Air pollution and acute exacerbations of idiopathic pulmonary fibrosis: back to miasma?
Authors: Mark G. Jones, Luca Richeldi
Journal: European Respiratory Journal (2014)

Air pollution might be the first modifiable risk factor for acute exacerbations of idiopathic pulmonary fibrosis http://ow.ly/rSpWbCenturies ago miasma (from mı ´asma, the ancient Greek word for pollution) was considered to be a poisonous vapour filled with particles from decomposed matter.The miasmatic theory held that diseases such as cholera or the Black Death were caused by a noxious form of ''bad air'', also known as ''night air'', emanating from rotting organic matter [1].In those days, breathing was considered to be a dangerous, although unavoidable, exercise.The theory was accepted from ancient times in Europe, India and China, and was eventually displaced only in the 19th century by the discovery of germs.In 1876, Robert Koch proved that a bacterium had caused anthrax and this discovery brought a definitive end to miasmatic theory.Contagionism prevailed over miasmatism and, thereafter, air was not considered a cause of human disease.Instead, the concept of ''fresh air'' as a beneficial factor for human health became widely accepted, until recently.After World War II, air pollution became an increasingly recognised threat, initially as a consequence of radioactive fallout from atomic warfare and testing.Subsequently, a non-nuclear event, the Great Smog of 1952 in London, which killed at least 4000 people [2], prompted some of the first major modern environmental legislation, the Clean Air Act of 1956 [3].Following this, air pollution began to draw major public attention worldwide.Recently, the European ''Year of Air'' initiative has again publicised that air pollution exposure is an important threat to public health.With formal classification of outdoor air pollution as a carcinogen and evidence of associations ranging from low birth weight to acute exacerbations of chronic lung diseases such as asthma and chronic obstructive pulmonary disease (COPD), it represents an obvious candidate as a risk factor or causative agent in the pathogenesis and/or the progression of every chronic respiratory disorder [4][5][6][7][8][9][10][11].An acute worsening of respiratory symptoms is a well-recognised phenomenon in various chronic respiratory diseases including asthma, COPD and idiopathic pulmonary fibrosis (IPF).Historically, bacteria, viruses and environmental pollutants have been proposed as aetiological factors of such acute events or exacerbations; however, there is increasing recognition that their pathogenesis is complex and that triggering factors may be very heterogeneous [12][13][14].In this context, one of the most enigmatic but clinically important events is an acute exacerbation of IPF.Epidemiological data from patients with IPF identify a 1-year incidence of 14.2% and an acute exacerbation is a significant predictor of poor survival, with a 50% in-hospital mortality rate [14].In 2007, a consensus definition with strict clinical and radiographic criteria was proposed: an unexplained new or worsening shortness of breath within the past 30 days, new lung infiltrates demonstrated by chest high-resolution computed tomography, and exclusion