Status of the indoor air chemical pollution in Japanese houses based on the nationwide field survey from 2000 to 2005

This paper describes the present state and the changes in indoor air pollution levels by Volatile Organic Compounds (VOCs) in houses in Japan, as revealed through measurements of indoor VOC concentrations and investigations on the actual conditions in the residential environment by means of a questionnaire survey covering a total of more than 10,000 newly built houses over six years (from 2000 to 2005). The VOCs initially measured were formaldehyde, toluene, xylene, and ethylbenzene, followed by the subsequent inclusion of styrene and acetaldehyde.The survey in 2000 revealed that the indoor concentrations of formaldehyde and toluene exceeded the guideline values established by the Ministry of Health, Labor and Welfare (MHLW) of Japan in more than 27% and 12% of houses surveyed, respectively. This rapidly led to the development of a variety of countermeasures for improving the indoor air environment, such as the amendment of the Building Standard Law (BSL) to a performance-based regulation and the enactment of the Housing Quality Assurance Act, which provides a housing performance indication system. This study presents the changes in the state of indoor air pollution (including the mitigation of indoor air pollution by VOCs as their concentrations decreased) on a nationwide basis in all the types of building structures during the period from 2000 to 2005, when the regulatory measures mentioned above were instituted, and discusses factors associated with these changes.