In Keith's post he says:
"An underlying premise is that lead is indeed as dangerous to health and well being as
is claimed by the toxicologists. The key point on lead toxicology seems to be that there
is no safe lower limit. It is always the case of less is better. "

The problem with this statement is that it is 1) meaningless and 2) not true.  You can
not say lead (or anything else for that matter) is "dangerous to health" unless you talk
about dose. There are, in fact, safe lower limits, because there are (and for millenia,
have been) exposures to lead that produce no discernible harm. Less always being better
is also not true. There are many chemicals, minerals and elements that are absolutely
essential to normal body functions and good health, at certain doses. But at higher
doses would be lethal.

Keith goes on to say "The fact that there is already a lot of lead scattered around the
earth as a result of the use of lead in paint, gasoline, car batteries etc does not
necessarily mean that it does not matter whether more is scattered."

I thought lead (Pb) was scattered around the earth as a result of nature. Man is not
scattering any more lead (Pb) around than existed a billion years ago. Granted, not all
lead in the world is found as pure, refined Pb. But then we are not really talking about
Pb in electronics, are we? We are talking about solder and CRT glass. What is it about
solder that makes its lead so mobile while lead in other materials is not so mobile?  If
lead leaches out of solder does it also leach out of lead sulphide?

Granted that impermeable liners are not absolutely impermeable. But, in the real world,
do the laws of physics and chemistry allow for conditions in a landfill to cause lead to
be leached out of solder, for lead to be transported to adjacent soil and then migrate
to water sources (or other sources that might lead to human exposures), in such
quantities as will be harmful to man and other living creatures?

That is the relevant question.


Chuck Dolci



[log in to unmask] wrote:
> Robin,
>
> There may be a lot of technically plausible reasons why leaching of lead from
> scrapped electronics in landfill does not by itself provide sufficient
> grounds for eliminating lead from solder.    However, I feel that there is more to
> the case for lead-free solder than simply that it is too late to stop the
> consequences of some misguided European legislation.
>
> I believe that there are two more general grounds that might be considered
> justification for the move to lead-free.     An underlying premise is that lead
> is indeed as dangerous to health and well being as is claimed by the
> toxicologists.   The key point on lead toxicology seems to be that there is no safe
> lower limit.   It is always the case of less is better.
>
> The first is that, given that lead is a toxic material, it seems unwise to
> continue to use it in an application which virtually ensures that it will be
> scattered widely around the world.    Electronic circuitry is becoming
> ubiquitous.    Even many of the very poor of this world have a radio and the middle
> class, whose numbers are growing rapidly around the world, typically own 5 - 50
> items which contain some sort of electronics.  And apart from private ownership
> electronics are being scattered around the earth in communication, control and
> monitoring equipment.   All of this electronics is eventually discarded and
> may not necessarily end up in a recycling program or in managed landfill.   It
> is as if someone were firing a shot gun  from space scattering tiny pellets of
> lead nearly everywhere.    The fact that there is already a lot of lead
> scattered around the earth as a result of the use of lead in paint, gasoline, car
> batteries etc does not necessarily mean that it does not matter whether more is
> scattered.   Lead has been largely eliminated from paint and gasoline and car
> batteries are largely recycled.   It may be argued that there are technical
> grounds for believing that those tiny pellets of lead are just going to lie
> there, largely inert with none of the lead finding its way into the water supply
> or food chain.   However, is it worth taking a risk when it is avoidable?
>
> The second is occupational health and safety.   In this forum the point has
> been made recently that at normal soldering temperatures the vapour pressure of
> lead is not high enough for its fumes to create a significant problem.
> However, it is my personal experience that if you are exposed to lead-containing
> solder it is likely that your blood lead level will increase.   Blood lead
> levels in most industrialised countries might already be elevated because there
> is still quite a lot of lead from other sources about but that does not
> necessarily mean that a further increase is of no consequence.   In electronics
> assembly the greatest risk is for people working with processes involving pots of
> molten solder, not because of lead vapour but because of the fine lead oxide
> dust that is inevitably generated.    For those working with solder paste there
> is always a small risk of ingesting the fine particles of solder powder on
> which this product is based as residues of paste dry out and disintegrate.
> Even for those handling solder wire, the lead oxide on the surface rubs off onto
> the fingers and can find its way into the body by ingestion or, more
> dangerously if the worker is smoker, by inhalation.   Of course precautions are
> normally taken to ensure that blood lead levels of people working with solder stay
> below the legislated limit.    Masks are worn when skimming dross off a solder
> bath.  Strict hand washing procedures are followed before eating or smoking
> and for people with the greatest risk of exposure there are periodic checks of
> blood lead.    However, there can be no guarantee that such precautions are
> always followed perfectly so the risk remains.   As contributors to this forum
> have pointed out recently there are other health risks associated with
> soldering, e.g flux fumes, but that does not necessarily mean that it is not worthwhile
> eliminating this lead risk from the work environment.
>
> It is true that the effects of the foregoing are small and so the question
> remains as to whether they justify causing such great inconvenience to the
> electronics industry.
>
> Some years ago there was concern that a change to lead-free solder was not
> technically possible.    There are certainly some challenges in making the
> change but it does seem that it is technically possible.    There are already
> hundreds of millions of printed board assemblies in service that have been made
> with lead-free solder over the past five years.   The question of reliability
> will remain at least partly unanswered until lead-free solders have been in
> service as long as tin-lead solder has been but so far no problems have emerged
> that seem to be beyond a technical solution.
>
> Is the change to lead-free justified?
>
> Since I am associated with a solder maker who might be considered to benefit
> from a change to lead-free I cannot make that call.   All that solder makers
> can ethically do is offer assistance to customers who find themselves obliged
> to make the change to lead-free.
>
> As a final comment, from my personal experience with Japanese I would say
> that it would be unfair to suggest that their leadership in the change to
> lead-free solder has been motivated by some devious commercial strategy.    Living as
> they do on a small crowded island the Japanese are very conscious of
> environmental issues.   And because of the Minamata disaster (thousands of people
> suffering from severe mercury poisoning as a result of industrial pollution) they
> have been acutely sensitised to the potential dangers of toxic metals in the
> environment.    Perhaps the Japanese should be given the benefit of the doubt
> that they are motivated by a genuine concern for the environment.
>
> Keith Sweatman
> Nihon Superior Co., Ltd.
>
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