Clean and fresh indoor air is an important factor promoting wellbeing and working ability.
The absolute thresholds defined in legislation may be quite low, as they are aimed at preventing adverse effects. Consequently, they cannot necessarily be used directly when assessing the cause of symptoms. Find out about local legislation and recommendations, as significant country-specific differences may apply. On the individual level, it is very difficult and often impossible to distinguish the causes of symptoms.
Indoor air-associated symptoms are a poor indicator of indoor air pollution as the symptoms are non-specific.
Diseases and symptoms linked to indoor air
The most significant pollutants increasing diseases are tobacco smoke and fine particles (cardiovascular diseases), asbestos and radon (cancer), and moisture damage (asthma).
There is no standard medical definition of indoor mould / indoor air disease (sick building syndrome).
Very many kinds of pollutants in indoor air may affect comfort and cause symptoms.
The symptoms are typically respiratory or mucosal.
In addition to the quality of the indoor environment, attitudes, expectations and community factors, among others, influence the reporting of symptoms. This is exacerbated by the fact that misconceptions about the health effects of indoor air are common in the population.
Some people may develop a long-term susceptibility to symptoms (environmental sensitivity) reducing their functional capacity and ability to work.
Symptoms typically stem from various organ systems and appear in many buildings with clean indoor air.
Studies of people with multiple chemical and electricity sensitivity show sound evidence that the symptoms are not due to exposure to a certain factor but associated with an awareness of exposure to an agent believed to be detrimental.
The most significant indoor air pollutants
Pollutants in buildings may come from outdoor air, the soil, building structures and many indoor sources, such as building or furnishing materials or human activity.
Ventilation has a decisive influence on concentrations in indoor air.
At the typically low concentrations in indoor air in Finland the associations between pollutants and adverse health effects are weak and detectable primarily in large population surveys.
In addition to pollutants, many indoor environmental factors, such as uncomfortableness, noisiness and too warm and dry indoor air, can increase the reported symptoms.
Fine particles (PM2.5; PM10) and chemicals attached to them mainly arise in burning processes. They either travel inside from outdoors or arise indoors (smoking, indoor wood-burning, candles). Exposure to fine particles increases the risk of cardiovascular and lung diseases (COPD, asthma) and lung cancer, and increases symptoms particularly in people with cardiac or respiratory disease.
The adverse effects of passive smoking resemble those of active smoking or fine particles.
Radon is an odourless and tasteless radioactive gas released from soil. It is a risk factor for lung cancer, particularly in smokers.
Moisture damage in buildings increases the risk of respiratory symptoms, in particular, and of asthma, particularly in childhood.
Moisture damage varies widely in severity and is associated with many types of exposure.
Even though microbial growth is the most probable factor causing health effects, evidence of this is weak and contradictory. There is no evidence that microbial toxins play a significant role, either.
Allergens (pollen, dog, cat, etc.) may cause allergic and respiratory tract symptoms in those sensitized to them (IgE-mediated sensitization) but avoiding these has little significance in preventing allergic diseases.
Industrial mineral fibres, such as glass fibres (glass wool) and stone fibres (mineral wool) may cause at high concentrations irritation symptoms. However, measured concentrations in office premises have been low and adverse health effects unlikely. The use of asbestos has been forbidden in many countries (in Europe since 2005, albeit earlier in some countries, e.g. in Finland since 1993). Asbestos causes asbestosis and cancer. Asbestosis, see Asbestos-Related Diseases.
There may be hundred thousands of volatile organic compounds (VOC) in indoor air. They are typically measured as an indicator of indoor air problems.
Studies done in Finland have shown that in homes and offices, levels are, except in occasional cases, well below the European health-based reference values. This may not be applicable in all countries.
Concentrations in homes are higher than in offices.
For many compounds, the odour threshold is lower than the absolute threshold, so the adverse effects may be limited to odour perceptions.
High levels may cause transient mucosal or respiratory tract symptoms. Individual compounds (such as formaldehyde, naphthalene or styrene) have also been linked to morbidity.
Increased symptoms in certain buildings
Indoor air in buildings should be healthy and safe. In addition, users should be able to trust that it is healthy.
The owner of the building is responsible for healthy indoor air of homes, schools and other premises, and this is supervised by health protection authorities. At workplaces, the employer, with the help of occupational health care, is responsible for healthy indoor air, and this is supervised by occupational safety and health authorities.
The preventive action limits set for indoor pollutants and conditions in homes, schools and other premises are usually defined by relevant authorities or in the legislation. If the limits defined in the legislation are quite strict, exceeding the action limits does not necessarily mean that the pollutant or condition has an important role as a cause of symptoms. Check local guidance on how to interpret locally relevant action limits.
In Finland, action limits are set for temperature, humidity, air velocity, ventilation, many volatile organic compounds, particles, fibres, tobacco smoke, microbes and noise, for example.
The same action limits are used also in office-type workplaces.
In difficult situations, there are often multiple problems, such as poor ventilation together with some low level pollutants. The situation may be complicated by odours experienced as unpleasant and by the thermal environment, by mistrust on the part of the users and, on the other hand, by the significant economic impact of structural solutions.
The occurrence of symptoms cannot be used as a direct measure of the condition of the building or of indoor air pollutants. Repair decisions should be based primarily on objective data on the condition of the building.
A multiprofessional, targeted approach, holistic consideration of the situation and regular, open communication are essential for successful solution of problematic situations.
Patients with symptoms associated with indoor air
Regardless of their aetiology, observed symptoms and diagnosed diseases must be treated according to conventional therapeutic guidelines.
Symptoms should not be dismissed. Meticulous differential diagnosis is an important part of the investigations because many diseases produce similar symptoms to indoor air problems.
Severe, diverse symptoms without detection of significant problems in indoor air quality may suggest long-term susceptibility to symptoms (environmental sensitivity), which is a functional disorder.
The patient may experience even mild symptoms as threatening. The doctor should explain the nature of the symptoms clearly, provide evidence-based information on adverse health effects of indoor air problems and support the patient's recovery and possibilities to continue in their work.
No position should be taken on the role of indoor air in the building in the patient's symptoms or disease, unless a reliable investigation of the situation in the building has been conducted. Nevertheless, assessment of the association will always be uncertain.