I've looked at David Suraski's very interesting paper. Before anybody
jumps down my throat at what I'll be saying here, I am, of course, fully
aware that the quantity of Sb in a solder alloy is generally small and,
proportionally speaking, is unlikely to cause problems.
Many thousands of years ago, when I was a student, I was told by my prof
that antimony was extremely toxic in both its metalloid allotropes and
all its compounds. As this seemed contradictory to what David is telling
us, I tried to quickly find out more.
First ref. of course is the Handbook of Chemistry and Physics: it just
says, "Antimony and many of its componds are toxic. Exposure to antimony
and its compounds should not exceed 0,5 Mg/M3 [sic!]". It gives the same
value for arsenic. I found similar info in a few other reference books.
I then did a quick Internet search. I found that medical science
hypothesises that exposure to Sb in young children may be a contributory
cause of autism. It is also hypothesised, on the other hand, that a
genetic disorder causing autism may fix Sb in the tissues of autistic
kids more readily than normal ones.
The toxicity data that David quotes is essentially US and it may be that
other countries may have different opinions on the toxicity and
environmental data. I did not do a search on this aspect but did find
that the effluent discharge of Sb from treatment plants in Switzerland
is fixed at 0,1 mg/l, much less than the figures in the USA, and equal
to lead and some other metals (only mercury is more severe). For further
info (in French), see
http://www.admin.ch/ch/f/as/1998/2863.pdf (large downloadable PDF file).
I also looked at the LEPC site (co-run by the US EPA) and I recommend
that the TRI data that is quoted in the paper should be read in full at
http://www.lepcnet.org/E1725T29.htm
to obtain a better picture of the data that is supplied. On the same
site at
http://www.lepcnet.org/E2058T31.htm
I found that there is a proposed ruling about antimony under the
Pollution Prevention Act.
I also search-engined "+antimony +landfill" and obtained literally many
hundreds of responses aggregated over a dozen engines. Many of these
concern sites which are already contaminated with Sb. I was not able to
find much about the landfill chemistry of Sb but, as with lead, anything
can happen because you never know what is going to be dumped upstream of
it.
I would therefore respectfully suggest that things may not be quite as
rosy as David suggests, when it comes to the pure metalloid or its
compounds. Whether dumping Sb-containing solder in a landfill is likely
to be hazardous or not may be anybody's guess. However, it should not be
forgotten that the soldering process may be done with any imaginable
kind of flux: we need to know whether antimonial compounds are likely to
be formed as a reaction product between the flux and antimony, tin
antimonate or any derivative.
Somebody recently (maybe from Hereaus) mentioned potential toxicity
problems in spraying tin/lead for solder powder. How about Sn/Ag/Sb (in
the order of concentration): would that be acceptable?
Just a few devil's advocate-type concerns...
Brian
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