Assessing personal exposure to PM using data from an integrated indoor-outdoor experiment in Athens-Greece

An integrated indoor-outdoor 15-day PM sampling campaign in a general area close to the centre of Athens, targeted to examine personal exposure. All microenvironments (MEs) (second and fourth floor flats, cafes, cars, restaurants, underground metro, outdoor etc.) frequented by the residents were included in the study. The instrumentation used was both stationary (low volume samplers) and portable/wearable to be able to measure continuously PM₁₀, PM_2.5, PM₁ and analyze chemically PM_2.5 and PM₁ samples. The study showed that the residences' air quality was determined by the type and intensity of outdoor sources and their vertical distance from the street. Indoor activities such as cooking, cleaning further increased PM levels and formulated the air quality, while particulate accumulation was evident. In general, PM_2.5 concentrations were higher outdoors, 11-43 μg/m³, than in the second floor flat as well as on days within different MEs, 13-33 μg/m³ and 8-35 μg/m³, respectively and finally in the fourth floor 10-18 μg/m³. PM_2.5 chemical composition was typical of a Mediterranean urban area predominantly composed on average of OC/EC (33%), sulfate (13%), ammonium (9%), nitrate (5%) and crustal material (Cl-, Na⁺, K⁺, Mg²⁺ and Ca²⁺) (5%). On days when other MEs were visited crustal material increased on average to 16%. The PM levels measured with the portable instrumentation at all mEs showed that the persons were exposed to higher PM₁₀ concentrations in the subway (avg. 218 μg/m³) due to the resuspension of crustal material, while maximum PM_2.5 and PM₁ were experienced in cafes where smoking was allowed (avg. 126 and 108 μg/m³, respectively). Using the car resulted to the lowest PM₁₀, PM_2.5 and PM₁ exposure (58, 10 and 6 μg/m³, respectively). Total exposure to particulates depended both on the time spent in each ME and on the mixture of MEs visited in 24 h.