Health: Indoor air pollution harmful even at low concentrations of particulate matter

A study conducted by ENEA and the CNR Institute of Atmospheric Sciences and Climate (CNR-ISAC), in collaboration with Sapienza University of Rome and Milano-Bicocca University as part of the project VIEPI^[1], funded by Inail and published in the journal Environmental Pollution, found that in urban areas indoor air conditions may be just as harmful to human health as outdoor conditions and can lead to lung, heart and cancer diseases.

The study showed that if fine (PM2.5) and ultrafine (PM0.1) particulate matter resulting from urban vehicular traffic infiltrates an indoor environment, it can trigger the response of human bronchial tissue through specific genes related to inflammation and a particular biochemical mechanism^[2] that allows our body, as a protective action, to recognize, transform and eliminate foreign substances.

In a classroom at Sapienza University of Rome the researchers examined the toxicological response of human lung tissue cells exposed to atmospheric aerosol nanoparticles (PM2.5, PM0.1) using an innovative portable biotechnology device they developed for the first time in the world. The campaign involved measurements over 24 hours, including lesson hours.

 “The study revealed that the chemical and physical characteristics of atmospheric aerosol from the outdoor environment, influenced mainly by urban vehicular traffic and external meteorological variables (low pressure, rainfall and wind), are significantly altered by infiltrating the indoor environment, thus increasing the toxicological potential of PM2.5 and PM0.1. To this must be added the presence of students in the classroom, which contribute to the variation of biomass inside the classroom and indoor air treatment systems,” explained Massimo Santoro (ENEA) and Francesca Costabile (CNR-ISAC), first authors of the paper, with the contribution of Maria Giuseppa Grollino and Barbara Benassi of the ENEA Biotechnology Division, Maurizio Gualtieri (Milano-Bicocca), Matteo Rinaldi (CNR-ISAC), Paolo Monti (Sapienza University of Rome), and Armando Pelliccioni and Monica Gherardi (Inail),.

 “These results provide an important basis for providing sound scientific support for policies to adapt regulations on indoor air quality- which includes other settings like offices, homes and sports and recreation venues- by highlighting the critical role of fine and ultrafine particles as vectors of molecules toxic to human health,” pointed out Massimo Santoro at the ENEA Biotechnology Division.

“Our research also suggests how outdoor weather, climate and air quality have a significant impact on PM2.5 and PM0.1 properties in the indoor environment,” said Francesca Costabile at the CNR-ISAC.

On average, people in urban areas spend up to 97% of their time indoors^[3]. The main sources of indoor air pollution in cities include air infiltration from outdoor (vehicular traffic and heating) and indoor sources (tobacco smoke, cleaning products, cooking food). “The scientific question to answer in this experiment was whether it was outdoor or indoor sources that had the greatest influence on toxicity in indoor environments. It turned out that PM0.1 generated by urban vehicular traffic, infiltrating into classrooms under particular atmospheric conditions (such as low pressure, rain, wind), undergoes a major change in its physicochemical properties, becoming the most toxicologically significant source in urban indoor environments.

This is especially true at very PM2.5 low concentrations (below 5 micrograms m3). This is crucial for future outdoor air quality standards and revision of outdoor quality standard as it indicates possible human health effects in association with exposures to low PM2.5 concentrations, a condition in which PM0.1 nanoparticles can act as a Trojan horse for toxic molecules within the human body,” concluded Costabile (CNR).

[1] VIEPI - Integrated Indoor Particulate Exposure Assessment

[2] xenobiotic metabolism

[3] https://www.salute.gov.it/portale/nutrizione/dettaglioContenutiNutrizione.jsp?id=4385&area=nutrizione&menu=alimentazione