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In recent years, the plastics pollution of 5mm or less size (microplastics) in marine ecosystems has been a global issue. The presence of microplastics (microfibers) is also a major concern in indoor environments of the residetial house. Many sources of microplastics in the marine environment also exist in the indoor environment. In the modern age where we spend most of our time indoors, the indoor environment is related to the health of residents, so it is important to investigate the presence and contamination status of microplastics in the indoor environment. There is limited the number of studies on microplastics in the indoor environment. In our previous studies have confirmed the presence of microplastics in indoor environments Kanto area including Tokyo of Japanese residential houses. The purpose of this study is to investigate the concentration of indoor microplastics in four regions; Kanto area including Tokyo, Chubu area, Tohoku area, and Kansai area. We focused on the indoor microplastics in settled dust on the floor of residential houses, and the survey was conducted on the 16 residential houses. Micro-Fourier transform infrared (µ-FT-IR) spectrophotometry was used for the qualitative analysis of microplastics. The detected components in the settled dust were cellulose, polyamide (PA), polyacrylamide (PAM), polyacrylonitrile (PAN), polybutylene terephthalate (PBT), polyethylene (PEs), polyester (PE), polyethylene terephthalate (PET), polypropylene (PP), polyvinyl acetate (PVAL).

This study aims to investigate the relevance of between SVOC concentrations in house dust and living environments. Using the newly proposed dust collecting and SVOC analysis method, we determined concentrations of the nine SVOC substances by dust size and made simultaneously the questionnaire about residential environments. Collected dusts were screened with sieves and then analyzed on nine components (DEP, DMP, BBP, DEHP, DINP, DBP, DNOP, DIDP, DIBP) by LC/MS/MS method. The results leaded to selecting less than 100μm and 100-250μm as the target size of dusts to be investigated intensively by considering the concentration distribution and the oral intake of humans. DEHP and DINP accounted for 96 to 97% of determined amount of SVOC and only the small amounts in the other seven components were detected. There was no significant difference in the component ratio depending on particle size. Significant difference was obtained between a few substances of SVOC and several living environment items.

The characterization of indoor PM2.5 has been concerned about health effects. PM2.5 in indoor air is affected by not only indoor emissions but also penetrations from outdoor air. Therefore, it is important for indoor PM2.5 to take into account of penetration factors of PM2.5 through air conditioning units in buildings. This study aimed at investigating PM2.5 concentrations and I/O ratios (indoor/outdoor concentration) in office buildings. As a result, the relationships between PM2.5 concentrations or I/O ratios and building characteristics could be classified as the types of buildings, such as specific or non-specific, and air conditioning units, such as the individual or central system. The I/O ratio for the specific buildings, over 3,000 m2 of total floor area and buildings that had the central air conditioning unit was relatively low because of medium performance filter in air conditioning units.

In order to retain good indoor air quality through the year in detached houses with passive ventilation systems, the authors investigated a mechanical control air-supply method. Firstly, indoor environments in houses with passive ventilation systems with thermal dampers, were examined using a simulation program (Fresh). Secondly, a passive ventilation system with a thermal damper, an under-floorheating system with a heat pump and were installed in an airtight house at Maebashi in Japan and measurements on its ventilation characteristics and indoor air quality were made. The simulation results showed that if the thermal damper is well tuned, this mechanically controlled air-supply opening keeps ventilation rates adequate through the year especially in airtight houses. The measurement results showed that the ventilation rates were kept above the required level through the year and the TVOC concentration decreases from 3000 to 200 μg/m3 in 5 months after the construction.