For a new mom, perhaps nothing is more terrifying than the idea that your baby might die suddenly and without explanation. Unfortunately, for every terror that shadows our modern lives, there is someone out there hoping to capitalize upon it.
When our babies were two or three months old and we were both still living in fear of Sudden Infant Death Syndrome (SIDS), a friend of mine called me and excitedly reported that she had just ordered something that would end her worries. "A researcher discovered the cause of SIDS!" she told me. "It's mold!" Furthermore, she went on to tell me, I could 100% eliminate the risk of SIDS by simply wrapping my baby's crib mattress in a special kind of plastic, which could be conveniently purchased from a company in New Zealand.
Now, I do a lot of reading, especially about things that concern my baby's health. In all my research (most of which was done on accredited SIDS websites like The First Candle SIDS alliance) I had never heard of such a thing. I cautioned my friend to be skeptical, then I proceeded to look into the so-called "toxic gas theory." Here's what I learned:
In 1989, a British researcher named Barry Richardson claimed to have done research that proved SIDS was caused by toxic gas producing bacteria living in crib mattresses. His findings were widely publicized in the British television broadcast "The Cook Report" in late 1994. The Cook Report caused minor panic amongst new parents in the UK, many of whom moved their babies from the relative safety of their cribs to hazardous sleeping areas such as adult pillows and sofas. Understandably, SIDS organizations were concerned and a few of them undertook research of their own with the intent of either confirming or rejecting Richardson's theory.
The most exhaustive of these studies was conducted by the "Limerick Committee," which spent three and a half years re-examining existing research and conducting new research of its own. In 1998 the Limerick Committee announced that it had discredited the toxic gas theory, but by then there were already several companies profiting from the sale of polythene mattress wraps that were supposed to protect sleeping infants against toxic gas. Since that time, the manufacturers and retailers of these wraps have sought to explain away the results of the study. Despite the fact that there is still no conclusive evidence that toxic gas causes SIDS, parents continue to fall victim to scare mongering and the bad science that surrounds the toxic gas theory and especially the sale of polythene mattress wraps said to guard against so called toxic gases.
Parents beware. Many of the merchants who sell these wraps provide shoppers with lengthy rebuttals to the Limerick Report, much of which is very badly argued and has no basis in scientific fact. In this document, I want to encourage you to be extremely critical of any website or document that claims validity of the toxic gas theory, but does not specifically quote any of the research that is supposed to discredit the findings of the Limerick Committee. Following is my own detailed critique of many of the popular arguments against the Limerick Report.
BACKGROUND:
The toxic gas theory is based almost entirely on the research of Barry Richardson, who claimed that the fungus S. brevicaulis was present on nearly all crib mattresses, and that his research had demonstrated that the fungus was capable of producing toxic nerve gases.
This is the basis for Richardon's "toxic gas" theory:
"[SIDS] … is caused by gaseous poisoning. The gases concerned are phosphines, arsines and stibines, which are all extremely toxic nerve gases. They are produced in a baby's cot (or any other bed where the baby sleeps) by the action of common household fungus on compounds of phosphorus, arsenic and antimony present in the mattress (and in certain other underbedding, e.g. sheepskins)." (http://www.cotlife2000.com)
Claim #1: The Limerick Report was flawed because it investigated only PVC mattresses, but not natural products such as sheepskins (which are widely used in New Zealand and are associated with a number of SIDS cases).
The committee was investigating the theory that certain funguses react with fire retardant chemicals in infant bedding, emitting toxic gases which lead to infant mortality—the basis for the toxic gas theory (as outlined above). Therefore, whether or not they studied every type of bedding containing those chemicals is irrelevant, as long as the chemicals were present in the bedding they did study.
Claim #2: The Limerick Report was flawed because it focused only on stibine, and not on the other two gases included in the theory (arsine and phosphine).
This is untrue. During the study, the researchers attempted to, but failed to show generation of all three gases. See chapter six of the Limerick Report abstract for details on how this research was conducted and what the findings were. (http://sids-network.org/experts/limerab.htm#six)
Claim #3: The Limerick Report has no validity in places such as New Zealand, where PVC mattresses are less common. To show relevance, the Limerick Committee should have included sheepskins in its study, since sheepskins are often used as baby bedding in New Zealand.
