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Chemical Name: Maleic Anhydride
CAS Number: 108-31-6
Synonyms: Cis-Butenedioic anhydride, Toxilic anhydride
Appearance: White, needle-like crystals or flakes, with a sharp, irritating odor
Common Uses: This compound often finds its way into the manufacturing of unsaturated polyester resins, copolymers, agricultural chemicals, coatings, and lubricants. Sitting around a production floor or a research lab, you hear about it mostly because of its versatility and reactivity, not because someone likes its smell.
Hazard Classification: Acute toxicity, Skin corrosion/irritation, Serious eye damage, Respiratory sensitizer, Carcinogenicity
Health Hazards: Breathing in the dust or fumes can hit your lungs hard, triggering coughing, chest pain, and sometimes even asthma-like symptoms in those with a history of breathing issues. The powder burns the skin and eyes. There’s a risk for chemical burns that nobody wants to experience twice. Some animal studies suggest it may carry a cancer risk after long, high-level exposure. If you’ve ever mixed resin with bare hands, you know firsthand how unforgiving the burning sensation feels.
Environmental Hazards: Harmful to aquatic life. Any sloppy spills run the risk of washing into storm drains, reaching streams, and disrupting plant and fish health further downstream.
Major Component: Maleic Anhydride (over 98 percent by weight)
Impurities: Trace amounts of maleic acid and fumaric acid can show up due to its manufacturing process. Certain firms note the importance of accounting for impurities when dealing with sensitive chemical reactions or regulations.
Inhalation: Fresh air means a lot after breathing maleic anhydride dust or fumes; move anyone exposed to clean air as soon as possible. Sometimes, deep or repeated exposure leaves behind a nasty cough or burning airway irritation. Medical help comes next, especially if shortness of breath or chest tightness follows.
Skin Contact: Strip off any affected clothing and rinse the skin thoroughly with running water for upwards of 15 minutes. Burns from the crystals sting like crazy, so prompt washing lessens long-term damage.
Eye Contact: Rinse for at least 15 minutes with water, lifting eyelids repeatedly. Some folks might find their vision blurred or doubled for a while after such exposure.
If Swallowed: Drinking water to rinse the mouth is common advice, but never try to make the person vomit. Medical help should be called, since this chemical rarely makes it into the GI tract without mishap.
Suitable Extinguishing Media: Dry chemical, CO2, or foam. Water may work, but it can react to form maleic acid – sometimes creating more problems than it solves.
Hazardous Combustion Products: Carbon oxides and toxic, acrid smoke come off in a fire, which is never pleasant for fire crews or anyone nearby.
Firefighting Advice: Firefighters suit up with self-contained breathing apparatus and chemical-resistant gear. If you’ve ever helped roll a hose into a hot, chemical-rich blaze, you remember how different these fires smell and feel compared to a wood fire.
Personal Protection: Dust mask, tight gloves, safety goggles, and protective clothing – the basics, learned after watching what happens without them. Spilled crystals sting bare skin, and dust hangs in the air if swept dry.
Spill Cleanup: Avoid creating dust clouds. Sweep carefully, use wet methods where possible, and transfer material to a closed container for disposal. If you ever cleaned a site without care, you probably remember the sneezing, eye-watering, and irritation lasting half the day.
Environmental Precautions: The run-off should never reach surface water or sewer systems. With others regularly checking containment berms and monitoring drain gates, labs often prevent a little mishap from turning into a hazardous fish kill downstream.
Handling: Work in well-ventilated areas; wear gloves and eye protection. Keep containers tightly sealed when not in use. Eating or drinking near the material means carrying a small but real risk of contamination.
Storage: Store dry, below 40°C, away from humidity and incompatible chemicals such as water, strong bases, or oxidizers. Anyone who has opened an old, damp barrel knows about the odd caking and corrosion that shows up when storage conditions go unchecked.
