Chemistry

A Fiery By-Product

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Science  10 Jun 2011:
Vol. 332, Issue 6035, pp. 1243
DOI: 10.1126/science.332.6035.1243-b

Fire has alternately salvaged and savaged human beings since the dawn of civilization. It's rather remarkable, after so much time, that the combustion process still holds mysteries for chemists to probe. One such mystery is unraveling the extraordinarily complex composition of the smoke-borne by-products that accompany release of the primary products, water and carbon dioxide. Among these by-products are a range of highly reactive small molecules that may cause physiological damage upon inhalation. Roberts et al. chart the abundance of one such molecule, isocyanic acid, by systematically probing the product stream of controlled laboratory biomass fires using a mass spectrometric technique especially sensitive to acids (negative-ion proton-transfer chemical ionization). In addition to documenting concentrations from these laboratory experiments of 600 parts per billion by volume, the authors detect hundreds of parts per trillion of the compound in urban Los Angeles air and in Boulder, Colorado, air after a wildfire. They furthermore estimate significant aqueous solubility of the compound at physiological pH, based on a Henry's Law partitioning measurement. Because previous studies have implicated isocyanic acid and its conjugate base in inflammation effects associated with protein carbamylation, the authors urge further study of the compound's exposure impact.

Proc. Natl. Acad. Sci. U.S.A. 108, 8966 (2011).

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