Silver occurs naturally in the environment. It is released into the environment and may be carried long distances in air and water. People make jewelry, silverware, electronic equipment, and dental fillings with silver in its metallic form. Silver also occurs in powdery white (silver nitrate and silver chloride) or dark-gray to black compounds (silver sulfide and silver oxide). It is used in photography and as a bactericidal agent to clean water in pools, coffee machines etc. Silver compounds can be found at hazardous waste sites mixed with soil and/or water.
Most people are exposed daily to very low levels of silver mainly in food and drinking water, and less in air. Skin contact and breathing in air containing silver compounds also occurs in the workplace. Other sources of exposure include the use of silver in medicines, and in activities such as jewelry-making, soldering, and photography. Exposure from everyday use, such as wearing jewelry or eating with silver-coated flatware, is not expected to cause health problems.
Silver may enter the body through the mouth, throat, or digestive tract after eating food or drinking water that contains silver, or through your lungs after breathing air containing silver. It can also enter through the skin and is known to enter the body when medicines containing it are taken or applied to the skin or gums. Generally, much less silver will enter the body through the skin than through the lungs or stomach.
No studies were located regarding cardiovascular or musculoskeletal effects in humans or animals after inhalation exposure to silver or silver compounds. Respiratory effects have been observed infrequently in workers exposed to the inhalation of silver dust. Gastrointestinal effects correlated significantly with blood silver levels, indicating that workers exposed to higher levels of airborne silver nitrate and/or oxide are more likely to suffer gastrointestinal pain.
Silver-containing food or water are the most common source of silver exposure. Most of the silver that is eaten or breathed in leaves the body in the feces within about a week. Very little passes through the urine.
Argyria occurs in people who eat or breathe in silver compounds over a long period (several months to many years). It is a harmless condition where the long-term intake of silver causes silver to be deposited in the skin and other parts of the body. It is assumed that this discoloration of the skin seen in argyria is the most serious health effect of silver.
There are reliable and accurate ways of measuring silver in the body. Silver can be measured in the blood, urine, feces, and body tissues of exposed individuals. Drinking water testing indicates how much silver is present.
According to WHO, the low levels of silver in drinking-water, generally below 5 µg/l, are not relevant to human health with respect to argyria. In contrast, special situations exist where silver salts may be used to maintain the bacteriological quality of drinking-water. Higher levels of silver, up to 0.1 mg/l could be tolerated in such cases without risk to health. There are no adequate data with which to derive a health-based guideline value for silver in drinking-water.
The German Environmental Agency recommends that drinking water treated with silver should not exceed 0.08 mg of silver per liter.
WHO (2017): Guidelines for Drinking-Water Quality, 4th edition incorporating the first addendum, Genf, in Internet under: http://www.who.int/water_sanitation_health/publications/drinking-water-quality-guidelines-4-including-1st-addendum/en/
Umweltbundesamt (2017): Bekanntmachung der Liste der Aufbereitungsstoffe und Desinfektionsverfahren gemäß § 11 der Trinkwasserverordnung – 19. Änderung. In Internet under: https://www.bundesanzeiger.de/pub/publication/Yeh06ouBQOzFODe2vhr/content/Yeh06ouBQOzFODe2vhr/BAnz%20AT%2019.12.2017%20B9.pdf