Chemistry Reference
In-Depth Information
determined high sensitivity to mercury and with an
incidence <1/100 exposed is very likely and is a prob-
lem relevant to mercury vapor exposure from dental
amalgam in the population.
6.1.2.1 Acute Poisoning
The lung is the critical organ in acute accidental
exposure to high concentrations of mercury vapor. The
mercury vapor causes erosive bronchitis and bronchi-
olitis with interstitial pneumonitis. The patient will
eventually succumb to respiratory insuffi ciency. The
symptoms of respiratory distress may be combined
with signs caused by effects on the CNS, such as tremor
or increased excitability. Garnier
et al
. (1981) reviewed
approximately 20 such cases that have been published
in the literature.
et al
., 1995), an observation that conforms with animal
experimental fi ndings on primates that mercury is
accumulated and retained in the retina (Warfvinge and
Bruun, 1996). In psychomotor tests, changes in coor-
dination ability, tremor, concentration capability, and
mood have been found (Echeverria
et al
., 1995; Liang
et al
., 1993; Netterstrom
et al
., 1996).
White
et al
. (1993) described a worker in a thermom-
eter factory. He was exposed for 3 years and developed
neuropsychological symptoms and was referred to a
psychiatric clinic for his behavioral problems. His
urine mercury level was 690
g/L. “The MRI showed
mild central and cortical atrophy. Punctiform foci of T2
were noted in both frontal regions, especially under-
lying the precentral gyri and in the subcortical white
matter and in the white matter of the gyri. The MRI was
interpreted as consistent with diffuse and focal white
matter disease. The lesions did not resemble those seen
in multiple sclerosis plaques or in microinfarcts.”
Another case of short-term, high-exposure to mer-
cury vapor with typical symptoms of mercurialism,
SPECT (single-photon emission computerized tom-
ography) showed clear signs of hypermetabolism in
the right posterior cingulum cortex but no changes
on the MRI image of the brain (O'Carroll
et al
., 1995).
Haut
et al
. (1999) studied 13 men (mean age, 45 years)
exposed to mercury vapor for 2-4 weeks through
welding on material painted with mercury-containing
paint. After the exposure ceased, the men's blood mer-
cury concentration averaged 48
µ
6.1.2.2 Chronic Poisoning
On long-term exposure to toxic levels of mercury
vapor, the CNS is the critical organ. Little is known
about the pathogenesis of the brain dysfunction that
is seen on exposure to mercury vapor. With increasing
dose, signs appear that can together be characterized
as a nonspecifi c, asthenic-vegetative syndrome involv-
ing symptoms like weakness, fatigue, anorexia, loss of
weight, and disturbance of gastrointestinal functions.
This syndrome has been called micromercurialism
(Friberg and Nordberg, 1972; Trachtenberg, 1969).
At higher exposure levels, the characteristic mercu-
rial tremor appears as fi ne trembling of the muscles
interrupted by coarse shaking movements every few
minutes. This begins in peripheral parts like fi ngers,
eyelids, and lips and has the characteristics of inten-
tional tremor. It disappears during sleep. In progressive
cases, it may develop into a generalized tremor involv-
ing the entire body, with violent chronic spasms of
the extremities. Parallel to the development of tremor,
mercurial erethism develops. This is characterized by
severe behavioral and personality changes, increased
excitability, and loss of memory and insomnia, which
may develop into depression. In severe cases, delirium
and hallucination may occur.
In addition to the effects seen in the CNS, cases of
severe poisoning may display infl ammatory changes
of the gums with ptyalism, possibly severe, with sali-
vation of up to several liters per day.
By use of electrophysiological methods on occupa-
tionally exposed cases, changes have been shown in
the brain's signals caused through visual, auditory,
or somatosensory stimulation (evoked potentials)
and reduced peripheral nerve conduction velocity
(Andersen
et al
., 1993; Chang
et al
., 1995; Discalzi
et al
.,
1993; Ellingsen
et al
., 1993b; Urban
et al
., 1996). Reduced
color vision has also been demonstrated (Cavalleri
µ
g/L of blood (corre-
sponding to approximately 150
µ
g/g creatinine), with
a range of 21-84
g/L. One year after exposure had
ceased, all the men were subjected to a battery of neu-
ropsychological tests and compared with a control
group of 13 nonexposed workers. Compared with the
control group, the exposed group displayed cogni-
tive defi cits in motor coordination, rapid reception of
information with and without motor elements, verbal
capacity, verbal memory, visual problem solving, and
comprehension. The men exposed also had more emo-
tional problems, such as an increased focus on bodily
functions, depression, anxiety, and were more socially
withdrawn (Haut
et al
., 1999).
µ
6.1.2.3 Persistent Effects of Mercury Exposure
In cases of slight poisoning, symptoms and signs
of mercury poisoning, so called erethism, seem to
regress and disappear when exposure has ceased.
However, in more severe cases, because of long-term
exposure, persistent sequelae related to the nervous
system are common. Baldi
et al
. (1953) followed 135
cases of mercurialism in whom exposure had been
interrupted for several years. Of these, 69 showed no
