(174d) Seasonal Variation and Source Apportionment of PAHs in PM2.5 and Study of Their Effect in Human Health

The aim of this study is to identify the main sources emitting PAHs in the atmosphere of medium-sized cities in Europe (i.e. cities with population on the order of a million) and to assess the risk of lung cancer induced by exposure to PAHs. Mid-sized cities are the majority of the urban settings in Europe; more than 60% of the European urban population lives in such settings. Furthermore, the study examines the variation of emission sources and PAHs induced lung cancer risk throughout the seasons of the year. Our pilot study was performed in the city of Thessaloniki, the second largest city in Greece. Measurements were included three different sampling sites in an effort to include areas of Thessaloniki with various atmospheric conditions. The concentrations of PAHs were higher in winter compared to summer. The combination of conditional probability function and Positive Matrix Factorization was used for the apportionment of the main PAHs emission sources and their geographical origin. The study shows the temporal trend and spatial variations in the concentration of PAHs.

PAHs are produced during the incomplete combustion of organic material. This fact is an indication for their emission sources which may include forest fires, volcanic activity, combustion of domestic heating fuels, coal and coal tar production, oil refinement, vehicle and means of transportation emissions (Tarantini et al., 2011). In Greece, the financial crisis that has been going on for over a decade now has forced citizens to search for cheaper and less eco-friendly fuels for domestic heating and their vehicles. The aim of this study examines the variation of emission sources and PAHs induced lung cancer risk throughout the seasons of the year 2017 and compare the cancer risk induced by PAHs, measured during the winter of 2013.

PM2.5 were measured in three different stations in the city (rural, urban background, traffic) during February-March (cold season) and June-August (warm season) of 2017 followed by chemical analysis of 19 PAHs. PM2.5 concentrations were higher at the traffic site during the winter while were higher at the background site during the summer. The mean concentrations for the rural site were 11.9 μg/m³ for the summer and 18.3 μg/m³ for the winter, whereas in the traffic site the corresponding values were 10.13 μg/m³ and 28.8 μg/m³. In the background site the concentrations were 16.9 μg/m³ for the summer and 28.6 μg/m³ for the winter. The average total PAH concentrations at the rural site were 4 ng/m³ for the summer and 6.5 ng/m³ for the winter. For the traffic station, the corresponding levels were 7.1 ng/m³ and 11.3 ng/m³. While for the background station the average total PAH concentrations were 5.9 ng/m³ for the summer and 9.3 ng/m³ for the winter. It was concluded that PAH levels were increased during the cold period of the year. Using the Positive Matrix Factorization model it was found that the main emission sources for the rural station were biomass combustion (28%) and vehicle emissions combined with industrial activity (72%); for the urban background station industrial activity (18%), vehicle emissions (38%) and biomass combustion (44%); and for the traffic station biomass combustion (36%), vehicle emissions (54%) and industrial activity (10%). Using PMF results, the conditional probability function indicates as the most possible sources of PAHs the oil refinery situated in the western part of Thessaloniki, the cement production factory and main roads of the city (Ring Road etc.). Based on the toxicity of benzo[a]pyrene, the Toxic Equivalent Quotients (TEQ) for the warm period of the year were calculated as follows: 0.29 ng/m³ for the rural station, 1.05 ng/m³ for the urban background station and 0.62 ng/m³ for the traffic station. For the cold time of the year the values were 1.01 ng/m³ for the rural station, 2.16 ng/m³ for the urban background station and 2.56 ng/m³ for the traffic station. Using the Multiple Path Particle Deposition model, the particle deposition along the human respiratory tract per age group was modelled in order to calculate the PAH-induced lung cancer risk. The maximum value of cancer risk was estimated for children (0-3 months old) in the urban traffic station, during the cold time of the year (1.741 x 10^-6) and the minimum risk was calculated for the female adults’ group, in the rural station, during the warm period of the year (0.043 x 10^-6). Cancer risk assessment has also been carried out by Sarigiannis et al. (2015) who studied PAH-induced lung cancer risk in Thessaloniki during the winter of 2012-2013. The measurements were performed the same period as in the present study. The results showed an increase in cancer risk in the traffic station, from 2013 to 2017 indicating an increase of PAHs emissions during that time and a relative stability of cancer risk for the urban background station. Furthermore, the population living in proximity to the traffic station is at higher risk, as the result of the extensive use of diesel vehicles.

Ambient air PAH levels in the urban environment are greatly affected by seasonal effects of emissions patterns. The use of a refined methodology assessing the levels of exposure and the health risk from exposure to PAHs, allows us to significantly differentiate the actual health risk between different urban sites as well as between different age groups. On the urban scale the most significant PAH sources in ambient air are industrial activities and road transport.

REFERENCES

Sarigiannis, D. Α., Karakitsios, S. P. & Kermenidou, M. V. 2015. Health impact and monetary cost of exposure to particulate matter emitted from biomass burning in large cities. Science of The Total Environment, 524-525, 319-330.

Tarantini, A., Maître, A., Lefèbvre, E., Marques, M., Rajhi, A. & Douki, T. 2011. Polycyclic aromatic hydrocarbons in binary mixtures modulate the efficiency of benzo[a]pyrene to form DNA adducts in human cells. Toxicology, 279, 36-44.