Can diesel particles cause asthma in healthy people? A question that both doctors and researchers has been doing for years and that now, a study led by the Vall d'Hebron Research Institute'shttp://en.vhir.org/portal1/grup-equip2.asp?s=recerca&contentid=187035 Pneumology Research Group (VHIR) belonging to the CIBER of Respiratory Diseases (CIBERES), has given response: There is evidence at both epidemiological and molecular level that pollution, not only aggravates asthma but can cause it. The study has been published in the journal https://doi.org/10.1016/j.scitotenv.2018.10.188 Science of the Total Environment.This is a review study that analyzed between 130 and 150 scientific articles on the role of diesel particles in the development of asthma. Unlike other review articles that are more focused on the aggravation of pathology, in this case the researchers focused on the cause.Diesel particles and asthma from an epidemiological point of view"Literature is quite conclusive in the studies carried out in children, in which it has been seen that the fact of living during childhood in areas with high levels of contamination by diesel particles is related to an increase in the prevalence of asthma in adulthood, "explains Dr. María Jesús Cruz, co-leader of the VHIR Pneumology Research Group. This may be due to the fact that the immune system and the lungs of children are formed in an environment with environmental pollution. In particular, the period between birth and four years is key. "In fact, the clearest evidence is that in children, asthma is mainly an allergic type," he adds.However, although it is suspected that it does exist, it is more difficult to demonstrate the relationship between prenatal exposure to diesel particles and the development of asthma. "In adults, there is also no clear evidence, probably because of the heterogeneity of the studies, since there are many other genetic factors and comorbidities that influence," notes Dr. Xavier Muñoz, principal investigator of the VHIR Pneumology Research Group and associate physician at the Vall d'Hebron Pneumology Service.Diesel particles and asthma from the molecular point of viewOnce it was found that epidemiologically, diesel particles could cause asthma, especially in children, the researchers studied whether molecular level could also be explained as the diesel particles can trigger asthma.Thus, they verified that the diesel particles increase the oxidative stress within the lung. "If small amounts are inhaled the lungs are able to activate defensive mechanisms to prevent oxidative stress, but by inhaling large amounts these defensive mechanisms are inadequate and diesel particles break the bronchial epithelium causing inflammatory processes, alterations in the immune system (activation of TH2 and TH17 lymphocytes) and asthma, "says Dr. Cruz.Diesel particles by themselves have an effect on the body, but also contribute to the fact that other allergens are more allergenic. That is, the diesel particles increase the allergy-related processes with asthma."Additionally, it has been seen that indirect changes also occur in the microbiome, not only pulmonary but also intestinal, which can cause asthma to be aggravated," concludes Dr. Muñoz.