Whether or not the committee investigated sheepskins is irrelevant to the larger question: whether or not mattress wrapping can help prevent SIDS. Sheepskins are not recommended as infant bedding by any SIDS organization, and they wouldn't ever be "wrapped" even if they were found to emit toxic gases.
Claim #4: New Zealand baby bedding is more likely to generate phosphines and arsines, and these gases were not focused on in the study.
Also not true, as seen in this excerpt taken directly from the Limerick Report:
"Phosphine and trimet hylphosphorus were not produced under the test conditions described by S. brevicaulis from cot mattress samples containing phosphate fire retardants and plasticisers, or from other phosphate compounds added to or present in the culture medium. No phosphorus gases were unequivocally generated when PVC and foam mattress materials were incubated under the anaerobic conditions in which trimethylantimony was generated by enriched soil cultures grown in antimony-supplemented media.
"Arsine and trimet hylarsenic have not been generated from cot mattress samples."
In laymen's terms: neither phosphines nor arsines were generated from crib mattress samples containing either fire retardant materials OR other phosphate compounds.
Claim #5: The Limerick Report actually confirms the toxic gas theory, since the committee replicated toxic gas generation and was able to generate a form of stibine during its laboratory tests.
The committee did not "replicate toxic gas generation." Their success at generating toxic gas under controlled laboratory conditions does not in any way suggest that the same thing could occur in an infant's mattress. They tried, but did not succeed in showing that toxic gas could be generated under the conditions that exist in an infant's mattress. See chapter six of the Limerick Report's abstract for details: (http://sids-network.org/experts/limerab.htm#six).
It is true that the committee was able to generate trimethylarsenic and trimethylantimony, but only under extreme laboratory conditions that are unlikely to occur in an infant's crib. For example, if the samples were heated to 110°C (230°F) in an autoclave or at 80°C (176°F) for three days, and the fungus was added to the samples afterwards (the growth of any fungus added before heating would be inhibited by the heating process). An infant, of course, would be unlikely to be sleeping in an autoclave or for three days at a temperature of 176°F.
From the report:
"As a result of our investigations we have established that antimony compounds can be volatilised by the fungus (S. brevicaulis) under very specific conditions which are wholly unlike any to be found in an infant’s cot. Even under these conditions there was no evidence that phosphorus, arsenic, or antimony encapsulated in cot mattress PVC could be volatilised."
Claim #6: Other researchers had already proved the generation of all three gases: phosphines from phosphorus, arsines from arsenic and stibines from antimony, so the Limerick Committee's inability to do so is irrelevant.
The basis of all valid scientific research is that it must be reproducible. In other words, a theory cannot be considered fact until the research that claims to support it has been duplicated using identical methods that achieve identical results. The fact that the Limerick Committee (and other groups) were unable to duplicate Richardson's results does not mean that the Limerick Committee's results were irrelevant, it means that Richardson's results were probably flawed. It is not the work of the other researchers that becomes invalid but the original study. If this particular argument against the Limerick Report were a valid one, it would mean that all original research is untouchable, and that no researcher who follows can disprove any theory since the theory was already "proven" by the original researcher. In other words, it would completely invalidate the idea that scientific research needs to be reproducible.
Claim #7: The fact that the fungus S. brevicaulis is rare in crib mattresses is irrelevant, since the committee did find it on some mattresses, and since they also found other micro-organisms (many of which can also generate toxic gas).
From the report:
"In marked contrast to [the toxic gas theory's] contention that S. brevicaulis is ubiquitous in used cot mattress materials, several subsequent investigations have demonstrated that contamination with this mould is rare, and that it is no more common in mattress materials from SIDS infants than in other used mattresses."
The toxic gas theory, as it was first written, focused almost entirely on S. brevicaulis, which is why the committee also focused on that organism. Even so, the assertion that a number of other microorganisms are "capable of generating toxic gas" was unsubstantiated by the committee, who were not able to generate toxic gas on crib mattresses under any conditions, including the presence of common household bacteria and other organisms.
