Free and combined amino acids in size-segregated atmospheric aerosol samples

•Distribution of free and combined amino acids in atmospheric sizesegregated particles.•Amino acid and total proteinaceous material concentrations in NIST SRM 1649b.•Protein bioaerosol concentrations in ultrafine fraction were studied.

Concentrations of free and combined amino acids in an urban atmosphere and their distributions in size-segregated particles were investigated in the cold and warm seasons. In particular this article provides the first investigation of protein bioaerosol concentrations in ultrafine fraction (PM0.1) of particulate matter.In addition the present work provides amino acid and total proteinaceous material concentrations in NIST SRM 1649b, useful as reference values. The reference material was also used to build matrix matched calibration curves.Free amino acid total content in winter and summer PM0.1 was respectively 48.0 and 94.4 ng m−3, representing about 0.7 and 7.4% by weight of urban particulate matter in the two seasons.Total airborne protein and peptide concentrations in the same ultrafine fractions were 93.6 and 449.9 ng m−3 respectively in winter and in summer, representing 7.5 and 35.4% w/w of PM0.1, and demonstrating an exceptionally high percentage in summer ultrafine fraction.The significant potential adverse health effects of ultrafine particulate matter include allergies mainly caused by protein particles and we assumed that in summer 162 ng h−1 of proteinaceous material, by means of ultrafine particles, can penetrate from the lungs into the bloodstream.