Abstract
The current understanding of water-soluble organic aerosol (OA) composition, sources, transformations, and effects is still limited to outdoor scenarios. However, the OA is also an important component of particulate matter indoors, whose complexity impairs a full structural and molecular identification. The current limited knowledge on indoor OA, and particularly on its water-soluble organic matter (WSOM) fraction is the basis of this feature paper. Inspired by studies on outdoor OA, this paper discusses and prioritizes issues related to indoor water-soluble OA and their effects on human health, providing a basis for future research in the field. The following three main topics are addressed: (1) what is known about the origin, mass contribution, and health effects of WSOM in outdoor air particles; (2) the current state-of-the-art on the WSOM in indoor air particles, the main challenges and opportunities for its chemical characterization and cytotoxicity evaluation; and (3) why the aerosol WSOM should be considered in future indoor air quality studies. While challenging, studies on the WSOM fraction in air particles are highly necessary to fully understand its origin, fate, toxicity, and long-term risks indoors.
Highlights
Particulate matter (PM) of different sizes has been one of the most studied outdoor air pollutants
The outdoor studies have made a remarkable progress toward the understanding of the importance, composition, sources, and transformation of the watersoluble organic carbon (WSOC) present in ambient PM
Because of the complex nature of aerosol WSOC, which reflects into both the aerosol–climate and aerosol–health interactions, there still remain many open questions to be addressed by the outdoor air chemistry community [4,5,10]
Summary
Particulate matter (PM) of different sizes has been one of the most studied outdoor air pollutants This interest in atmospheric PM is fueled by the realization of its negative impacts on air quality and human health, and large, but uncertain, effects on radiative climate forcing and atmospheric chemistry [1,2]. The outdoor studies can provide guidance on issues such as the characterization and cytotoxicity of WSOM in indoor environments Encouraged by this topic, this feature paper aims to reflect on (1) what is known about the origin, contribution, and health effects of the WSOM in outdoor PM2.5; (2) the current state-of-the-art on the WSOM fraction in indoor air particles, the main challenges and opportunities for its chemical characterization and toxicity assessment; and (3) why the WSOM should be considered a key particle-phase component in indoor air quality studies
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