Standards for workplace environments

The occupational exposure limits for the UK are published in EH40. Since April 2005, when the fifth edition of COSHH Regulations 2002 (as amended) was issued, the previous system of setting occupational exposure limits (OELs) as maximum exposure limits (MELs) and occupational exposure standards (OESs) has been discontinued. They have been replaced by a single type of OEL known as the workplace exposure limit (WEL) which has legal status under regulation 7(7)(b) of COSHH. Incorporated in the data on exposure limits contained in the HSE s publication EH40 are the Indicative Occupational Exposure Limit Values (lOELVs) adopted by the EU. 

Regulation 7(7)(b) requires that the WEL must not be exceeded. The conditions described in 7(7)(c) are as follows for a substance that carries a risk phrase R42, R42/43, R45, R46 or R49 for a substance listed in schedule 1 of COSHH for a substance which is listed in section C of HSE publication Asthmagens Critical assessments of the evidence for agents implicated in occupational asthma or any other substance which the risk assessment has shown to be a potential cause of occupational asthma, the exposure must be reduced below that limit to as low as is reasonably practicable. 

There are far fewer substances listed in the current version of EH40 than in previous editions where MELs and OESs were listed. This means that many substances previously listed now have no legal occupational standard. THIS DOES NOT MEAN THAT THEY ARE SAFE. The advice is to apply principles of good practice as described in COSHH Essentiai and to control the substance to a level to which nearly all the working population could be exposed day after day without adverse effect. The principle of assigning a level to the now defunct OESs was based on that premise so it would be prudent to keep the previous copies of EH40 as a guide. All the previously listed MELs are included in the latest list of WELs. 

The standards in the above document are quoted in units of parts per million (ppm) and milligrams per cubic metre (mgm ). They are given for two periods Long-term exposure which is an 8-hour time weighted average 

It should be remembered that all exposure limits refer to healthy adults working at normal rates over normal shift duration. In practice it is advisable to work well below the recommended value, as low as one-quarter, to provide a good margin of safety.  

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