Types of respiratory disease and causative agents

Table 1: Classification of occupational and exposure associated lung disease

Upper respiratory tract disorders

Disease category

Representative causative agent (Allergen)

Symptoms and further info

Nonspecific irritation

Irritant gases (eg ammonia; chlorine), fumes, dust

Symptoms include cough, nasal irritation and congestion

Rhinitis (allergic and non-allergic)

Pollens, animals, house dust mites, various chemicals

  • Symptoms include sneezing, rhinorrhoea, nasal obstruction and itching of the nose, eyes and palate
  • If due to an allergic mechanism, sneezing occurs immediately, then nasal discharge followed by nasal obstruction over a few hours

Upper airway dysfunction (vocal cord dysfunction, work associated irritable larynx syndrome)

Chemicals with a high water solubility, alkaline and acids gases, dust and mists

  • Dysfunctional behaviour of the larynx is an important and underappreciated cause of recurrent respiratory symptoms
  • It may imitate symptoms suggestive of asthma – or it may also co-exist with asthma
  • Symptoms are due to inappropriate vocal cord movement causing partial airway obstruction, especially when breathing in
  • Typical symptoms are recurrent episodes of difficulty breathing, chest tightness, throat tightness and cough
  • Frequently, episodes have a rapid onset
Airway disorders

Disease category

Representative causative agent (Allergen)

Symptoms and further info

Occupational asthma - Sensitiser induced asthma / Reactive airways dysfunction syndrome

Currently there are over 400 known respiratory sensitising agents (substances that cause an allergic asthmatic response)

Examples include:

  • Some volatile organic compounds such as formaldehyde, aldehydes, rosin fume
  • Isocyanates (chemicals mainly used to make polyurethane products, such as rigid and flexible foams, paint coatings, adhesives and sealants)
  • wood dust (eg western red cedar, redwood, oak etc)
  • flour
  • animals
  • Occupational asthma is the development of new onset asthma (or the recurrence of pre-existing asthma) due to an exposure specific to a workplace
  • Occupational asthma is the most common occupational lung disease in developed countries. Over 90% is sensitiser induced
  • There is a clear association between occupational allergic rhinitis and asthma
  • Asthma affects the lung’s bronchioles (small airways), causing tightening of muscles around the airways (bronchospasm). During the asthma attack, the airway’s lining also becomes swollen / inflamed producing lots of thicker mucus. Symptoms often vary from person to person, but they are most commonly breathlessness, wheezing, chest tightness and continuing cough. If the asthma symptoms are worse during the working week (and improve on weekends or when away from work), then the worker may be experiencing occupational asthma
  • Occupational asthma is generally characterised by a period of latency between first exposure to the substance and development of asthma symptoms, which may vary from a few weeks to several years

Occupational asthma - Irritant induced asthma

Examples include:

  • Irritant dusts and gases
  • smoke
  • Irritant induced asthma is a common condition that is influenced by environmental exposures – including at the workplace
  • Irritant induced asthma affects and symptoms are the same as for sensitiser induced asthma
  • There is no latency period between exposure and development of symptoms – can happen within minutes to hours of the exposure

Reactive airways dysfunction syndrome (RADS)

Irritant gases, corrosive mists or solvent vapours

  • RADS is the clearest example of irritant induced occupational asthma
  • Recurrent lower levels of irritant exposure may also lead to the development of irritant induced occupational asthma
  • Often occurs as part of an industrial accident or spillage
  • Symptoms include temporary breathlessness and a wheeze similar to asthma that usually occur within 24 hours of a single exposure
  • Usually, symptoms will gradually improve as the airways heal, but occasionally, workers can be left with permanent symptoms

Work exacerbated asthma

Irritants (eg cotton dust), fumes, exertion, cold air, emotion

  • Refers to worsening of pre-existing asthma due to workplace factors (eg inhalation of airborne substances, physical exertion or exposure to cold air)
  • Occurs in an estimated 22% of adults with asthma

Chronic bronchitis / chronic obstructive pulmonary disease (COPD)

Irritants, mineral dust, coal, welding fumes, organic dusts, grain and flour dusts

  • Often, there may be a period of latency (inactivity) between the actual exposure and the development of the disease, which can vary from years to decades
  • Chronic respiratory diseases (eg COPD, pulmonary fibrosis and bronchiectasis) are likely to damage the respiratory tract defence mechanisms, causing the worker to be more susceptible to the effects of adverse exposures

Byssinosis

Inhalation of cotton dust, or dusts from other vegetable fibres (such as flax, hemp and sisal)

  • This disease is a form of reactive airways disease characterised by bronchoconstriction
  • Byssinosis manifests with asthmatic like symptoms, tightness in the chest along with wheezing and coughing

Bronchiolitis

Noxious chemicals such as oxides of nitrogen, Diacetyl (‘popcorn worker’s lung’)

