Following is an
overview of the 1998 UK Limerick Report regarding the
toxic gas theory for cot death (the Richardson
hypothesis). Contrary to
publicity, the Report did not disprove the theory - in
fact, it provides further confirmation of it.
BACKGROUND
At the end of
1994 the British Government faced huge potential legal
claims by bereaved parents. In the 1980s the Government
had required manufacturers to include a fire retardant
in cot mattresses, and had approved antimony trioxide
for the purpose. The result was the generation within
cot mattresses of stibine gas, which caused thousands of
cot deaths. If the Limerick Report had supported the
toxic gas theory for cot death, the British Government
would have been liable for millions of pounds in
damages.
What did the Limerick Committee investigate?
They
investigated whether certain toxic gases are generated
from fire retardant chemicals contained in PVC-covered
cot mattresses.
Was this a full investigation of
the toxic gas theory for cot death?
No. It had
serious limitations:
The Committee
did not investigate any mattresses other than those
covered with PVC. They did not investigate natural
products used as bedding (despite the fact that many cot
deaths occur on such materials, e.g. sheepskins). They
focused on only one of the three relevant gases (stibine).
Is the Limerick Report relevant in New Zealand?
Largely, no.
This is because PVC-covered mattresses are very rarely
used in New Zealand. Sheepskins (which are frequently
used as baby bedding in New Zealand) were specifically
excluded from the study. New Zealand mattresses very
rarely contain fire retardants. The toxic gases most
likely to be generated from New Zealand baby bedding (phosphines
and arsines) were not focused on in the study.
How then does the Report provide confirmation of the
toxic gas theory?
It confirms (yet
again) the gas generation which causes cot death: the
Committee achieved generation of a form of stibine.
Other researchers had already proved the generation of
all three gases: phosphines from phosphorus, arsines
from arsenic and stibines from antimony.
But the Report's conclusion states that the toxic gas
theory is unsubstantiated. Why?
Although the
Committee had replicated the toxic gas generation, they
said such gas was not the cause of cot death. This
conclusion was based on a large number of errors and
irrelevancies. For example:
The Report
stated that one particular fungus which can cause gas
generation (S. brevicaulis) was not found on any
mattresses on which babies had died of cot death.
Irrelevant. The Committee found S. brevicaulis and many
other micro-organisms on cot mattresses - and a number
of these are capable of generating toxic gas if
phosphorus, arsenic or antimony are present in a
mattress. Whether babies had died on the mattresses
tested by the Committee is immaterial.
Household fungi
become established in nearly every mattress which is
slept on, and in underbedding which is washed
infrequently.
The Report stated that what
Richardson had identified as a fungus was actually
bacteria. Irrelevant.
Bacteria as well as fungi can generate toxic gas from
the chemicals concerned.
The Report stated that while toxic
gas was produced under laboratory conditions, no gas
could be produced in cot conditions.
Irrelevant. Gas generation
has already been achieved in cot conditions, and failure
by the Limerick Committee to do so doesn't negate this
fact.
Various
researchers have found it difficult to achieve gas
generation consistently using media with a neutral pH.
But the pH of a cot mattress is often higher, owing to
the conversion of urea to ammonia. Experiments carried
out using high pH (say, 10) have achieved more
consistent gas generation. In these tests fungus
flourished and the amount of gas produced was greater
than at neutral pH.
The Report stated that cot death
babies did not show the typical physiological effects of
phosphine, arsine or stibine poisoning, e.g. haemolysis
and pulmonary oedema. Of
course they didn't. Babies die so quickly from
this type of poisoning that these effects don't have
time to develop.
Haemolysis, for
example, takes many hours to develop; so does pulmonary
oedema. But this gaseous poisoning can kill a baby
within minutes.
The
toxicological data contained in the Report relates to
adults and older children. None of it relates to babies
- and it is well known that babies' blood and
physiological responses differ materially from those of
older children and adults.
The Report stated that cot death
babies had the same amount of antimony in their body
tissue as babies who had died of other causes.
Wrong. Research carried out in 1994 showed that
post mortem body tissue of cot death babies contained
many times more antimony than tissue of babies who had
died of other causes.
The Report stated that antimony
present in the tissue of cot death babies could have
come from many sources other than their mattresses.
