The airtightness of buildings has been increasing in Europian countries since the 1970s. This has resulted in an increase in health problems caused by poor indoor air quality (IAQ) termed sick building syndrome (SBS). In the 1990s, some Japanese people living in newly built or renovated houses reported a variety of nonspecific subjective symptoms resembling SBS, which was designated sick house syndrome (SHS). Since SHS patients dwell in new or renovated houses, indoor chemicals emitted from building materials, including formaldehyde and volatile organic compounds (VOCs), are acknowledged as the major sources of SHS in Japan. However, this Japanese concept of SHS lacks many other factors such as biological, physical, and psychosocial factors as well as dampness problems. Therefore, since SBS/SHS problems contribute to IAQ, we are continuing to conduct epidemiological studies in homes involving both environmental monitoring and questionnaires.
Table 1 summarizes each epidemiological study.
The first study began in April 2001. Using the list of single-family dwellings constructed by 24 housing companies in Sapporo, we distributed questionnaires to 564 occupants and subsequently conducted environmental measurements in 96 dwellings. The concentrations of aldehydes and VOCs in the air were measured. Viable airborne fugal species were determined, and floor dust was collected to measure dust mite allergens. Dampness signs were inquired about in a questionnaire.
In 2003, we organized a study group from 6 different regions in Japan to initiate the second study (Figure 1).
Surveys were conducted according to the same protocol in all regions. The questionnaires were distributed to the occupants of 6,080 dwellings built within the last 7 years from a list of approved building plan applications. There were a total of 2,297 respondents. The first environmental measurements were conducted in 425 dwellings in 2004, and all inhabitants filled in health questionnaires including questions about SHS and allergies. The international standardized questionnaire for SBS, the MM questionnaire, was used to determine SHS. Follow-up measurements were conducted twice in 2005 and 2006. In addition to measuring aldehydes, VOCs, fungi, and mite allergens, semi-volatile organic compounds (SVOCs including 7 phthalates, 11 phosphorus flame retardants [PFRs], 16 pyrethroids, and organophosphate pesticides in the air and dust) and microbial VOCs (MVOCs) were measured in 2006. The research group published a book based on these studies in 2009 titled, Manuals of Sick House Syndrome: Consulting and Countermeasures (ISBN978-4-8192-0215-2).
In the first 2 studies, the prevalence rate of SHS was higher among children than among adults. Thus, the third study focused on elementary school children. We approached public schools in each region for cooperation. A total of 10,816 questionnaires were distributed; the response rate was 71%. Like previous studies, environmental measurements were conducted in 178 homes over the following 2 years. This study differed in that we included not only newly built single-family dwellings, but also multi-family apartments and old single-family dwellings. In this study, we also collected urine samples from all family members for biological monitoring.
Since 2011, we have been conducting an IAQ study on 7-year-old children participating in the Hokkaido Study on Environment and Children’s Health. This fourth study is targeting asthma and allergies as primary health outcomes. In parallel to investigators’ home visits for environmental measurements, we ask each participant to collect dust and urine samples. This challenge enables sample collection throughout the Hokkaido area (83,457 km2). In addition, the prospective cohort study design will eliminate recall bias as a potential confounder.
We hope our research provides scientific evidence to improve IAQ and thus people’s health. In addition, we intend to continue our research projects in related fields.
We would like to acknowledge that these studies are financially supported by a Health Science Research Grant for Research on Environmental Health from the Ministry of Health, Labour, and Welfare of Japan and by the Environment Research and Technology Development Fund of the Ministry of the Environment, Japan. We thank all the study participants and are grateful to all of our colleagues.