Airborne particle emissions from 2-and 4-stroke outboard marine engines: Polycyclic aromatic hydrocarbon and bioassay analyses

Outboard and personal watercraft (marine) engines are re ported to be significant sources of air pollutants accounting for approximately 141 tons of reactive hydrocarbons emitted per day in California alone, far example. The emissions from 2-stroke marine engines have traditionally been investigated for the regulated pollutants hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx). However, very few studies have been published on airborne particulate matter (PM) and PM-associated unregulated toxic air pollutants emitted during the normal operation of the engine in the water. In the current investigation, we report on the airborne PM emissions from two types of 2-stroke marine engines (carbureted and direct fuel-injected models) and a 4-stroke engine (carbureted) that were operated in water at a special emissions testing facility. The engines were from 1998 or 1999 model years and were rated at 90 hp (maximum). The sampled airborne PM was analyzed for polycyclic aromatic hydrocarbons (PAHs) using gas chromatography/ mass spectrometric (GC/MS) analyses and further tested for genotoxic (DNA-damaging) activity using a microsuspension Salmonella bioassay procedure. The particle emissions were <0.47, 1.95, and 9.23 g/67-min test procedure for the 4-stroke carbureted (4-Strk/Cb), 2-stroke direct fuel-injected (2-strk/FI), and 2-stroke carbureted (2-Strk/Cb) engines, respectively. The total particle-associated PAH emissions followed a different order with the 4-Strk/Cb, 2-Strk/ FI, and 2-Strk/Cb engines having emissions of < 27, 3600, and 1900 mu g/test, respectively. The emissions for the genotoxic activity followed the order of particle emissions with relative ratios of approximately 1:30:45 for the 4-Strk/ Cb, 2-Strk/FI, and 2-Strk/Cb, respectively. The 2-stroke engines overall, including the direct fuel-injected model that meets U.S. Federal HC and NOx emission standards for the year 2006, had considerably higher emissions of PM, PAHs, and genotoxic activity than the 4-stroke engine.