Toxicological assessment of particulate and unregulated emissions from methanol and gasoline fueled reactivity controlled compression ignition engines

Reactivity-controlled compression ignition (RCCI) engines have emerged as a promising technology for achieving higher thermal efficiency while minimizing particulate (PM) and NOx emissions. However, concerns arise from the unregulated emissions of RCCI engines due to low temperature and premixed combustion. These unregulated species may condense on formed PM, potentially elevating the toxicity potential. This study investigates the toxicity potential of PM and unregulated emissions from RCCI engines employing gasoline and methanol as low-reactivity fuel and diesel as a high-reactivity fuel. In-vitro cytotoxicity tests with the BEAS-2B (human epithelial cell line) are conducted to characterize PM toxicity. A lung compartment model is used to estimate the particle risk, focusing on lung retention of PM particles emitted. Cancer risk potential is calculated for formaldehyde and acetaldehyde, constituents of unregulated emissions, to evaluate their impact on human health. Environmental risk assessment includes estimation of global warming potential, acidification potential, eutrophication potential, and ozone-forming potentials equivalents. Results indicate that with premixing ratio increases, unregulated emissions, cancer risk, cytotoxicity, and adverse environmental impacts increase. Methanol Diesel-RCCI engine particles exhibit lower lung retention than Gasoline Diesel-RCCI under all tested conditions. Methanol reduces cytotoxicity and particle inhalation toxicity at medium engine load. This study offers insights into the complex relationship between fuel, operating parameters, and the toxicity potential of emissions from RCCI engines.