Wrong. The same 1994
research showed that the body tissue of babies who had
died of causes other than cot death contained no
detectable antimony (or in one case very little). If the
Report were correct, there would have been similar
amounts of antimony in the tissue of all the babies
tested, whether they had died of crib death or of other
causes.
The Report stated that the
introduction of antimony and phosphorus into mattresses
in Britain did not coincide with a rise in the cot death
rate. Wrong. These
chemicals were first introduced into cot mattresses in
the early 1950s, and the British cot death rate
increased steadily from that time onwards. (In fact the
term "cot death" was coined in 1954 as a result of the
marked increase in the number of such deaths.)
The highest cot
death rate in Britain (2.3 deaths per 1000 live births
in 1986-1988) coincided with the highest concentration
of antimony in cot mattresses. The British Government
had required a fire retardant to be incorporated in cot
mattresses by 1988. Manufacturers were given four years'
warning and during this period moved towards compliance
with the new standard.
The Report stated that the
steepest fall in cot deaths in Britain occurred when
antimony was very prevalent in cot mattresses and
coincided with the "Back to Sleep" campaign.
Highly misleading.
Certainly the British cot death rate fell while the
amount of antimony in mattresses was high - but that was
because from mid-1989 onwards parents took preventive
measures against toxic gas generated in their babies'
mattresses. Furthermore, manufacturers began to remove
antimony from mattresses.
In June 1989 the
toxic gas theory was publicized nationwide and the crib
death rate immediately began to fall (see graph). It had
fallen 38 % (to about 1.4 deaths per 1000 live births)
by the time "Back to Sleep" was launched in December
1991 - two-and-a-half years later. The fall was steepest
following the commencement of "Back to Sleep" because
that campaign added to the success already being
achieved by advice based on the toxic gas theory.
What about the claim in the Report that three babies
have died of crib death on polythene-wrapped mattresses?
This claim is unsubstantiated.
The types and thicknesses of the plastic are not known.
Was it thick, clear polythene (safe) or thin or coloured
polythene (unsafe)? Was there bedding containing
phosphorus, arsenic or antimony on top of the plastic?
Were sheepskins used? Or mattress protectors? These
questions have not been answered, and without this
information the claim is not valid.
In February 2000
Dr Peter Fleming, a co-author of the Limerick Report,
stated that the claim that three babies had died of crib
death on polythene-covered mattresses could not be
substantiated.
Are there
other findings which support the toxic gas theory?
Yes. For
example:
Scottish
research has proved that the crib death rate rises as
mattresses are re-used from one baby to the next. This
is because micro-organisms become better established in
a mattress as it is used. When re-use commences, toxic
gas is generated sooner and in greater volume.
Statistics show that the cot death rate jumps from first
babies to second babies; and jumps again from second
babies to third babies; and rises still further for
later babies. The reason is that parents frequently buy
a new mattress for their first baby and then re-use it
for subsequent babies. Research in the USA has reported
that cot death babies show neurochemical deficits
relating to heart function and breathing. This is
accounted for by the fact that phosphines, arsines and
stibines are all "nerve gases". They shut down the
central nervous system, causing cessation of heart and
breathing functions. (This is why crib death babies do
not show any apparent symptoms.)
The
conclusions of the Limerick Report should be disregarded.
Other researchers have disproved them; and so has the
practical experience of mattress-wrapping in New
Zealand. Since late 1994 many tens of thousands of New
Zealand parents have wrapped their babies' mattresses
for cot death prevention, and since that time the New
Zealand crib death rate has fallen markedly. The
practical experience of mattress-wrapping proves the
toxic gas theory for crib death. If mattress-wrapping
did not prevent crib death, many deaths would have
occurred by now on polythene-wrapped mattresses.
THERE HAS NOT
BEEN ONE REPORTED CRIB DEATH ON A BabeSafe MATTRESS COVER
OR
BabeSafe MATTRESS.
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SIDS Sudden Infant Death "Syndrome"
by Lendon H. Smith, MD, with Joseph
G. Hattersley, Ma SIDS Sudden Infant Death "Syndrome"
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Orthodox Crib Death
Prevention Advice by Dr. Sprott
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