Indoor–outdoor pollution dynamics of fine particulate matter-bound polycyclic aromatic hydrocarbons and heavy metals in office buildings: Source identification and lifetime cancer risk assessment

In recent years, increasing time spent indoors has led to widespread concern regarding health problems associated with indoor air quality issues. This study conducted a 6-month monitoring and sampling campaign of indoor and outdoor air pollutant in an office building in northeastern China. The trends of indoor and outdoor polycyclic aromatic hydrocarbons (PAHs) concentrations were generally consistent, but indoor concentrations of PAHs showed significantly greater fluctuations, with Pyrene, Phenanthrene and Fluoranthene accounting for a higher proportion. Carcinogenic risk assessment revealed that the total incremental lifetime cancer risk exceeded that of all individual's exposures in the following order: dermal contact > ingestion > inhalation. Furthermore, analysis of heavy metals in indoor (particulate matter (PM)) PM 2.5 found high enrichment factors of these elements. The primary sources of these heavy metals included vehicle wear, natural dust, vehicle exhaust, industrial emissions and coal combustion. Amongst these, as posed a significantly higher carcinogenic risk than other elements, with exposure risks ranked as follows: the total average daily dose through ingestion > dermal average daily dose > inhalation average daily dose. This study has systematically elucidated the distribution characteristics and potential health risks, providing theoretical support and data references for improving indoor air quality and formulating scientifically sound environmental policies.