Permissible Exposure Limits (PELs): Occupational exposure limits vary, but most workplaces keep airborne concentrations under 1 mg/m³, as recommended by groups like OSHA or ACGIH.
Engineering Controls: Local ventilation, fume hoods, and direct exhausts on filling and bagging lines. Old buildings with dusty corners and weak vent fans often leave you itchy and sore-throated, a reminder that the best PPE sometimes starts with a well-designed air-handling system.
Personal Protective Equipment: Chemical-resistant gloves, goggles, face shield, and protective clothing; a particulate-filtering respirator when dust hangs in the air.
Physical State: Solid, flakes or crystals
Color: White
Odor: Sharp, irritating, acrid
Melting Point: 52.8 °C
Boiling Point: 202 °C
Solubility: Reacts with water to form maleic acid
Vapor Pressure: Low at room temperature, but enough to matter in confined spaces
Density: Around 1.48 g/cm³
Stability: Stable under dry, cool storage conditions, but humidity cracks open crystals and triggers maleic acid formation.
Reactivity: Violently reacts with water, alcohols, strong bases, oxidizing agents, and amines. Keeping incompatible chemicals separated sometimes means more than just reading a rulebook; it’s about trust in coworkers and routine double checks.
Decomposition: Heat and fire kick off toxic fumes like carbon monoxide, carbon dioxide, and corrosive gases.
Exposure Routes: Inhalation, skin contact, eye contact, ingestion
Acute Effects: Eye and respiratory tract irritation, severe skin burns, possible allergic reactions or asthma-like symptoms especially among new workers during the first season or two
Chronic Effects: Persistent asthma, dermatitis, and in some long-term animal studies, tumor development at high doses
Carcinogenicity: Some evidence of cancer risk exists in rodent studies, but no widespread links in humans have been seen in daily industrial practice.
Other Notes: Regular training and rotations often reduce the number of health complaints in a workplace, especially compared to periods of understaffing or overtime.
Acute Aquatic Toxicity: Harmful to fish and aquatic invertebrates in concentrated spills, especially during transport mishaps or failed containment.
Environmental Fate: Gains water solubility quickly and converts to maleic acid, which persists but eventually degrades by microbial action in soil and water.
Bioaccumulation: Low likelihood – the molecule doesn’t tend to build up in animals, so regulatory bodies focus mostly on point-source incidents rather than food-chain transfer.
Waste Disposal: Sweep or vacuum spilled solids, package in sealed, labeled drums, and send them to certified chemical waste facilities. Incineration is common for bulk disposal, but you need proper scrubbers to capture the harsh fumes.
Container Disposal: Triple-rinsed, punctured empty containers avoid re-use for food or drinking water. Some workers have strong feelings about disposal, especially after witnessing contaminated tools returning from “thorough” washing.
Regulatory Waste Codes: Disposal routines are shaped by local, state, and national hazardous waste codes, shaping everything from landfill fees to spill response plans.
UN Number: UN 2215
Proper Shipping Name: Maleic Anhydride
Transport Hazard Class: Class 8 (Corrosive substances)
Packing Group: II
Labeling Requirements: Corrosive diamond and proper documentation. Loads need to avoid contact with moisture, and trucks must keep the material separated from incompatible cargo.
Spill Precautions in Transit: Secondary containerization and emergency response kits often ride along with larger shipments, especially on routes crossing waterways or protected land.
OSHA: Listed under hazardous chemicals for the workplace; employers track worker exposure and provide regular training.
EPA: Regulated as a hazardous air and water pollutant; spill notification rules trigger fast reporting after a major release.
Other Regulations: Reference to SARA Title III, TSCA, and relevant European REACH or CLP regulations. These rules cover handling, labeling, and downstream use, so users stay aware of both immediate health risks and broader community impact.
Industry Best Practices: Most facilities now document exposure incidents, near-misses, and mitigation steps, improving outcomes and reducing repeat mistakes.
