Experts from Vall d'Hebron have published an editorial in the journal of the Spanish Society of Pneumology and Thoracic Surgery (SEPAR), Archives of Bronchopneumology, on the relationship between asthma and environmental pollution.The editorial is signed by Dr. Maria Jesús Cruz, head of the http://en.vhir.org/portal1/grup-equip2.asp?t=pneumologia&s=recerca&contentid=187035 VHIR Pneumology Group, and by the doctors Christian Romero-Mesones and Xavier Muñoz, from the Pneumology Service of the Vall d'Hebron Hospital and points out that all health professionals agree that the high levels of diesel particles, ozone, sulphur dioxide and nitrous oxide can precipitate symptoms in asthmatic patients that can cause medical consultations, hospitalisation or emergency admissions.Asthma is a disease that has a great impact worldwide. In recent decades, it has experienced an increase in its prevalence in industrialised countries, ranging from 8% to 10% of the population. This growth is due to an improvement in the diagnostic techniques and criteria, but also to the influence of environmental pollution since it can aggravate the disease in patients with asthma and even be the cause of the disease.On the one hand, exposure to high concentrations of contaminants produces changes in pulmonary function in people with asthma by altering and increasing the inflammatory and irritative response. On the other hand, it has been shown that pollution can act in three ways that increase the risk for people who do not suffer from this disease to produce asthmatic responses by causing genetic, epigenetic changes or by altering certain immunological mechanisms.The consequences of the increase in asthma patients result in a high socioeconomic cost in terms of absences from work, school, health resources (consultations, hospitalisations and emergencies) and death.