Abstract
With the improvement of airtightness of Japan house, it has become easy for fungi to proliferate in the high humidity environment such as bathroom. The primary purpose of this study is to clarify the density and composition of dirt on various parts of prefabricated bathroom and to elucidate relationship between the dirt density and fungal density. In addition, the assimilating test with actual dirt was conducted by Cladosporium sp., a typical fungi species in bathroom.
Our results showed that dirt density was in the range of 57-790 μg/cm2. Ceiling had the lowest and outlet port wall region had the highest dirt density among the different parts in each tested bathroom. The mean compositions of keratin protein, triglycerides and sodium fatty acids in dirt were 50, 24, and 15%, respectively and those three components consisted about 90% of the total dirt. Fungal density was significantly positively correlated with keratin protein and triglyceride density.
The assimilating test showed that human dirt in a bathroom can be a source of nutrients for Cladosporium sp.. A component of sebum, triglyceride, in addition to keratin protein promoted the mycelial growth of Cladosporium sp..
From the observation in this study, we showed that the kinetics of outbreak, adhesion, discharge and persistence of dirt were different depending on the part of a bathroom. In addition, we also showed that keratin protein and a sebum component (triglyceride) were important to the proliferation of Cladosporium sp.. This is the first report that showed Cladosporium sp. can proliferate with dirt density that occurs in actual bathroom environment.
