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.