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10. Conclusions and recommendations

Assessing the health risks of indoor air pollution is very difficult as indoor air may contain over 900 different chemicals, particles and biological materials with potential health effects.

Also, many different factors influence air quality, for example ventilation, cleaning conditions, properties of buildings, products used in households, cultural habits, climate and outdoor environment. Therefore, large variations in indoor environments can be expected across the EU.

The European Commission Scientific Committee on Health and Environmental Risks (SCHER) concludes the following:

• The principles used in the EU for risk assessment of chemicals should also be applied to health risk assessment of pollutants in indoor environments.
• The information available to assess the risk of indoor air is in general limited. More data are needed, particularly on health effects of particles and microbes, levels of exposure, and effects of indoor pollutants on vulnerable populations. Several gaps in knowledge have been identified (see Question 9) and should be addressed by European-wide multidisciplinary research.
• Carbon monoxide, formaldehyde, benzene, nitrogen oxides and naphthalene are compounds of particular concern because they have caused adverse health effects as indoor pollutants or have a high potential to do so. Environmental tobacco smoke, radon, lead and organophosphates are also of concern.
• Data on true exposure to volatile organic compounds emitted by numerous consumer products is insufficient to establish a link with possible health effects because of the many confounding factors. Some of these emitted substances may react in air and on surfaces and produce secondary pollutants such as fine and ultrafine particles whose health effects are poorly understood.
• More research is needed to understand how humidity and mould problems in buildings can affect health and to evaluate the seriousness of the problem in EU countries.

The SCHER also recommends the following:

• Gathering more data on combined effects of indoor pollutants, which are so far limited.
• Considering all possible routes of exposure (through inhalation, ingestion, or through the skin) when assessing the risks.
• Developing health-based guideline values for key pollutants and other practical guidance in general to help risk management.
• Collecting and systematizing practical experiences to establish evidence-based risk assessment approaches.
• Considering the impact of indoor exposure when evaluating the health effects of outdoor air pollution, given that concentrations of air pollutants are usually higher indoors and that people tend to spend more time indoors.
• Evaluating all relevant sources known to contribute to indoor air pollution, such as tobacco smoke, candles and open fires, building materials, furniture, pets and pests, use of household products, and conditions that lead to the growth of moulds.

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