The Risk Assessment Information System

Toxicity Profiles

RAGs A Format for Silver - CAS Number 7440224

Silver is a relatively rare naturally occurring element found in the environment combined with other elements such as sulfide, chloride, and nitrate. Pure silver is "silver" colored, but silver nitrate and silver chloride are powdery white and silver sulfide and silver oxide are dark-gray to black. Silver is often found as a by-product during the retrieval of copper, lead, zinc, and gold ores. Silver is used to make jewelry, silverware, electronic equipment, and dental fillings. It is also used to make photographs, in brazing alloys and solders, to disinfect drinking water and water in swimming pools, as an antibacterial agent, and in chewing gum to help people stop smoking.

Exposure to high levels of silver for a long period of time may result in a condition called arygria, a blue-gray discoloration of the skin and other body tissues. Lower-level exposures to silver may also cause silver to be deposited in the skin and other parts of the body; however, this is not known to be harmful. Argyria is a permanent effect, but it appears to be a cosmetic problem that may not be otherwise harmful to health. Exposure to high levels of silver in the air has resulted in breathing problems, lung and throat irritation, and stomach pains. Skin contact with silver can cause mild allergic reactions such as rash, swelling, and inflammation in some people.

Data adequate for evaluating the carcinogenicity of silver to humans or animals by ingestion, inhalation, or other routes of exposure were not found. The only available animal studies showed both positive and negative results when silver was implanted under the skin. Based on U.S. EPA guidelines, silver is placed in weight-of-evidence group D, not classifiable as to human carcinogenicity.

The following is a presentation of the toxicity information associated with Silver.

• The Oral Chronic Reference Dose is 5.00E-03 (mg/kg-day).
• The Oral Chronic Reference Dose has a modifying factor of 1.
• The Oral Chronic Reference Dose has an uncertainty factor of 3.
• The Oral Chronic Reference Dose is based on the Gaul and Staud study from 1935.
• The Oral Chronic Reference Dose study critical effect is argyria.
• The overall confidence in the Oral Chronic Reference Dose is low.

• The Dermal Chronic Reference Dose is 9.00E-04 (mg/kg-day).
• The Dermal Chronic Reference Dose is based on a gastrointestinal absorption factor of 0.1800.