Methane is the simplest of the hydrocarbons. It is one carbon atom surrounded by four hydrogen atoms. It's description is reminiscent of iocaine powder: odorless, colorless, and tasteless. It poses no known health risks other than the possibility of it displacing oxygen, and its tendency to burst into flames at high enough concentrations (between 5 and 15%).
It can even dissolve in water. The water becomes cloudy with the dissolved methane, but is safe to drink. Just so long as you don't go swallowing lit matches.
And a certain community in Colorado has enough methane in their groundwater, thanks to a nearby methane pumping field, that they can set their tap water (pumped in from a groundwater well) on fire as seen in this video.