Time-dependent Change in Symptoms of Sick House Syndrome and in Indoor Environment of Patient Dwellings

Abstract

Sick house syndrome (SHS), which comprises various non-specific complaints, has been reported in Japan since the 1990s. SHS patients are mainly said to have irritation of the mucous membranes and skin, often with headaches and fatigue. The present report describes time-dependent changes in indoor formaldehyde (FA) levels and in SHS symptoms. Indoor FA levels have been decreasing in homes built recently. In 2000, the effect of FA levels on the symptoms of SHS patients were studied in 71 dwellings. Similar studies were performed again in 2006 and 2007. The data were compared with the results obtained in 2000. Occupants of rooms with FA levels greater than 0.2 ppm were SHS patients; the average FA level was higher in patient houses than in non-patient houses. FA levels were highest in houses built around 1997, and decreased gradually thereafter. The average FA level decreased with occupation period, falling by about 50% between 2000 and 2007. From a diagnostic perspective, SHS patient characteristics included not only falling ill on entering the dwelling, but also recovery on leaving them. The FA levels in the dwellings of patients with such symptoms were significantly higher. The percentage of headaches and coughs correlated positively with FA level, and were lower for lower FA levels. Nevertheless, the percentage of allergies was not found to relate to FA level. The possibility of fungi as well as FA being the cause of SHS in patients examined in the study was suggested. The importance of indoor ventilation for controlling SHS symptoms was recognized.