The effects of nanoadditives on the performance and emission characteristics of spark-ignition gasoline engines: a critical review with a focus on health impacts

Gasoline is currently the main fuel of choice in many cities worldwide, and hence, the consequent exposure to its emissions, i.e., CO, NO_X, unreacted hydrocarbons, particulate matters, lead, sulfur dioxide, and ozone, is inevitable. Among the various solutions put forth to mitigate the toxic gasoline-related air pollution, while improving fuel performance at the same time, is the application of nanoparticles. Considering the above, the present paper aims to review and critically discuss the improvements made in engine performance and exhaust emission parameters by adding nanosized fuel additives in gasoline. Overall, the addition of fuel nanoadditives enhances the thermo-physical properties of the fuel and improves combustion characteristics. Moreover, the inclusion of the fuel nanoadditives generally results in early combustion and shortened ignition delay. In more detail, the optimum quantity of fuel nanoadditives is associated with improvements in ignition characteristics and reductions in exhaust emissions. The present work also scrutinizes the adverse health effects of various gasoline-related emissions. Finally, possible mechanisms underlying the improvements in gasoline properties and its combustion in the presence of nanoadditives are also reviewed and discussed.