Occupational and environmental lung disease: mainly of the airways

Irritant effects of gases

Examples: Sulphur dioxide, Nitrogen dioxide, Ozone, Ammonia and Chlorine

These gases produce their harmful effect by irritating eyes, airways and even the respiratory units of the lungs. Many of them may be detected by their smell and irritant effect, but if evasive action is not taken in time, and if exposure is high enough they can produce severe damage throughout the lungs.

Occurrence: Exposure to ammonia and chlorine occurs as a result of industrial accidents. High levels of nitrogen dioxide can be encountered in agriculture (silo filling), during arc welding, as a result of shot firing in the mines and in the chemical industry. It can achieve high levels in the vicinity of internal combustion exhausts. Ozone is usually a secondary pollutant. Sulphur dioxide results from the combustion of sulphur containing substances.

Symptoms: Sulphur dioxide, chlorine, and Ammonia are highly irritant and cause pain in the eyes, mouth and chest. In high concentrations they can produce inflammation of the lining of the lungs and this causes breathlessness and may be fatal. (See chronic effects below).

Nitrogen dioxide has less effect on the eyes, nose and mouth but can cause severe inflammation of the lungs. It is important to realise that although symptoms at first may be mild, serious breathing problems may follow later if the exposure is high enough.

Asthma

Asthma is a condition characterised by inflammation of the lining of the airways and intermittent spasm of the underlying smooth muscle. Comparatively more is known about the cause of asthma caused by work (See: Occupational asthma on the Agius website) than about other forms of asthma. It is often but not always the result of allergy to an inhaled dust or vapour in the workplace. Its symptoms include cough, wheeze, chest tightness and shortness of breath which improve on days off work or longer holidays but the association with work may be difficult to establish in some cases. In the UK there are probably more than 2000 new cases every year and there have been a few fatalities from agents such as isocyanates or reactive dyes.

Important causative agents include:

  • Isocyanates (e.g. in twin-pack spray paints)
  • Hardening/curing agents e.g. anhydrides
  • Rosin (colophony) fumes from soldering flux
  • Dusts from various cereals (including flour)
  • Animals such as mammals (rats, mice) but also arthropods (such as locusts)
  • Wood dusts - various e.g. Canadian red cedar
  • Aldehydes e.g. formaldehyde or glutaraldehyde
  • Cyanoacrylates (as in "superglue")
  • Antibiotics

In the home, exposure to allergens from house dust mites can be a contributing factor in the development of asthma as well as a cause of its symptoms. Other allergens from pollen, moulds, animal dander etc can cause asthmatic symptoms. Outside the home in the general environment increase in asthmatic symptoms has been attributed to exposure to soya bean dust and to oil seed rape. The contribution to the causation of asthma by irritant gases such as sulphur dioxide, nitrogen dioxide and ozone is still unclear, although it is known that these substances can certainly aggravate symptoms in those who are already asthmatic.

Chronic bronchitis

The best documented and probably most important environmental cause of chronic bronchitis is tobacco smoke. Other substances could cause bronchitis but this is not yet clear. Certainly many substances (such as sulphur dioxide) can aggravate the symptoms of bronchitis and cause premature deaths from this condition, as occurred in the smogs that affected many big cities in the early 1950's.