[Dioxin-l] Open List?

[david bell]

Hi Carl

<snip>
>I have
>conceeded that organo-halogens can be found in nature, but the hitch is to
>what degree of presence compared to the plethora of anthropogenic
>organo-halogens (both quantity and variety) now found in nature that were 
>not
>there one hundred years ago.

I learnt quite a lot from the EPA site, some of which I found surprising. If 
you look at the bottom of the page:
http://www.epa.gov/ncea/dei.htm
There is data about deposition of dioxins in lake sludge since 1884. To my 
amazement, the peak levels of industrial production of dioxin in the 
1960's/70's give an environmental deposition of dioxins which are only 6-10 
fold above the 'normal' level of deposition when there was no 
dioxin-producing chemical industry.

I don't wish to be complacent- this is nothing to be happy about- but I 
hadn't realised the normal environmental processes gave such a high level of 
production of dioxins.

<snip>
>I would like to know what yours and David's views are with regard to
>organo-halogens in the environment. Are there there to many, or to much? 
>Are
>there not enough? Should we worry about them in baby food?

There is a great deal of concern on this; see for example, :
http://www.doh.gov.uk/pub/docs/doh/toxic98.pdf
page 34 is the relevant discussion for PCBs and children.

<snip>
>Since I feel (perhaps irrationally) that the level and diversity of
>organo-halogens in our environment is growing and showing little sign of
>doing otherwise, I am formally announcing that I have been, and remain a
>"CHLORO PHOBE".

I understand that there is a consensus that dioxin levels are generally 
falling.

There are several tests you can use when you make a more general claim about 
organo-halogens.
(1) are they useful ? (clearly, dioxin has no use)
(2) are they a toxic problem in the environment ?
(3) do they accumulate ?

(3) is perhaps quite a key issue; after all, if many organohalogens are 
broken down and metabolised naturally, they are less likely to be a problem. 
Many problems occur when agents persist and accumulate in the environment- 
those that do, are things like PCBs, dioxins, dibenzofurans, even DDT, which 
are known problems. These are where effort should be concentrated, I think.

(1) is also key. Many organochlorines play a large part in maintaining the 
fabric of society; thus you have to balance gain against cost. The WHO won't 
ban DDT, because it's the only insecticide many third world countries can 
afford; a ban would result in tens of thousands of deaths from malaria.

I am not advocating the use of DDT; merely to say that everyone makes their 
own cost-benefit calculations, whatever they may be. Once you start making a 
list of things which require organochlorine compounds, it starts to affect a 
lot of things you do.

cheers
david








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