Amalgam fillings classified as 'hazardous waste'

Mercury is the second most toxic metal in the world, and yet it's still being used to make fillings. Nick Kettles wonders if the dental establishment is away with the tooth fairies.

It’s official: it’s safe to put hazardous waste in your mouth – and not just any run-of-the-mill hazardous waste, either. According to the European Waste Catalogue (entry 18 01 10), this particular hazardous waste possesses the hazardous property H6, meaning that it is toxic if inhaled or ingested, and may result in serious, acute or chronic health risks – even in death. Is this claim for safety being made by magician David Blaine? Or mystic yogis demonstrating their mastery over the mindbody continuum? No, this spectacular claim is the direct implication of separate advice given by the Department of Health (DoH) and Department of Environment, Food and Rural Affairs (DEFRA) on dental amalgam.

Clearly not everybody knows that dental amalgam – the ‘silver’ fillings in their mouths – contains 50 per cent mercury, the second most toxic metal on the planet after plutonium, or the reason why it’s considered a hazardous waste in the first place.

According to DEFRA’s guidance for dentists – published in December 2005 and based on England and Wales Hazardous Waste Regulations, which in turn adhere to EU Waste Directives – in addition to being a H6 hazardous waste, dental amalgam also has a H14 classification. H14 means it is ‘ecotoxic’ and presents, or may present, immediate or delayed risks to the environment, and so must be disposed of responsibly in order to prevent it getting into the food chain. DEFRA’s definition of waste amalgam includes old fillings, grindings, unused, surplus amalgam, residues containing amalgam and removed teeth containing fillings. These teeth were presumably removed from the mouths of people whom the DoH’s Committee on Toxicity was happy to advise that dental amalgam was a safe and effective restorative material.

These are presumably the same people whose amalgam fillings, should they stipulate in their last will and testament a wish to be cremated, will be vaporised in the furnace, releasing mercury into the environment, where, as it’s understood today, it can stay long enough to travel around the world.

Did anyone notice this lack of joined-up thinking? If DEFRA considers filled teeth a H14 and a H6 hazardous waste, a risk both to the environment and indirectly to people’s health, then why doesn’t the DoH also consider dental amalgam a H6 hazardous waste and a direct risk to people’s health? Does some strange protective alchemy occur when dentists place hazardous waste into children’s and adult’s teeth?

Writing about mercury in The Handbook on the Toxicology of Metals, a must-have reference handbook for toxicologists and regulatory scientists, contributing author Dr M Berlin states that this is a subject the dental profession is ill-equipped to deal with.

‘Modern progress in molecular biology and genetic research has considerably improved our understanding of the mechanisms behind mercury toxicity,’ he writes. ‘The problem of systemic effects of mercury vapour from amalgam is a medical problem largely ignored by the medical profession, leaving the oral cavity to the dentists. The odontological profession acknowledge a rare occurrence of local immune reactions to amalgam but are generally not aware of the possibility of systemic side effects from mercury vapour released from amalgam restorations and they mostly lack competence in this area.’

When it comes to discussing the contribution of crematoria to the level of mercury pollution in the UK, the argument is quite lucid. In response to DEFRA’s commitment to have filters installed in the UK’s 600-plus crematoria by 2012, the Federation of Burial and Cremation Authorities says, ‘Mercury is toxic, accumulates in the air and water, and can harm the brain, kidneys, nervous system and unborn children. Due to the number of fillings in teeth, up to 16 per cent of all mercury emitted in the UK comes from crematoria. This figure is expected to increase to 25 per cent by 2020 without action.’

When the focus turns to the health risks of dental amalgam fillings being placed in the teeth of people who are alive and kicking, however, the discussion becomes suddenly vague. It’s left to the unfortunate British Dental Authority (BDA) to spin the DoH and DEFRA’s spectacular oxymoron (‘safe and effective hazardous waste’) to the public.

The BDA has implemented a rigorous communication campaign to inform dentists of the statutory requirement to install waste dental amalgam separators in their clinics (for which they must be applauded). At the same time, however, it is having to toe the DoH party line that dental amalgam has been used for 150 years with little sign of systematic toxicity and can be employed universally, apart from in a very small minority of cases with people who are hypersensitive to mercury.

