Silica Gel Dangers
Silica gel is synthetic amorphous silica and contains no crystalline silica. It is not actually a gel, but a white solid with the consistency of super-fine sand that is almost powdery. It has a generally low toxicity by all routes of exposure and should not be confused with crystalline forms of silicon dioxide that can cause severe problems such as the lung disease silicosis.
To avoid confusion when talking about silica gel, the Chemical Abstract Services (CAS) has assigned a unique registry number to each form of silica gel. When information in the article refers only to one form of silica gel, the CAS No. will be used to indicate which form of silica gel is being referred to.
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Inhalation
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Inhalation of high concentrations of airborne silica gel may cause coughing and mild temporary irritation. Most silica gel will be cleared from the lungs after inhalation exposure ends and effects of exposure will usually disappear.
Skin and Eye Exposure
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Silica gel is not expected to cause unusual skin irritation beyond mild mechanical irritation upon contact. Silica gel is not absorbed through the skin; however, if it is deposited under the skin, it may cause foreign body granulomas, which are tissue growths formed in early wound healing and repair. Eye contamination with silica gel may cause some tearing, blinking and mild temporary pain caused mostly by mechanical irritation.
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Ingestion
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According to limited animal studies, the toxicity of silica gel by ingestion is low.
Chronic Exposure
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Long industrial exposure to low levels of silica gel is not expected to adversely affect serial lung function.
Embryotoxicity, Teratogenicity, Mutagenicity and Carcinogenicity
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Currently, there is no information available regarding the toxicity to an embryo, ability to cause malformations of an embryo or fetus and capability of inducing mutation or increasing the rate of mutation in DNA of silica gel. The International Agency for Research on Cancer (IARC) has assigned the following rating to silica gel (7631-86-9): 3---Not Classifiable as to Carcinogenicity to Humans.
Fire Hazards
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Silica gel is not combustible. All types of silica gel are converted to crystalline silica when heated to a high enough temperature for a long enough period of time. The temperature the silica gel converts at depends on the type of silica gel. Because crystalline silica can cause silicosis, great care should be taken to minimize exposure in fire situations.
Exposure Limits
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Exposure limits are the highest concentration it is considered safe to be exposed to a chemical without wearing protective equipment. The American Conference of Governmental Industrial Hygienists (ACGIH) Time-Weighted Average (TWA) exposure concentration for a conventional 8-hour workday and a 40-hour workweek for silica gel (112926-00-8) has been withdrawn. The Occupational Safety and Health Administration (OSHA) TWA for amorphous silica is 20 mppcf (million particles per cubic meter) or 80 mg/m3. The National Institute for Occupational Safety and Health (NIOSH) TWA exposure concentration for up to a 10-hour workday and a 40-hour workweek for silica gel (7631-86-9) is 6 mg/m3. The NIOSH Immediately Dangerous to Life and Health (IDLH) for silica gel (7631-86-9) is 3000 mg/m3.
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