Chloromethane emissions in human breath

Abstract Chloromethane (CH 3 Cl), currently the most abundant chlorinated organic compound in the atmosphere at around ~ 550 parts per trillion by volume (pptv), is considered responsible for approximately 16% of halogen-catalyzed stratospheric ozone destruction. Although emissions of CH 3 Cl are known to occur from animals such as cattle, formation and release of CH 3 Cl from humans has not yet been reported. In this study a pre-concentration unit coupled with a gas chromatograph directly linked to a mass spectrometer was used to precisely measure concentrations of CH 3 Cl at the pptv level in exhaled breath from 31 human subjects with ages ranging from 3 to 87 years. We provide analytical evidence that all subjects exhaled CH 3 Cl in the range of 2.5 to 33 parts per billion by volume, levels which significantly exceed those of inhaled air by a factor of up to 60. If the mean of these emissions was typical for the world's population, then the global source of atmospheric CH 3 Cl from humans would be around 0.66 Gg yr − 1 (0.33 to 1.48 Gg yr − 1 ), which is less than 0.03% of the total annual global atmospheric source strength. The observed endogenous formation of a chlorinated methyl group in humans might be of interest to biochemists and medical scientists as CH 3 Cl is also known to be a potent methylating agent and thus, could be an important target compound in future medical research diagnostic programs.