We summarized about Japanese research reports according to chemical`s kinds and concentrations in indoor air atmosphere from 1970's to today. The study reports before 2000 were mainly carried out on indoor air pollution of NO₂, CO, CO₂ and particle. The studies after 2000 were carried out on a relationship between sick building syndrome and chemicals. Therefore, studies were what measurement of volatile organic compounds and aldehydes, and about chemical sensitivity. We reviewed main researches in these many reports in Japan.

View full abstract

Exposure to house dust is known to cause and exacerbate allergic diseases in many patients. However, house dust contains many kinds of allergens and the amount of each allergen varies between houses. Both in Japan and internationally, mite allergens are one of the most important allergens as a cause of asthma and allergic rhinitis. Many studies have shown that increased mite allergen levels in indoor environments is related to the development and exacerbation of asthma. Internationally, cockroach allergens are regarded to be as important respiratory allergens as mite allergens. However, in Japan, cockroach allergens are hardly detected in house dust, and the sensitization rate to cockroach allergens among Japanese allergic patients is low. Some research into insects in house dust in Japan has shown that Psocoptera, Diptera, and Lepidoptera are detected at a high frequency. Therefore, these insects allergens are thought to have more impact as a cause of allergic disease than cockroaches.

View full abstract

In a measurement for styrene vapor, the following method is widely used: collection on sorbent tubes, desorption with solvent, and analysis by gas chromatography. In the analysis of low concentration in indoor environment with this method, however, the measurement values have been underestimated because the recovery rate on solvent desorption is low. For this reason the analysis accuracy including the recovery rate needs to be reexamined, and it is essential for that purpose to provide calibration vapor. The continuous generation method using a permeation tube(P-tube) is effective for the preparation of low concentration vapors. In this study, we generated styrene vapor with the P-tube method for preparing calibration vapor in indoor level. The P-tube was made by injecting styrene monomer and stabilizer into polytetrafluoroethylene tubes with a constant diameter. It was kept at a constant temperature to generate vapor and diluted with fresh dry air continuously. The weight of the P-tube was measured at voluntary intervals, and the vapor generated was analyzed qualitatively with gas chromatograph. The results are shown as follows: the weight of the P-tube kept on decreasing at a constant rate for more than a year by adding the stabilizer. A permeation rate was determined by the weight loss of the P-tube per measurement intervals. When a vapor concentration was calculated from the obtained rate and a quantity of dilution gas flow, it became clear that styrene vapor in indoor level was generated from the P-tube. As a result of a qualitative analysis of the vapor, styrene monomer was detected, and dimer and stabilizer were not detected. Therefore, the use of the P-tube made possible stable generation of styrene vapor in indoor level for a prolonged time.

View full abstract

Since children spend most of their time indoors and they have hand-to-mouth behavior, house dust ingestion can be a potential exposure pathway for some non-volatile chemicals. In order to identify which chemicals in house dust need to be further investigated in Japan, we collected literature data on the concentration of selected chemicals (metals, polybrominated diphenyl ethers, polycyclic aromatic hydrocarbons (PAHs), phthalates, dioxins, DDT, chlorpyrifos, perfluorooctanesulfonic acid, bisphenol A and nonylphenols) in house dust and estimated the exposure level via the house dust ingestion. We calculated hazard quotients (HQs) and excess cancer risks for the chemicals. The HQ at 95 percentile of estimated exposure level for lead and 2,4-diethylhexyl phthalate (DEHP) was 0.2 and 1.7, respectively. These exceeded acceptable HQ of 0.1 that was tentatively set in this study. The excess cancer risk at 95 percentile of estimated exposure level for inorganic arsenic, PAHs and dioxins was 3×10^-5, 1×10^-3 and 8×10^-5, respectively. These exceeded acceptable excess cancer risk of 10^-5. In addition, intake of lead, DEHP and PAHs via the house dust ingestion was significant when compared with that from other pathways such as food, air and soil. On the other hand, contribution of house dust ingestion to total inorganic arsenic and dioxins exposure level was negligible, so any countermeasure to house dust was not considered effective to lessen health risk due to inorganic arsenic and dioxins exposure. We concluded that lead, DEHP and PAHs are the chemicals of priority to be further investigated for Japanese house dust to fully characterize its health risk to children.

