For one thing, coal mining is one of the most water-intensive industries, often requiring 2.5 tons of water for every ton of coal produced, creating three to six billion tons of water waste per year. This can affect the water table by dramatically increasing its PH and greatly altering groundwater levels (due to the amount of water needed to refine coal). Additionally, mining releases burning coal into the air which combines with oxygen to form SO2. This SO2 can then mix with moisture in the air to form acid rain which can be harmful to the environment. Of course, coal mining not only affects the environment around us, but can also be disastrous for coal mine workers. One of the worst events in history occurred in 1970 in West Virginia, when a coal dust explosion at the Upper Big Branch mine killed 29 to 31 workers. The company that owned the mine was forced to sell it to a competitor and pay $209. After this event, coal prices skyrocketed for over 10 years, before falling again (shown by the graph on the right). Other events like this have occurred around the world and always represent a constant threat lurking in the back of every miner