Claim #8: The committee claimed that no babies had died on mattresses infected with S. brevicaulis, but "whether babies had died on the mattresses tested by the committee is immaterial," since fungi grow on nearly all mattresses and underbedding.
Whether babies had died on mattresses tested by the committee is completely material. If a scientific study aims to substantiate the theory that toxic gas emitted from crib mattresses causes SIDS, then it follows that mattresses belonging to SIDS victims should be tested for the presence of toxic gas.
If fungi capable of generating toxic gas exist on all mattresses, then why do some babies die from SIDS, but others don't? Why isn't the SIDS rate 100%?
Claim #9: The fact that the Richardson apparently mistook a common household bacteria for the fungus S. brevicaulis is irrelevant, since both fungus and bacteria are capable of generating toxic gas.
The bacteria identified by the committee (which Richarson mistook for S. brevicaulis) was actually a mixture of Bacillus, a very common domestic bacteria. During the committee's tests, this and other bacterium present on crib mattresses was not shown to be capable of generating toxic gases. In fact, under extreme laboratory conditions (of the type that would never exist on an infant's mattresses), only S. brevicaulis was capable of generating toxic gas. "Under the same conditions bacteria and other fungi isolated from cot mattresses did not volatilise antimony."
Claim #10: Studies that rejected the toxic gas theory were conducted using a neutral pH media. The pH of a crib mattress is higher, which helps fungi to thrive and become more efficient at producing toxic gas.
The committee conducted many tests using crib mattresses (which presumably fit the criteria of having a high pH), and they were unable to achieve gas generation.
Claim #11: SIDS babies don't show the effects of nerve gas poisoning (such as haemolysis and pulmonary oedema) because they die so quickly that these effects don't have time to develop. Nerve gas poisoning can kill a baby within minutes.
This statement has no basis in scientific or medical fact. Phosphine, arsine and stibine poisoning lead to haemolysis and pulmonary oedema, which lead to death. You can't skip the haemolysis and pulmonary oedema and go straight to death. One causes the other, which causes the other.
If it is true that these gases kill "within minutes," why would an infant be able to sleep safely and with no ill effects on the same mattress only one day before succumbing to SIDS? Wouldn't these gases and the organisms that caused them be building up over a gradual period of time?
Claim #12: The toxicological data outlined by the Limerick Report is taken from research focusing on adults and older children. Since babies' bodies respond differently to toxins, none of the information is relevant.
While it is true that there are age related differences in metabolism, absorption, and detoxification of chemical compounds, it is unclear as to which part (if any) of the Limerick Report contains toxicology data taken from studies done on adults and older children. This is the type of assertion that needs to be backed up by specifics: where does this data appear and in what way does it demonstrate that it is not relevant to infant physiology?
Claim #13: The Limerick Report stated that there were similar amounts of antimony present in the tissue of all babies, whether they had died of SIDS or other causes—but research conducted in 1994 showed that babies who died from causes other than SIDS had no detectible levels of antimony in their bodies. Therefore, the Limerick Report must be wrong.
The research cited here—presumably the 1994 Cook Report—has not been validated by any of several independent studies. Notably, one study in Ireland and another in Scotland were unable to find any differences between the antimony levels in SIDS infants and in infants who died from other causes. This suggests that the Cook Report, which is the only one to date that claims to have discovered the discrepancy, is the one suffering from a fundamental flaw. Remember also that the Cook Report was not "true" scientific reporting, but a tabloid style television "expose," described by the US based non-profit SIDS organization The SIDS Alliance as "ill-defined, unsubstantiated, and wildly speculative."
Claim #14: The Limerick Report claimed that the introduction of antimony and phosphorus into UK crib mattresses did not coincide with an increase in SIDS, but these chemicals were actually introduced in the 1950s, when the SIDS rate began to increase markedly.
Antimony was first added to crib mattresses in 1988, not the early 1950s. This argument is simply incorrect.
Claim #15: In the UK, the SIDS rate was highest between 1986 and 1988. This coincides with the British Government's 1988 requirement that manufacturers add fire-retardant (antimony) to crib mattresses.
