Lung function and self-rated symptoms in healthy volunteers after exposure to hydrotreated vegetable oil (HVO) exhaust with and without particles

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 mu g-m(-3), EC: 54 mu g-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: similar to 1 mu g-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 -HVO(PM+ NO)x was 27 mu g-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.

Automated summary

This study investigated the health effects of exposure to renewable diesel exhaust. The results showed that exposure to HVO exhaust can lead to an increase in self-reported irritation symptoms and a slight decrease in nasal patency.