Research in molecular biology has elucidated mechanisms that may underlie the

enhanced

Clinical

mercury

Clinical studies of the effects of mercury on occupationally exposed workers,

Relation between symptoms and mercury concentrations in saliva after chewing.
The Tübingen amalgam study could establish in the especially examined group of
21-40 year old persons a statistically significant relation between mercury
levels in saliva and symptoms. Only symptoms which are characteristic of
subacute or chronic mercury exposure in the low-level range were studied.

Low-level chronic exposures to mercury may affect the peripheral nervous system
resulting in polyneuropathies (reduced sensory and motor nerve function) and
neuropsychological effects (visual alterations, sensory loss, stress) (ATSDR
1989); these effects correlate to tissue levels of 20 to 40 µg/g.
Neuropsychological effects were also reported by Smith et al. (1970) for
occupational exposure to mercury levels of > 0.1 mg/m3. Mercury concentrations
below this value did not appear to cause observable effects. Kishi et al.
(1993) reported that neurobehavioral and motor function effects persisted in
ex-mercury miners more than 10 years after cessation of exposure.    

Once inhaled, elemental mercury is mostly converted to an inorganic divalent or
mercuric form by catalase in the red blood cells. This inorganic form has
similar properties to organic mercury. Small amounts of non-oxidized elemental
mercury continue to persist and account for CNS toxicity.

Elemental mercury, as a vapor, which escapes from fillings, penetrates the
blood-brain-barrier and enters the CNS, where it's ionized and trapped,
attributing to its significant toxic effects

http://www.floridalcv.org/FLCVEdFund/environmental_effect_of_dental_a.htm

Environmental Effect of Dental Amalgam

Mercury is one of the most toxic substances commonly encountered, and according
to Government agencies causes adverse health effects in large numbers of people
in the U.S.[1]  The extreme toxicity of mercury can be seen from documented
effects on wildlife by very low levels of mercury exposure. The average amalgam
filling has more than ½ gram of mercury, and has been documented to
continuously leak mercury into the body of those with amalgam fillings due to
the low mercury vapor pressure and galvanic current induced by mixed metals in
the mouth.

1.  Hg plasma concentration correlated with no.of amalgam fillings.

2.  Correlation between number of fillings and salivary Hg.

3. The amount of organic and inorganic mercury in paraffin-stimulated

5.  Amalgam causes nerve cell toxicity in culture.

6.  Plasma concentrations of mercury before and after treatment

7  None of the materials tested consistently prevented microleakage.

8.  In neither of the nonamalgam groups was this [wastewater] limit

9.  I-Hg levels in placenta increased with an increasing number of

10  Evidence of a pro-oxidant role of the amalgam Hg chronically released

http://www.chem-tox.com/pregnancy/mercury.htm

Low Level Mercury Causes Behavior Problems During Pregnancy

Subtle behavior problems were observed in mice offspring exposed to a single
low level mercury dose.

In summarizing the results of their study, the researchers stated,

"This hypothesis generating study showed highly significant correlations
between mood scores and most measures of low level Hg (mercury) exposure. The
specific mood measures most associated with Hg exposure were tension, fatigue,
and confusion. The strength of these associations suggests that mood should be
included for investigation in future hypothesis-testing studies..... Among the
cognitive and motor function tests, only the digit span and simple reaction
time (nondominant hand) scores were associated with any measure of
exposure...... Overall, and despite the small size of the study population,
this investigation found some evidence of adverse preclinical effects at
mercury doses averaging 36 ugs/l in urine. The mood and symptom results of this
study agree with prior evaluations of both high and low urinary mercury doses.
These preliminary survey findings support a critical evaluation of the adequacy
of the 50 ug/g creatinine biologic threshold for mercury proposed by the World
Health Organization This is the first U.S. dental study to detect potential
behavioral deficits at such a low level of exposure. A larger and more
comprehensive study is required to accurately determine a biologic threshold of
adverse central and peripheral nervous system effects for elemental mercury."

Drs. Diana Echeverria, Nicholas J. Heyer, Michael D. Martin, Conrad A Naleway
Depart. of Environ. Health, Univ. of Washington, School of Dentistry, Univ. of
Washington
Neurotoxicology and Teratology, Vol. 17(2):161-168, 1995

Dopamine Uptake in Brain Cells Changed By Methylmercury

Attention Deficit Disorder children were reported in other headings in this
book as having altered dopamine levels. Several compounds, including alcohol,
have been shown to alter dopamine levels in test animals. Now, researchers at
Duke University Medical School have shown that even very low levels of
methylmercury result in dopamine and norepinephrine brain neurotransmitter
changes.