The concentration of airborne particulate matter has a well-documented correlation with people’s health. The chemical composition of the particles is less well studied but must also play a role as many diseases are associated with occupations involving the specific dusts breathed by workers, such as silicosis or asbestosis, and black lung disease from coal dust. Single-particle studies to determine composition by IR microscopy are hampered by scattering effects and low intensity.

Dust particles with diameters that enable them to enter the lungs have been captured by James Coe and co-workers, Ohio State University, USA, in plasmonic metal films with 5 μm square holes. This allowed the recording of scatter-free IR absorption spectra of high intensity. The team built up a library of 63 dust particles found in their lab. The most common component in the particles was organic matter, followed by quartz. Carbonates and gypsum were also present in small amounts.

This technique, and the dust library, could be used not only by researchers in public health, but also in astronomy, geology, environmental science, and atmospheric science.

• Scatter-Free IR Absorption Spectra of Individual, 3–5 μm, Airborne Dust Particles Using Plasmonic Metal Microarrays: A Library of 63 Spectra
  K. E. Cilwa, M. McCormack, M. Lew, C. Robitaille, L. Corwin, M. A. Malone, and J. V. Coe
  J. Phys. Chem. C 2011, 115(34), 16910–16919.
  DOI: 10.1021/jp205383h