In-vehicle exposure of carbon monoxide, nitrogen dioxide and total volatile organic compounds from ethanol versus gasoline fuel

Alternative fuels, such as ethanol-based fuels (E85), have attracted attention as promising approaches for reducing emissions from on-road mobile sources. However, the in-vehicle exposure to pollutants when using E85 has not yet been addressed. This study aims to examine the contribution of E85 to in-vehicle exposure to carbon monoxide (CO), nitrogen dioxide (NO2) and total volatile organic compounds (TVOCs) under different scenarios. A one-compartment mass-balance model incorporating outdoor concentration, infiltration, makeup and recirculated air exchange rate (λ), volume of the vehicle (V) and the internal emissions source (E) is developed to obtain the in-vehicle concentrations. The intake fraction (pollutant mass inhaled by an exposed individual per unit release of pollutant) was used to estimate the mass emission rate. The results show a small increase in interior CO and TVOC concentrations for vehicles fueled by E85 compared to those fueled by gasoline, mainly due to the increase in mass emission rate resulting from the exhaust system when E85 is burned. The in-vehicle concentration of CO and TVOCs for ethanol-fueled vehicles ranged from 6.2 to 42.2 mg/m3 (5.4–36.2 ppm) and from 67.9 to 1851 (µg/m3), respectively. The maximum increases in CO and TVOC concentrations were 2 (mg/m3) and 303.3 (µg/m3), observed when the air exchange rate was 2 h−1 and the vehicle was stationary. Despite the increase in CO and TVOC levels, the penetration of E85 positively impacted in-vehicle NO2 concentrations, with a maximum reduction of 293 (µg/m3). The study also developed a mathematical model to estimate the intake fraction under different scenarios for both E85 and gasoline fuels. The difference in intake fraction of CO is estimated to be in the range (2–1) (mg of pollution is inhaled per kg emitted). The difference in intake fraction of NO2 and TVOCs ranged from 10 to 2 and from 5 to 1, respectively.