Hydrogen Cyanide Exhaust Emissions from In-Use Motor Vehicles

Abstract

Motor vehicle exhaust emissions are known to contain hydrogen cyanide (HCN), but emission rate data are scarce and, in the case of idling vehicles, date back over 20 years. For the first time, vehicular HCN exhaust emissions from a modern, in-use fleet at idle have been measured. The 14 tested light duty motor vehicles were operating at idle as these conditions are associated with the highest risk exposure scenarios (i.e., enclosed spaces). Vehicular HCN was detected in 89% of the sampled exhaust streams and did not correlate with instantaneous air-fuel-ratio or with any single, coemitted pollutant. However, a moderate correlation between HCN emissions and the product of carbon monoxide and nitric oxide emissions was observed under cold-start conditions. Fleet average, cold-start, undiluted HCN emissions were 105 +/- 97 ppbV (maximum: 278 ppbV), whereas corresponding emissions from vehicles operating under stabilized conditions were 79 +/- 71 ppbV (maximum: 245 ppbV); mean idle fleet HCN emission rates were 39 +/- 35 and 21 +/- 18 microg-min(-1) for cold-start and stabilized vehicles, respectively. The significance of these results is discussed in terms of HCN emissions inventories in the South Coast Air Basin of California and of health risks due to exposure to vehicular HCN.

Long-path measurements of pollutants and micrometeorology over Highway 401 in Toronto

“…EPA, 2010b). HCN has been reported previously in vehicle exhaust (Bradow and Stump, 1977;Keirns and Holt, 1978;Cadle et al, 1979;Garbe, 1979, 1980;Karlsson, 2004;Baum et al, 2007;Moussa et al, 2016). It may form over the catalytic converters in the vehicle emission control systems (Voorhoeve et al, 1975;Suárez and Löffler, 1986;Baum et al, 2007).…”

Hydrogen cyanide in the upper troposphere: GEM-AQ simulation and comparison with ACE-FTS observations

“…Small amounts of HCN (∼0.01 Tg N yr −1 ) are released into the atmosphere from gold mining (Korte and Coulston, 1998). HCN exhaust emissions from vehicles are small (Baum et al, 2007;Karlsson, 2004). Li et al (2003) argued that enhanced HCN observed in the Chinese urban plumes during TRACE-P could indicate an HCN source from hard coal burning.…”

Background levels and diurnal variations of hydrogen cyanide in breath and emitted from skin

“…Hydrogen cyanide (HCN) is a colourless, highly poisonous gas released to the atmosphere mainly by anthropogenic sources such as biomass burning [1], industrial processes and vehicle exhausts [2], but also found in cigarette smoke [3]. Mean mixing ratios of HCN in the unpolluted lower troposphere are typically around 200 parts per trillion by volume (pptv) [1].…”