Carefully selected studies

The truth is that this is a well-ploughed field. An intense debate has been raging for many years about the risks of dental amalgam fillings. It is a story of claim and counter-claim. On the one hand scientists, campaigners and dentists who work in ‘mercury-free’ practices admit that amalgam is easy to use but express concern over the lack of conclusive proof about its safety. Many mercury-free dentists also point to the thousands of case studies of people claiming improvements to their health and wellbeing after having amalgam fillings replaced with alternatives.

On the other side of the fence are the prodental amalgam lobby, including the majority of dentists, Government health departments, and dental authorities, all insisting that it is both safe and effective, and pointing to the lack of conclusive proof about its dangers. Most admit that some mercury escapes during amalgam restorations, but question how much is released, inhaled and absorbed into the bloodstream, and whether that amount poses any kind of risk.

The most recent round in this protracted debate is currently unfolding. In November 2007, two ‘independent’ EU Scientific Committees on Emerging and Newly Identified Health Risks (SCENIHR) and, Health and Environmental Risks (SCHER) issued preliminary reports that reached similar conclusions: that with the exception of a few local adverse effects, dental amalgam does not pose any direct or indirect (via the environment) health risks, and that it remains a safe and effective restorative material.

As if that didn’t already rub salt into the wound of campaigners, the SCENIHR report, which uses the words ‘no evidence’ 27 times, claims there is no justification for removing clinically satisfactory amalgam restorations, except in patients allergic to amalgam constituents, because the main exposure to mercury in individuals occurs during the placement or removal of fillings. They also cast just a soupççon of doubt on the toxicology of alternatives, and say there isn’t enough data to conduct proper comparative assessments of amalgam and its alternatives.

We have nothing to worry about, it seems. Indeed, at the time of writing, although both preliminary reports are currently in consultation, the BDA and the DoH are already citing them as the most up-to-date ‘peer-reviewed, scientific’ opinion on the subject. Campaigners say this is simply another attempt to quash dissent and preserve the status quo. Not only are they concerned that neuro-developmental toxicologists and epidemiologists are poorly represented on these committees, but also about the strength of some of the evidence.

For example, the SCENIHR report cites two randomised clinical trials conducted in 2006 by Bellinger and DeRouen, which analysed urine samples from children with either amalgam or composite resin fillings, as evidence that dental amalgam doesn’t affect kidney function or psychological development. But Dr Herbert Needleman, whose research into the toxicity of lead played a key role in securing a fivefold reduction in the prevalence of lead poisoning among American children, thinks the conclusions of the studies are constrained by several factors that make them statistically inadequate.

Writing in the August 2007 Journal of The American Medical Association, he says: ‘These studies represent thoughtful and important contributions to understanding the question of dental amalgam risks in children, but the question of more subtle effects remains open. Given the numbers of children exposed to dental amalgam, it is critical that further rigorous studies examine the molecular effects of the toxicant at appropriate doses, measure exposure as precisely as possible, and explore the important question of vulnerability factors.’

He then adds: ‘It’s predictable that some outside interests will expand the modest conclusions of these studies to assert that use of mercury amalgam in dentistry is riskfree. This conclusion would be unfortunate and unscientific.’

Needleman isn’t the only one to point up the equivocal nature of the data. The International Academy of Oral Medicine and Toxicology (IAOMT) points to a 2007 study in the journal Environmental Health Perspectives, which followed up the Bellinger and DeRouen studies, and suggested that urine is an unreliable reference for exposure or daily dose of mercury released from dental amalgam.

Similarly, the SCENIHR study references an American Dental Association (ADA) study to claim that there was no kidney dysfunction on the part of the dental personnel exposed to dental amalgam. The IAOMT cites another one that shows there is.

Amazingly for a substance that has been in use for so long, there has been a deplorable lack of interest in studying the potential toxic effects of dental amalgam. As recently as 1997, the World Dental Federation (FDI) and the World Health Organization joint consensus statement on dental amalgam stated: ‘No controlled studies have been published demonstrating systemic adverse effects from amalgam restorations.’ In the language of scientific obfuscation that doesn’t mean it’s safe; it simply means the studies have not been done.

New studies on amalgam toxicity are emerging, linking it with, among other things, a higher incidence of neurological disorders such as Alzheimer’s disease and Multiple Sclerosis. While such findings remain disputed, however, the net result is that for the consumer, the task of making an informed choice about dental healthcare is complex.

