Maleic anhydride (butenedioic anhydride, toxilic anhydride, 2,5-dioxofuran) is an organic compound with the formula C2H2(CO)2O. [fusion_builder_container hundred_percent=”yes” overflow=”visible”][fusion_builder_row][fusion_builder_column type=”1_1″ background_position=”left top” background_color=”” border_size=”” border_color=”” border_style=”solid” spacing=”yes” background_image=”” background_repeat=”no-repeat” padding=”” margin_top=”0px” margin_bottom=”0px” class=”” id=”” animation_type=”” animation_speed=”0.3″ animation_direction=”left” hide_on_mobile=”no” center_content=”no” min_height=”none”] Under normal conditions, maleic anhydride is found as colourless crystals or a white solid, with a choking, acrid smell. It melts at 58 degrees Celsius. Maleic anhydride is corrosive. It dissolves in water to give maleic acid. It also dissolves in most organic (carbon-containing) solvents. 
Maleic anhydride is used primarily in the formation of unsaturated polyester resins for use in boats, autos, trucks, buildings, piping, and electrical goods. Lube oil adhesives synthesised from maleic anhydride are used to prolong oil-change intervals and improve engine efficiency. Maleic anhydride is also used to make copolymers, pesticides, and other organic compounds, and in Diels-Alder syntheses.
In the Environment 
Maleic anhydride in soils is readily broken down. It does not bind particularly strongly to soil particles, so can leach to groundwaters where it will be broken down naturally. In air, it reacts fairly quickly and so has a short life. Maleic anhydride does not accumulate in the environment. It is not considered likely that maleic anhydride pollution has any effects on the global environment.
Sources & Routes of Exposure
Sources of Exposure [2,3]
Releases of maleic anhydride may occur from industry manufacturing, transporting, storing and using it. There are not thought to be any natural sources of maleic anhydride to the environment. Exposure to maleic anhydride would primarily be occupational from contact with spills, fugitive emissions, or vent gases. It may also be spilled or emitted into the atmosphere during its manufacture, transport, or use.
Routes of Exposure 
The major routes of exposure for maleic anhydride are:
- Skin contact
- Eye contact
Health Effects 
Acute inhalation exposure of humans to maleic anhydride has been observed to cause irritation of the respiratory tract, burning in the larynx, reflex cough, lacrimation, headaches, eye irritation, and corneal burns (that healed within 48 hours). Bronchial asthma was observed in guinea pigs acutely exposed to maleic anhydride. Acute animal tests in rats, mice, rabbits, and guinea pigs have demonstrated maleic anhydride to have moderate to high acute toxicity by ingestion and moderate acute toxicity from dermal exposure.
Chronic exposure to maleic anhydride has been observed to cause chronic bronchitis, asthma-like attacks, pulmonary oedema, upper respiratory tract irritation, eye irritation, and dermatitis in workers. In some people, allergies have developed so that lower concentrations can no longer be tolerated. Nose and eye irritation, upper respiratory lesions, nasal discharge, dyspnea (shortness of breath), and sneezing have been observed in rats, hamsters, and monkeys chronically exposed to maleic anhydride by inhalation. Renal lesions were observed in rats chronically exposed to maleic anhydride via gavage (experimentally placing the chemical in the stomach). Decreased body weight and increased kidney weight have also been observed in orally exposed rats. EPA has not established a Reference Concentration (RfC) for maleic anhydride. The Reference Dose (RfD) for maleic anhydride is 0.1 milligrams per kilogram body weight per day (mg/kg/d) based on renal lesions in rats. The California Environmental Protection Agency (CalEPA) has calculated a chronic inhalation reference exposure level of 2 x 10-4 milligrams per cubic metre (mg/m3). The CalEPA reference exposure level is a concentration at or below which adverse health effects are not likely to occur.
No information is available on the reproductive or developmental effects of maleic anhydride in humans. No teratogenic or fetotoxic effects were observed in the offspring of rats exposed via gavage or diet.
No information is available on the carcinogenic effects of maleic anhydride in humans. A study reported no treatment-related increased tumour incidence in rats exposed in their diet. EPA has not classified maleic anhydride for carcinogenicity because it has not been adequately tested regarding potential carcinogenicity.
First Aid Measures
- Eye Contact: Check for and remove any contact lenses. Immediately flush eyes with running water for at least 15 minutes, keeping eyelids open. Cold water may be used. Do not use an eye ointment. Seek medical attention.
- Skin Contact: If the chemical got onto the clothed portion of the body, remove the contaminated clothes as quickly as possible, protecting your own hands and body. Place the victim under a deluge shower. If the chemical got on the victim’s exposed skin, such as the hands: Gently and thoroughly wash the contaminated skin with running water and non-abrasive soap. Be particularly careful to clean folds, crevices, creases and groin. Cold water may be used. If irritation persists, seek medical attention. Wash contaminated clothing before reusing.
- Serious Skin Contact: Wash with a disinfectant soap and cover the contaminated skin with an anti-bacterial cream. Seek immediate medical attention.
- Inhalation: Allow the victim to rest in a well-ventilated area. Seek immediate medical attention.
- Serious Inhalation: Evacuate the victim to a safe area as soon as possible. Loosen tight clothing such as a collar, tie, belt or waistband. If breathing is difficult, administer oxygen. If the victim is not breathing, perform mouth-to-mouth resuscitation. WARNING: It may be hazardous to the person providing aid to give mouth-to-mouth resuscitation when the inhaled material is toxic, infectious or corrosive. Seek immediate medical attention.
- Ingestion: Do not induce vomiting. Examine the lips and mouth to ascertain whether the tissues are damaged, a possible indication that the toxic material was ingested; the absence of such signs, however, is not conclusive. Loosen tight clothing such as a collar, tie, belt or waistband. If the victim is not breathing, perform mouth-to-mouth resuscitation. Seek immediate medical attention.
Exposure Controls & Personal Protection
Use process enclosures, local exhaust ventilation, or other engineering controls to keep airborne levels below recommended exposure limits. If user operations generate dust, fume or mist, use ventilation to keep exposure to airborne contaminants below the exposure limit.
Personal Protective Equipment
The following personal protective equipment is recommended when handling maleic anhydride:
- Splash goggles;
- Synthetic apron;
- Vapour and dust respirator (be sure to use an approved/certified respirator or equivalent);
Personal Protective Equipment in Case of a Large Spill:
- Splash goggles;
- Full suit;
- Vapour and dust respirator;
- A self-contained breathing apparatus should be used to avoid inhalation of the product.
- Suggested protective clothing might not be sufficient; consult a specialist BEFORE handling this product.
United States 
OSHA: The Occupational Safety & Health Administration has set a Permissible Exposure Limit (PEL) for maleic anhydride of:
- General Industry: 0.25 ppm, 1 mg/m3
- Construction Industry: 0.25 ppm, 1 mg/m3 TWA
ACGIH: The American Conference of Governmental Industrial Hygienists has set a Threshold Limit Value (TLV) for maleic anhydride of 0.25 ppm, 1 mg/m3 TWA
NIOSH: The National Institute for Occupational Safety and Health has set a Recommended Exposure Limit (REL) for maleic anhydride of: 0.25 ppm TWA
Safe Work Australia: Safe Work Australia has established a Time Weighted Average (TWA) concentration for maleic anhydride of: 0.25ppm, 1 mg/m3