Abstract
Background
Diesel engine exhaust causes adverse health effects. Meanwhile, the impact of renewable diesel exhaust, such as hydrotreated vegetable oil (HVO), on human health is less known. Nineteen healthy volunteers were exposed to HVO exhaust for 3 h in a chamber with a double-blind, randomized setup. Exposure scenarios comprised of HVO exhaust from two modern non-road vehicles with 1) no aftertreatment system ('HVOPM+NOx' PM1: 93 µg m-3, EC: 54 µg m-3, NO: 3.4 ppm, NO2: 0.6 ppm), 2) an aftertreatment system containing a diesel oxidation catalyst and a diesel particulate filter ('HVONOx' PM1: ~ 1 µg m-3, NO: 2.0 ppm, NO2: 0.7 ppm) and 3) filtered air (FA) as control. The exposure concentrations were in line with current EU occupational exposure limits (OELs) of NO, NO2, formaldehyde, polycyclic aromatic hydrocarbons (PAHs), and the future OEL (2023) of elemental carbon (EC). The effect on nasal patency, pulmonary function, and self-rated symptoms were assessed. Calculated predicted lung deposition of HVO exhaust particles was compared to data from an earlier diesel exhaust study.
Results
The average total respiratory tract deposition of PM1 during HVOPM+NOx was 27 µg h-1. The estimated deposition fraction of HVO PM1 was 40-50% higher compared to diesel exhaust PM1 from an older vehicle (earlier study), due to smaller particle sizes of the HVOPM+NOx exhaust. Compared to FA, exposure to HVOPM+NOx and HVONOx caused higher incidence of self-reported symptoms (78%, 63%, respectively, vs. 28% for FA, p < 0.03). Especially, exposure to HVOPM+NOx showed 40-50% higher eye and throat irritation symptoms. Compared to FA, a decrement in nasal patency was found for the HVONOx exposures (- 18.1, 95% CI: - 27.3 to - 8.8 L min-1, p < 0.001), and for the HVOPM+NOx (- 7.4 (- 15.6 to 0.8) L min-1, p = 0.08). Overall, no clinically significant change was indicated in the pulmonary function tests (spirometry, peak expiratory flow, forced oscillation technique).
Conclusion
Short-term exposure to HVO exhaust concentrations corresponding to EU OELs for one workday did not cause adverse pulmonary function changes in healthy subjects. However, an increase in self-rated mild irritation symptoms, and mild decrease in nasal patency after both HVO exposures, may indicate irritative effects from exposure to HVO exhaust from modern non-road vehicles, with and without aftertreatment systems.
