Decline of VOC Concentrations with the Aging of Houses in Japan

With the development of the society, many new building materials have been produced and “sick house” occurred, then many countermeasures against indoor air pollution in houses have been taken by the Japanese government, building companies, building material manufacturers and other related groups.

The purpose of this investigation was to know the long-term characteristics of VOC concentrations in houses built before the building code in 2003 and to clarify the countermeasures against indoor air pollution in the houses already built, such as the improvements of living habits, ventilation and the remove of building materials.

In the study, the concentrations of formaldehyde, toluene, xylene, ethyl-benzene, styrene and acetaldehyde were measured in winter and in summer for five years in about two hundred and fifty houses in which formaldehyde concentration was higher than the guideline: 0.08ppm in 2000. The concentrations were specified using gas chromatographs in the laboratory. The characteristics of buildings and residents were checked using questionnaires. The indoor temperatures and the humidity were measured by residents and were checked on the questionnaires.  

The results showed that the concentration of formaldehyde decreased in the first year. After that the decline of the concentration was not seen and the concentration changed only with the temperature. The characteristics of decline were thought to be caused by two sorts of emission. One was an emission of concealed formaldehyde in the process of material production and the other was an emission with the generation of formaldehyde from adhesives of urea resin and moisture. The concentration of toluene decreased rapidly in the first year. The concentrations of xylene, ethyl-benzene and styrene showed a similar change. But the concentrations of acetaldehyde which were measured from the summer of 2002 did not decrease and its concentration in some houses was higher than the guideline even in the winter of 2005.

In conclusion, the long-term countermeasure against chemical pollution in summer is thought to be necessary. And if residents have suffered some impairment by indoor chemical pollution, renovations of buildings especially considering indoor air quality will be necessary not only in new houses but also in old houses.

Article by Motoya Hayashi and Haruki Osawa, from Japan.

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