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Results of consultation - HSC agrees new exposure limit for subtilisins

The Health and Safety Commission has agreed a new occupational exposure limit for subtilisins of 0.00004 mg.m-3 (40 ng.m-3)1 (8-hour TWA). There is no short-term limit. The limit will not come into force formally until early 2005, but users of this enzyme are advised that they should take appropriate steps to ensure that the exposure of their workforces is controlled accordingly.

Subtilisins are proteolytic enzymes of bacterial origin and come in the form of light-coloured, free-flowing powders. They are derived from Bacillus subtilis by a fermentation process and are readily soluble in water. They are not manufactured in Great Britain but are imported for use in the manufacture of detergents and animal feeds. They are also used for food and leather processing. They are recognised as being respiratory sensitisers and are classified under the Chemicals (Hazard Information and Packaging for Supply) Regulations 2002 to be labelled with the following risk phrases:

The previous occupational exposure standards (OESs) of 0.00006 mg.m-3 (or 60 ng.m-3) for both long-term and short-term exposure were withdrawn in May 2003. In June 2001 the Health and Safety Executive issued a Chemical Hazard Alert Notice (CHAN 24), which advised users of subtilisins that the HSC's Advisory Committee on Toxic Substances (ACTS) was unable to identify a safe limit of exposure for subtilisins. As a result, work commenced on setting a Maximum Exposure Limit (MEL).

Since that time HSE has reviewed its overall framework for exposure limits and has proposed replacing MELs and OESs with a single type of limit 2.

It is anticipated that the new limit will come into force formally in early 2005, with the introduction of the new framework for occupational exposure limits.


  1. Nanograms per cubic metre of air.
  2. The HSC's proposals for a new limit for occupational exposure limits were contained in Consultative Document CD189, which was published in October 2003.
Updated 2009-05-28