|Fig. 1: Coal has toxic chemicals with relatively low levels of radioactivity. (Source: Wikimedia Commons)|
Amongst the fossil fuels, coal is leading source of energy used by everyone in the world because of its low cost and efficiency. However, if coal is going to be used as the main energy source going into the future the public must consider the pollution coal causes the environment. Specifically, what are the impacts of the radiation emitted from the energy source on the environment around it? And are people exposed to the radioactivity emitted from coal in danger?
When coal is processed in a plant, it emits several chemicals which are toxic to the environment such as arsenic, cadmium, mercury, and the radioactive elements uranium, thorium and their decay daughers (see Fig. 1).  Just in the year 1974 there were 1400 tons of uranium emitted from coal processing plants into the United States.  But studies have proven that lower grades of coal contain higher levels of uranium and thorium. Combined with coal cleaning technologies such as Coal Scrubbers which remove mercury contents from the coal, the amount of radiation emitted from coal firing plants is not significant enough to cause serious harm to the environment. But lower grades of coal can contain high amounts of thorium, uranium and mercury levels vary typically up to 10ppm and exceptionally to as high as the order of 1000ppm.  One of the environmental hazards from producing coal is its ash. Ash is the inorganic material left after all the combustible matter has been burned off.  The problem with coal ash is how to safely dispose of it without it harming the environment because it contains toxic chemicals such as lead, ammonia, uranium, thorium and actinium. Coal ash releases particles from these dangerous chemicals into the atmosphere that are harmful to people inhaling them. 
Coal radioactivity is potentially dangerous to man (depending on the quality of the coal) and the scrubbers that have been engineered since the early 2000s have brought mercury levels down (as well as other chemical toxins) and made the process of burning coal more environmentally friendly. Ultimately, the radioactivity levels coal emits are low and not alarmingly significant to man's health but they still pose a threat that should not be ignored.
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 B. G. Miller, Coal Energy Systems (Academic Press, 2004).
 J. Tadmor, "Radioactivity From Coal-Fired Power Plants: A Review," J. Environ. Radioactiv. 4, 177 (1986).