Since this high death rate occurred in 1986 and 1987 as well as 1988, it cannot be linked to antimony, which was not added to mattresses until 1988.
Claim #16: Although the SIDS rate did begin to fall when antimony levels in mattresses were still high, it was because parents learned about the toxic gas theory and began to take preventative measures. It was not because of the "Back to Sleep" campaign.
SIDS decreased by 70% between 1988 and 1995, after antimony began to be added to crib mattresses. By 1993 to 1995, only 2% of babies were sleeping on wrapped mattresses. This shows that the drop in SIDS rates wasn't associated with parents taking "preventative measures against toxic gas."
Claim #17: The SIDS rate was beginning to fall during a time when manufacturers were removing antimony from mattresses.
Manufacturers were just beginning to add antimony to mattresses in 1988, not the other way around. Although some manufacturers may have begun removing antimony from mattresses around that time, the practice is still more common than not and the removal from some mattresses cannot be shown to correspond to a decline in SIDS rates.
Claim #18: The SIDS rate declined by 38% between 1989 (the year that Richardson's theory was first publicized) and 1991, when the "Back to Sleep" campaign was launched. The fall was steepest after the "Back to Sleep" campaign because it helped add to the "success already being achieved by advice based on the toxic gas theory."
While the SIDS rate in Britain did decline between 1989 and 1990 (beginning the year after antimony was first added to crib mattresses), the decline was 11%, not 38%. While still a significant decline, there is no proof that it is directly related to the publication of the toxic gas theory, which was not even widely known until the Cook Report aired in 1994. The greatest decline did indeed occur after the "Back to Sleep" campaign was launched, but it is unclear how toxic gas theory proponents can claim that the "Back to Sleep" campaign "added to the success already being achieved by advice based on the toxic gas theory" beyond the extremely questionable contention that toxic gases "are heavy and lay close to the surface of the mattress thus not causing much risk to babies whose noses are up and away from the mattress." According to the SIDS Alliance, such a claim is "akin to saying that you can avoid poisoning by carbon monoxide leaks by opening the windows."
The Foundation for the Study of Infant Deaths (a UK based SIDS organization) explains further:
"The toxic gas theory fits some but not all the known epidemiological features of SIDS. SIDS is not a new phenomenon. In the mid 1950s, well before the introduction of PVC and these chemicals, the number of babies dying suddenly and unexpectedly was estimated at 1400 annually, a figure comparable to that reported in 1990 before the national "Reduce the Risk" campaigns. It has been suggested that the rise in SIDS between 1986-88 is linked to the introduction of higher levels of these chemical compounds and that the decline in 1989 and 1990 before the Reduce the Risk campaign was because some manufacturers stopped using these chemical compounds and parents covered cot mattresses with polythene sheeting (Richardson, personal communication). But fluctuations in the incidence have occurred over the years so the significance of changes need to be interpreted with caution. A significant fall in SIDS is not seen until 1991 and there is no evidence, as yet, that lower levels of chemicals were used in 1989 or that parents covered mattresses with polythene." (http://www.sids.org.uk/fsid/mattresscont.htm)
Claim #19: The Limerick Report states that three babies died from SIDS even though they were sleeping on polythene wrapped mattresses, but this claim is unsubstantiated since the thickness, coloration and type of plastic are unknown. Only thick, clear polythene works as a protection against toxic gas.
The type of polythene used in the three SIDS deaths in question hasn't been shown to NOT be thick, clear polythene, nor has it been shown that any of the bedding used contained phosphorus, arsenic or antimony. In fact, according to New Zealand's SIDS foundation, where mattress wrapping is widespread, there have been numerous other deaths on polythene-covered mattresses. Yet the manufacturers of these wraps always claim that the mattresses were not wrapped according to their specifications, which is a particularly easy way out considering that this claim can never be validated. Since SIDS organizations long ago rejected the toxic gas theory, post mortem investigations are not likely to ever evaluate a death scene to see if mattress wrapping conformed to manufacturer standards.
