[Dioxin-l] Re: Dioxin-l digest, Vol 1 #14 - 13 msgs

[Miguel Oliveira e Silva]

david bell wrote:
> Below is correct; EPA regulates an acceptable daily dose (TDI) as 0.01p=
g/kg
> of TEQ. However, as Tony says, there is quite a bit of interest in this=

> figure and how you arrive there. For example, the WHO says 1-4 pg/kg sh=
ould
> be the TDI, and the UK government says 10 pg/kg should be the TDI (see
> http://www.doh.gov.uk/pub/docs/doh/pcddfish.pdf for references). All of=

> these agencies use the same data, are trying to get the same safety lev=
el,
> so it is surprising to see such divergence of TDI figures.

The UK government dioxin TDI level was based on WHO's old limits
(as your reference clearly shows), so they are not independent!

david bell wrote:
> I suspect that part of the difference is due to the long half-life of T=
CDD
> in humans, at 7 years (2000+ days), versus twenty-one days in rat. This=

> introduces a scaling factor of 100.

Unfortunately I suspect that the differences have little to do with
science, but mostly with politics...

Observing the time-evolution of the dioxin levels that are considered
"acceptable" (by EPA, WHO, etc.), there has been a systematic lowering
of this values (the more we know about it, the more it lowers). From
this fact, we can reach a few conclusions, and raise some questions:

1. The so called proposed public health "secure" levels, were not so
   secure after all. What has failed in their estimation? Was it a
   scientific problem? Or was it a political problem, underestimating
   far too much, what was unknown? (and largely it still is... little
   scientific data exists on the ~70000 synthetic chemicals that are
   being massively released to the environment, and close to none, on
   the impact of mixtures of them)

2. The slowly increasing scientific knowledge (which by definition is,
   and always will be, incomplete... [unlike human stupidity]), on the
   environment impact of this chemicals, is pushing down this so
   called "acceptable" limit, showing that the dioxins are a very
   serious problem (why minimize it?).

3. Science does not give "ready-to-use" (or should I say "abuse" ;) )
   answers: The acquisition of knowledge takes time.
   Does it make sense, when dealing with persistent toxic pollutants
   (as is the case of too many organo-halogenated compounds), to rely
   mainly on risk analysis (knowing that we know so little...), just
   because it gives us "numbers"? What about the environmental effects
   that have not yet been studied (which are the majority)?

When we drive our cars with low visibility, do we use high velocity
assuming -- just because we don't know -- that there is no heavy turn
ahead? Or do we choose to be cautious, lowering the speed, exactly
because we just don't know what is ahead?

Why do chemical industry, and governments all over the world CHOOSE the
to do the opposite when dealing with pollution and wastes? The past and
present experience shows, that unfortunately there are lots of "heavy
turns" on this matters! Why persist on repeating the same [policy] errors=
?
(This is not a scientific error, it is a policy error!)

Dioxins are extremely toxic (most of actual scientific data points to
this conclusion). Their sources are MAINLY anthropogenic, and related
to the [eventual burning of] massive uncontrolled release of synthetic
halogenated organic compounds in the environment. Clearly (at least
to me) the solution should be applied on the source, not on the destiny!

david bell wrote:
> I think EPA has known for a long time that average intake of dioxin TEQ=
s is
> 1 pg/kg/day- about 100 times greater than the set TDI. ( see
> http://www.epa.gov/ncea/docs/food99.wpd). It is not clear that it would=
 be
> possible to reduce TEQ exposure to the EPA recommended guidelines.

It will not, if the waste strategy continues to rely mainly on end-of-pip=
e
"solutions", such as burning or burying wastes!

I don't think it is necessary more knowledge (although that is always
desirable), to seriously start promoting clean[ner] production and
products (instead of investing most of the money, on "new" combustion
or landfield technologies, or better filtering)! That way, it would
be possible to reach those levels... and even lower ones.

>
> cheers
> david
>
> (...)
>

-miguel

--
Miguel Oliveira e Silva   email: mos@det.ua.pt
Dep. de Electr=F3nica e Telecomunica=E7=F5es / IEETA
Universidade de Aveiro - PORTUGAL
phone: +351 234 370375    fax: +351 234 370545
www: http://www.inesca.pt/~mos

"Sometimes I think the surest sign that intelligent life exists elsewhere=

 in the Universe is that none of it has tried to contact us", Calvin & Ho=
bbes