Pollution de l’air intérieur

• Contemporary lifestyles lead populations to spend most of their time in enclosed environments where numerous pollutants may be present. In the professional world, certain sectors of activity (chemistry, metallurgy, etc.) also lead to chronic exposure of workers to certain chemical or biological agents. • These pollutants are of varied nature: chemical (volatile organic compounds – VOCs), biological (molds, bacteria) and physical (particles, fibers). They can have repercussions on human health, both in the short and long term.

An initial study conducted in 2014 by ANSES and the Indoor Air Quality Observatory (OQAI) estimates approximately 28,000 the annual number of new cases of illnesses and over 20,000 the annual number of premature deaths linked to six indoor air pollutants, excluding workplaces with specific pollution. This study evaluates the socio-economic cost of indoor air pollution at approximately 19 billion euros per year, based on healthcare expenditures and external costs, or social costs (mortality and loss of well-being) of indoor air pollution.

The home, a primary living space, was the subject for the first time in 2003–2005 of a national indoor air quality measurement campaign conducted by OQAI.

• Over a hundred chemical, physical and biological parameters were measured in a sample of 567 homes representative of France's residential housing stock. Since then, new analyses have contributed to improving knowledge concerning indoor concentrations of nearly 70 semi-volatile organic compounds (SVOCs). These compounds are emitted by plastic materials (phthalates, bisphenol A), computers and upholstery textiles (polybrominated flame retardants or PBDEs), detergents (synthetic musks) or insecticide treatments (pyrethroids). • Some, such as polychlorinated biphenyls (PCBs), are no longer authorized today. They can, however, continue to be emitted, particularly by sealing gaskets used in the 1970s and still in place in buildings. Finally, polycyclic aromatic hydrocarbons (PAHs) come from combustion processes. Due to their physicochemical characteristics, SVOCs are not only present in the air in gaseous and particulate form, but also in dust deposited on floors, furniture and objects. Most of them are confirmed or suspected endocrine disruptors. • Measurements show that these compounds are omnipresent: if in one home in two, more than thirty SVOCs are detected in the air, phthalates and PAHs are present in all homes. Concentrations are particularly high for DEHP and DINP, two phthalates. They are lower for PCBs, PBDEs, alkylphenols and organochlorine and organophosphorus pesticides.

• Furthermore, at a time when building issues are part of energy-saving priorities, questions arise about air quality in buildings constructed or renovated according to the most recent thermal performance regulations. • Improving building energy performance indeed requires air tightness of the building envelope, which must not be done to the detriment of indoor air quality. In 2012, OQAI launched a program dedicated to studying indoor air quality and comfort in 72 homes distributed across 43 new or recently renovated buildings. Compared to France's housing stock, concentrations are lower or equivalent in energy-efficient homes for all substances searched except hexaldehyde (or hexanal), α-pinene and limonene. • Statistical analysis shows that the presence of wood in homes increases alpha-pinene concentration (wood frame, presence of wood furniture, natural wood-based insulation at attic level) and hexaldehyde (wood frame, raw or reconstituted wood-based flooring). Regarding limonene, the introduction of new furniture during the measurement week and storage of cleaning products in the home increase indoor concentrations.

Furthermore, active fungal development is identified in 47% of studied homes compared to 37% in France's housing stock, or nearly one home in two contaminated by molds. However, these are not visible in the majority of situations (only 1% of homes show visible mold traces compared to 15% in the national "Homes" campaign). Molds would develop according to the type of thermal insulation, the number of home occupants and humidity problems, infiltrations and water damage.

• After the home, school is the second place of life frequented by children. Approximately 6 million students attend preschools and elementary schools in France. The importance of furniture, the use of products for activities (glues, paints, markers, etc.) and frequent cleaning of spaces can have repercussions on indoor air quality, with specificities different from those of homes. • Furthermore, chalk use, proximity to traffic routes and high children's activity resuspending dust deposited on floors are factors that promote particulate pollution in classrooms. All these specificities prompted the conduct of a measurement campaign led by OQAI between 2013 and 2017 on a sample of 301 preschools and elementary schools representative of schools in metropolitan France.

• Regarding concentrations of VOCs and aldehydes, the vast majority of schools comply with national regulatory guideline values for formaldehyde and benzene. Limit values, requiring additional investigations and departmental prefect notification, are never exceeded. Compared to homes, concentrations of VOCs and aldehydes in schools are significantly lower, with the exception of formaldehyde and hexaldehyde, similar to those observed in homes. • Among the 47 SVOCs searched in the air, only two are never detected. Two phthalates (DiBP and DEP), two musks (tonalide and galaxolide), one pesticide (lindane) and four PAHs (phenanthrene, fluoranthene, fluorene and acenaphthene) are present in 100% of schools. Concentrations are highly variable depending on the compounds, with the highest measured for phthalates.

The median indoor concentration of PM2.5 particles is 18 µg/m³. These concentrations exceed the WHO guideline value proposed for long-term exposure (10 µg/m³) in virtually all (96%) schools. Conversely, nitrogen dioxide, also a marker of outdoor atmospheric pollution in the absence of combustion sources in school buildings, is not detected in a quarter of schools and has a low median concentration below 5 µg/m³. The indoor air quality guideline value proposed by ANSES is exceeded in 13% of schools.

Finally, indoor air confinement was evaluated using the confinement index (Icone), calculated from CO2 concentrations measured in classrooms during occupancy periods. This index reflects the quality of the room's air renewal relative to its occupancy rate. A high index indicates potentially degraded indoor air quality. Respectively 22% of preschools and 55% of elementary schools present at least one classroom with very high or extreme air confinement.

In office spaces, specific sources and activities (presence of printers and photocopiers, regular cleaning with products that may emit VOCs, etc.) could be at the origin of indoor pollution specificity. In this context, a national measurement campaign was conducted by OQAI in 129 office buildings from 2013 to 2017. Parameters measured were VOCs and aldehydes, particles with diameter between 10 nm and 1 µm, temperature, relative humidity and CO2.

• The first available results for 645 office spaces show globally low indoor concentrations for the substances searched. The median formaldehyde concentration is 14 µg/m³ and VOCs with the highest medians are 2-ethylhexanol (4.3 µg/m³) and toluene (4.2 µg/m³). • High limonene concentrations (> 100 µg/m³) are measured in 5% of offices. Similarly, benzene concentrations exceeding 10 µg/m³ are occasionally observed and are, in virtually all situations, related to also high concentration in outdoor air in dense urban areas. Some offices (8%) are multipolluted, with presence of all searched compounds in concentrations higher than in the entire sample. Finally, the median particle concentration is 6,900 particles/cm³.

Degraded indoor air quality in office spaces is associated with decreased worker performance. Between 2011 and 2013, an initial French study analyzing this relationship was conducted under the European Officair project. Aimed at studying air quality and comfort in new or recently renovated office buildings in Europe, it reveals that, while individual characteristics remain the main determinants of work performance, indoor concentrations of xylenes and ozone measured during the summer period can have an influence.

Knowledge about pollutants present in indoor air has progressed significantly in recent years and progress has been made in reducing exposures to certain chemical substances. Indoor air quality is now taken into account in building construction and building operation. However, further research is still necessary to investigate other locations (daycare centers, hospitals, nursing homes, shops, etc.) and pollutants.

Meanwhile, buildings are constantly evolving and new concerns are emerging, linked for example to the increasing use of nanomaterials, the resurgence of asbestos issues during building energy renovation programs or the impact of climate change on material emissions.

This article is an excerpt from the Environment and Health focus.