Cellular Responses to Biodiesel and Diesel Exhaust from a Marine Engine

Marine vessels are a major source of air pollution near ports, due to lack of regulations and aftertreatment equipment.

The sector accounts for 3% of GHGs, switching from fossil diesel to renewable alternatives such as biodiesel can reduce carbon footprint. Despite climate benefits, switching to biodiesel does not necessarily mean “safer for health”. Engine operating mode strongly shapes emissions. Low-load conditions such as idling and cold starts often increase incomplete combustion, and the particle and gas mixture can differ from the emission at high-loads.

While many studies quantify regulated pollutants and particulate mass, fewer directly test how real-world marine exhaust affects human health under realistic operating conditions, especially when using biodiesel as fuel.

Here, we conducted field studies on a working barge. The engine used in this study is built in 2019, a medium-speed, 4- stroke, inline 6-cylinder, turbocharged diesel engine with a rated power output of 1920 kW and a rated speed of 750 rpm. Briefly, the exhaust from the marine engine was diluted approximately 12 times and was kept as constant as possible in field. Particle size distribution was measured by FMPS; organic carbon mass and speciation was measured by AMS; and black carbon concentration was measured by PAX. We used Cultex, an air–liquid interface cellular exposure system, to expose A549 cells, representing lung epithelial region, to the diluted exhaust for 30 minutes under multiple engine loads (cold-start idling, steady-state idling, and high-speed cruising) using both diesel and biodiesel as fuel. Cell viability, cytotoxicity and inflammation were investigated with MTT, LDH, and ELISA IL-8 assay, respectively. We found that idling conditions generally posed the higher health impact: cold-start idling when using diesel caused most cell death, whereas steady-state idling when using biodiesel was the most cytotoxic. Cold-start idling, whether using diesel or biodiesel caused comparably high inflammation. These cell exposure results help define which combinations of fuel and operating mode cause more toxicity at cellular level and provide guidance upon fuel-switching.