ground.  Have no idea if it is the
  same pigment used in plastic production, but it is easy to see how very
  small amounts of Hg can get caught up with everything to make a pigment of
  any type.
  
  A (sadly) more important source of trace contamination is our own
  environment.  Because we have used mercury for so many things, it can be
  found almost anywhere in the environment.  The term "mad as a hatter" come
  from workers suffering nervous disorders because Hg was used in felt
  production of hats, and most people know/remember of the Minamata (sp?)
  disaster of 52 (Japan).  So it can get picked up in a lot of things.
  
  What does this mean for PVC production and incineration.  1)  Incineration
  of anything will generally emit trace contaminants of metals, though with
  plastics those numbers are NORMALLY going to be quite low (not a
  significant health risk).  2) The PVC facility may have elevated emission
  levels of mercury because a) someone is burning something in the scrap
  incinerator they are not supposed to, b) an additive or compound is coming
  from a source with extremely high trace contamination (see previous
  discussions of lead), or c) some new process or catalyst is having Hg
  leached from production/surface.  (a) and (b) above would be rare cases,
  (c) I suspect would be very rare.  But it COULD happen, just like any other
  "simple" mistake when it comes to manufacturing anything in our society.
  On the plus side, if Hg were found in air or water discharge from any
  facility in detectable amounts, it should be relatively easy to figure out
  where it was coming from.
  
  Normally, you would not look for Hg discharges from a PVC facility.
  
  Sam McClintock
  mac@ensanity.com