Claim #20: Scottish research has proven that the SIDS risk increases as mattresses are passed down from one baby to another. This is because fungus and other organisms are better established on older mattresses. Statistics also show that the SIDS rate is higher for second babies, higher still for third babies, and so on. This is because parents often reuse mattresses for subsequent babies.
The Scottish study referred to here did show a link between used mattresses and SIDS, but it did not show that the death rate increases as mattresses are passed down from one baby to another. Furthermore, no research to date has shown that there is necessarily a causal relationship between used mattresses and SIDS deaths, nor that the reused mattresses are more likely to harbor organisms that will produce toxic gas. There are many other factors associated with used mattresses that could explain the link. For example, mattresses are more likely to be reused in lower income households, and parents in such households are less likely to be educated about SIDS prevention, more likely to use nicotine or other drugs during pregnancy, etc. Used mattresses may also be worn and not as firm as new mattresses (another risk factor for SIDS).
Claim #21: US research has shown that SIDS victims have neurochemical deficits in breathing and heart function. This is because phosphines, arsines and stibines are "nerve gases," which shut down the central nervous system, leading to cessation of heart and lung functions.
Deficit is not the same thing as damage. A deficit is a fundamental flaw, an innate problem that an infant is born with. The neurochemical deficit spoken about here is a defect in the mechanism that controls the infant's protective responses to changes in oxygen and carbon dioxide levels. This is not caused by exposure to toxic gases or any other type of damage to the central nervous system, it is a problem the infant possessed at birth. Furthermore, this statement is a laughable misinterpretation of scientific fact. Death, regardless of its cause, is marked by a cessation of heart and lung functions. The fact that arsines are nerve gases has no particular relevance as to whether or not death would be marked by a cessation of heart and lung function.
Claim #22 (probably the one that has made many parents disregard the research of accredited SIDS organizations): Tens of thousands of parents have wrapped their babies' mattresses with polythene wraps, and there have not been any reported SIDS among infants sleeping on these wrapped mattresses.
Again, there have been SIDS deaths on wrapped mattresses. Every time this happens, the manufacturers of polythene mattress wraps claim that the mattresses were not wrapped according to their specifications, even though this claim can never be substantiated. This makes it very easy for mattress wrapping proponents to go on claiming that their campaign has a 100% success rate. If they can claim, but never have to prove, that the wrapped mattresses where SIDS deaths occur were not wrapped "correctly," they will always be able to say that their wraps save babies' lives 100% of the time, regardless of how many babies actually die on wrapped mattresses.
CONCLUSION:
Think of it like this: if you were to believe the arguments against the Limerick Report, you would have to believe that non-commercial medical/scientific research lasting three and a half years was flawed to the extent that its authors did not understand basic physiology, were unable (or unwilling) to find accurate facts and statistics that are well known and readily available to the public, and that nearly every aspect of their research was somehow flawed and/or irrelevant. You would have to believe that every major non-profit SIDS foundation that exists worldwide is simply masquerading as an organization concerned with saving babies, but beneath the surface is actually conspiring to prevent you, the parent, from knowing "the true cause of SIDS," and that there is some dark and sinister reason why they would want to do this. You would also have to believe that manufacturers and retailers who are profiting from the sale of Polythene mattress wraps somehow have access to better, more trustworthy research and information and that they are disseminating that information out of a sincere desire to protect babies, which is not in any way tainted by the desire to sell more mattress wraps.
Another tragic side effect of this debate: mattress wrapping may actually increase a child's risk of succumbing to SIDS, since parents who use these wraps are often lulled into a false sense of security and are therefore more likely to place babies to sleep on their tummies, use soft bedding, allow their babies to sleep with stuffed toys, etc. In fact, the instruction book that comes with one of these wraps actually encourages parents to place their babies to sleep on their stomachs, since mattress wrapping will provide 100% protection against SIDS.
PARENTS: Toxic gas is not the cause of SIDS, and a wrapped mattress does not offer 100% protection against SIDS. Please take the $32.95 you were planning to spend on a polythene mattress wrap and donate it instead to your local SIDS charity. If each of the 100,000 parents who spent $32.95 on a mattress wrap instead donated that money to SIDS research, we would be more than $3,000,000 closer to discovering the true cause of this terrible syndrome.
