Hazardous Chemical Information System (HCIS)

Methyl ethyl ketone (MEK)

E/S first adopted in 1990

Documentation notice: National Occupational Health and Safety Commission documentation available for these values.

No standard should be applied without reference to Guidance on the interpretation of Workplace exposure standards for airborne contaminants.

1. IDENTITY

2. CHEMICAL AND PHYSICAL PROPERTIES

MEK is a clear, colourless, volatile liquid with an acetone-like odour. Its chemical and physical properties include:

3. MAJOR INDUSTRIAL USES

MEK is used as a solvent, usually in mixtures with acetone, ethyl acetate, toluene and/or alcohols. MEK is also used in the manufacture of colourless synthetic resins, and in the surface coating industry.

4. ANIMAL STUDIES

Krasavage et al ⁽²⁾ reviewed the available data and reported that the oral LD₅₀ for rats ranged from 3.3-3.6g/kg body weight; inhalation exposure to 4000ppm for two hours killed four of six rats. Rats exposed to 2150ppm MEK vapour for 6 weeks showed no signs of neurotoxicity.

In an inhalation study, Saida et al ⁽³⁾ exposed groups of rats for 24 hours per day, 7 days per week, at 1125ppm MEK vapour, or 225ppm methyl n-butyl ketone (MBK) vapour, or a mixture of both. MEK produced no signs of peripheral neuropathy after 5 months. MBK alone produced paralysis after 66 days. Rats exposed to both MEK and MBK developed paralysis at 25 days. These results indicated that MEK could potentiate the neurotoxic effects of MBK in rats.

In another inhalation study ⁽⁴⁾ , rats were exposed to 6000ppm MEK, or 10000ppm n-hexane, or a mixture of both vapours (MEK, 1000ppm, n-hexane, 9000ppm). MEK alone produced no signs of neuropathy. Rats exposed to the mixture showed shortened onset of morphologic and clinical signs of n-hexane-induced neuropathy.

5. HUMAN STUDIES

5.1 Irritation

Krasavage et al ⁽²⁾ reported that workers exposed to 300-500ppm of MEK complained of headache, irritation and nausea.

In 1943, Nelson et al ⁽⁵⁾ exposed 10 unacclimatised human subjects to MEK vapour in a test chamber for 3-5 minutes. Slight irritation to the nose and throat was experienced at 100ppm. Mild eye irritation appeared in some subjects at 200ppm. A level of 300ppm was objectionable. This irritation threshold study has certain shortcomings. The concentration of MEK vapour in the exposure chamber was calculated rather than measured analytically. Moreover, the exposure periods of 3-5 minutes were not long enough to show if adaptation would occur.

5.2 Neurological Effects

In a clinical survey ⁽⁶⁾ of 42 Swedish steelworkers who worked with plastic coatings, some possible signs of neuropathy were observed in three workers. These workers were predominantly exposed to MEK at levels ranging between 150-450ppm. However, clear dose-response evidence of a neurotoxic effect has not been demonstrated.

Another study ⁽⁷⁾ on the same group of workers showed an improved reaction time performance when the environmental MEK levels were reduced to 31-105 ppm.

5.3 Interaction Effects

The interaction effects of MEK and other organic solvents (for example, n-hexane, methyl n-butyl ketone) on the nervous system are well known.

Altenkirch et al ⁽⁸⁾ reported that people who had sniffed a commercially available glue thinner developed "glue sniffer's neuropathy". The thinner contained n-hexane and MEK. Apparently, MEK shortened the onset of the neurotoxicity produced by n-hexane.

Billmaier et al ⁽⁹⁾ reported an outbreak of peripheral neuropathy in a coated fabrics factory in which workers were exposed for more than six months to 85-763ppm MEK and 2.3-156ppm MBK.

The interaction effects of MEK and ethyl acetate, isopropyl alcohol, toluene, xylene or 1,1,1-trichloroethane have been reviewed by the (Swedish) National Board of Occupational Safety and Health ⁽¹⁰⁾ and Krasvage et al ⁽²⁾ .

6. OVERSEAS EXPOSURE STANDARDS

7. CONCLUSION

Exposure to 100-200ppm MEK for 3-5 minutes caused irritation of the eyes, nose and throat. A level of 300ppm was objectionable.

Long-term neurotoxicity studies in animals have shown that MEK alone is not likely to cause peripheral neuropathy . A human study has not produced adequate evidence of neurotoxicity at levels of 150-450ppm.

MEK can interact with methyl n-butyl ketone or n-hexane to shorten the onset of neuropathy.

8. RECOMMENDATION FOR EXPOSURE STANDARD

To minimise sensory irritation, the Exposure Standards Working Group recommends a time-weighted average exposure standard of 150ppm and a STEL of 300ppm. In the absence of other organic solvents, these levels should also be low enough to protect the workers from possible neurotoxic effects.

1. American Conference of Governmental Industrial Hygienists, Documentation of threshold limit values and biological exposure indices, 5th edition, Ohio, 1986

2. Krasavage JL et al, Ketones, In: Patty's Industrial Hygiene and Toxicology, ed. by Clayton GD & Clayton FE, 3rd revised edition, Vol 2C, John Wiley & Sons, p.4709-4800, 1982

3. Saida K et al, "Peripheral nerve changes induced by methyl n-butyl ketone and potentiation by methyl ethyl ketone", J Neuropathol Exp. Neurol, 35, 207-225, 1976

4. Altenkirch H et al, "Experimental studies on hydrocarbon neuropathies induced by methyl ethyl ketone (MEK)", J Neurol, 219, 159-170, 1979

5. Nelson KW et al, "Sensory response to certain industrial solvent vapours", J Ind Hyg Tox, 25, 282-285, 1943

6. Fagius J & Gronqvist B, "Function of peripheral nerves and signs of polyneuropathy in solvent exposed workers at a Swedish steel works", Acta Neurol Scand, 57, 305-316, 1978

7. Anshelm Olson Bet al, "Reaction time changes among steel workers exposed to solvent vapors", Int Arch Occup Environ Health, 48, 211-218, 1981

8. Altenkirch H et al, "Toxic polyneuropathies after sniffing a glue thinner", J Neurol, 214, 137-152, 1977

9. Billmaier DJ et al, "Peripheral neuropathy in a coated fabrics plant", J Occup Med 16, 665-671, 1974

10. National Board of Occupational Safety and Health, Consensus report for methyl ethyl ketone, Scientific Basis for Swedish Occupational Standards VI, ed. Per Lunberg, 1985:32, Solna, Sweden, p.58-65

11. National Institute for Occupational Safety & Health, Criteria for a Recommended Standard...Occupational Exposure to Ketones, DHEW (NIOSH) Publication No.78-173, June 1978

Entries carrying a notice for National Occupational Health and Safety Commission documentation indicate that these substances have been reviewed in detail by the Exposure Standards Expert Working Group and that documentation supporting the adopted national values is available in the National Commission's Documentation of the Exposure Standards [NOHSC:10003(1995)].