When we talk about air quality and its influence on our health, we often think of air pollution from transport, construction sites, and environmental sources such as wildfires. These pollutants do not always stay outdoors but can infiltrate buildings and enter our homes. When these pollutants enter our bodies, they can increase the risk of respiratory and cardiac diseases (among others), and worsen pre-existing symptoms and conditions. Indoor air quality is also influenced by the products and amenities we use every day. Burning, or the combustion of, fossil fuels for heating and cooking, the use of cleaning products, and emissions from building materials and furniture are all examples of factors than can contribute to poor indoor air quality and adverse health outcomes. Air pollution is experienced unequally across Europe, with vulnerable groups less able to evade the damaging impacts and suffering more severe consequences.
BEST-COST attended the Indoor Air 2026 Conference in Singapore, represented by Maria-José Rueda Lopez, engineer at the Centre Scientifique et Technique du Bâtiment (CSTB). In this article, Maria José talks about her takeaways from the conference.
Humanity has achieved significant advances in public health and its connection to environmental health over the past decades. We are becoming increasingly aware of the effects that environmental pollution and climate change can have on human health. To address these issues, more effective tools and strategies have been developed to monitor key environmental parameters, such as temperature and the concentration of pollutants in outdoor air.
However, although people spend approximately 90% of their time indoors, the study and monitoring of air quality in these environments have traditionally received less attention than in outdoor settings. This disparity limits our ability to accurately assess population exposure to environmental factors that may affect their health and wellbeing, potentially leading to an underestimation of scientific evidence used to guide policy interventions.
Today, a growing number of researchers are working on this topic, and many of them presented their latest findings at the Indoor Air 2026 conference. The BEST-COST project was represented at this important scientific event to highlight its research on the interactions between outdoor and indoor pollution in dwellings.
In this context, I had the opportunity to present the results of BEST-COST concerning the estimation of the nitrogen dioxide (NO₂) infiltration factor in 47 dwellings across France, as well as the indoor-generated NO₂ concentration in 61 dwellings. Both of these were based on NO₂ concentrations measured in the immediate outdoor environment of each dwelling. NO₂ mainly comes from the combustion of fossil fuels, such as in road traffic and industrial activity, but also from the use of housing appliances such as stoves, ovens, and fireplaces. Exposure to NO₂ can lead to respiratory symptoms such as coughing and wheezing, as well as chronic respiratory illnesses such as asthma. The findings offer valuable reference values for air exchange rates (i.e., how often the air volume in a room is completely replaced within an hour), infiltration factors (the fraction of outdoor air pollutants that enter indoors and remain suspended in the indoor environment), and indoor-generated concentrations of NO₂ in French dwellings.
The findings from the BEST-COST project can serve as a basis for broader European-wide measurements. The results also contribute to the understanding of how outdoor pollutants influence indoor air quality by quantifying both the level of outdoor pollutants that infiltrate homes and the level generated indoors. These results represent an important step towards the development of methodologies capable of estimating population exposure to indoor NO₂ on a large scale. Rather than relying on the installation of sensors in every dwelling, these methodologies use outdoor monitoring data together with information on dwelling-specific infiltration characteristics to predict indoor exposure levels. This approach can improve the assessment of individual exposure to this pollutant, optimise resources required for monitoring, and contribute to a better understanding of its potential impacts on human health.
Overall, the study contributes to broader public health efforts to reduce environmental pollution by offering standardised exposure modelling. These can be applied in epidemiological studies, risk assessments, and policy development aimed at reducing indoor exposure to air pollutants.
