The fine particles are mostly made from gases. There are four major origins for that gases which are responsible for these particles: rock (vaporized during combustion or casting), carbon from combustion, organic carbon, sulfates and nitrates. Take sulphur dioxide. It is created during engine combustion, but when it climbs into the atmosphere and mixes with rain it will become sulphuric acid. We all probably know very well what that will do- since it is highly corrosive and dangerous in concentration. The practical options for energy range from the standard fuels, natural gas, petroleum (or oil), and coal. Fossil fuels are referred to as nonrenewable energy sources because, once used, they are gone. Scientists are exploring the practicality of other sources called renewable energizes. These include sun, wind, geothermal, water, and biomass. The renewable power resources are very important in long range energy planning simply because they will not be depleted.