The BDA says patients can choose to have composite (white) filling material used as an alternative if they wish, and that dentists will discuss concerns about dental amalgam. Often such discussions centre around aesthetics rather than health, though, and even then tend not to happen unless prompted by the patient. The fact is that dentists have no reason proactively to inform consumers; in addition to it being an easier material to work with than composite resins, they have been taught at dentistry college that amalgam is safe. This, of course, includes many dentists who studied before the 1980s, when it became widely known that the mercury in dental amalgam remained active after it was placed in the mouth.

Reasonable doubt 

The use of dental amalgam may be decreasing as the nation’s oral health improves, but there are still millions (nine million in the UK alone) of amalgam fillings fitted every year in adults and children. This amounts to tonnes of mercury, some of which, via crematoria, will find its way back into the environment as toxic mercury vapours. The question remains: should we be taking this risk?

Even if the risk is very small – the BDA admits that some three per cent of people are sensitive to mercury – this will nevertheless result in a large number at risk, since a majority of the population is exposed to mercury through dental amalgam. For the sake of comparison, in a flu season, infection in just 0.4 per cent of the population counts as an epidemic. By that standard we should be taking some form of preventative action.

Clearly there are many scientists who believe there is room for reasonable doubt. As Dr Needleman says: ‘With the application of better epidemiological designs and more robust statistical methods to investigate toxicity, the usual consequence is uncovering effects at lower thresholds. The trajectory of discovery of the toxic effects of another metal, lead, has followed this path and may offer insight into the future path that mercury investigations may follow.’

David Kennedy, of the IAOMT, believes we need to reconsider our attitude to risk.

‘The understanding of the concept of “risk” has received much attention in toxicological and regulatory circles,’ he observes. ‘To say that something is “not without risk” has little meaning if one considers there is a finite health risk associated with virtually every human activity and chemical exposure. The real issue is what level of risk do we accept in the context of simultaneous benefits?’

We are developing a more conscientious attitude to the health risks of mercury via the environment, and bans on non-electronic measuring devices that contain mercury, such as barometers, thermometers and bloodpressure devices, as well as on mercury exports, are becoming more widespread.

When it comes to the direct health risks of the dental amalgam that sits in our mouths, though, is it really acceptable, or even accurate, to say that because we’ve been using it for 150 years, it must be safe? We used tobacco for nearly 300 before definitive evidence was available about its health risks.

To date, Government health departments and dental health bodies have been content to take a ‘decide, announce, defend’ approach to communicating the health risks of dental amalgam. If you’re pregnant, for instance, you might already be aware of the risk of mercury crossing over the placenta into the foetus. While there are health advisories in place to warn pregnant women not to eat fish that may be contaminated with mercury, the BDA insists there is no evidence of any link between amalgam use and birth defects or stillbirth.

Dr Berlin is more emphatic, saying because it isn’t always possible to predict when a woman will become pregnant that, in order to prevent exposure to the foetus during pregnancy, those of childbearing age should not have amalgam fillings. It sounds like sage advice, and yet no provision is being made for mercury-free dentistry for this vulnerable group, which amounts to some 10 million women in the UK alone.

In his paper, written for DEFRA, ‘Understanding Risk in Everyday PolicyMaking’, Dr Kevin Edson Jones says this approach is based on the assumption that there is an intellectual deficiency in people’s understandings [of risk] as measured against some objective or authoritative body of scientific knowledge. This in turn leads governments to adopt paternalistic and often derisory attitudes towards the public’s perception of risk, such as that ‘the public are irrational’, ‘public concerns are the result of scaremongering and perpetuated by a cynical media’ or ‘the public won’t understand the truth about risks’.

Perhaps also there is genuine fear of what might happen if the public were informed. One mercury-free dentist says the worst thing that could happen would be a mad rush of people wanting dental amalgam removed; dentists would be at risk of increased toxic exposure as a result of having to drill out so much amalgam. Many 19th-century milliners suffered from a neurological condition, St Vitus’s Dance, as a result of chronic intensive exposure to mercury used to treat felt. In other words, our dentists could become the ‘mad hatters’ of the 21st century.

Hard to legislate

At the very least, we should be taking the same approach with dental amalgam as we are with other medical devices and drugs.

Even the British Dental Health Foundation, the leading UK-based independent oral health charity, concedes that if amalgam for dental restorations were to be evaluated according to the criteria used today for approval of drugs, it would never be approved. And if it can’t be approved as a drug then maybe it should be assessed as a commercial chemical compound? The new European law known as REACH (Registration, Evaluation and Authorisation of Chemicals), described as the most important EU legislation for 20 years, says that the burden of proving a previously untested chemical is safe to today’s standards should be borne by the business using them.

