System Concepts' health and safety consultant, Matthew Henderson, explains how occupational asthma can be easily prevented by controlling exposure to sensitising agents.

In the UK, around 5.4 million people have asthma, among whom are children sufferers and adults that develop the disease in later life.

According to the World Health Organization (WHO), asthma rates vary between 2% and 20% in industrialised nations, making it the most common industrial lung disease in the developed world.

Occupational asthma is the most common cause of adult-onset asthma. Every year, it is estimated up to 3000 people throughout the UK develop the disease, though the actual figure could be much higher:

  • It accounts for 9–15% of asthma cases in adults of working age.

  • In some industries up to 10% of employees develop occupational asthma.

The Health and Safety Executive (HSE) estimates that occupational asthma will cost the UK economy £1 billion over the next 10 years.

In terms of human cost, some workers are left severely disabled and obliged to take early retirement, while others have no option but to seek suitable alternative work. On average one third to one half of patients are out of work between three and five years from diagnosis.

How is occupational asthma different from “ordinary” asthma?

Asthma is an inflammatory disorder of the airways in which symptoms occur in response to triggers such as viruses, pet allergens and pollens. For some people the sensitisers that trigger their asthma occur only in the work environment, a condition known as occupational asthma. These can include substances in the workplace that irritate the airways of individuals with pre-existing asthma. Respiratory irritants may trigger attacks in those with occupational asthma or pre-existing asthma. Examples include chlorine, general dust and even cold air.

When an asthma attack occurs, the muscles surrounding the airways become tight and the lining of the air passages swell. This reduces the amount of air that can pass by, and can lead to wheezing sounds. Other symptoms include shortness of breath, coughing and chest tightness. Asthma attacks can last minutes to days and can become dangerous if the airflow becomes severely restricted.

According to the HSE, occupational asthma falls into two main categories: allergic occupational asthma and irritant induced occupational asthma.

Allergic occupational asthma

Allergic occupational asthma accounts for almost 90% of all cases of occupational asthma. Allergens that cause occupational asthma are called respiratory sensitisers, which, breathed in, can trigger an allergic reaction in the respiratory system leading to an asthma attack. Symptoms will often develop over a period of weeks or months from first exposure to the sensitiser.

Irritant-induced asthma

Irritant-induced asthma develops after a single, very high exposure to an irritant chemical in the workplace. The high levels of exposure required are usually the result of accidents or some major failure of controls, often in enclosed spaces. Symptoms occur within hours of exposure.

How would someone develop occupational asthma?

Occupational asthma can develop even if a person does not already have asthma. It is possible to develop occupational asthma in almost any workplace, however, the risk remains higher for workers in certain occupations.

More than 300 workplace substances have been identified as possible causes of occupational asthma and more are being identified all the time. The substances responsible for this are known as respiratory sensitisers, and many are well known.

These substances include the following.

  • Animal substances, such as proteins found in dander, hair, scales, fur, saliva and body wastes.

  • Chemicals, such as anhydrides, diisocyanates and acids used to make paints, varnishes, adhesives, laminates and soldering resin. Other examples include chemicals used to make insulation, packaging materials, foam mattresses and upholstery.

  • Enzymes used in detergents and flour conditioners.

  • Metals, particularly platinum, chromium and nickel sulphate.

  • Plant substances, including proteins found in natural rubber latex, flour, cereals, cotton, flax, hemp, rye, wheat and papain, a digestive enzyme derived from papaya.

  • Respiratory irritants, such as chlorine gas, sulphur dioxide and smoke.

There are many more substances (agents) that are known to be capable of causing occupational asthma, and these will affect a whole host of occupations. These include:

  • healthcare and dental care workers

  • laboratory animal workers

  • car repairers, spray painters

  • electricians

  • those working in welding, soldering and metalwork

  • woodworkers

  • food processing workers

  • chemical processing workers

  • textile, plastics and rubber manufacturing workers

  • cleaners

  • hairdressers.

  • those working in other jobs where they are exposed to dusts and fumes.

Workers are also at increased risk of developing occupational asthma if they:

  • have existing allergies or asthma

  • allergies or asthma runs in the family

  • smoke.

What are the signs and symptoms of occupational asthma?

Signs and symptoms of occupational asthma are basically the same as other types, and may include wheezing, coughing, difficulty breathing, and a blocked/stuffy nose. How occupational asthma affects people depends on many factors, including the person, age, type of irritant, and whether they already had asthma.

People with occupational asthma may find that their symptoms get worse as the working week progresses — on Monday it is not too bad, but by Friday it is worse (if they do not work weekends). The same may be noticed during holidays, with symptoms going away, and then coming back when they return to work. In some cases asthma symptoms may continue even after there is no exposure to the irritant, especially if there has been long-term exposure to it.

What is an employer required to do?

Employers are required by the Control of Substances Hazardous to Health (COSHH) regulations to take all practical measures to protect employees from occupational asthma.

The employer should:

  • identify any potentially harmful substances

  • ensure adequate control measures are in place

  • provide information to employees

  • provide health surveillance where appropriate.

Ways to reduce the impact of occupational asthma

The Chartered Institute of Environmental Health recommends the following measures.

  1. Prevent exposure. Eliminating or substituting the sensitising agent with another substance that is not a known sensitiser is the best control measure.

  2. Detect early or pre-symptomatic disease by monitoring levels of exposure in the workplace. All employees exposed to or at risk of being exposed to a substance that may cause occupational asthma should be offered appropriate health surveillance based on their level of risk.

Health surveillance is important. Early removal from exposure can lead to a complete recovery, so employers should have systems in place to detect symptoms at an early stage.

It is extremely important that health surveillance is combined with education and training; employees should be informed of the causes, risks and symptoms of asthma so they can report them.

Further advice for workers and employers is available from the Health and Safety Executive or the British Occupational Hygiene Society.

Keep an eye on the early warning signs...

The risk of developing occupational asthma is connected to the level of exposure to the agents; put simply, the more someone is exposed to a substance that causes occupational asthma, the greater the chance they will develop an allergy to the substance. Once someone has been sensitised and has developed occupational asthma, their symptoms are likely to subsequently be triggered by very small exposures.

When any one worker develops confirmed occupational asthma, the exposure and presence of symptoms of other workers should be investigated to identify whether any other worker is at risk or has developed relevant symptoms.

Early diagnosis and early avoidance of further exposure offer individuals the best chance of complete recovery.

Treatment for occupational asthma is basically the same as for asthma that is not work-related. However, an individual with occupational asthma may have the option of avoiding the irritant, by either changing jobs or working with his/her employer to improve working conditions. However, workers who remain in the same job and continue to be exposed to the same agent after diagnosis are unlikely to improve and may worsen; possibly resulting in permanent damage to the lungs and lifetime asthma symptoms.

Last reviewed 10 August 2015