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From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: comp.misc
Subject: Re: Computer Tape Disposal
Message-ID: <2086@kitty.UUCP>
Date: Thu, 8-Oct-87 11:05:52 EDT
Article-I.D.: kitty.2086
Posted: Thu Oct  8 11:05:52 1987
Date-Received: Sun, 11-Oct-87 02:09:41 EDT
References: <276@cbnscs.UUCP>
Distribution: na
Organization: Recognition Research Corp., Clarence, NY
Lines: 58
Keywords: Environmental Risks?
Summary: Probably safe for landfill disposal...

In article <276@cbnscs.UUCP>, pc6300@cbnscs.UUCP (Linda Dunlap  - AT&T Network Systems, Columbus OSTC) writes:
> Our Environmental department asked me if there is anything they need
> to be concerned with regarding the disposal of a large number of
> 700' and 2400' reels of magnetic tape.  They seemed to think there were
> trace amounts of mercury in them.  Can anyone advise?

	My organization did a lab study for a toy manufacturer a few years
back to determine if there were any materials in magnetic recording tape
which could injure a young child if they were to ingest the tape from a
broken tape cassette.  I won't event begin to speculate what would possess
a child do do this. :-)  In this day and age, manufacturers of consumer
products - especially toys - are concerned to the point of paranoia about
product liability.
	In any event, I am have some familiarity with magnetic recording
tape composition as a result of this study.  Computer tape does have a
different formulation from that of audio tape, but it's close enough for
the present discussion.
	The tape itself (sans magnetic compounds) is a polyester film;
chemically, it is (poly) 1,4-butylene terephthalate or (poly) tetramethylene
terphthalate.  The film also contains small amounts of stabilizers and a
coloring agent.
	While we did not study computer tapes per se, my educated guess is
that a 2,400 foot 1/2 inch computer tape with a magnetic coating thickness
of 250 microinches will contain approximately one ounce (weight) of magnetic
coating material.  The magnetic coating material will most likely be a
blend of ferric oxide and chromium dioxide, along with a resin which binds
the material together and causes adherence to the polyester film.  There
may also be a small amount of a molybdenum compound (like molybdenum
disulfide) as a lubricant.
	That's it.  All of the above compounds in the quantities which may
be found in magnetic recording tape are intrinsically safe to the
environment.  Magnetic recording tape is not "bio-degradeable", but over
hundreds of years it will probably depolymerize into powder.
	There is no mercury or mercury compounds intentionally added to
any magnetic recording tape that I am aware of.  In our study for the
toy manufacturer, we examined about 20 samples of tape from different
manufacturers of audio cassettes.  We conducted a general analysis for
heavy metals by means of AA and ICP spectrophotometric analysis.  While
we did find traces of heavy metals (including mercury), the amounts were
insignificant (in the ppb range); this is no more than would be found by
analysis of any common object like say, a paperclip.
	I suppose I shouldn't say this, but the only possible environmental
hazard of magnetic recording tape could result from burning it.  At
temperatures between 250 and 500 deg C the chromium dioxide would be
converted to chromium trioxide, which is a rather corrosive substance. 
However, the quantities involved in the tape are still rather small, and
burning probably represents no worse a scenario than the production of
hydrogen chloride by the burning of PVC. 
	So, to sum up: I don't see any potential environmental harm posed
by the landfill disposal of magnetic recording tape.  There is a slight
potential environmental harm posed by incineration of recording tape, but
the effects of this can be mitigated by combustion in an incinerator
equipped with a waste gas scrubber (pretty common these days).

<>  Larry Lippman @ Recognition Research Corp., Clarence, New York
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