title: Role of microbial and chemical composition in toxicological properties of indoor and outdoor air particulate matter.
abstract: BACKGROUND
  Ambient air particulate matter (PM) is increasingly considered to be a causal factor evoking severe adverse health effects. People spend the majority of their time indoors, which should be taken into account especially in future risk assessments, when the role of outdoor air particles transported into indoor air is considered. Therefore, there is an urgent need for characterization of possible sources seasonally for harmful health outcomes both indoors and outdoors.
  
  
  METHODS
  In this study, we collected size-segregated (PM(10-2.5), PM(2.5-0.2)) particulate samples with a high volume cascade impactor (HVCI) simultaneously both indoors and outdoors of a new single family detached house at four different seasons. The chemical composition of the samples was analyzed as was the presence of microbes. Mouse macrophages were exposed to PM samples for 24 hours. Thereafter, the levels of the proinflammatory cytokines, NO-production, cytotoxicity and changes in the cell cycle were investigated. The putative sources of the most toxic groups of constituents were resolved by using the principal component analysis (PCA) and pairwise dependencies of the variables were detected with Spearman correlation.
  
  
  RESULTS
  Source-related toxicological responses clearly varied according to season. The role of outdoor sources in indoor air quality was significant only in the warm seasons and the significance of outdoor microbes was also larger in the indoor air. During wintertime, the role of indoor sources of the particles was more significant, as was also the case for microbes. With respect to the outdoor sources, soil-derived particles during a road dust episode and local wood combustion in wintertime were the most important factors inducing toxicological responses.
  
  
  CONCLUSIONS
  Even though there were clear seasonal differences in the abilities of indoor and outdoor air to induce inflammatory and cytotoxic responses, there were relatively small differences in the chemical composition of the particles responsible of those effects. Outdoor sources have only a limited effect on indoor air quality in a newly built house with a modern ventilation system at least in a low air pollution environment. The most important sources for adverse health related toxicological effects were related to soil-derived constituents, local combustion emissions and microbes.
authors.affiliation: Department of Environmental Science, University of Eastern Finland, P.O. Box 1627, FI-70211, Kuopio, Finland. mikko.happo@uef.fi.
authors.forename: Mikko S
authors.initials: MS
authors.lastname: Happo
authors.affiliation: Department of Environmental Science, University of Eastern Finland, P.O. Box 1627, FI-70211, Kuopio, Finland. olli.sippula@uef.fi.
authors.forename: Olli
authors.initials: O
authors.lastname: Sippula
authors.affiliation: Department of Environmental Science, University of Eastern Finland, P.O. Box 1627, FI-70211, Kuopio, Finland. pasi.jalava@uef.fi.
authors.forename: Pasi I
authors.initials: PI
authors.lastname: Jalava
authors.affiliation: Mikrobioni Oy, Microkatu 1, P.O. Box 1188, FI-70211, Kuopio, Finland. helena.rintala@mikrobioni.fi.
authors.forename: Helena
authors.initials: H
authors.lastname: Rintala
authors.affiliation: Finnish Meteorological Institute, Atmospheric Research Centre of Eastern Finland, P.O. Box 1627, FI-70211, Kuopio, Finland. ari.leskinen@fmi.fi.
authors.forename: Ari
authors.initials: A
authors.lastname: Leskinen
authors.affiliation: Finnish Meteorological Institute, Atmospheric Research Centre of Eastern Finland, P.O. Box 1627, FI-70211, Kuopio, Finland. mika.komppula@fmi.fi.
authors.forename: Mika
authors.initials: M
authors.lastname: Komppula
authors.affiliation: Department of Environmental Science, University of Eastern Finland, P.O. Box 1627, FI-70211, Kuopio, Finland. kari.kuuspalo@uef.fi.
authors.forename: Kari
authors.initials: K
authors.lastname: Kuuspalo
authors.affiliation: Department of Applied Physics, Kuopio, University of Eastern Finland, P.O.Box 1627, FI-70211, Kuopio, Finland. santtu.mikkonen@uef.fi.
authors.forename: Santtu
authors.initials: S
authors.lastname: Mikkonen
authors.affiliation: Finnish Meteorological Institute, Atmospheric Research Centre of Eastern Finland, P.O. Box 1627, FI-70211, Kuopio, Finland. kari.lehtinen@uef.fi.|Department of Applied Physics, Kuopio, University of Eastern Finland, P.O.Box 1627, FI-70211, Kuopio, Finland. kari.lehtinen@uef.fi.
authors.forename: Kari
authors.initials: K
authors.lastname: Lehtinen
authors.affiliation: Department of Environmental Science, University of Eastern Finland, P.O. Box 1627, FI-70211, Kuopio, Finland. jorma.jokiniemi@uef.fi.|VTT Technical Research Centre of Finland, Fine Particles, Espoo, P.O. Box 1000, FI-02044, Espoo, Finland. jorma.jokiniemi@uef.fi.
authors.forename: Jorma
authors.initials: J
authors.lastname: Jokiniemi
authors.affiliation: Department of Environmental Science, University of Eastern Finland, P.O. Box 1627, FI-70211, Kuopio, Finland. maija-riitta.hirvonen@uef.fi.|Department of Environmental Health, National Institute for Health and Welfare, P.O. Box 95, FI-70701, Kuopio, Finland. maija-riitta.hirvonen@uef.fi.
authors.forename: Maija-Riitta
authors.initials: MR
authors.lastname: Hirvonen
mesh_terms: D000391:Air Microbiology; D016902:Air Pollution, Indoor / Q000009:adverse effects*; D000818:Animals; D002453:Cell Cycle / Q000187:drug effects; D002461:Cell Line, Transformed; D002470:Cell Survival; D016207:Cytokines / Q000378:metabolism; D004391:Dust / Q000032:analysis; D005387:Finland; D006094:Gram-Positive Bacteria / Q000254:growth & development / Q000276:immunology / Q000302:isolation & purification; D006801:Humans; D008264:Macrophages / Q000166:cytology / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D051379:Mice; D003904:Mitosporic Fungi / Q000254:growth & development / Q000276:immunology / Q000302:isolation & purification; D009569:Nitric Oxide / Q000378:metabolism; D010316:Particle Size; D052638:Particulate Matter / Q000737:chemistry / Q000633:toxicity*; D025341:Principal Component Analysis; D012111:Residence Characteristics; D012621:Seasons; D012906:Smoke / Q000009:adverse effects / Q000032:analysis; D012988:Soil Microbiology
chemical_list: D016207:Cytokines; D004391:Dust; D052638:Particulate Matter; D012906:Smoke; D009569:Nitric Oxide