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Poor indoor air quality may cause, contribute to or exacerbate respiratory diseases, including infections, cancer and chronic conditions. It is particularly dangerous for people who already have a chronic respiratory condition. Many factors can contribute to poor indoor air quality, including some construction and insulation materials (notably asbestos), paints, furnishings, carpets, chemicals from furniture and household products (among others), by-products of fuel burning appliances and chimneys, crowding, second-hand smoke, allergens from pets, cockroaches and dust mites, radon, mould and dampness. Several of these are highlighted in a previous web report on cancer and chemicals in occupational settings, and are detailed in Box 1. This section will focus on one often-overlooked indoor environmental risk of high importance for respiratory health: mould and dampness.
Mould, dampness and respiratory disease
Every sixth household in the EEA member and cooperating countries is impacted by dampness (WHO, 2022). While humidity itself is increasingly considered a potential health risk, it is most commonly used as a proxy for mould growth since it is easier to measure and is strongly related to mould infestation. Mould is caused by increased humidity, which can be caused by insufficient ventilation, water damage, poor building design, leaking pipes, overflows, rain seeping through cracks or gaps in roofs, spills from blocked gutters, leaky window frames, and so on. Exposure to mould is not only problematic at homes, but also at the workplace and in other places where people spend a lot of time, like children in schools (see the EEA briefing on children and air pollution) (Urlaub and Gruen, 2016; WHO, 2009; Caillaud et al., 2018; EU-OSHA, 2020).
Exposure in mouldy indoor environments is complex and diverse. A number of micro-organisms are related to mould infestation, such as mould fungi, yeasts, bacteria (especially actinobacteria) and organisms that can use mould as a food source, such as mites. Furthermore, microbial metabolites and other microbial substances such as toxins, endotoxins, allergens, β-glucans, microbial volatile organic compounds (MVOC) and microbial fragments are released to and detected in indoor air and dust in households with mould infestation.
Mould affects respiratory health and can cause allergic bronchopulmonary aspergillosis (ABPA) and mould-induced mycoses, allergic respiratory disease, asthma (manifestation, progression and exacerbation), allergic rhinitis, hypersensitivity pneumonitis (extrinsic allergic alveolitis) and an increased likelihood of respiratory infections or bronchitis. Irritations of the mucous membranes of the respiratory tract are the most common respiratory health effect from mould, as well as allergic reactions and diseases. It is difficult to obtain overall figures of the respiratory health impacts of mould and dampness, partly on account of the diversity of mould-related respiratory symptoms. One estimate puts the number of mould-related asthma cases in Europe at 2.2 million (Urlaub and Gruen, 2016).
Trends in mould and dampness in Europe
As with any other indoor environment variable, it is challenging to obtain data on the prevalence of mould in households and buildings generally. However, an indicator on dampness self-reported periodically in the Eurostat EU-SILC survey estimates that the share of total population in the EU-27 living in a dwelling with dampness has increased from 12.7% (the series minimum) in 2019 to 15.5% in 2023. Trends and magnitudes vary among non-EU member countries, with the lowest proportion in Switzerland (6.3%) and highest in Türkiye (34.7%). These countries also exhibit generally downward trends over the past four years.
What the EU is doing about mould and dampness
In line with the principle of subsidiarity (i.e. it is considered by member states that this issue can be dealt with effectively by Member States themselves at central, regional or local level) housing is not a direct competence of the EU. Nevertheless, as agendas of urban regeneration expand, EU policies are starting to touch upon housing inadequacy. For example, the renovation wave initiative builds on the national long-term building renovation strategy, the Energy Performance of Buildings Directive and building-related aspects of each EU country’s national energy and climate plans (NECPs). By tackling energy poverty and public building renovation, it indirectly promotes better insulation and housing less likely to suffer from mould.