Senior Research Fellow, Ken Donaldson looks at the causes of Environmental anthracosis or ‘lung black spots’.
The image is of the cut surface of a specimen of normal lung that was preserved in the early 19th century. At that time coal, candles and oil were burnt in homes for heat, light and cooking and as a consequence, indoor air was habitually loaded with tiny soot particles. Outdoor air was also heavily polluted with soot particles from domestic chimneys and from industrial sources. These particles of soot were breathed into the lungs continually, on a daily basis and a fraction of them deposited, especially in the alveolar region. In the picture the spongy appearance of the alveolar region of the lungs is clearly seen, but most striking are the black spots that are scattered throughout. These represent the points where the bronchial tubes that warm and moisten the incoming air, finally end in the alveolar region. Here the flow of air slows to zero and soot particles, present in every breath, fall out, causing this region to become blackened. The likely adverse health significance of the accumulation of particles in the lungs was much debated in the early 20th century but the severe smogs that beset UK cities in the nineteen forties and fifties posed a unique opportunity to study the health impact air pollution. These studies revealed that, within a few hours of an increase in airborne particles and also gases like sulphur dioxide, there were dramatic increases in mortality from lung and cardiovascular causes and hospital admissions of patients with asthma and bronchitis. Subsequently research worldwide has shed light on the mechanisms leading to such effects after increased exposure to air pollution. With the passing of the Clean Air Acts in the 1950s and the electrification of homes in the early to mid-20th century, both outdoor air and indoor air became much cleaner. Subsequently this appearance of ‘black spots’ is not seen now, except in older people who lived through the period when air pollution was bad. However, the problem of air pollution has not gone away and pollution, mostly from motor vehicles, continues to exert a huge toll in terms of ill-health, on a global scale.