The sources of air pollution in buildings are numerous. Typically, indoor pollutants are categorized by type: chemical (semi-volatile and volatile organic compounds or VOCs, inorganic gases), biological (viruses, bacteria, molds, pet allergens, mite allergens) or physical (particulates, asbestos fibers, artificial mineral fibers, electromagnetic fields). Indoor pollution may also be described according to the three types of sources typically recognized: i) external pollution (air or ground in the case of radon, or soil contaminated by past or present industrial activity), ii) building constituents (construction materials and floor, wall and ceiling coverings) and fixtures, and iii) the occupants themselves (bioeffluents, smoking, cleaning, DIY, personal hygiene, etc.).
The respective contribution of each of these sources to indoor concentrations is difficult to determine, due not only to the specific characteristics of each space and its occupants’ habits, but also to the variability over time of indoor concentrations and chemical reactivity phenomena leading to the formation of secondary pollutants. For example, terpenes are chemical substances mainly used in indoor cleaning and deodorizing products, which can react with ozone from outside and lead to the formation of formaldehyde and ultra fine particulates. Temperature and relative humidity also play a role by encouraging materials to release emissions into the indoor air.
Indoor air pollution constantly changes over time. New practices such as electronic cigarettes or 3D printing generate new forms of pollution. Additionally, some substances now banned from sale may still be present in buildings. This is the case with polychlorinated biphenyls(PCBs), for example, which were used in sealants in the 1970s and are frequently detected in the air in buildings constructed during that period. The same may be said of lindane, which was used as an insecticide in timber frames and head lice treatment shampoo, and is still often detected in indoor air. The France Observatory on Indoor Air Quality (OQAI) has updated its directory of substances that may be present in indoor air. The list includes substances that have either: i) previously been detected in air or dust deposited on the ground, ii) previously been measured in an environmental chamber in emissions from construction materials or consumer products, or iii) been recorded in the composition of materials and products used in buildings.
The health effects of indoor air pollutants are just as varied as the pollutants that cause them. They range from mild annoyance linked to odours to serious effects such as lethal poisoning due to carbon monoxide, asthma, cancer, cardiovascular illnesses and reproductive problems. Poor indoor air quality may also be associated with headaches, nausea, and irritation of the eyes, nose and respiratory tract.
While some associations between substances present in indoor air and health effects are well established (as is the case with asbestos fibers and mesothelioma, or radon and lung cancer), the effects of a large number of other pollutants have not been clearly identified and remain merely suspected. Moreover, determining health effects can be made more complex by several features: effects are sometimes delayed; exposure is often to weak doses or occurs through various routes, including the ingestion of dust deposited on surfaces and skin contact, as well as inhalation; and these effects may be cumulative, synergic or antagonistic due to the mix of substances present.
Currently, concerns regarding indoor pollution are centred on endocrine disruptors, pesticides (especially near crops), bio contamination (for example, the dispersion of viruses in buildings in the case of flu pandemics) and nano particulates. These particulates are less than 100 nm in diameter and may be incorporated into construction materials and consumer products to give them particular properties, for example to strengthen or preserve. While studies are revealing the troubling implications of particulates of this size for respiratory health, questions remain about how they are emitted into indoor air during use of said materials and products, or through their decomposition.
As the number-one indoor environment in terms of time spent, dwellings were the subject of the OQAI’s first national campaign in 2003-2005. More than a hundred
chemical, physical and biological parameters were recorded over one week, in a sample of 567 randomly selected dwellings representative of the stock of primary residences in mainland France. This campaign showed that some pollutants, such as formaldehyde, particulates, and certain phthalates and polycyclic aromatic hydrocarbons were systematically present in the dwellings. Air pollution in dwellings is not homogeneous, however, and different pollution profiles were identified.
Examination of the concentrations recorded alongside the characteristics of the buildings, their location, their occupants and their lifestyles identified factors leading to degradation of indoor air quality. For example, in single -family homes , the presence of a connecting garage increases concentrations of benzene and toluene in the rest of the dwelling. These substances are emitted by vehicles (exhaust gases and fuel tanks) and DIY products that may be stored in the garage. Cooking, care and hygiene (showers, drying laundry) activities may contribute to high humidity in the building, which favours the growth of molds. Behaviour with regard to opening windows and the state of mechanical ventilation systems also play a role in indoor air quality. After dwellings, schools are the location frequented second most often by children. In schools, the high density of furniture, use of products for activities (glues, paints, markers, etc.) and frequent cleaning of the premises may have repercussions on indoor air quality and represent distinctive features of these buildings in comparison with dwellings. In addition, the use of chalk, proximity to major highways, and children’s high activity level (which causes dust deposits to become airborne) are all factors that contribute to particulate pollution in classrooms.
The four points for consideration that the majority of schools conformed to the indoor Air quality regulatory guideline values. Firstly, fine particulate pollution is omnipresent, with indoor concentrations higher than the World Health Organization’s (WHO) guideline values. Secondly, Some pollutants were present in the air in 100% of classrooms, including phthalates, which are used as plasticizers; polycyclic aromatic hydrocarbons, produced by combustion, including from road traffic outside; and lindane. Thirdly, the presence of lead in deteriorating paint was observed in concentrations above the regulatory limit of 1 mg/cm2. Lastly, the schools had at least one classroom in which air renewal was unsatisfactory with regard to occupation, with a confinement index equal to 4 or 5 out of 5.
Modern lifestyles effectively lead the population to spend the majority of their time in indoor environments where a large number of pollutants may be present. In response to the need for deeper understanding and to better direct government policies and improvement solutions, the responsible Ministry / authority / Stakeholder / Agency, conduct research on new pollutants and investigates new problems. It is important to secure breathing in future climate changing atmosphere.
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