Inhalation disorders

Inhalation disorders are dysfunctions associated with the breathing in of a substance which can be in the form of a dust, fume, mist, gas or vapour.


The air in many workplaces contains hazardous substances in the form of dusts, fumes, mists, gases and vapours. These substances can be chemical or biological agents, for example, animal allergens, fungal spores and bacteria. When workers inhale them, they can harm the lungs and other parts of the airways. In some cases, hazardous agents move through the lungs to other parts of the body, harming other organs.

The respiratory system is divided into three areas:

  • the upper airways or respiratory tract, which includes the mouth, nose, sinuses, pharynx and larynx
  • the middle airways, including the trachea and bronchi
  • the lower airways, including the bronchioles and alveoli.

Many people have a genetic tendency towards allergic disease. After they’ve been exposed to chemical or biological agents, they’re more likely to develop conditions such as rhinitis and asthma. Many of the diseases described in this section of the website can occur without occupational exposure.

Types of inhalation problems: definitions and symptoms

  • Irritation
  • Asthma
  • Rhinitis
  • Chronic obstructive pulmonary disease (COPD)
  • Byssinosis
  • Pneumoconiosis
  • Extrinsic allergic alveolitis
  • Inhalation fever
  • Cancer (including mesothelioma)
  • Infections
  • Asphyxiation

Irritation of the airways can be produced by a number of dusts, gases, vapours and fumes. These gases can also irritate the eyes. The part of the respiratory tract affected by a gas or fume is determined by its solubility. Highly soluble gases, such as ammonia, have immediate effects on the upper respiratory tract (and eyes). Usually, if someone is exposed to an irritant they’ll move away from the source, limiting any damage. Very high exposure or continual exposure to a dangerous substance can lead to the smaller airways being affected, leading to inflammation and oedema in the bronchiolar and alveolar walls (pulmonary oedema), which can be fatal if not treated. Other soluble gases include chlorine and sulphur dioxide. Relatively insoluble gases, such as phosgene, might have no immediate effect, but can cause pulmonary oedema some hours after exposure. Nitric acid, fluorine and ozone can also cause a delayed reaction.

Some irritants can also cause permanent lung damage, especially if exposure is very high or occurs frequently. Others can predispose people to conditions such as chronic obstructive pulmonary disease (COPD) or pneumonia.

Asthma is the most commonly reported occupational respiratory disease in Britain. Its a chronic condition characterised by periodic inflammation of the bronchi and tightening of the muscles surrounding them. It occurs in response to one or more triggers. Typical symptoms include wheezing, coughing, tightness in the chest and shortness of breath.

Asthma caused by work can be divided into two categories: occupational asthma and asthma that is aggravated by work.Occupational asthma can be caused by a wide range of agents, known as asthmagens. These include chemicals such as isocyanates and acid anhydrides, as well as biological material such as flour dust and some proteins and laboratory animal allergens such as the skin, urine, fur or saliva of rats and mice.

Typically, the condition of employees who suffer from occupational asthma worsens during the working week, and improves at the weekend or while away from work.

Asthma which is aggravated by work is pre-existing asthma that's exacerbated by something in the workplace. It is sometimes referred to as work-related asthma.

Hazardous substances that irritate the airways can cause asthma attacks in people with occupational asthma, as well as those with work-related asthma.

To find out more about the causes of asthma, check out the HSE’s list of workers commonly affected and the substances which cause occupational asthma and asthmagen compendium.

Rhinitis is inflammation of the cells that line the nose. Symptoms include congestion, itching, sneezing and nasal discharge. Asthma and rhinitis often coexist. Associated with asthma and rhinitis is conjunctivitis, which is characterised by itchy, watery and inflamed eyes. It’s important that employers and employees take rhinitis seriously, as it can develop into occupational asthma.

Chronic obstructive pulmonary disease (COPD) is a lung disease in which the airways become narrower over time, making it difficult to breathe. Other symptoms include coughing, wheezing and an increase in the production of phlegm. Chronic bronchitis and emphysema are types of COPD.

The main cause of COPD is smoking, although exposure to different types of hazardous substance can cause or contribute to its development.

Byssinosis is caused by breathing in unprocessed cotton dust. It’s now very rare in the UK and other developed countries. Symptoms include shortness of breath, coughing and obstruction of the airways. Symptoms typically occur on the first day of the working week and subside on later days. If an employee is exposed to cotton dust for a long time, their symptoms can become chronic.

Pneumoconiosis covers a group of lung diseases that are caused by breathing in insoluble dusts, mostly mineral dusts, that the lungs can’t get rid of. The most common diseases in this group are silicosis, coal miners’ pneumoconiosis and asbestosis.

