Butanone—also known as methyl ethyl ketone (MEK)—is a colourless liquid organic compound. The chemical formula for MEK is C4H8O or CH3COCO2CH3. It has a sweet sharp odour, reminiscent of acetone or mint. The compound is naturally occurring in some fruits and vegetables in trace amounts—however it is usually produced on an industrial scale for chemical use. Butanone can also be found in the air, as a by-product of car and truck exhausts. It is soluble in water [1,2]
Butanone is most commonly used across chemical industries as a solvent and as a plastic welding agent. As a solvent, it is often used in paints, resins and other coatings because it effectively dissolves many substances and due to its quick evaporation time. As a plastic welding agent, MEK effectively dissolves polystyrene and other plastics—an application which is often used in scale model kits.
Routes of Exposure 
Methyl ethyl ketone can be found in both indoor and outdoor air.
It can be produced in the outdoor air by the photo-oxidisation of butane.
The compound has also been found in drinking and surface water.
Methyl ethyl ketone poisoning affects a range of systems including the respiratory, nervous and blood systems.
Acute Effects 
Severity of symptoms depend on the level and type of exposure.
Acute, but high concentrations, of MEK can result in irritation to the eyes, nose and throat.
Acute exposure can also result in CNS depression, nausea and headaches.
Dermal exposure to the compound has resulted in dermatitis.
Chronic Effects 
Methyl ethyl ketone is toxic to multiple body systems. Long-term exposure to the compound can result in severe chronic headaches, loss of balance, memory loss, fatigue and tachycardia. It can also cause encephalopathy, distal axonopathy, persistent neurological problems, cerebellar and brainstem atrophy and general central nerve fibre degeneration. It is not a carcinogen.
~h2First Aid Measures 
· Ingestion: DO NOT INDUCE VOMITING. If the victim is not convulsing, and is conscious, give them one or two glasses of water to dilute the compound. If they are unconscious or convulsing, put the victim in the recovery position. Immediately contact a medical professional.
· Skin contact: Immediately wash affected skin with water, while removing contaminated clothing. Do not re-wear until it has been thoroughly de-contaminated. Wash affected areas with soap and water. If symptoms persist, contact a healthcare professional.
· Eye contact: Check for and remove contact lenses if easy to do so. Rinse eyes carefully with water or normal saline solution for 20-30 minutes. Take the victim to a medical centre.
· Inhaled: Take victim to the nearest fresh air source and monitor their breathing. Allow them to rest and contact a medical professional.
· General: Never administer anything by mouth to an unconscious, exposed person.
Exposure Controls/Personal Protection 
· Engineering controls: Emergency eyewash fountains and safety showers should be accessible in the immediate area of the potential exposure. Ensure there is adequate ventilation. Whenever possible, material should be handled in a laboratory.
· Personal protection: Safety glasses, protective and dustproof clothing, glove, an apron and an appropriate mask.
The Occupational Safety and Health Administration (OSHA) has set an 8-hour time weighted average (TWA) concentration for butanone of 200ppm. The National Institute of Occupational Health and Safety (NIOSH) has set a short-term exposure limit (STEL) of 300ppm.
Safe Work Australia has set an 8-hour time TWA for butanone of 150ppm. They have set a STEL of 300ppm.