Toxicity of airborne dust as an indicator of moisture problems in school buildings

Abstract

Moisture-damaged indoor environments are thought to increase the toxicity of indoor air particulate matter (PM), indicating that a toxicological assay could be used as a method for recognizing buildings with indoor air problems. We aimed to test if our approach of analyzing the toxicity of actively collected indoor air PM in vitro differentiates moisture-damaged from non-damaged school buildings. We collected active air samples with NIOSH Bioaerosol Cyclone Samplers from moisture-damaged (index) and non-damaged (reference) school buildings (4 + 4). The teachers and pupils of the schools were administered a symptom questionnaire. Five samples of two size fractions [Stage 1 (>1.9 μm) and Stage 2 (1–1.9 μm)] were collected from each school. Mouse RAW264.7 macrophages were exposed to the collected PM for 24 h and subsequently analyzed for changes in cell metabolic activity, production of nitric oxide (NO), tumor necrosis factor (TNF)-α and interleukin (IL)-6. The teachers working in the moisture-damaged schools reported respiratory symptoms such as cough (p = 0.01) and shortness of breath (p = 0.01) more often than teachers from reference schools. Toxicity of the PM sample as such did not differentiate index from reference building,s but the toxicity adjusted for the amount of the particles tended to be higher in moisture-damaged schools. Further development of the method will require identification of other confounding factors in addition to the necessity to adjust for differences in particle counts between samples.

Keywords:

• Indoor air
• moisture damage
• PM
• school
• toxicity
• in vitro

Acknowledgements

This work was supported by Tekes – the Finnish Funding Agency for Innovation, New knowledge and business from research ideas – HOVAVART (Homevaurion vakavuuden arviointi toksisuustestin avulla) Grant agreement no. 2285733-9, the Academy of Finland grant no. 252718, HES foundation (Hengityssairauksien tutkimussäätiö), The Finnish Work Environment Fund, OLVI Foundation, Väinö and Laina Kivi Foundation, as well as Juho Vainio Foundation grants no. 201310268 and 201410288. We would also like to thank Kati Järvi for technical assistance and the participating schools for their collaboration. The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health.

Additional information

Funding

This work was supported by Tekes – the Finnish Funding Agency for Innovation, New knowledge and business from research ideas – HOVAVART (Homevaurion vakavuuden arviointi toksisuustestin avulla) Grant agreement no. 2285733-9, the Academy of Finland grant no. 252718, HES foundation (Hengityssairauksien tutkimussäätiö), The Finnish Work Environment Fund, OLVI Foundation (OLVI säätiöö), Väinö and Laina Kivi Foundation (Väinö ja Laina Kiven säätiö), as well as Juho Vainio Foundation (Juho Vainion säätiö) grants no. 201310268 and 201410288.