Source apportionment for indoor air pollution: Current challenges and future directions.

Area of Science:

• Environmental Science
• Indoor Air Quality Research
• Chemical Analysis

Background:

• Indoor air pollution (IAP) source apportionment (SA) is complex due to numerous sources, chemical processes, and outdoor air infiltration.
• Understanding the balance between indoor and outdoor pollutant contributions is crucial for effective IAP management.
• Existing research has identified major indoor sources but requires further investigation into complex interactions.

Purpose of the Study:

• To review current understanding of indoor air pollution source apportionment.
• To summarize SA techniques, targeted pollutants, identified sources, and knowledge gaps.
• To highlight challenges and future directions in indoor air SA.

Main Methods:

• Literature review of existing studies on indoor air pollution SA.
• Analysis of commonly used SA techniques, including Positive Matrix Factorization, Principal Component Analysis, and Chemical Mass Balance.
• Compilation of data on identified indoor PM sources and organic compounds.

Main Results:

• Most SA studies (78%) focused on particulate matter (PM) composition and size, with fewer on organic compounds.
• Positive Matrix Factorization (31%) and Principal Component Analysis (26%) are dominant SA methods.
• Identified indoor PM sources include building materials, cooking, combustion, resuspension, consumer products, and secondary formation.

Conclusions:

• Significant variability exists in the contribution of outdoor air to indoor pollution (10%-90%).
• Future research needs to optimize monitoring, data selection, and integrate physical/chemical processes into SA models.
• Further investigation is needed on the interplay between indoor/outdoor sources and complex atmospheric chemistry within indoor environments.