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8. How serious are the risks of indirect exposure to mercury from disposal dental amalgams?

    Mercury is present throughout the environment and is released by a variety of sources, one of which is the use and disposal of dental amalgams. The general population can for instance be exposed to mercury present in the environment by breathing in elemental mercury vapours in ambient air and by ingesting water and food contaminated with organic mercury.

    Daily intake and retention of mercury in the general population

    Table 1: Estimated average daily intake and retention of total mercury and mercury compounds in the general population.

    Sources of exposure Elemental mercury vapour Inorganic mercury compounds Methylmercury
    Air 0.030 (0.024) 0.002 (0.001) 0.008 (0.0064)
    - Fish 0 0.600 (0.042) 2.4 (2.3)
    - Non-fish 0 3.6 (0.25) 0
    Drinking water 0 0.050 (0.0035) 0
    Dental amalgams 3.8 – 21
    (3 – 17)
    0 0
    Total 3.9 – 21
    (3 – 17)
    4.3 (0.3) 2.41 (2.31)

    The most important source of mercury for people who do not work in mercury-related industries is the diet, particularly fish and other seafood products contaminated with methylmercury. The main sources of exposure to elemental mercury vapours are certain workplaces and the placement of dental amalgams. In general, the toxic effects of mercury depend on the way it reaches the body and on the form of mercury (elemental, inorganic or organic).

    The highest risks to human health from mercury in the environment come from methylmercury, an organic form of mercury. It is highly toxic and, in contrast to elemental and inorganic mercury, most of the methylmercury swallowed is absorbed by the gut and distributed rapidly and evenly throughout the body. Human exposures following high dose poisonings can result in mental retardation and impaired senses and movement. Similar effects have also been noted in animals. Long term, low dose exposures in the womb due to consumption of contaminated fish by the mother, have been associated with milder harmful effects on the nervous system.

    Limit values have been set for the concentration of methylmercury in fish and for the total daily intake of methylmercury by humans.

    Table 2. Limit for mercury intake

    Limit for mercury intake

    Dental amalgams are not a major source of methylmercury. The releases to the environment resulting from the use and disposal of dental amalgam are mainly in the form of elemental and inorganic mercury. Only a small fraction of this will be converted into methylmercury. Therefore, the predicted indirect exposures of humans to methylmercury resulting from emissions due to the use of dental amalgams are low. These exposures are much lower than tolerable limits and thus constitute a low risk of serious health effects. More...

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