Butanone (MEK)

Interpretive data for breath butanone

WEL: 200 ppm (8h TWA) Skin notation

Other names: methylethylketone, MEK

Context

This information provides interpretation of breath solvent values obtained using the Bio-VOC™ breath sampler. Further information regarding the implementation of a biological monitoring strategy can be found in HSE's guidance on Biological monitoring in the workplace booklet.

Sampling

Samples should be taken approximately 10 minutes post-shift in a 'clean' area, such as medical room, office or canteen. Refer to the breath sampling instructions for details of how to take samples.

The initial half-life of butanone in breath is about 5 minutes, followed by a second half-life of around 50 minutes. End of shift sampling will therefore not reflect exposure over the entire shift but rather the last hour or two.

Interpretation

The HSE Bio-VOC sampler has been used in a field survey of workers in the shoe manufacturing industry. Workers provided post-shift breath and urine samples that were analysed for butanone. The correlation between breath and urine indicated that the breath butanone equivalent of a urine sample at the current guidance value ⁽¹⁾ would be ~280 nmol/l. In a volunteer study conducted at HSL ⁽²⁾, 4 hours' exposure at the WEL resulted in mean post-exposure breath levels of ~200 nmol/l.

Recommendations

If breath butanone levels:

are below 100 nmol/l and exposure is uniform throughout the shift, exposure is likely to be below the WEL. A suggested biological monitoring strategy is once yearly, providing no change in working practices.
exceed 100 nmol/l, peak levels of exposure may approach the WEL. Analysis of a post-shift urine sample for butanone is recommended to give a more accurate comparison with the WEL, by reference to the UK guidance value.
exceed 300 nmol/l, it is likely that butanone exposure exceeds the WEL for at least part of the shift. A routine monitoring strategy using urinary butanone measurements is recommended.

If exposure is intermittent, task-related sampling is recommended. Breath samples should be taken within 10 minutes of completing tasks with the potential for high exposure.

Other biological monitoring

Other means of biological monitoring include butanone in urine (for which there is a biological monitoring guidance value.

Exposure control

Butanone can be absorbed by inhalation or skin absorption of either the liquid solvent or solvent vapours ⁽²⁾.

References

Workplace Exposure Limits (EH40)
Brooke I et al. Ann Occup Hyg 1998 Nov;42(8):531-40 (http://annhyg.oxfordjournals.org/content/42/8/531.long).

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