Natural gas is considered a relatively clean burning fossil fuel as it results in fewer emissions of air pollutants and carbon dioxide (CO2) than burning coal or petroleum products, however the production and use of natural gas has some environmental and safety concerns. These include all of the following except: O Methane, the largest component of natural gas, is a strong greenhouse gas O Natural gas naturally contains mercaptan, a foul-smelling gas that can cause nose, throat, and lung irritation O Natural gas production can produce large volumes of contaminated water Fracking, a process that is used to open up natural gas reserves, can cause small earthquakes.