- Sodium selenite (Na₂SeO₃) is an inorganic salt composed of sodium (Na⁺) and selenite (SeO₃²⁻) ions. It typically appears as a white or colorless, water-soluble crystalline powder. Sodium selenite is a selenium-based compound and serves as one of the most common inorganic sources of selenium, a trace element that is essential for human and animal health in small amounts but toxic at higher concentrations. Its dual nature as both a nutrient and a potential toxin makes it an important yet carefully regulated substance in nutritional, pharmaceutical, and industrial applications.
- In nutrition and medicine, sodium selenite is used as a dietary supplement to prevent or treat selenium deficiency. Selenium plays a crucial role in antioxidant defense systems, especially as a component of the enzyme glutathione peroxidase, which protects cells from oxidative damage. It also supports thyroid hormone metabolism, immune function, and DNA synthesis. Sodium selenite is commonly added to multivitamin and mineral formulations, as well as to animal feeds, particularly for livestock in regions where soils are selenium-deficient. However, because of selenium’s narrow therapeutic range, supplementation must be carefully dosed—excess selenium can lead to selenosis, a condition marked by symptoms such as hair and nail loss, gastrointestinal disturbances, and neurological damage.
- In cancer research and therapy, sodium selenite has attracted attention for its potential anticancer properties. At controlled doses, it can selectively induce apoptosis (programmed cell death) in certain cancer cells through mechanisms involving oxidative stress and DNA damage. Experimental studies have explored its use as an adjunctive treatment, though clinical application is still under investigation and must balance efficacy with its inherent toxicity risk.
- Sodium selenite also has industrial uses, particularly in the glass and ceramics industry, where it is used as a decolorizing agent to remove green tints caused by iron impurities in glass. It can also serve as a colorant, imparting red or pink hues when combined with cadmium or other metal oxides. In chemical synthesis and laboratories, sodium selenite is used as a reagent for introducing selenium into organic or inorganic compounds.
- From a toxicological and environmental perspective, sodium selenite is classified as hazardous and must be handled with care. It is toxic when ingested or inhaled in excessive amounts and can pose a risk to aquatic life if improperly disposed of. In humans, acute selenium poisoning may result in symptoms such as metallic taste, garlic-like breath odor, nausea, vomiting, and fatigue. Chronic exposure to elevated levels may have more serious long-term health consequences. For these reasons, sodium selenite is subject to strict regulatory controls in both environmental and occupational contexts.
- In agriculture, small amounts of sodium selenite are sometimes used to fortify soil or fertilizers, helping to increase the selenium content of crops grown in deficient regions. This practice can help prevent dietary deficiencies in human populations and livestock but must be managed to avoid environmental accumulation and toxicity.
