Risk assessment concepts and approaches for indoor air chemicals in Japan

Individuals living in general indoor environments are exposed to a greater variety of chemical pollutants, albeit at lower concentrations, compared with industrial workers in occupational environments. These pollutants can result in a variety of adverse health effects, including those affecting the respiratory, neurological, reproductive, dermatologic, and cardiovascular systems. In Japan, indoor air quality guidelines have been established for 13 chemicals since 1997, and these developments have continued on the basis of scientific discussions in the Committee on Indoor Air Pollution (CIAP) that was set up by the Ministry of Health, Labour and Welfare. However, the types and concentrations of these pollutants have been observed to be inconsistent over time due to lifestyle changes and the development of novel household products and building materials. Therefore, continuing the monitoring of indoor chemicals and the development of indoor air quality guidelines for substances that pose potential high health risks are essential for the protection of public health. In indoor environments, there are multiple media by which humans come in contact with indoor chemicals and multiple exposure pathways that can affect human health, particularly for semi-volatile organic compounds (SVOCs). This is defined as aggregate exposure. Furthermore, combined exposure to multiple low-level pollutants occurs in indoor environments. In this article, a comprehensive overview of the indoor air quality guidelines in Japan and assessment approaches for developing indoor air quality guidelines is provided. In addition, future issues facing approaches for indoor chemicals, including aggregate exposure to SVOCs and combined exposure to multiple pollutants with common toxicological effects in indoor environments, are discussed.