Exposure to Silver Compounds
Historically, because of its bactericidal properties, silver was used for surgical prosthesis and splints, fungicides, and coinage. Soluble silver compounds, such as silver salts, have been used in treating mental illness, epilepsy, nicotine addiction, gastroenteritis, and infectious diseases, including syphilis and gonorrhea. Principle routes of human exposure to silver nowadays are through its widespread use as an antimicrobial agent in wound care products and medical devices, including in-dwelling catheters, bone cements, cardiac valves and prostheses, orthopedic pins, and dental devices. Antimicrobial properties of silver are dependent upon release of biologically active silver ion (Ag*) from metallic silver (including nanocrystalline forms), silver nitrate, silver sulfadiazine, and other silver compounds incorporated in the various devices, and its lethal effect on pathogenic organisms.
Rain-making has used silver iodide with the emission of silver iodide crystals during cloud seeding estimated to result in a silver concentration in air of about 0.1 ng/cubic metres.
Cloud seeding has been ongoing in the USA in Utah since 1973. It is estimated that cloud seeding increased runoff by 59.2 billion gallons, during the 2009-2010 season. In 2014, there are four large-scale projects in the Utah state, all of which use ground-based silver iodide generators. The generators use silver iodide-containing pyrotechnic flares which produce trillions of extremely small silver iodide particles. These particles increase the probability of ice crystal formation in a cloud, which then increase in size at the expense of surrounding cloud moisture and eventually fall to the ground as snow.
There have been a number of studies investigating the concentration of silver in snow and groundwater following cloud seeding activities. While most found levels of silver that were higher than the local background level, few if any identified silver concentrations in excess of EPA’s SMCL of 100 ppb. A recent 2013 investigation of sources of metal accumulation in an alpine tarn in a cloud seeding area in the Snowy Mountains of Australia determined that the contribution of cloud seeding to silver levels in lake sediment was negligible Ref: Concerns Regarding Silver Iodide Cloud Seeding.
Anti-smoking tablets, lozenges and gum can contain silver acetate, and the habitual use of silver foil-coated mouth refreshers can build up silver.
Industrial applications, jewelry and silverware, and the photographic industry were the largest consumers of silver in 2003, using 40%, 31% and 22%, respectively with the photographic industry also a big user (photosensitive silver halides). Medically, silver sulfadiazine, is used as a topical antibacterial agent for the treatment of burns.
Liberation during mining and purification from ore. Use in manufacture of silver nitrate for use in mirrors, plating, inks, dyes, and porcelain; and as germicides, antiseptics, caustics, and analytical reagents. Use in manufacture of silver salts as catalysts in oxidation-reduction and polymerization reactions; in chemical synthesis; in glass manufacture, in silver-plating and as lab reagents.
Liberation from manufacture and casting of alloys; during fabrication of silver metal, alloys, and bimetals for electrical uses; and during electroplating operations and fabrication of solders and brazing alloys and during manufacture of silver powder pigments and paints.
Localized argyria can be caused by silver earrings due to the cutaneous implantation of a silver earring backing, either in the ear lobes or directly behind the ear. Discoloration was confined to the skin around the embedded earring backings.
Occupationally, silver exposure occurs in factories involved in bullion production, silver chemical manufacturing, jewelry manufacturing, silver reclamation, and production of tableware and polishing silver cutlery. Workers are exposed to both metallic and soluble silver. Workers classified as melters, refiners, and silver nitrate producers were found to have the highest blood-silver levels, with values ranging from 0.1 to 20 μg/l.
It has been estimated that a person developing six rolls of film could be exposed to up to 16 grams of silver through dermal contact with photographic solutions. However, many people use implements or wear gloves during film developing and therefore this is not expected to result in widespread, high level exposures.
Therefore, principle routes of gastrointestinal absorption of silver include –
(i) contaminated food,
(ii) occupational exposures to metallic silver dust, silver oxide, and silver nitrate aerosols,
(iii) drinking water (including use of silver : copper filters in water purification),
(iv) silver nitrate or colloidal silver therapies in oral hygiene and gastrointestinal infection,
(v) colloidal silver preparations labelled as “food supplements” or “alternative medicines”,
(vi) silver acetate antismoking therapies,
(vii) silver amalgams used in dentistry,
(viii) accidental consumption of silver nitrate or other colourless silver compounds.
REF: Exposure-Related Health Effects of Silver and Silver Compounds: A Review
Silver nanoparticles in the environment: Sources, detection and ecotoxicology
and A Pharmacological and Toxicological Profile of Silver as an Antimicrobial Agent in Medical Devices
and SILVER IODIDE