What is "contamination" though, 1ppm? 20ppm?

I think it would go a lot further if you considered "contaminated" to be 1
atom per gallon, than if you considered contaminated to be 1 gram per litre
for example

> -----Original Message-----
> From: Jim Franklin [SMTP:jim.franklin@BTCONNECT.COM]
> Sent: Tuesday, March 02, 2004 11:20 AM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: ] My first PCB production
>
> I followed that link,
>
> "..Two pounds of root killer contain 0.5 pound of pure elemental copper
> enough to contaminate 20 million gallons of water..."
>
> It makes you think, doesn't it when you see those kinds of numbers...
>
> Jim
>
> -----------------------------
>
> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of William Chops Westfield
> Sent: 01 March 2004 23:15
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: ] My first PCB production
>
>
> On Monday, Mar 1, 2004, at 13:54 US/Pacific, Spehro Pefhany wrote:
>
> >
> > But my wife, who is an expert in wastewater and other environmental
> > technical and legal matters, thinks a bit down the home drain with lots
> > of water isn't a technical problem.
> >
> >
> Note that in the US, it is relatively common (or WAS relatively
> common, anyway) to dump a couple pounds of copper sulfate down
> your toilet to kill roots that might have been invading your
> underground pipes.  Or something.  (Not that everyone is happy
> with this: http://www.city.palo-alto.ca.us/cleanbay/pdf/root.pdf )
>
> Copper sulfate is also pretty widely used as an agricultural
> fungicide.
>
> If you get up to several ounces of copper per year (at 1oz per
> square foot of typical PCB, so, serveral square feet of finished
> PCBs), you should probably start thinking about being nicer than just
> flushing your used etchant down the drain.  But that's a awful LOT
> of PCBs for the average hobbyist...
>
> BillW
>
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