STATS ARTICLES 2005
PIRG's Toxic Warnings on Trace Chemicals
November 07, 2005
EU finds common flame retardant poses no health risk; NIH panel pour cold water on PIRG's phthalate baby fears
Over the past year, there has been a steady stream of alarming stories about chemicals in nail polish, perfume, frying pans, paper bags, carpet, insulation wire, baby teethers, toothpaste, and anti-bacterial soap among other common household products.
In each case, the quantity of chemicals is miniscule – often capable of being measured only in parts per billion. In each case the regulatory limits are stringent, incorporating extremely cautious safety factors, which if applied to a cup of coffee or your dinner would prevent you from consuming either.
Nevertheless, the unrelenting message from activist groups to the public is one of hidden danger and looming crisis; of reproductive harm, endocrine disruption and spiraling cancer rates; of regulatory failure and the need for government to adopt the precautionary principle (meaning, in effect, that if there might be a risk, the government should regulate as if there is a risk).
The latest example of this was “The Right Start: The Need To Eliminate Toxic Chemicals From Baby Products,” a recent hyperbolic report from the Public Interest Research Group which began:
“The media reports it, scientists have proven it, and American families are experiencing it: chronic diseases are on the rise in this country. Cancers, birth defects, childhood asthma, learning and behavior disorders, even obesity and early puberty are growing more prevalent in our society.
“Scientists do not know why more children are developing chronic problems. We do know, however, that this rise in chronic disease has occurred alongside a rise in the prevalence, use, and pervasiveness of toxic chemicals in the air we breathe, the water we drink, and the consumer products we use. Many of these chemicals are associated with chronic disease, and many others have never been tested for human health impacts.”
This message, especially when reiterated without critical reflection by the media, possesses great rhetorical force; but it is one based on suggestion rather than evidence. We know that some chemicals are associated with chronic disease and we know that chronic diseases are on the rise, therefore our general exposure to toxic chemicals must be causing the “rise” in chronic diseases.” This associative play tempts us into seeing causality where, in fact, there is an absence of evidence.
The Dose is the Poison
First of all, everything is toxic if ingested in large enough quantities. This easily-overlooked truth was first enunciated by the Swiss thinker Paracelsus in the 16th century, when he observed that the difference between a poison and a remedy is the dose.
As the British biochemical toxicologist John Timbrell notes in his recent book ‘The Poison Paradox,’ “This is a fundamental concept which underlies toxicology and is crucial to the assessment of risk from chemicals and their safe use. The corollary to this principle is that all chemicals are potentially safe at some, perhaps extremely low, dose and therefore can be used safely.”
As Timbrell explains, in order for a chemical to produce an effect, toxic or otherwise, it needs to interact with receptors or enzymes in a cell molecule. If the amount of the chemical is insufficient to bind itself to most or all of the receptors in a cell there is no effect. As a consequence, most regulatory bodies that assess the risk from chemicals work on the principle that there is a threshold below which there will be no effect. This is known as the “no observed adverse effect level” (NOAEL). Exposure guidelines then add a margin of safety 100 to 1000 times lower than the NOAEL.
The upshot is that it is simply wrong to assume – as many activist groups seeking greater regulation do – that the risk from a “toxic” chemical is always linear, meaning that it decreases as exposure to the chemical decreases but never disappears.
There is an important caveat to note here, namely that in the case of chemicals considered to be carcinogenic, some scientists believe there is no threshold below which they are safe: the process of molecular interaction is genotoxic, meaning that the chemical damages the DNA of the cell irrespective of the degree of exposure. The risk, in other words, is linear. The Environmental Protection Agency issues exposure guidelines based on this theory.
It is fair to say that this hyper-cautious approach to risk is controversial for the following reasons: not all carcinogens are genotoxic; there is experimental data which suggests that there are thresholds for genotoxic carcinogens; and more generally, there are barriers that reduce absorption into the body and mechanisms which repair cellular damage. Timbrell illustrates why one shouldn’t assume that exposure to very low doses of a chemical – even one that is a demonstrated carcinogen - is necessarily harmful:
“[S]uppose there is a poisonous chemical, a carcinogen, in a foodstuff. Not all the food will be contaminated, so some individuals will escape exposure. If the food eaten is contaminated, suppose it contains 1mg of carcinogen but only 1 percent is absorbed (0.01mg). Of that 1 percent suppose that only 1 percent is metabolized to the toxic (carcinogenic) substance (0.0001mg). Of that toxic substance, suppose that only 1 percent reaches the target, for example the DNA (0.000001mg). Of the damage caused, suppose that 99 percent is repaired, and that only 1 percent is potentially damaging (effectively 0.00000001mg). This means that only 100 millionths of the original dose reaches the target and causes damage, and damage to DNA does not necessarily result in cancer.”
It is important to understand the basic principles and controversies in toxicology and risk assessment because neither the groups claiming that we are at risk from trace amounts of chemicals nor the media that cover their studies and reports ever seem to acknowledge or address them. Without addressing each potential risk at this level of analysis, scare headlines may convey the idea of a risk to public health that, in effect, might be zero.