  • This disease is an inflammation of the lung’s bronchioles
  • Diacetyl is a chemical used to produce artificial butter flavouring and is found in many products. Inhalation may cause bronchiolitis obliterans (extensive scarring that blocks the airways)
  • First symptoms resemble a common cold (runny nose, mild cough, nasal stuffiness) that may last 1-2 days
  • Then followed by increased breathing problems, eg increased breathing rate; poor appetite; wheezing; and fever)

Acute inhalation injuries

Disease category

Representative causative agent (Allergen)

Symptoms and further info

Toxic pneumonitis

Inhalation of metal fumes, or toxic gases and vapours

  • Toxic pneumonitis is acute inflammation of the lungs
  • The two types of pulmonary agents:
    • Central: are water soluble and injure the upper airways (ammonia gas, hydrogen chloride)
    • Peripheral: are less water soluble and penetrate into the deeper lung areas (ozone, phosgene, oxides of nitrogen). This can give rise to pulmonary oedema (excess fluid in the lungs) which can be delayed and fatal

Metal fume fever

Metal oxides, oxides (zinc, magnesium, silver, gold, beryllium, cadmium, cobalt, copper, etc

  • Signs and symptoms are nonspecific but are generally flu-like and include fever, chills, nausea, headache, fatigue, muscle aches, joint pains, lack of appetite, shortness of breath, pneumonia, chest pain, and cough
  • A sweet or metallic taste in the mouth may also be reported along with a dry or irritated throat which may lead to hoarseness
  • Symptoms of a more severe metal toxicity may include a burning sensation in the body, shock, no urine output, collapse, convulsions, shortness of breath, yellow eyes or yellow skin, rash, vomiting and watery or bloody diarrhea, all of which require prompt medical attention

Smoke inhalation

Combustible products (carbon monoxide, oxides of nitrogen, formaldehyde, hydrogen cyanide, etc)

Smoke particulate containing absorbed irritants and carcinogenic polycyclic aromatic hydrocarbons (PAHs)

  • Severe smoke inhalation can prove fatal as the gases of combustion can lead to chemical asphyxiation (particularly cyanide and carbon monoxide)
  • Also, the particulate matter breathed in can mechanically obstruct the lung’s small airways, leading to asphyxiation
  • Severe irritation of the lung can lead to pulmonary oedema
Malignancies

Disease category

Representative causative agent (Allergen)

Symptoms and further info

Sino-Nasal Cancer

Wood dust

Often, there may be a period of latency (inactivity) between the actual exposure and the development of disease, which might take decades. However, the inhalation of radioactive materials can induce sino-nasal and lung cancer reasonably rapidly.

Lung Cancer

Asbestos, radon, silica dust

Mesothelioma

Asbestos

Further respiratory injuries and illness

Disease category

Representative causative agent (Allergen)

Symptoms and further info

Hypersensitivity pnueumonitis

Bacteria, fungi, animal and plant proteins

  • This is a complex syndrome caused by an immunological reaction to an inhaled agent. Can be acute of chronic
  • Acute symptoms may mimic an infective process, and include fevers, chills, malaise, cough and shortness of breath. Symptoms generally subside within hours or a few days of removal from the exposure
  • Chronic symptoms may include features of pulmonary fibrosis such as difficult or uncomfortable breathing
  • Some industries and exposure associated with hypersensitivity pneumonitis include:
    • farming (‘farmer’s lung’, ‘mushroom worker’s lung’)
    • bird or poultry handling (‘bird breeder/fancier’s lung’)
    • water-related contamination (‘humidifier lung’)
    • grain processing (wheat weevil disease)
    • plastics industry workers
    • textile workers

Infectious disorders

Bacteria (eg legionella), pneumonia, tuberculosis, viruses

More information can be obtained from NSW Health and Dept of Primary industries.

Pneumoconiosis

Asbestos, silica, coal

Often, there may be a period of latency (inactivity) between the actual exposure and the development of disease, which might take decades. There are very rare cases where pneumoconiosis can be relatively rapid and take a year or less.

Non-specific building related illness (‘Sick building syndrome’)

  • Some volatile organic compounds from new paint, office furniture and cleaning products
  • Formaldehyde, aldehydes
  • Mould spores, bacteria
  • Fungal endotoxin
  • Inadequate air circulation

The main identifying observation is an increased incidence of workers reporting symptoms such as headache, eye, nose, throat irritation, fatigue, dizziness and nausea.

Adapted from RACGP website article, “Respiratory problems”; Occupational and environmental exposures; Volume 41, No.11, November 2012 Pages 856-860 (initially adapted from Fishman AP, editor. Fishman’s Pulmonary Diseases and Disorders. 4th edn. New York: McGraw Hill, 2008)

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