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Employers’ Guide to Occupational Asthma

Occupational asthma is a serious condition which can cause workers to be severely disabled; unable to continue in the normal jobs and sometimes having to be retired on the grounds of ill health. Around one third of employees with occupational asthma are unemployed up to six years after diagnosis; and yet, it is a preventable disease.

Important facts

  • Occupational asthma is the most frequently reported work-related lung disease in the UK. 
  • Occupational asthma is caused by exposure to a substance in the air at work.
  • Reducing airborne exposure levels reduces the incidence of occupational asthma.
  • The best opportunity to reverse or improve occupational asthma occurs with early diagnosis, before lung function is too impaired and with early removal from further exposure to the causative agent.

Are any job applicants at increased risk?

  • Smokers and people who have a history of asthma or hay fever may be more likely to develop asthma to some substances.
  • Such personal risk factors are poor predictors of disease and people without such history can develop occupational asthma.
  • The only justifiable reason to review a job offer would be if:
    • Someone has pre-existing occupational asthma caused by previous exposure to a substance that they would encounter in a new job;
    • A workplace risk assessment has determined they are at risk of being exposed; and
    • Following expert advice from a specialist occupational physician.

How is occupational asthma prevented?

  • Be aware of your responsibilities under health and safety laws and regulations.
  • Appoint competent persons to support you for the purposes of health and safety.
  • Assess exposure to substances which can cause occupational asthma.
  • Implement control programmes using the ‘hierarchy of controls’ – elimination > substitution > enclosure > ventilation > personal protective equipment.

While RPE reduces the numbers of new cases of of occupational asthma, it does not completely prevent the disease; so, it should never be the only or primary means of controlling exposure. Its effectiveness depends on proper supervised use. Even brief removal of RPE can lead to the development of occupational asthma.  Employers should ensure that when RPE is worn, the appropriate type is used and maintained, fit testing is performed and workers know how to wear, remove and replace RPE.

Health Surveillance

The most important measure is the primary prevention of occupational asthma by eliminating or reducing exposure to its causes at work. Secondary prevention involves detecting signs of asthma in employees at an early stage, ideally before they are aware of any symptoms. This is achieved by regular health surveillance and is important because:

  • Outcome is improved in workers who are included in health surveillance programmes
  • It provides additional information to inform employers if their control measures are effective

The content and frequency of health surveillance should be determined by a competent person and be informed by a suitable and sufficient risk assessment. Further information is available in HSE General Guidance G402.

If you do not have an occupational health service you should appoint an occupational physician to develop and review the health surveillance programme. They will advise on the frequency and content of the programme, who can operate the programme, how to manage any people at increased risk, communication of results to employers and the referral arrangements when there are borderline or abnormal test results.

The process for communicating anonymised group data to employers should be agreed after consultation between employers, employees and their representatives. It should be noted that occupational health professionals will only provide health surveillance information to employers in general terms stating whether an employee is or is not fit for work and with the consent of the employee.

For more information about the value of occupational health services see: Occupational health: A guide for line managers and HR professionals.

How to manage an employee who is suspected of having occupational asthma

Confirming a diagnosis of occupational asthma is not a simple matter and requires the knowledge and skills of a doctor who has expertise in occupational asthma.  Where an employee is suspected of having or being in the process of developing occupational asthma they should be referred to such a physician at the earliest opportunity.  This is because the best chances of avoiding irreversible disease is within one year of first developing symptoms.  Left unmanaged occupational asthma will become established.

How to manage an employee with confirmed occupational asthma

The outlook is best in those employees who have shorter duration of symptoms and better lung function both at the time of diagnosis and prior to beginning to avoid exposure.  This means that employers should ensure that employees diagnosed as having occupational asthma avoid further exposure to its cause in the workplace completely and early in the course of the disease. This offers the best chance of recovery.

Where complete avoidance of exposure is not possible, employees should be redeployed to low or occasional exposure areas; however, while redeployment to a low exposure area may improve symptoms in some employees it is not always effective.  Redeployment should be discussed and agreed with the employee and the occupational physician.  Employers should note that when asthma affects an employee’s normal daily activities they will meet the criteria to be regarded as disabled under The Equality Act 2010, which requires employers to make reasonable adjustments.

Remember, if health surveillance identifies one person as having occupational asthma or impaired lung function that their colleagues may suffer similar exposures and be at risk. The identification of one case should lead to a multi-cause investigation or root cause analysis to discover the source of exposure and identify the additional control measures required.

What to do if an employee is off sick with occupational asthma

Whatever the cause of an employee’s sickness absence there is good evidence in support of early assessment and early rehabilitation, including work and/or workplace adjustments. As an employer your support in providing access to modified work is particularly critical. It is also good to establish early and good communication with the employee and the occupational health professional and maintain that communication while the employee is absent and upon their return to work.


The most important action to prevent cases of occupational asthma is to reduce exposure at source.  Thereafter surveillance should be performed to identify early signs or symptoms of asthma, rhinitis and conjunctivitis.  Employees suspected to have occupational asthma should be referred for further tests immediately that suspicions arise.  The symptoms and disability caused by occupational asthma may persist for many years after avoiding further exposure to the causative substance.  The likelihood of symptoms improving or disappearing is greatest in employees who have no further exposure to the causative agent.  Therefore, early diagnosis and early avoidance of ongoing exposure, either by substitution of the hazard or by redeployment of the employee offer the best chance of improvement or recovery.

The Occupational Safety and Health Consultants Register (OSHCR) is a register of consultants who can offer general advice to UK businesses to help them manage health and safety risks.

You can search for a local Occupational Health Professional on the SOM website.