Mark Richardson P.h.D.
previously of Health Canada
explains the amalgam risk assessment he presented to the FDA
Why was this Report Prepared?
To date, no population-based assessment of Hg exposure from dental amalgam specific to the US general population has been undertaken. The quantification of Hg dose associated with dental amalgam is required to complete a proper risk assessment. Determining the amalgam associated dose can be directly compared to the dose associated with regulatory reference exposure levels (RELs) prescribed for the protection of the health of the general population.
Such RELs are published by the USEPA (1995), the USATDSR (1999), the California EPA (2008), and others; these RELs are discussed in greater detail later in this report.
dental amalgam is composed of approximately 50% elemental (liquid)
Hg by weight. It has been used in North American dentistry for perhaps 150 years (Clarkson
and Magos, 2006) and during that time has been the subject of repeated controversy, often
referred to as the Amalgam Wars (Clarkson and Magos, 2006). A brief historical account of its
introduction, use and controversy is provided by Molin (1992). Scientific articles regarding
amalgam’s potential toxicity date back at least to 1885 (Talbot, 1885). These wars or debates
have been due to the recurring concern for the potential health risks posed by exposure to the
Hg used in the manufacture of dental amalgam.
The quantity of Hg0 released from amalgam is often referred to as ‘minute’ (ADA, 2008; CDA,
2005) or ‘very small’ (AGD 2007). However, it is not the dose itself that determines safety, it is
how that dose compares to levels considered ‘safe’ or without anticipated harm that determines
whether or not the dose is significant (hazardous or free from harm). Irrespective of quantity, a
minute dose can be very hazardous if the substance is very toxic and the received dose
exceeds the toxic dose. Dental amalgam has been identified as the single largest source of
continuous Hg exposure for members of the general population who possess amalgam fillings
(WHO, 1991; Heath Canada, 1996). Also, previous assessments have demonstrated that the
dose of Hg received from amalgam exceeds what is considered to be a safe or reference dose
(see HC, 1995; Richardson and Allan, 1996).
The Academy of General Dentistry (AGD 2007) goes on to say that “mercury in dental amalgam
is not poisonous”. However, the mercury that evolves from amalgam, as for any other source, is
toxic; for example, Hg0 originating from amalgam has been shown to cause neurobehavioral
and other toxic effects in dental staff that place amalgam fillings. The Hg0 from amalgam is no
different chemically or toxicologically than the Hg0 from any other source. The American Dental
Association (ADA) recommends storing scrap amalgam and used amalgam capsules in airtight
containers (ADA 2007). The ADA’s mercury hygiene recommendations are predicated on
protecting the safety of dental professionals (ADA 2003; ADA Council on Scientific Affairs).
In a recent survey of members of the Society of Toxicology (STATS et al 2009) Hg was
surpassed as the primary toxic substance of concern only by smoking-related issues (direct use
of cigarettes, use of chewing tobacco, second-hand smoke).
Adding further to the controversy surrounding the continued use of amalgam in North America is
the fact that Norway has now banned the use of amalgam in dental treatment (with certain
minor exemptions) (Norway Ministry of Environment, 2007). Sweden has also banned the
further use of amalgam in general dentistry (Sweden Ministry of Environment, 2009). Those
bans were based predominantly on the health concerns related to exposure to Hg0 from this
2.3 Who is Exposed and How are They Exposed?
Those people who possess one or more amalgam filled tooth surfaces will be directly exposed
to Hg from dental amalgam. The fetus is also exposed due to maternal amalgam load, as are
breast-fed infants as breast milk Hg content reflects maternal amalgam load. Excluding the
fetus and infants, the primary route of exposure to Hg from dental amalgam is via inhalation of
Hg0 emanating from in-place amalgam fillings (WHO, 1991; Richardson and Allan, 1996;
The chart below represents the estimated daily dose of mercury (from amalgam fillings) compared to mercury safety levels as established by the EPA and CalEPA. EPA safety levels were determined almost 20 years ago, whereas CalEPA was recently completed in 2008.
..it was determined that some 67.2 million Americans would exceed the Hg dose associated with the REL of 0.3 ug/m3 established by the US Environmental Protection Agency in 1995, whereas 122.3 million Americans would exceed the dose associated with the REL of 0.03 ug/m3 established by the California Environmental Protection Agency in 2008.”
Published Estimates of Hg Exposure in Adults With Dental Amalgam (Mercury Fillings)