Differential determination of plasticizers and organophosphorus flame retardants in residential indoor air in Japan

A variety of chemicals have been used in a wide range of indoor materials, such as wallpaper and furniture, and some of them are released into the indoor air. The level of consumption as well as the diversity of these chemicals has been increasing. The particle size of the materials in the air is known to affect the depth of human exposure, e.g., particles >10 μm can only reach the nasal cavity, whereas particles 2.5–10 μm can reach the respiratory tract and particles <2.5 μm can reach the bottom of the lungs. However, information on the concentrations and form of these chemicals in indoor air is very limited. In this study, we measured 54 compounds, including plasticizers (phthalates, adipates, and others) and organophosphorus flame retardants, in indoor air samples from the living rooms of 21 dwellings in 11 prefectures across Japan. For sampling, we used a four-stage air sampler (multi-nozzle cascade impactor) equipped with three quartz fiber filters to capture chemical particulates in three size ranges (<2.5, 2.5–10, and >10 μm) and a C₁₈ solid-phase extraction disk to capture chemicals that exist in a gas phase in indoor air. Each of the chemicals in the three particulate phases and single gas phase was extracted by acetone and measured separately using GC/MS. Of the 54 compounds tested, 37 were detected in the indoor air samples. The highest concentration observed was that of 2-ethyl-1-hexanol (5.1 μg/m³), which was detected in samples from all 21 houses. The 37 compounds were captured in the four fractions at different rates roughly based on their molecular sizes. Compounds with a smaller molecular size were commonly detected as a gas phase, whereas compounds with a larger molecular size were detected as one or more of the three particulate phases in the indoor air samples. Among the three particulate phases, many of the compounds were detected from the filter capturing the smallest (<2.5 μm) particles. Therefore, these results suggest that the chemicals measured in this study might penetrate deeply into the lungs as many of them tend to exist as a gas and/or as particles smaller than 2.5 μm.