The document discusses the negative impacts of carbon-based fuels on human health and the environment. It notes that vehicle emissions contain pollutants like carbon monoxide, nitrogen oxides, sulfur oxides, and particulate matter which can cause cancer, respiratory illnesses, and other health problems. These emissions also harm the environment. The document then provides an overview of various alternative fuels like propane, natural gas, ethanol, biodiesel, and renewable diesel that can be used instead of carbon-based fuels to reduce emissions. It also discusses various laws and regulations enacted over time to limit vehicle emissions and encourage the use of cleaner alternative fuels.