Relationship of environmental exposure to nitrogen oxide with the severity of rhinovirus infection

Researchers at Institut de Recerca Sant Joan de Déu (IRSJD) · SJD Barcelona Children's Hospital have found that exposure to higher concentrations of atmospheric nitrogen oxide in childhood is associated with greater severity of rhinovirus infection and a higher number of admissions to the Paediatric Intensive Care Unit.

The research conducted by Dr Georgina Armero and a multidisciplinary research team led by Dr Cristian Launes, with the participation of Dr Carmen Muñoz-Almagro and Dr Iolanda Jordan, has been published in the journal Pediatric Pulmonology. The National Epidemiology Centre and the Institute of Environmental Science and Technology of the Universitat Autònoma de Barcelona have also participated.

Nitrogen oxides are environmental pollutants emitted in the combustion processes of vehicles, especially diesel engines, but also in other means of transport and industrial installations. Nitrogen oxides include chemical compounds that combine oxygen and nitrogen, such as nitrogen monoxide or nitrogen dioxide. Vehicles emit more than 75% of atmospheric nitrogen dioxide in urban environments. According to the National Emissions Inventory, big cities like Barcelona and Madrid, and their metropolitan areas, found the highest levels of nitrogen oxides.

"As shown in previous studies, rhinovirus infections vary in severity in infants and children. But we do not know the exactitude that causes this variability. We decided to study whether environmental contamination could be related to severity as part of our project to analyse demographic, environmental, epidemiological and microbiological variables." Says Dr Cristian Launes, member of the Infectious Diseases and Microbiome group of the IRSJD and paediatrician at the SJD Barcelona Children's Hospital.

More than nine years of analysed data on rhinovirus infections in infants and children

To carry out the research, data from 9 years (2010-2018) in which 150 admissions with rhinovirus infection occurred, mainly in children under four years of age, were analysed. We contrasted these data with different environmental variables: temperature, rainfall, relative humidity, wind, airborne levels of pollens, fungal spores, and nitrogen compounds (oxides) recorded at various weather stations near the SJD Barcelona Children's Hospital.

"We cross-referenced the PICU admission data with environmental data. And we observed higher concentrations of nitrogen oxide pollutants three days before the infections. Therefore, we believe this ecological data could be related to higher admissions to the PICU."

"Given these results, we analysed what could be the reasons for this relationship. On the one hand, we found that the virus incubation period is between 1 and 4 days, which could explain why the peak of admissions was three days after the high levels. On the other hand, in cellular models, we observed that rhinovirus viral receptors (ICAM-1) increase their expression in environments rich in nitrogen oxides. And finally, we believe that the airway epithelium may suffer from free radical damage when exposed to environmental pollutants and cause viral infections to be more severe". Dr Cristian Launes concludes.

This study is one of the first to analyse a more significant number of patients with rhinovirus infections and their relationship with environmental variables. Understanding how the environment influences respiratory virus infection severity, such as rhinovirus, can help to establish better policies to mitigate the nitrogen compounds production from fossil fuel combustion.

Rhinovirus responsible for the common cold and severe respiratory infections

Rhinovirus is one of the viruses responsible for the common cold. This virus usually causes a mild clinical picture, but 10% of infants and children develop more severe symptoms in the form of bronchiolitis and bronchospasm that can lead to hospital admissions. In addition, 1 in 10 admissions requires care in the Paediatric Intensive Care Unit (PICU).

In recent years, a team led by IRSJD researchers and SJD Barcelona Children's Hospital paediatricians has developed different studies to find the explication for high variability in clinical pictures of rhinovirus infection.

About the research

The publication in Pediatric Pulmonology is part of the studies on analysing demographic, environmental, epidemiological and microbiological variables led by Dr Cristian Launes and Dr Carmen Muñoz-Almagro. Dr Launes and Dr Muñóz Almagro have been IRSJD researchers and CIBER of Epidemiology and Public Health since 2017. The annual competitive call for Strategic Action in Health (PI17/00349) has founded these studies.

This research is the result of the collaboration with the National Epidemiology Centre of Dr Amparo Larrauri and Dr Diana Barroso, and Dr Jordina Belmonte, coordinator of the Xarxa Aerobiològica de Catalunya and professor at the Universitat Autònoma de Barcelona.

Reference paper

Armero G, Penela-Sánchez D, Belmonte J, et al. Concentrations of nitrogen compounds are related to severe rhinovirus infection in infants. A time-series analysis from the reference area of a pediatric university hospital in Barcelona. Pediatr Pulmonol. 2022;57(9):2180-2188. doi:10.1002/ppul.26021

We crossed PICU admission data with environmental data and found higher concentrations of nitrogen oxide contaminants three days before infections.