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Substance name: L-Cystine
Chemical formula: C6H12N2O4S2
CAS number: 56-89-3
Physical form: L-Cystine usually shows up as a white, crystalline powder and doesn’t carry much of a smell, so it’s easy to overlook if spilled in a workspace. Its taste or other physical cues rarely stand out outside the lab setting, so reading the label and checking the context remains the way to go to avoid any confusion with other similar-looking materials.
Potential hazards: Most reports find L-Cystine sits in a category where risk isn’t high, but anyone breathing it in as a dust, swallowing it by accident, or handling it with bare skin may see minor irritation or discomfort. Not classified as a carcinogen by IARC, ACGIH, or NTP. Breathing issues or sneezing after dust exposure sometimes crop up.
Signal word: Warning
Pictograms: None required
Precautionary statements: Avoid breathing dust. Wash any exposed skin after handling. Don’t eat, drink, or smoke around the material.
Chemical identity: Only L-Cystine is present in its pure form.
Concentration: 100% pure in laboratory or industrial settings unless noted otherwise.
Impurities: Commercial samples may carry traces of other amino acids or processing byproducts, but these rarely register significant health concerns.
Inhalation: Move the person into fresh air. Let them sit and breathe comfortably and rinse their mouth with water if any irritation sticks around.
Skin contact: Wash off with soap and water. If irritation keeps up, find a healthcare provider for help.
Eye contact: Rinse with plenty of water for several minutes, blinking whenever possible, to flush out particles.
Ingestion: Rinse mouth with plain water. If feeling unwell, seek medical advice. No known life-threatening reactions at typical exposure levels.
Flammability: Not known to burst into flames under normal use, but fine dust can grow risky near open flames or sparks.
Suitable extinguishing media: Water spray, CO2, dry chemical, or foam.
Special protective equipment for firefighters: Firefighters should suit up with standard gear and have breathing protection ready, as some smoke and irritating gases might form if the powder burns.
Spill response: Scoop up spilled powder carefully to stay clear of dust clouds. Sweeping up slowly using a damp cloth or a HEPA vacuum collects powder safely. Wearing gloves and a dust mask cuts down on irritation and inhalation risks.
Environmental precautions: Although not thought to harm water or soil by itself, L-Cystine should stay out of drains and open ground to avoid contributing to unexpected chemical loads.
Safe handling: Use gloves, avoid breathing dust, and work in well-ventilated spaces. Don’t create dust clouds or eat and drink around L-Cystine.
Storage: Keep stored in a cool, dry place, away from strong acids and bases, and out of the reach of children or unauthorized personnel. Opened containers should close tightly after use, keeping exposure to air and humidity as limited as possible.
Exposure limits: Not under strict regulatory exposure limits set by OSHA or ACGIH.
Respiratory protection: A NIOSH-approved dust respirator for dusty tasks.
Skin protection: Gloves and a lab coat or protective apron keep direct contact to a minimum.
Eye protection: Chemical splash goggles for mixing or transferring L-Cystine powder.
Ventilation: Work with good airflow, such as a chemical fume hood, during weighing or mixing.
Appearance: White crystalline powder
Odor: Odorless
Melting point: About 260°C (500°F), with decomposition
Solubility: Slightly soluble in water, insoluble in alcohol
pH: Neutral to slightly acidic in solution
Boiling point, vapor pressure, and flash point: Not applicable for this solid
Density: Roughly 1.68 g/cm³
Chemical stability: L-Cystine remains stable at room temperature under regular laboratory conditions.
Reactivity: It may react with strong oxidizers. Avoid mixing with acids or bases since that can break it down or make it less stable.
Hazardous decomposition products: Sulfur oxides and nitrogen oxides may form if heated too strongly or during a fire.
Routes of exposure: Inhalation, skin, and eye contact
Acute toxicity: Has low toxicity; large oral doses may cause gastrointestinal discomfort.
Chronic exposure: There are no long-term effects established for casual laboratory or dietary exposure, but regular direct contact can leave some with mild skin or respiratory irritation. No solid data connects L-Cystine exposure to major health disorders in the general population.
Environmental behavior: Not flagged as persistent, bioaccumulative, or toxic under current regulations. Practically, that means spills won’t turn waterways toxic, but unnecessary release still adds to chemical loads and should be avoided.
Aquatic toxicity: No strong evidence for harm to fish or aquatic life under normal accidental release scenarios.
Disposal methods: Small quantities go into regular chemical waste streams per local rules. Do not flush down the drain. Collect and seal in suitable chemical waste containers. Incineration at standard waste facilities works best for larger amounts.
Recycling or reuse: Rarely possible due to contamination and low economic value of recovered L-Cystine.
UN number: Not assigned. L-Cystine does not fall under dangerous goods for transport by most international rules.
Packing group: None assigned
Special precautions: Package in sealed containers, keep dry, and protect from crushing or mechanical damage to avoid dust spread if the container opens accidently. No labeling required for non-bulk shipments.
Global regulations: Classified as non-hazardous under OSHA, CLP, and many national regulations, as long as it’s handled without generating excessive dust.
Labeling requirements: No hazard pictograms or specific risk phrases needed for pure L-Cystine under the GHS system. Employee training about good handling practices covers risk reduction effectively.
Inventory status: L-Cystine sits on most chemical inventories globally, including TSCA and REACH.
