[Dioxin-l] Re: Poor efficacy of residual chlorine in drinking water distr...

[david bell]

Hi Carl
>Connie,
>
>I would be more interested in knowing about any contamination from the PVC
>pipe now used in many water systems than of the chlorination of the water
>itself.

PVC is long-chain, and essentially insoluble in water. Hence it has no 
toxicity. Vinyl chloride monomer is a good human carcinogen, but there is 
very little of it in PVC, it gets diluted out a lot, and you can detect the 
resulting cancer very easily. VCM gives cholangiocarcinoma in humans, and I 
am not aware in any variation in the rate of this rare human cancer.

>My other concern is the combination of chlorine and organic compounds to 
>form
>triholomethane for example. I don't think that we can just look at free
>chlorine by itself.

I guess you are probably aware that there is a massive ongoing debate around 
this issue. Some people argue that the (potential) cancer risk from tiny 
quantities of chloromethanes are significant. Others, that the public health 
benefits of chlorination vastly outweigh any cancer risk. There is a 
well-founded argument that the carcinogenicity of trichloromethane has a no 
effect level- and that the low levels in water are without significance.

cheers
david

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