Mike

All the reports are anecdotal and subjective.  Chinese officialdom would probably prefer
to deny they exist and/or try to eliminate these uncontrolled entrepreneurial practices
than to test.

The myths are propagated by enthusiastic environmentalists who have a single-minded
agenda-- lead is bad--ban it.
Unfortunately, over the millennia, we've taken the lead genie out of its earthen bottle
and distributed it where we live, all over the place.  Banning lead is something like
banning water or alcohol.

Harvey Miller

----- Original Message -----
From: "Mike Fenner" <[log in to unmask]>
To: <[log in to unmask]>all over
Sent: Monday, July 26, 2004 9:35 AM
Subject: Re: [LF] "lead vapors" myth


If they are " holding boards over .... coal stoves" then surely Pb is not
going to be the biggest hazard they face.
Suggest the major risk is Burns and ingesting Coal smoke and pyrolysis
products/fumes from the organics of the PCB etc. These will be laden with
nasties and small lung penetrating particulates. Possibly even some Pb, but
in this article no doubt the authors gave the actual Pb blood levels of a
carefully worked out sample of these exposed workers and also locals who
were not similarly exposed as a control, so as to properly illustrate the
concerns they expressed. (Pb blood testing is relatively simple and easy to
do). Alternatively of course they may not have wanted to intrude on people's
privacy for taking blood and so sampled the atmosphere instead, again there
are standardised ways of doing this. I have not read this particular article
so out ofrest can anyone tell me the numbers they gave. I would like to
compare them to numbers for Western Europe and so on.


Regards

Mike



-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Eric Williams
Sent: 20 July 2004 02:26
To: [log in to unmask]
Subject: Re: [LF] "lead vapors" myth


Did a Google search on lead exposure from soldering. Came up with this MSDS
sheet (http://www.frymetals.com/pdf_uploads/MSDS%203.5.PDF), which suggests
that resin vapors are the main problem, saying that lead fumes don't form
until 700 degrees Fahrenheit. The following websites suggests that these
fumes contain lead oxides (http://www.sentryair.com/solder%20fume.htm).
Haven't found definitive sources yet though....

In pictures I've seen of dismantling operations in China and India, workers
are holding circuit boards over little coal stoves. I presume an important
question w.r.t. lead exposure is then what temperature do those stoves heat
the solder to. Don't know the answer to that one though...

Best, Eric

---------------------------------------------------------------------
Eric Williams
United Nations University
Environment and Sustainable Development Programme
IT and Environment Project
http://www.it-environment.org
53-70 Jingumae 5-chome  Shibuya-ku  Tokyo, Japan
Phone: 81-3-5467-1352    Fax: 81-3-3406-7346
------------------------------------------------------------------------


> -----Original Message-----
> From: Brian Ellis [mailto:[log in to unmask]]
> Sent: Sunday, July 18, 2004 4:50 PM
> To: [log in to unmask]
> Subject: Re: [LF] "lead vapors" myth
>
> As far as I'm aware, metallic lead is not toxic per se, because it
> cannot be metabolised. It is the lead compounds, starting with the
> various oxides, that are toxic. That having been said, airborne lead
> particles could be easily oxidised and sulfided. It should also be
> mentioned that lead is not absent from the so-called "cosmic dust" or
> micrometeoroids. In fact, scientists use the U:Pb ratio of these to
> determine their age and origin. I cannot state the quantities but it is
> not insignificant.
>
> One thing that should be realised is that the toxic effects of lead (and
> most other elements and compounds) are not linear. There is a threshold,
> below which the effect is negligible. Above the threshold, the effect
> can follow a law with an exponent of the mass absorbed of anything
> between 1 and 2.
>
> Another popular myth is that the toxic effects of lead are irreversible.
> Sure, brain cells that have already been destroyed cannot be regenerated
> but long term treatment with calcium EDTA and penicillamine will remove
> the lead from the system and prevent further damage; at the same time,
> it will eliminate all the other symptoms of plumbism (painful
> gastrointestinal degradation, reduction of haemoglobin production
> causing anaemia, gum disease etc.), which often kick in before severe
> mental deterioration.
>
> Brian
>


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