Have you heard of Carbon-14 dating? Of course you did. All things containing carbon that we interact with contain a bit of C14 ( * ) . Including the things we eat. Yes, we ingest every single day, and we inhale every single second radioactive things. If you eat one banana a day you get a yearly dose of 2.6 millirems [1]. That one comes from Potasium-40, but it's the same idea.
So the dose SA was talking about, 18 millirems/year, was equivalent to 7 bananas a day.
Here's a more scientific study than the SA articles [2].
"The radiation hazard from airborne emissions of coal-fired power plants was evaluated in a series of studies conducted from 1975–1985. These studies concluded that the maximum radiation dose to an individual living within 1 km of a modern power plant is equivalent to a minor, perhaps 1 to 5 percent, increase above the radiation from the natural environment. For the average citizen, the radiation dose from coal burning is considerably less."
( * ) Fun fact: fossil fuels contain essentially no C14 (the half-life of C14 of about 6000 years is many times smaller than the age of the fossil fuels). This is used in testing alcoholic beverages. Natural alcohol (obtained via fermentation) has the usual ratio of C14/C12 and emits a recognizable radiation spectrum. Alcohol industrially produced from petroleum is much cheaper. It does not have C14, so this is how you can detect if an unscrupulous producer uses synthetic ethyl alcohol (which is a dangerous because it has traces of methanol and benzene).
[1] https://newatlas.com/radiation-explained-food-sources-danger...
"Even at low levels, these isotopes represent health hazards as they can accumulate in the human body (eg, in lungs), gradually enter the blood circulation, and deposit in bones and teeth to remain for life."
http://www.ncmedicaljournal.com/content/79/5/289.full
So there are three things that you really miss: doses are essentially permament (due to half-life), cumulative and localized in small areas of body.
And you miss problem of coal ash waste which needs to be stored and there is plenty of it.
Elephant Foot and natural background radiation are outside of your body. Coal ash gets inside. There is profound difference in effect - skin and outer layers of body cannot shield the rest.