Nuclear Accumulation of Mercury in Neutrophil Granulocytes Associated with Exposure from Dental Amalgam

Abstract

Corrosion and wear of dental amalgam may be associated with unexpectedly high levels of endogenous exposure to heavy metals. According to WHO, the resulting uptake of mercury exceeds that from all other sources in persons not occupationally exposed (WHO 1991) and a daily uptake level of 100 μg has been reported (Barregard et al. 1995). Due to the distribution patterns of mercury, standard blood and urine analyses give meager information on the response of the organism to this exposure. We here present data from nuclear microscopy analysis of neutrophil granulocytes (short-lived cells in the immune system cascade) in peripheral blood. Blood samples were drawn from patients suffering from possible side effects from dental amalgam. Their symptoms resembled those of the Chronic Fatigue Syndrome (Fukuda 1994), and the onset or intensity of the symptoms were related to occasional increased exposure to dental amalgam e.g., unprotected placing/drilling of the material. Data showed profound derangement of several cellular trace elements in the patient group and in some cases the substitution of mercury for zinc in the nuclear area. This supports the contention that systemic side effects from dental amalgam may occur. Venous blood samples were drawn from a cohort of Caucasian patients (n = 25) with a chronic debilitating illness, possibly related to the exposure from dental amalgam, and cell preparations were done as previously described (Johansson 1984, Lindh 1997). The same procedure was performed on blood samples from an age- and sex-matched healthy control group (n = 22) with similar numbers of amalgam fillings. A freeze-dried monolayer preparation of neutrophil granulocytes from each subject was investigated by means of nuclear microscopy (Zidenberg-Cherr). Thirty cells from each subject were analyzed in a subsequent manner and means and variances of the elemental concentrations of calcium (Ca), manganese (Mn), iron (Fe), zinc (Zn), and mercury (Hg) were calculated. In addition, the intracellular distribution of zinc and mercury was investigated in a few cells from both patients and controls by means of a nuclear microscopy elemental mapping technique. Cells with mercury levels above the detection limit (0.5 μg/kg dry weight) were investigated as well as cells with no detectable mercury.