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132 Chapter 3: Respiratory system

Table 3.18 Patterns of occupational lung disease curly, but only micrometers thick. They are least fi-
brogenic.Itisdebatablewhethertheyarecarcinogenic,
Pattern of disease Causative agents
but their use has now been banned in new buildings
Pulmonary fibrosis Mineral dusts such as coal, silicon in the United Kingdom.
and asbestos
Occupational asthma Multiple – may be animal, 2 Amphibole asbestos (including amosite/brown and
vegetable, bacterial or chemical crocidolite/blue asbestos) fibres are short and straight,
precipitants this allows them to reach and penetrate the lung
Extrinsic allergic Organic dusts causing a local parenchyma more easily. They persist in the lung for
alveolitis allergic response many years and are very fibrogenic and carcinogenic.
Acute bronchitis, Irritant gases such as sulphur
pulmonary dioxide, chlorine, ammonia,
oedema oxides of nitrogen
Bronchial carcinoma Asbestos, polycyclic hydrocarbons, Macroscopy/microscopy
radon in mines
Asbestos bodies: These are long thin asbestos fibres in
the lung parenchyma coated with haemosiderin and
Aetiology/pathophysiology protein to form brown filaments with a beaded or
Asbestos is made up of various silicates. It exists natu- drumstickpattern.Theyaretheresultofmacrophages,
rally as a fibre, and has been widely used for its insulative which surround and attempt to engulf the fibres, but
properties. It was used in sheets in buildings, sprayed on fail to clear them leading to fibroblast proliferation
pipes as lagging, in shipbuilding and for boiler insula- and fibrosis.
tion. However, it is easily inhaled and the fibres induce Pleural plaques are well-circumscribed elevated
afibrogenic reaction in the lung. The risk of developing plaques of white hyaline fibrous tissue arranged sym-
pathology from asbestos is dependent on the duration metrically on the parietal pleura over the ribs and di-
and intensity of exposure, and the type of asbestos (see aphragm. Calcification is common.
Table 3.19). Asbestosis: The lower lobes are usually affected ini-
1 Serpentine asbestos (includes white asbestos) is the tially, then progressively the mid-upper lobes. There
commonest form. Fibres are long (up to 2 cm) and are fibrotic changes in the interstitium, obliteration of

Table 3.19 Patterns of asbestos-related disease
Disease Exposure Symptoms Chest X-ray Outcome
Asbestos bodies Light None Normal Normal lung function
Pleural Plaques Light/moderate Usually none Pleural thickening, and Mild restrictive lung
calcification disease at most
Asbestosis Heavy (5–10 years Progressive Fine linear shadows initially Lung fibrosis leads to
from exposure) dyspnoea seen best on CT. Late stage severe restrictive
honeycomb lung defect & reduced gas
exchange. Poor
prognosis
Asbestos-related
malignancy:
Mesothelioma Any degree. Peaks Dyspnoea. Pleuritic Pleural effusion and knobbly Median survival 2 years
30–35 years from or dull chest wall pleural thickenings with after diagnosis
exposure. Not pain reduction in volume in the
related to affected area, possibly with
smoking other signs of asbestos
exposure
Asbestos-related Risk related to level As for bronchial Evidence of asbestos exposure As for bronchial
carcinoma of the of exposure and carcinoma may be seen together with carcinoma
bronchus smoking features of the carcinoma