PubMed: extracts of abstracts:
"Critical observations on the neurotoxicity of silver" by Lansdown AB.
Faculty of Medicine, Investigative Sciences, Imperial College, London.
United Kingdom. [email protected]
Although silver is metabolized throughout the soft tissues, available
evidence from experimental animal studies and human clinical reports
has failed to unequivocally establish that it enters tissues of the
central nervous system or is a cause of neurotoxic damage...Transitory
silver sulfide deposits seen in the tissues of the blood-brain and
blood-CSF barriers are mostly lysosomally bound or deposited on
basement membranes or collagen without toxic effect. Silver is mostly
excreted from the body in the urine and feces. Further research is
indicated to evaluate the role of metal binding proteins including
metallothioneins as cytoprotectants for neurological tissue.
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Scand J Work Environ Health. 1989 Jun;15(3):210-21.Links
Absence of toxic effects in silver reclamation workers.
Pifer JW, Friedlander BR, Kintz RT, Stockdale DK.
Health and Environment Laboratories, Eastman Kodak Company,
Rochester, New York 14652-3615.
Recent reports have alleged that silver presents a toxic hazard to
exposed workers. To define the potential risks of long-term exposure to
silver better, a cross-sectional investigation was conducted of 27
Caucasian males occupationally exposed to primarily insoluble silver
compounds and 27 matched referents. Physical examination and electron
microscopy of skin biopsies revealed no cases of generalized argyria.
Measurements of facial discoloration, judged from color photographs by
panels of laymen and physicians, showed no significant difference
between the two groups. Although 29% of the silver workers and none of
the referents exhibited ocular silver deposition, optometric and
contrast sensitivity test results revealed no significant deficits in
visual performance. The kidney and respiratory findings were
essentially normal in both populations. Despite the increased presence
of silver in the blood, feces, and hair of the recovery workers versus
the referents, there was no evidence that chronic silver exposure
adversely affected the health of these employees.
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Exposure-related health effects of silver and silver compounds: a
review.
Ann Occup Hyg. 2005 Oct;49(7):575-85. Epub 2005 Jun 17.Click here to
read Links
Drake PL, Hazelwood KJ.
National Institute for Occupational Safety and Health, Spokane
Research Laboratory, 315 E. Montgomery Avenue, Spokane, WA 99207, USA.
[email protected]
A critical review of studies examining exposures to the various
forms of silver was conducted to determine if some silver species are
more toxic than others. The impetus behind conducting this review is
that several occupational exposure limits and guidelines exist for
silver, but the values for each depend on the form of silver as well as
the individual agency making the recommendations. For instance, the
American Conference of Governmental Industrial Hygienists has
established separate threshold limit values for metallic silver (0.1
mg/m3) and soluble compounds of silver (0.01 mg/m3). On the other hand,
the permissible exposure limit (PEL) recommended by the Occupational
Safety and Health Administration and the Mine Safety and Health
Administration and the recommended exposure limit set by the National
Institute for Occupational Safety and Health is 0.01 mg/m3 for all
forms of silver. The adverse effects of chronic exposure to silver are
a permanent bluish-gray discoloration of the skin (argyria) or eyes
(argyrosis). Most studies discuss cases of argyria and argyrosis that
have resulted primarily from exposure to the soluble forms of silver.
Besides argyria and argyrosis, exposure to soluble silver compounds may
produce other toxic effects, including liver and kidney damage,
irritation of the eyes, skin, respiratory, and intestinal tract, and
changes in blood cells. Metallic silver appears to pose minimal risk to
health. The current occupational exposure limits do not reflect the
apparent difference in toxicities between soluble and metallic silver;
thus, many researchers have recommended that separate PELs be
established.
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Brain barrier systems: a new frontier in metal neurotoxicological
research. Zheng W, Aschner M, Ghersi-Egea JF.
School of Health Sciences, Purdue University, West Lafayette, IN 47907,
USA. [email protected]
Toxicol Appl Pharmacol. 2003 Oct 1;192(1):1-11
The concept of brain barriers or a brain barrier system embraces the
blood-brain interface, referred to as the blood-brain barrier, and the
blood-cerebrospinal fluid (CSF) interface, referred to as the blood-CSF
barrier. These brain barriers protect the CNS against chemical insults,
by different complementary mechanisms. Toxic metal molecules can either
bypass these mechanisms or be sequestered in and therefore potentially
deleterious to brain barriers. Supportive evidence suggests that damage
to blood-brain interfaces can lead to chemical-induced neurotoxicities.
This review article examines the unique structure, specialization, and
function of the brain barrier system, with particular emphasis on its
toxicological implications. Typical examples of metal transport and
toxicity at the barriers, such as lead (Pb), mercury (Hg), iron (Fe),
and manganese (Mn), are discussed in detail with a special focus on the
relevance to their toxic neurological consequences. Based on these
discussions, the emerging research needs, such as construction of the
new concept of blood-brain regional barriers, understanding of chemical
effect on aged or immature barriers, and elucidation of the
susceptibility of tight junctions to toxicants, are identified and
addressed in this newly evolving field of neurotoxicology. They
represent both clear challenges and fruitful research domains not only
in neurotoxicology, but also in neurophysiology and pharmacology.
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