  • Silicosis is caused by inhaling crystalline silica (quartz) dust. It commonly occurs in people who work in quarrying, mining and sand blasting, as well as those who work in the pottery industry and iron and steel foundries. It’s a ‘progressive’ disease – it gets worse even after exposure has stopped – and is marked by an increasing difficulty in breathing, at times leading to death.
  • Coal miners’ pneumoconiosis is caused by inhaling coal dust. It is characterised by a slight cough and the production of black sputum. In some people, it leads to progressive massive fibrosis, disability and death. With the decline of the mining industry in the UK, this disease has become less prevalent.
  • Asbestosis is characterised by scarring or fibrosis of the lungs following long-term asbestos exposure. Symptoms include shortness of breath, a non-productive cough and ‘finger clubbing’ – a deformity of the fingers and fingernails. It’s typically progressive, invariably resulting in death. It’s also associated with mesothelioma and cancer of the bronchus (see below).

Extrinsic allergic alveolitis is caused by breathing in certain organic materials, commonly fungal spores. Alveolitis is the inflammation of the alveoli by an allergen. Symptoms usually start a few hours after exposure, with flu-like symptoms: fever, fatigue and shivering. As the disease progresses, the sufferer experiences breathlessness and develops a cough. Continued exposure can lead to chronic symptoms and fibrosis of the lungs. ‘Farmer’s lung’ is a type of extrinsic allergic alveolitis and is caused by inhaling dust or spores from mouldy hay, grain or straw.

Inhalation fever includes polymer fume fever and metal fume fever. Polymer fume fever is caused by breathing in fume that’s released when polytetrafluoroethylene is heated to a high temperature. The symptoms resemble flu and include fever, cough, and pains or tightness in the chest.

Metal fume fever is caused by breathing in fume that contains some types of metal oxides, for example, zinc oxide and magnesium oxide, or by breathing in fume that’s released when heating or melting metals. The sufferer experiences flu-like symptoms, including fever, cough, and pains or tightness in the chest. It’s typically found in welders and foundry workers.

Cancer can occur anywhere in the respiratory tract, from the nose to the lungs. Although, the biggest cause of lung and other respiratory cancers is smoking, hazardous substances found in some workplaces can also cause cancer, for example, crystalline silica, diesel exhaust particles and radon gas.

Exposure to asbestos can cause lung cancer or mesothelioma – cancer of the lining of the lung or bowel. Relatively low level or short term exposure to asbestos can cause both types of cancer. People typically exposed to asbestos, and therefore at higher risk, are plumbers, carpenters and other construction and building maintenance workers. There’s usually a long delay between first exposure and the onset of symptoms (up to 50 years). If workers are exposed to asbestos and they also smoke, they have a much higher risk of developing lung cancer than those who are exposed to asbestos only, or who only smoke. For information, visit the HSE's guide on asbestos-related diseases.

People who are exposed to polycyclic aromatic hydrocarbons, such as coke workers, face a higher risk of lung cancer. Other lung carcinogens include arsenic, cadmium, chromium and nickel.

People who work with wood or leather and who are exposed to dusty conditions are at an increased risk of cancer of the nasal sinuses.

You can get information on the impact of cancers of the lung, mesothelioma and the nose/sinuses in the HSE’s Burden of occupational cancer in Great Britain.

Infections caused by agents in the workplace account for a very small proportion of more serious work-related inhalation problems. In 2006, 51 cases of occupational respiratory infectious diseases were reported to THOR.

Occupationally related infections include anthrax, psittacosis, Legionnaires’ disease and avian influenza (bird flu). You can find out more in the HSE’s report on Infections at work: controlling the risks.

Asphyxiation is a hazard for people who work in confined spaces, such as welders. When oxygen is displaced by a gas or vapour, it can be difficult and even impossible for people to breathe. Asphyxiants can be divided into simple and chemical asphyxiants. Simple asphyxiants are inert gases or vapours such as nitrogen, carbon dioxide, hydrogen and methane, which displace oxygen from the air when they’re in high concentrations. Chemical asphyxiants include carbon monoxide, which combines with haemoglobin to prevent the delivery of oxygen to the cells, and hydrogen cyanide and hydrogen sulphide, which disrupt respiration at a cellular level.


Approximately 12,000 people die each year due to occupational respiratory disease and about two-thirds of these due to asbestos-related diseases or COPD.

According to the Labour Force Survey, an estimated 33,000 workers who had worked in the year 2014/15 suffered breathing or lung problems which they believed were caused or made worse by their work. This estimate includes respiratory diseases other than occupational asthma. The survey also concludes that 664,000 working days were lost due to breathing or lung problems in the same year, resulting in an average of 12.5 working days lost per case.

The HSE-financed THOR Scheme estimates that there were 1,550 new cases of work-related respiratory disease in 2014. However, the THOR scheme is subject to under reporting and other evidence suggests that the true incidence rate may be much higher.

The HSE has web pages on the latest available statistics for occupational asthma, COPD, pneumoconiosis and silicosis.

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