Man-Made Vitreous Fibers in Office Buildings in the Helsinki Area

Abstract

Several sources of man-made vitreous fibers (MMVFs) may exist in an office environment causing irritation symptoms among occupants. In 258 office buildings, the occurrence and density of settled MMVFs on surfaces were measured by two sampling methods. Altogether, 1113 samples of settled dust were collected from surfaces with plastic bags and gelatine tape and were analyzed with a scanning electron microscope and a stereomicroscope, respectively. Tape samples from 68 buildings were collected from frequently cleaned (n = 162) and seldom cleaned (n = 57) room surfaces in 56 and 29 offices, respectively, and from supply air ducts (n = 24) in 10 offices. MMVFs longer than 20 μm were counted with a stereomicroscope. Irritation symptoms were recorded with a questionnaire. More than 60% of the surface dust and almost 90% of the samples collected from supply air ducts contained MMVFs. The density of MMVFs longer than 20 μm ranged from < 0.1 to 5 fiber cm^{− 2}. The mean density of the MMVFs was about two times higher on the seldom cleaned surfaces than on the frequently cleaned surfaces. The density was usually under 0.2 MMVF cm^{− 2} in surface dust of offices without emission sources of MMVFs. The measurements combined with qualitative analysis of settled dust can help to localize relevant sources of fiber emissions. Altogether, in 40% of the buildings, several occupants had repeated irritation symptoms that were verified by occupational health care personnel.

Keywords:

• irritation symptoms
• man-made vitreous fibers (MMVF)
• office building
• surface dust

ACKNOWLEDGMENTS

The authors warmly thank the indoor air researchers of the Finnish Institute of Occupational Health in Helsinki for their excellent field investigations and laboratory work. We also wish to thank Rauno Holopainen and Reima Kämppi for their valuable comments and advice.

Notes

^A The number includes samples collected with plastic bags and/or with special tape.

^B Of these buildings, 66 were the same buildings as the buildings where room surface samples were collected. In addition, only supply air duct samples (not room surface samples) were collected in eight buildings.

^C Of these buildings, eight were the same buildings as the buildings where room surface samples were collected. In addition, only supply air duct samples (not room surface samples) were collected in two buildings.

^A The differences in occurrences of MMVFs by construction or renovation year were statistically significant (Chi-square, p = 0.002).

^A The difference between the means was statistically significant (t-test, p < 0.05).