Conference Agenda

Air quality, particularly concerning particulate matter (PM), is a critical determinant of human health. Inhalation of PM is associated with respiratory, cardiovascular, and systemic health issues, with global PM exposure linked to over 2 million premature deaths each year. Reducing PM exposure is therefore essential. This study compares European Union (EU) air quality standards (2008 values) with World Health Organization (WHO, 2021) guidelines, focusing on mean annual concentrations of PM₂.₅ and PM₁₀ and their associated health impacts. These impacts were quantified using Disability-Adjusted Life Years (DALYs) per 100 000 people—a metric reflecting years of healthy life lost due to disease. Findings show that EU standards for mean annual PM₂.₅ and PM₁₀ (20 μg/m³ and 40 μg/m³) remain substantially higher than WHO recommendations (5 μg/m³ and 15 μg/m³). This discrepancy results in significant health impact, correlating to approximately 1 389.75 and 1 985.3 DALYs per 100 000 people annually under current EU standards, compared to 347.44 and 744.51 DALYs under WHO guidelines for PM₂.₅ and PM₁₀, respectively. In March 2024, the EU proposed updating its standards to more closely align with WHO goals, including a 2030 target for annual mean PM₂.₅ to 10 μg/m³—though this remains double the WHO guideline. To illustrate the effect of outdoor air quality on indoor environments, this analysis includes case studies of a hospital waiting room and a three-bedroom apartment. Results show that outdoor PM concentrations significantly impact indoor air quality through ventilation and building infiltration, leading to indoor concentrations that nearly match those outdoors. These findings emphasize the critical need for strict outdoor air quality standards and effective ventilation strategies to maintain safe indoor environments. Overall, this analysis supports the substantial public health benefits of aligning EU standards with WHO guidelines to reduce the disease burden associated with PM exposure.

Temperate climates are expected to have an expansion of the number of hours where ventilative cooling is needed and where potential is available even under climate change scenarios. Further to this, the use of free cooling in the form of untreated outdoor air has the potential to be a renewable energy source that adds flexibility to national electricity grids if used appropriately and is critical in decarbonising cooling more generally, particularly where coupled with significant thermal mass in buildings. The following study utilises external air quality measurements from the PASSESPARTOUT project and were collected from unique external air quality systems located in Cork in Ireland. The study characterises this data according to constraints based on control limits for cooling systems and for individual external air quality parameters. While the work aims to demonstrate the barriers to cooling potential that may exist due to poor external air quality, it also offers insights into where good urban air quality supports diurnal ventilative cooling strategies that are best suited given these limitations. The findings show that out of seven outdoor pollutants investigated, NO2 and PM2.5 were consistently above recommended threshold limits in suburban areas and present a barrier to the use of indoor-outdoor direct airflow coupling using natural ventilation strategies for ventilative cooling purposes. Indoor concentration levels within the surrounding areas to those investigated should be evaluated to develop Indoor-Outdoor ratios for designers for barrier pollutants.

Particulate matter (PM) is a leading contributor to indoor air-related health harm. While population-level estimates of harm are typically based on outdoor PM concentrations linked to epidemiological studies, most exposure occurs indoors, particularly in homes where people spend the majority of their time. Indoor concentrations differ from outdoor values due to the presence of both indoor and outdoor sources, and are shaped by building characteristics, ventilation regimes, filtration, and occupant activities. The indoor-to-outdoor (I/O) concentration ratio provides a useful metric for quantifying these differences and varies with transport, removal, and emission processes. This paper reviews the evidence on I/O ratios in homes, focusing on fine and coarse particles, which is currently thought to account for the majority of harm from indoor air contaminants. It evaluates how infiltration, penetration, deposition, filtration, and indoor sources influence I/O ratios, and examines how these variations affect estimates of population harm. The results show that relying on outdoor PM concentrations as a proxy for exposure introduces bias. In homes with few indoor sources, effective filtration, or limited infiltration, harm is overestimated; in homes with dominant indoor sources, harm is underestimated. We conclude that robust public health assessments should incorporate indoor exposure dynamics and I/O ratio variability to improve exposure estimation and support the evaluation of mitigation strategies, including air cleaning, envelope improvements, and source control.

Air pollution is a leading global cause of morbidity and mortality, and indoor environments play an important role in personal exposure because people spend more of their time indoors. Outdoor monitoring data is frequently used to assess health impacts –using metrics such as the Disability-Adjusted Life Year (DALY)- but it may not closely represent indoor exposures influenced by building characteristics, ventilation practices, and occupant activities. In fact, personal exposures may align more closely with indoor exposures, indicating that current health impact analyses should account for indoor air quality .

This study takesa top-down approach using indoor-outdoor (I/O) ratios to examine exposure variability and influencing factors. Indoor concentrations were measured every ten minutes in eight dwellingdwellings in Santiago (Chile) in 2023 and 2024, and are compared to hourly outdoor data from nearby government monitoring stations. The analysis shows spatial and temporal variations in I/O ratios, which were then grouped by shared factors such as building characteristics, dwellinghold profiles, and occupant activities. Ratios often exceeded unity during the heating season, mainly due to by combustion-based heating systems, including gas and kerosene heaters. These findings emphasize the important role of structural and behavioral factors in shaping indoor air quality.

This research highlights the limitations of using outdoor air quality data for assessing health impacts. It does not capture the variable and prolonged exposures experienced indoors. The findings enhance our understanding of particle dynamics in urban housing and reinforce the need to consider indoor air pollution in public health policy.