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Biocontamination of indoor air

Indoor air quality has become an important field of research in the last decades. However, it is a very old problem. Human beings have always been subjected to the indoor pollution, most of the time due to heating or cooking in closed areas. Pollution became an outdoor problem when the usage of coal and the generalized production of electric power increased and later also with dense traffic. The use of coal for heating of houses and in industry increased SO2 and particle levels locally so high that it caused pollution episodes. The energy crisis in the early 1970's lead to change in building construction manner leading to more air tight buildings with more efficient use of energy. The current trend also today is to save as much energy as possible, and the building industry aims at providing more efficient and consequently tighter houses. Moreover, in urbanised societies people spend more than 90% of their time indoors or in vehicles. According to The World Health Organization report 2002, indoor air pollution is responsible for 2.7% of the global burden of diseases ( Nowadays indoor air problems can even surpass those caused by outdoor pollution. For instance mould contamination in buildings has recently been one of the main issues regarding the environmental problems. Therefore the good indoor air quality is important in order to avoid adverse health outcomes.

People living in densely populated and confined habitat are especially subject to microbial exposure. It has been showed that the average concentrations of bacteria in the air in closed habitats (university auditorium, office of a public building, apartment) were higher in the presence of people and furnishing compared to empty rooms (Sessa et al., 2002). Other areas of dense population are e.g., jails, and transportation vehicles (car, train, plane and underground) (Awad, 2002). Also when Concordia station in Antarctic was tightly closed and crew activity was confined indoors, the level of microbes increased consistently (Van Houdt et al., 2009). Problem is similar in school facilities which are densely populated. Indeed, children are more likely to suffer more seriously from the indoor pollutants than adults because of their physical development (Karkowska, 2003, Zhao and Liu 2009). Microbial spreading is of particular concern in hospitals. There nosocomial infections warrant a very strict control because of immunodepressive persons. Also fungal spores, propagules and metabolites possess detrimental health effects not only to the immunocompromised individuals (Ortiz, 2009), and hospital-acquired fungal infections are viewed as a great threat to human health.

All moulds have the potential to cause adverse health effects such as headache, breathing difficulties, skin irritation, allergic reactions and aggravation of asthma symptoms (US Environmental Protection Agency, 2001). It is well known that prolonged exposure to high levels of bioaerosols may lead to allergic hypersensitivity reactions (Eduard, 2006). The mechanisms how the microbial contamination causes the symptoms are still not well known.

When the temperature and moisture conditions are favourable, even the dust on various surfaces is enough to provide nutrients for the microbial growth (Korpi et al. 1997, Pasanen et al. 1993, 1997a), and the growth can start within hours (Pasanen et al. 1993, 1997b). Besides spores, micro-organisms produce also a mixture of volatile metabolites, the composition of which depends on the nutritional and environmental conditions (Korpi et al. 1998). Certain fungi are also capable of producing mycotoxins that are present in spores and hyphal fragments. However, the direct health outcomes caused by these metabolites at the concentrations present in the indoor environments are difficult to state (Korpi et al. 2009, Gottschalk C, Bauer J, Meyer K. 2008).


      Awad AHA. 2002. Environmental study in subway metro station in Cairo, Egypt. Journal of Occupational Health 44 (2) : 112-118.

Karkowska E. 2003. Microbiological air contamination in some educational settings. Polish Journal of Environmental Studies 12 (2) : 181-185.

Gottschalk C, Bauer J, Meyer K. 2008. Detection of satratoxin G and H in indoor air from a water-damaged building. Mycopathologia 166:103-107

Korpi A, Pasanen A-L, Pasanen P, Kalliokoski P. 1997. Microbial growth and metabolism in house dust. International Biodeterioration and Biodegradation 40:19-27.

Korpi A, Pasanen A-L, Pasanen P. 1998. Volatile compounds originating from mixed microbial cultures on building materials under various humidity conditions. Applied and Environmental Microbiology 64:2914-2919.

     Korpi A, Järnberg J, Pasanen A-L. 2009. Microbial volatile organic compounds. Critical Reviews in Toxicology 39:139-193.

Ortiz G, Yagüe G, Segovia M, Catalan V. 2009. A study of air microbe level in different areas of a hospital. Current Microbiology 59 (1): 53-58.

Pasanen P., Pasanen A-L., Jantunen M. (1993) Water condensation promotes fungal growth in ventilation ducts. Indoor Air (3) 106-112

Pasanen P, Korpi A, Kalliokoski P, Pasanen A-L. 1997a. Growth and volatile metabolite production of Aspergillus versicolor in house dust. Environment International 23:425-432.

Pasanen A-L., Heinonen-Tanski H., Kalliokoski P., Jantunen M.J. 1997b.  Fungal microcolonies in indoor surfaces  - an explanation for the base level fungal spore counts in indoor air. Atmospheric Environment 25A:459-462 

Sessa R, Di PM, Schiavoni G, Santino I, Altieri A, Pinelli S, Del PM. 2002. Microbiological indoor air quality in healthy buildings. New Microbiol 25(1): 51-56.

US Environmental Protection Agency, Office of Air and Radiation, Indoor Environment Division. 2001. Mold remediation in school and commercial buildings. 6609J, EPA 402-K-01-001. Appendix B p 40.

Van Houdt R, De Boever P, Coninx I, Le Calvez C, Dicasillati R, Mahillon J, Mergeay M, Leys N. 2009. Evaluation of the airborne bacterial population in the periodically confined Antarctic base Concordia. Microbial Ecology 57 (4): 640-648.

Zhao and Liu. 2009. Experimental investigation of airborne micro-organisms in classroom. In: Proceedings of Health Buildings 2009, Syracusa, USA.