Background and rationale
There is growing evidence that household environments are subject to high concentrations of air pollutants of emerging concern (APECs)(1) which are suspected to significantly affect human health. However APECs are not yet regulated due to a lack of quantitative evidence of their health impacts(2). This includes ultrafine particles (UFPs) and black carbon (BC)(3,4). In addition, airborne micro and nanoplastics (MNPs) also have high indoor-to-outdoor ratios and have recently emerged as a health concern(5). APECs are harder to characterize than most commonly studied pollutants which partly explains the scarcity of data on their health impacts. Children and adolescents are particularly vulnerable to the health effects of APECs due to the immaturity of their organs and immune system, to their specific metabolism, and to a higher ratio of inhaled air volume to body weight compared to adult subjects. Short-term exposure to UFPs is associated with decreased lung function and asthma exacerbation in children with asthma and allergies(6). Similar effects are documented for BC (7,8) and suspected for MNPs (9,10). Indoor or household residential APEC concentrations might thus contribute to the high current childhood asthma prevalence of approximately 10% in EU countries.
Indoor sources may co-emit APECs along with regulated1 air pollutants (RAPs) which are also known to have a negative impact on respiratory health (decrease in lung function, asthma exacerbation, lower tract infections), and suggested impact on the respiratory health of new-borns after in-utero exposure (11). Gas stoves for instance, which are the main cooking appliance for 20%-68.5% of the population in 13 of the 27 EU-member countries(12), emit both UFPs and NO2 among other pollutants. This points to a need to study APECs jointly with classical regulated air pollutants such as NO2 or PM2.5 in the case of asthma.
Household air pollution (HAP) is therefore a major source of population exposure to both APEC and RAPs with demonstrated or hypothesized impacts on lung health, notably in children and adolescents. HAP exposure could in particular be reduced thanks to individual behaviour change if people had access to information, to individual monitoring devices, and to alternative technical solutions to replace polluting devices. With the emergence of new tools such as low-cost sensors for user-friendly HAP measurements and recent progress in involving citizens in participatory research, there is an opportunity to develop innovative approaches based on citizen science to conduct research on the impacts and mitigation of air pollutants. Involving policy-makers and relevant professionals such as medical professions during the research phase is also key to ensure that interventions evaluated by researchers will later on be promoted and adopted by public authorities. Likewise involving populations from the Global South and from overseas EU territories where HAP has both global environmental impacts and local health impacts is essential in a time of climate change.