Will dentists, who in the absence of free universal dental healthcare are within the commercial sector, bear the onus of responsibility in proving that the dental amalgam that sits inside the mouth, inches from our brains – a chemical compound classified hazardous waste – is also safe? That remains to be seen, but whoever grasps the nettle should be aware of the lesson presented by the precautionary principle communicated so clearly by the Stern report on Global Warming. Quite simply, that when an activity poses a risk to human health or the environment, precautionary measures should be taken, even if some cause and effect  relationships are not fully understood scientifically. The burden of proof falls on those advocating taking the action, who must take into consideration not only ‘what we know we don’t know’, but also the more troublesome ‘what we don’t know that we don’t know’.

It is quite possible, in the face of continuing pressure, that governments will opt for more stringent minimum recommendations, such as a requirement for dentists to acknowledge patients’ autonomy by actively making known the risks and benefits of all dental materials, but if we want to address the considerable environmental impact of dental amalgam too, nothing short of an all-out ban will do.

‘Mercury is a non-essential element [in the human body], having no biochemical or nutritional function,’ says Kevin Brigden, a member of Greenpeace’s science unit. ‘Today, alternatives are commercially available for virtually all applications of mercury. Unless it can be established there isn’t a suitable, less hazardous alternative for a specific use, it’s time to stop using it.’ This is what is already happening in Norway, where, as of 1 January 2008, dental amalgam was banned on environmental and indirect health grounds. In Sweden, a decision to ban dental amalgam on environmental grounds is imminent, while Austria and Germany have restricted its use. A recent Bank of America market analysis that advises dental products company Dentsply – the world’s second largest manufacturer of mercury fillings – to realign its operations to sell only resin and other filling materials, suggests the writing is on the wall in the US. The question now remains: will the UK choose to follow and be among those who lead patients away from putting hazardous waste in their mouths?

Mercury 101

Mercury is a highly reactive metal that exists in a liquid state, evaporates at room temperature and has neurotoxic properties at high doses, including parethesias, loss of muscle co-ordination and motor speech disorders, as well as deteriorating vision. It is a cumulative poison that is quick to enter the body and slow to be eliminated, thus even small, chronic exposure can cause an accumulation in body tissues over time. Since the 1970s, environmental concern has resulted in the reduction and/or removal of mercury from many industrial processes and commercial products.

Mercury can change from its natural ‘elemental’ form to another form – methylmercury – in the environment through its interaction with micro organisms. Methylmercury accumulates in all fish, especially those at the top of the food chain, such as sharks, swordfish and tuna, and is absorbed by the large intestine, from where it can spread throughout the body. Methylmercury is considered by health authorities to be more toxic and of more concern to the public than dental amalgam, which they say releases less than the World Health Organization’s recommended daily amount for exposure. However, elemental mercury vapour, which is more toxic than methylmercury and can freely pass through all normal barriers in the body, is as much as 10 times as damaging to the developing brain.

Diagnostically, determining the role of amalgam in a range of symptoms, particularly those indicating nervous or immuno-systemic illness, is problematic, as there are many other things that can cause the same symptoms – and yet scientists and campaigners alike say there are now simply too many individual case reports of people who have removed dental amalgam and shown a recovery or a marked improvement in their symptoms to ignore.

The amount of mercury released from amalgam fillings is dependent on many things, including: the number fitted, size, age and location of placement, chewing habits, food texture, grinding and brushing teeth. Smoking Teeth, a video widely shown on YouTube (, shows mercury vapour coming off a 25-year-old filling, under a phosphorescent screen, in amounts the video-makers claim far exceed ‘recommended’ levels.

Moreover, there have been numerous studies that suggest elemental mercury can be bio-transformed into methylmercury by bacteria in oral plaque or the gut, and that long-term exposure to low concentrations of elemental mercury vapour itself may cause symptoms similar to those of methylmercury.

How to find a mercury-free dental practice

In the UK you can request composite (or ‘white’) fillings on the NHS, but the chances are that the dental practice you
visit is not mercury-free, meaning every time you go to the dentist you may be exposing yourself to toxic mercury vapours. To locate a mercury-free dentist in your area, contact the British Society for Mercury-Free Dentistry at The College of Naturopathic Medicine ( also keeps a register of UK mercury-free practices.

Nick Kettles is a freelance journalist

This article first appeared in the Ecologist May 2008

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