View full abstract

We conducted a survey regarding the number of furniture items and electrical appliances possessed in Japanese residential houses, and the time spent by the residents in each room, categorized according to the activity. The participants were asked the survey questions through internet questionnaires (N = 1035). "Dining," "relaxing," "sleeping," and "hobby & studying" were selected as the activities. The rooms used for "sleeping" were generally used for a single purpose (65%), while the rooms used for "relaxing" were often used for other purposes as well (77%); in particular for "dining" (66%). The items that were often located in the room used for "dining" include table (91%), chairs (89%), cupboard (89%), refrigerator (78%), and ventilation fan (53%), whereas the items that were often located in the room used for "relaxing" include couch (58%), television set (89%), air conditioner (80%), and carpet (68%). What there is often in the rooms used for "sleeping" include bed (49%), wardrobe (68%), and cloth storage case (61%), whereas what there is often in the rooms used for "hobby & studying." include desk (74%), chair (74%), bookshelf (76%), and personal computer (65%). There were some significant differences in the holding ratios among regions for certain kinds of furniture. Combined with the data on the emission of chemical substances from the items, this information enables us to evaluate the exposure attributable to the items in Japan.

View full abstract

This study examined the effects of building materials to regulate an indoor humidity on indoor environment and psycho-physiologic conditions of the occupants. Individuals were allowed to stay in two different Gifu University Hospital single-occupancy rooms for 24 hours, respectively. One of the rooms had its interior refurbished with building materials to regulate an indoor humidity and the other conventional room had interior walls finished with gypsum wallboards. The indoor environment was monitored during the occupancies. The individuals were asked to self-evaluate their psychological parameters using a questionnaire (State-trait anxiety inventory). Several physiological parameters including body temperature and heart rates were also measured. The results demonstrated that the variations in indoor humidity were reduced inside the room finished with the materials by virtue of their humidity-regulating property and that there was also a tendency to reduce body temperature and heart rates during some part of the stay in the same room. Although no direct causation was determined, the findings suggested possible effects of the materials on psycho-physiologic conditions of the refurbished room occupants.

View full abstract

Bioassay, which detects biohazardous property of environmental contaminants, is still being an unexplored field of air quality monitoring. This study aims to develop a simple testing system of toxicity of the indoor particulate matter by detecting bioluminescence reduction of marine bacterium Vibrio fischeri. Suspended particulate matter in indoor and outdoor air was collected on a quartz fiber filter at a flow rate of 23.5 L/min by a low volume air sampler for 7-day duration, at the terrace and living room of an apartment house in Kanagawa, Japan. Collected materials were extracted with sterilized distilled water by mild shaking. After filtration with 0.45 μm pore size filter, the extracts were subsequently mixed with a bacterium solution in a well of 24-well plate and time courses of bioluminescence intensity were measured by a luminometer. Meanwhile, House dust samples were collected from filter bags of household cleaners of 4 houses in metropolitan area. House dust samples were size-fractionated by stainless steel sieves and then served for bioassay as well. As a result, the water extracts of indoor and outdoor aerosol samples significantly reduced the bioluminescence of Vibrio fischeri and the inhibition per sampling volume increased with increasing of TSP (Total Suspended Particles) concentrations. The inhibition per unit mass of the indoor aerosols became greater than that of outdoor aerosols, when increasing in air change rate. On the other hand, the water extracts of house dust also showed the inhibition of bioluminescence especially in fine mode. The inhibition tended to correlate with nitrate and sulfate concentrations in the extracts. This study showed possible application of bioassay to the monitoring of indoor particle contamination.

View full abstract

A heat exchange type of ventilator, equipped with a dehumidification function is a central type ventilator equipped with an additional dehumidification function. To demonstrate the inhibitive effect for mold growth with the operation of this ventilator, one room equipped with this ventilator, and one room with a normal central type of whole heat exchange ventilator (as a control) were prepared. The mold growth environments were examined using a mold sensor (test pieces of enclosed mold samples) and the temperature and humidity were measured at the same time. In the room equipped with this ventilator, no growth of mold was observed in any of the sample molds during the examination period. This indicates that the room equipped with this ventilator was an environment where molds could not grow. In the room equipped with the control ventilator, growth of several sample molds (xerophilous Aspergillus and Eurotium) were observed during the examination period at several measurement points. This indicates that the room equipped with the control ventilator was an environment where molds could grow. The results of temperature and humidity measurement demonstrated that the room equipped with this ventilator maintained both lower absolute humidity and relative humidity compared to those in the normal whole heat exchange type of ventilator. The above statements demonstrated that the installation of this ventilator maintains low humidity in a room and inhibits the growth of molds. Molds will not grow in buildings equipped with this ventilator and molds will grow in buildings equipped with a normal whole heat exchange ventilator. There is a possibility that during the summer, when the outside absolute humidity is high, due to water in the air being taken into the building, the inside of a building may change to an environment where molds can grow. In such seasons, it is necessary to use ventilation methods, such as this, with additional dehumidification.

View full abstract