Seasonal particulate matter protein and lipid content: a preliminary study in Évora atmosphere

Abstract

The PM existing in the atmosphere, is considered as one of the most harmful pollutants for human health and exposure to PM by inhalation, depending on its variable composition over the different seasons, can cause several inflammatory responses. However, there is little knowledge about the seasonal composition and its impacts on human respiratory health is not yet fully understood. The aim of this preliminary study was assessing the seasonal variation of protein and lipid content of PM over 12 months. The seasonal profile of pollen and fungal spores was evaluated using a Hirst type sampler following the standardized methodology by the Spanish Aerobiology Network. The Black Carbon (BC) was determined using the MAAP Model 5012. Lipid and protein content was assessed using a ChemVol 2400 impactor equipped with PM>10 and PM10 stations. All the samplers were installed at the top of the Évora Atmospheric Sciences Observatory (EVASO). The protein, a marker for allergens, was extracted with NaHCO3 buffer and the content was measured using the micro- BCA method. Lipids were assessed by the Folch method followed by a thin layer

chromatography. Correlation analysis of protein and lipids with pollen, spores and BC was also performed. Seasonality in the composition of PM was observed; the pollen, fungal spores and BC presented their main seasons in March-June, May-December, and December- March, respectively. The highest concentration of protein (0.510μg/m3) and of lipids (0.645 μg/m3) in PM was recorded during the week 20 of the year (middle of May), coinciding with the pollen peak, suggesting that pollen is their main source. The protein association with pollen was higher in PM>10 (R=0.746; p<0.01) compared to PM10 (R=0.393; p<0.01), suggesting that might be retained at the upper respiratory system. The concentration of fungal spores correlated only with PM>10 (R=0.689; p<0,01) and the concentration of BC correlated with both PM10 (R=0.881; p<0.01) and PM>10 (R=0.680; p<0.01), suggesting that BC is transported in particles of varying dimensions, potentialy affecting the upper and lower respiratory system. Conclusion In conclusion, these results suggest that there is seasonality in type, size and biochemical composition of inhalable PM throughout the year, thus having the potential of inducing diverse effects on human respiratory health, namely evoking inflammatory conditions of distinct nature. This knowledge might contribute to a better management of respiratory aflictions.