Assessment of the Occurrence of Phthalate Esters (PAEs) in Indoor Office PM2.5 from Brazil and the UK

Phthalate esters (PAEs) are ubiquitous synthetic chemicals, known pollutants and health hazards. Due to their adverse health effects, including those associated with inhalation exposure, PAEs have been relatively well studied in outdoor particulate matter with aerodynamic diameter <2.5 μm (PM 2.5 ) . However, limited data exist on indoor emissions of PAEs, despite the fact that nearly 90 % of human daily activities occur indoors, indicating a potential gap in understanding human exposure to those pollutants. This pilot study aimed to perform a preliminary assessment on the presence of six priority PAEs and the alternative plasticiser bis-2(ethylhexyl) adipate (DEHA) in indoor PM 2.5 from three offices in the UK and Brazil. DEHP (bis-2(ethylhexyl) phthalate), was consistently detected in PM 2.5 (with concentrations up to 34 ng/m 3 ) from all studied offices. DEHP concentrations had consistently low airborne variability, especially within the occupied offices suggesting that human activities could facilitate the continuous resuspension of DEHP-bound particles, maintaining a steady-state indoor concentration. Although mean DEHP levels in all studied offices were below the UK HSE workplace exposure limit, they represent a continuous chronic exposure source not accounted for by industrial safety standards. Reliance on oral reference values due to unavailability of inhalation reference standards for PAEs may underestimate risks due to route-specific metabolic differences. The study provides the first region specific data from the UK and Brazil suggesting indoor environments as contributors to PM 2.5 -bound DEHP exposure, highlighting the need for more systematic and long-term monitoring initiatives. • DEHP was consistently detected in indoor PM 2.5 at concentrations up to 34 ng/m 3 • Occupied offices had up to 7x greater DEHP levels than the unoccupied one • DEHP showed low variability, suggesting steady indoor emissions • DEHP concentrations were below regulatory limits yet contribute to chronic exposure