The monitoring of air pollution, especially the detection and characterization of biological aerosols (bioaerosols) in the atmosphere continues to be a challenging task. Most biosensors rely on the presence of specific molecules, such as antigens on the surface, DNA sequences, or the common fluorescents tryptophan, flavins, or reduced form of nicotinamide adenine dinucleotide (NADH). However, the de- tection signatures from either of these technologies can change significantly when the bioaerosol is released into the atmosphere, and the observed changes are strongly dependent upon the environmental conditions. In developing bioaerosol detection and characterization methods, researchers must account for the potential changes in their physical, chemical, and biological properties caused by various atmospheric conditions. The experimental results presented here show how the fluorescence spectral profile and intensity, the viability, and the PCR signature of bioaerosols, in particular for the vegetative bacteria Escherichia coli, change with time in the presence of one, or combinations of two, three, or four of the following variables: relative humidity <30% or ~75%, ozone ~100 ppb, α-pinene ~5 ppb, toluene ~45 ppb, and simulated solar ultra-violet light illumination with the typical levels in common atmospheric constituents and meteorological conditions. Large changes have been observed, e.g. UV fluorescence intensity dropped to be less than 1/10 of its initial value and the ratio of UV/visible fluo- rescence intensity flipped from 2 to ½ within 3 h. These changes could happen on a typical day in any city or suburban area. Recording data of the ageing processes measured here should be very useful in developing biosensors and monitoring air pollution.
age process, bioaerosol, environmental factors, fluorescence spectra, PCR signature, viability
 Rosenfeld, D., Sherwood, S., Wood, R. & Donner, L., Climate effects of aerosol-cloud interactions, Science, 343, pp. 379–380, 2014.
 Huang, R.J., Zhang, Y., Bozzetti, C. et al., High secondary aerosol contribution to particulate pollution during haze events in China, Nature, 514, pp. 218–222, 2014.
 Ariya, P.A., & Amyot, M., New directions: the role of bioaerosols in atmospheric chemistry and physics, Atmospheric Environments, 38, pp. 1231–1232, 2004.
 Fröhlich-Nowoisky, J., et al., Bioaerosols in the Earth system: climate, health, and ecosystem interactions, Atmospheric Research, 182 pp. 346–376, 2016.
 Pan, Y.L., Detection and characterization of biological and other organic-carbon aerosol particles in atmosphere using fluorescence, Journal of Quantitative Spectroscopy & Radiative Transfer, 150, pp. 12–35, 2015.
 Deguillaume, L., Leriche, M., Amato, P., et al., Microbiology and atmospheric processes: chemical interaction of primary biological aerosols, Biogeosciences, 5, pp. 1073–1084, 2008.
 May, K.R., Druett, H.A. & Packman, L.P., Toxicity of open air to a variety of microorganisms, Nature, 221, pp. 1146–1147, 1969.
 Cox, C.S., Hood, A.M. & Baxter, J., Method for comparing concentrations of the openair factor, Applied Microbiology, 26(4), pp. 640–642, 1973.
 Dennis-Smither, B.J., Marshall, F.H., Miles, R.E., et al., Volatility and oxidative aging of aqueous maleic acid aerosol droplets and the dependence on relative humidity, Journal of Physical Chemistry A, 118, pp. 5680–5691, 2014.
 Kanaani, H., Hargreaves, M., Ristovski, Z. & Morawska, L., Performance assessment of UVAPS: influence of fungal spore age and air exposure, Journal of Aerosol Science, 38(1), pp. 83–96, 2007.
 Ignatenko, A.V., Use of the method of tryptophan fluorescence to characterize disruptions of the structure of ozonized proteins, Journal of Applied Spectroscopy, 49(1), pp. 691–695, 1988.
 Fujimori, E., Changes induced by ozone and ultraviolet light in type I collagen. Bovine Achilles tendon collagen versus rat tail tendon collagen. Europe Journal of Biochemistry, 152(2), 299–306 (1985).
 Santarpia, J.L., Pan, Y.L., Hill, S.C., et al., Changes in fluorescence spectra of bioaerosols exposed to ozone in a laboratory reaction chamber to simulate atmospheric aging, Optics Express, 20(28), pp. 29867–29881, 2012.
 Pan, Y.L., Santarpia, J.L., Ratnesar-Shumate, S., et al., Effects of ozone and relative humidity on fluorescence spectra of octapeptide, Journal of Quantitative Spectroscopy & Radiative Transfer, 133, pp. 538–50, 2014.
 Ratnesar-Shumate, S., Pan, Y. L., Hill, S. C., et al., Fluorescence spectra and biological activity of aerosolized Bacillus spores and MS2 bacteriophage exposed to ozone at different relative humidities in a rotating drum, Journal of Quantitative Spectroscopy & Radiative Transfer, 153, pp. 13–28, 2015
 Lu, J., Gerke, T. L., Buse, H. Y. & Ashbolt, N. J., Development of an Escherichia coli K12-specific quantitative polymerase chain reaction assay and DNA isolation suited to biofilms associated with iron drinking water pipe, Journal of Water and Health, 12(4),pp. 763–771, 2014.