Occupational Asthmagens

Formerly Asthmagens topic inspection pack


This guidance replaces the Topic Inspection Pack on Asthmagens.  It provides information to support HSE and LA inspectors with enforcement activities in relation to the control of exposure to occupational asthmagens (agents causing occupational asthma).  It also enables inspectors to raise awareness of the standards duty-holders need to meet to comply with the law.


Asthma is a serious and common health problem in the general population and for the purposes of EMM it is considered a serious health risk.  Occupational asthma (OA) is causally related to exposure to a substance at work. It can be divided into allergic occupational asthma and irritant induced occupational asthma.  This inspection pack is concerned with the former and this is what is meant when OA is referred to subsequently in this document.  It is well established that exposure, to a number of agents (asthmagens), can lead to OA or make it worse.  Asthma symptoms include severe shortness of breath wheezing, coughing and chest tightness.  Some sufferers are unable to work again.


Inspectors should be familiar with the relevant legislative framework and when checking compliance need to ensure that the duty-holder has a good understanding of COSHH and the relevant guidance for the control of asthmagens.

COSHH reg. (6) places duties on the duty-holder to carry out a risk assessment. A suitable and sufficient risk assessment will identify the asthmagens and will help the duty-holder to make valid decisions about the measures needed to prevent or adequately control the exposure.

Exposure to known asthmagens must either be prevented or adequately controlled. COSHH reg. 7(7) states that control can only be deemed adequate when:

  1. The principles of good practice have been applied:
  2. Any WEL is not exceeded; and
  3. Exposure is reduced to the lowest level reasonable practicable

Inspectors should ensure that duty-holders have an effective management system in place that can identify all the asthmagens, assess the risks, and if exposure cannot be prevented then, adequately controlled.  COSHH regulation 9 requires that engineering controls are maintained and, in addition, systems of work and supervision are reviewed at suitable intervals and revised where necessary. Inspectors should ensure that duty-holders provide suitable and sufficient information, instruction, and training and suitable health surveillance.  Inspectors should ask to see copies of health surveillance records, COSHH risk assessments and records for the examination and testing of LEV.

Inspectors should determine if there is a breach of law and take action in accordance with the Enforcement Management Model (EMM: Appendix 2). OG273/19 provides additional guidance.


Occupational asthma is an allergic reaction that can occur in some people only after previous exposure to certain substances.  For example the most common substances associated with OA are flour dust, isocyanates and wood dust though others are listed in Appendix 1.  These substances are called respiratory sensitisers, allergens, or asthmagens. They can cause a permanent immunological/allergy mediated change causing sensitisation. Not everyone who becomes sensitised will develop asthma. But once the airways in the lungs become hyper-reactive, because of sensitisation, further exposure to the substance, even at very low levels, may trigger an attack. There is very little information on how much exposure is required to induce this sensitised state so control of exposure is very important.  Those with occupational asthma can still have symptoms when not at work as the hyper-reactive airways, react to other triggers for example cold air, irritant vapours or dust.  Further information on OA can be found on the HSE website.



While HSE have no proactive inspections in relation to asthmagens, occupational asthma should be treated as a 'targeted matter of evident concern' during inspections where appropriate.

Recording and reporting

No special reporting arrangements apply.


Long Latency Health Risks Division, CCID


Appendix 1

The following list shows asthmagens most likely to be encountered. Please note this list is not exhaustive.

Appendix 2: Enforcement Management Model (EMM)

Enforcement is likely to be under COSHH regulations 2002  (6th Edition). Interpretation of EMM in relation to asthmagens is difficult because of the wide range of substances and processes where they are used. When considering enforcement action inspectors should also refer to OC273/19.

Information on the EMM is available online.

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Updated 2024-02-09