Acute effects of diesel emission from the urea selective catalytic reduction engine system on male rats

Abstract

Short-term inhalation experiments were performed using Fischer 344 rats exposed to emission from the urea selective catalytic reduction (SCR) diesel engine system to identify health effects and compare them to those of the conventional diesel engine system. Rats were exposed to high-, middle-, or low-concentration emission (dilution ratio 1:29, 1:290, or 1:580) or clean air (control) for 1, 3, or 7 days (6 h/day), under driving conditions at a speed of 1320 rpm and a torque of 840 Nm. For the high-concentration group, the major components of the urea SCR emission were 0.04 mg/m³ particulate matter (PM) and 0.78 ppm nitrogen dioxide (NO₂); those of the conventional emission were 0.95 mg/m³ PM and 0.31 ppm NO₂. The authors evaluated the respiratory effects of each emission on rats. Lymphocytes for 3-day exposure of both emissions significantly increased in bronchoalveolar lavage fluid, but there were slight differences. With an increase in potential antioxidant (PAO), 8-hydroxy-2’-deoxyguanosine for the urea SCR emission was significantly decreased, but that of the conventional emission was highest among all groups and did not show a response to PAO. In lungs, heme oxygenase (HO)-1 and tumor necrosis factor (TNF)-α mRNA expressions for the urea SCR emission showed a tendency to increase compared to those of the conventional emission. Thus, gene analysis results suggested that NO₂ from the urea SCR emission affected the expressions of mRNAs in lungs. However, as a whole, the results suggested that the health effects of the urea SCR emission might be less than the conventional emission on rats.

Keywords::

• Acute
• diesel
• F344
• lung
• rats
• SCR
• urea

Acknowledgments

The authors thank the members of the Health Effects Research Working Group (led by Prof. emeritus Jun Kagawa, MD, PhD, Tokyo Women’s Medical University, Japan) for technical advice on this research project. We are grateful to Ms. Kumiko Tamura and Ms. Naomi Muraki for technical assistance. We also thank a member of a chemical analysis team, an engine control team, and a breeding control team of experimental animals at JARI, for their technical assistances.

Declaration of interest

The authors report no conflicts of interest. This work was supported by a grant from the New Energy and Industrial Technology Development Organization, Japan.