The second problem with the PIRG report is that it not clear which chronic diseases are actually on the rise. For example, cancers, with the exception of lung and bronchial cancer in women (causal hint: smoking), are falling, and have been doing so since the 1970s. Much recent theorizing on the rise of asthma is that our environment is too clean to stimulate the immune system in infancy (a reminder that, at least in the West, our exposure to environmental hazards has never been lower or more regulated).
But, in October, Rod Dietert a professor of immunotoxicology at Cornell University, presented a paper at a conference in Lyon which argued that prenatal and newborn exposure to low levels of environmental toxins, such as lead, mercury, ethanol, nicotine and dioxin, could account for the increased incidence of asthma, allergies and autoimmune disorders. Dietert called for safety testing to address whether an immune system that is not fully developed will react to toxins in a different way to a fully developed immune system.
This kind of research may well change our understanding of what constitutes safe exposure; but it is important to note that nothing has been proved yet, and the toxins mentioned by Dietert are not the chemicals tackled by PIRG in their report.
No account of the rise in behavioral disorders can be honest without noting that the very diagnosis of such disorders is only a recent phenomenon, and we have no way of knowing whether they were just as prevalent in 1905 or 1005. But research has begun to suggest that one combination of chemicals may indeed be a causal factor in learning disability, and to such a degree to make it a public health priority; but the PIRG report has nothing to say about fetal alcohol syndrome and the dangers of drinking during pregnancy.
As for obesity, it has nothing to do with toxic chemicals and everything to do with ingesting toxic quantities of food.
The data does not support PIRG’s argument
The PIRG report looked at two chemical groups of particular toxic concern – phthalates (which make plastic flexible) and PBDEs (flame retardants). Unfortunately (for PIRG), the report was published just as independent expert panels were demolishing some of PIRG’s key “evidence” for gloom, doom and greater regulation.
Under the heading “Phthalate exposure linked to reproductive defects” PIRG observed that “A recently published study by Dr. Shanna Swan and her colleagues reveals that normal exposure to phthalates can harm the genital development of unborn baby boys.”
As STATS first noted, this was not what the Swan study said at all (no baby boys showed evidence of harm); but even the suggestion that Swan’s study found some important and troubling link between phthalates and reproductive health was called into question when an independent expert panel under the auspices of the National Institutes for Health (NIH) announced that they were unable to validate one of Swan’s key findings, and that there was no evidence, as yet, to consider the anogenital index a biomarker for phthalate-induced reproductive harm.
As for the risk from phthalates in baby products, in February 2003, the Consumer Product Safety Commission (CPSC) rejected PIRG’s petition to ban plastic containing the phthalate DINP in toys for children aged five and under. The CPSC’s decision that there was no demonstrable risk was based on studies showing the rate that DINP migrates from vinyl toys and on the way children “mouth” toys. A child would have to suck on a toy for 39 minutes for there to be a potential risk; however, on average, children mouth toys for just 1.9 minutes per day.
And in August of the same year, the European Union’s Institute for Health and Consumer Protection produced a risk assessment report for DINP, which concluded that:
“The end products containing DINP (clothes, building materials, toys and baby equipment) and the sources of exposure (car and public transport interiors, food and food packaging) are unlikely to pose a risk for consumers (adults, infants and newborns) following inhalation, skin contact and ingestion…. The indirect exposure via the environment is unlikely to pose a risk to humans following the main route of exposure, the oral route… As combined exposure of adults is almost exclusively related to occupational exposure, the overall assessment indicates no concern for adults. For infants, combined exposure which is mainly related to exposure from toys and via the environment is not considered of concern.”
PIRG points out that the EU have since enacted a ban on DINP – but without noting that it was over the objection of the EU’s own risk assessment.
PBDEs are blended into plastics and foams during manufacturing. When exposed to flames, they release bromines that starve the air of oxygen that would otherwise feed the fire. Roughly 600 children 14 and under die in fires each year and 47,000 are injured, so the use of flame-retardants in products is not a trivial matter.
On October 15, the European Union decided to exempt Deca-BDE – the most widely used flame-retardant in consumer products – from their Directive on Hazardous Substances after a 10-year risk assessment evaluated 588 studies and found it posed no health risk.
And yet, despite the fact that the EU employs the precautionary principle in evaluating the risk from chemicals, the PIRG report insisted that we should be concerned about a “possible link” between Deca-BDE and cancer in humans because tests have shown that “high levels of Deca exposure created tumors in the liver, thyroid, and pancreas in laboratory animals.”
Additionally, while noting that two variants, Octa and Penta have been banned in the EU since 2004, and are being phased out in the U.S. (due to demonstrable aquatoxicity and bioaccumulation), the PIRG report tends to lump all three PBDEs together in discussing health risks, so that one is led to assume that Deca is as likely to be harmful as the others, which given its chemical make-up is not the case.
Dispiritingly, the PIRG report wasn’t so much reported in the media as announced - as if the very mention of public interest, risk and toxic chemicals required no more of journalists than to write a summary of the group’s findings – and, at most, quote an industry source denying the charges.
At the same time, there was barely any coverage of the NIH finding on Swan’s study or the EU’s exemption of Deca-BDE.