Isophorone is a α,β-unsaturated cyclic ketone with the molecular formula C9H14O. It is a colourless to yellowish liquid with a characteristic peppermint-like smell. [1] Isophorone evaporates faster than water but slower than charcoal starter or paint thinner, and it will not mix completely with water. It is a manmade chemical for use commercially, but it has been found to occur naturally in cranberries. Isophorone does not remain in the air very long, but can remain in water for possibly more than 20 days. The length of time that isophorone will remain in soil is not known, but it probably is about the same as the length of time it remains in water. [2]

Uses [3]

Isophorone is used mainly as a solvent for concentrated vinyl chloride/acetate-based coating systems for metal cans, other metal paints, nitrocellulose finishes, and printing inks for plastics. In addition, it is used in some herbicide and pesticide formulations and in adhesives for plastics, polyvinylchloride, and polystyrene materials. Isophorone is an intermediate in the synthesis of 3,5-xylenol, 3,3,5-trimethylcyclohexanol, and plant growth retardants.

In the Environment [4]

Isophorone is released to the air from inks, paints, and other products containing it. It disappears in air very quickly, half of it disappears in less than 5 hours. It may be present in water from industrial releases. In water, bacteria can break it down over a period of several days to about a month. In soil, it may be broken down by bacteria, filter to groundwater, or evaporate to the air; however, there is not much information on its presence in soil. It does not build up in the food chain.

Sources and Routes of Exposure

Sources of Exposure [4]

  • Breathing low levels found in air.
  • Drinking water contaminated with isophorone.
  • Eating food that contains isophorone.
  • Working in the printing, adhesives, and coatings industries where isophorone is used.

Routes of Exposure [5]

The major routes of exposure to isophorone are:

  • inhalation
  • ingestion
  • skin and/or eye contact

Health Effects [3]

Acute Effects

The only acute effects of isophorone reported in humans are irritation of the skin, eyes, nose, and throat, headache, and dizziness. Exposure to high concentration of isophorone via inhalation in animals causes inactivity and coma. Tests involving acute exposure of rats and guinea pigs have shown isophorone to have moderate toxicity from oral and inhalation exposure.

Chronic Effects

Workers exposed to isophorone over a long-term period experienced dizziness, fatigue, and depression. Animal studies indicate that long-term inhalation of high concentrations of isophorone causes central nervous system effects such as narcosis, staggering, depression, ataxia, lethargy, prostration, and coma. The Reference Dose (RfD) for isophorone is 0.2 milligrams per kilogram body weight per day (mg/kg/d) based on no observed effects in dogs. EPA has determined that there are inadequate data for establishing a Reference Concentration (RfC) for isophorone. In the final listing rule for solvents, EPA calculated a provisional RfC of 0.012 milligrams per cubic metre (mg/m3) based on body weight effect in rats. The provisional RfC is a value that has had some form of Agency review but is not on IRIS. The California Environmental Protection Agency (CalEPA) has calculated a chronic inhalation reference exposure level (REL) of 2 mg/m3 for isophorone based on developmental effects in rats. The CalEPA reference exposure level is a concentration at or below which adverse health effects are not likely to occur.

Reproductive/Developmental Effects

No studies were located regarding developmental or reproductive effects in humans. Limited evidence in animal studies suggests that isophorone may cause birth defects such as foetal malformations and growth retardation from inhalation exposure to isophorone during pregnancy.

Cancer Risk

No studies were found concerning the carcinogenicity of isophorone in humans. One study demonstrated an increased incidence of kidney tumours and preputial gland (a male reproductive gland) tumours in male rats exposed to isophorone by gavage. However, the type of kidney tumour observed in male rats is of questionable relevance to humans. EPA considers isophorone to be a possible human carcinogen (cancer-causing agent) and has ranked it in EPA’s Group C.

Safety [6]

First Aid Measures

  • General advice: Immediately remove contaminated clothing. If danger of loss of consciousness, place patient in recovery position and transport accordingly. Apply artificial respiration if necessary. First aid personnel should pay attention to their own safety.
  • If inhaled: Remove the affected individual into fresh air and keep the person calm. Assist in breathing if necessary. Immediate medical attention required.
  • If on skin: Wash affected areas thoroughly with soap and water. Remove contaminated clothing. Immediate medical attention required.
  • If in eyes: In case of contact with the eyes, rinse immediately for at least 15 minutes with plenty of water. Immediate medical attention required.
  • If swallowed: Rinse mouth and then drink plenty of water. Do not induce vomiting. Never induce vomiting or give anything by mouth if the victim is unconscious or having convulsions. Immediate medical attention required.
  • Note to physician: Treat according to symptoms (decontamination, vital functions), no known specific antidote. Pulmonary oedema prophylaxis. Medical monitoring for at least 24 hours.

Exposure Controls & Personal Protection

Engineering Controls

  • Provide local exhaust ventilation to control vapours/mists.
  • Eye wash fountains and safety showers must be easily accessible.

Personal Protective Equipment

The following personal protective equipment is recommended when handling isophorone:

  • Respiratory protection: Wear a NIOSH-certified (or equivalent) organic vapour/particulate respirator.
  • Hand protection: Chemical resistant protective gloves
  • Eye protection: Tightly fitting safety goggles (chemical goggles). Wear face shield if splashing hazard exists.
  • Body protection: Impermeable protective clothing


United States [3]

  • ACGIH: American Conference of Governmental and Industrial Hygienists’ has set a threshold limit value ceiling of 28 mg/m3 for isophorone. This concentration should not be exceeded during any part of the working exposure.
  • NIOSH: The National Institute of Occupational Safety and Health has set a recommended exposure limit of 23 mg/m3 for an 8- or 10-h time-weighted-average exposure and/or ceiling.
  • NIOSH: The National Institute of Occupational Safety and Health has set an immediately dangerous to life or health concentration for isophorone of 140 mg/m3. This recommended exposure limit is set to ensure that a worker can escape from an exposure condition that is likely to cause death or immediate or delayed permanent adverse health effects or prevent escape from the environment.
  • OSHA: The Occupational Safety and Health Administration has set a permissible exposure limit of 140 mg/m3 expressed as a time-weighted average; the concentration of a substance to which most workers can be exposed without adverse effect averaged over a normal 8-h workday or a 40-h workweek.

Australia [7]

Safe Work Australia: Safe Work Australia has established a time weighted average concentration for isophorone of 5ppm and 28mg/m3 for an 8-hour workday.