This is because of two reasons. 1) Truly clean coal technologies are expensive - more expensive than solar powered or wind power. So practically nobody uses it. and
2) Coal companies - more than any other power industry - have found ways to avoid complying with regulations. Specifically, they campaigned hard to allow existing plants to go unregulated until after they 'modernized' in the normal course of time. Then they refused to modernize - for the past 60 years.
Tuna fish is one of the healthiest cheap foods you can eat - or rather would be EXCEPT for the mercury in it which comes from coal. Coal burning plants are more radioactive than nuclear power plants because small bits of thorium are in coal and when you burn it, it gets wafted up into the air and settles around the coal plant. Not to mention the acid rain and the green house gas issues.