As stated that not that unusual. At 45 a man has a 0.3285% chance of death per year at 55 that bumps to 0.7766%. https://www.ssa.gov/oact/STATS/table4c6.html 3 deaths per year out of 900 works out to 0.3333%. So, depending on the age of workers that’s anything for fairly normal to low.
As time goes on, more workers are experiencing health effects that might be due to their years of work cleaning up the spill:
>...More than 30 cleanup workers at the December 2008 TVA Kingston Fossil Fuel Power Plant coal ash spill are dead and at least 200 are sick or dying — all with common ailments known to be caused by long-term exposure to arsenic, radium and the host of other toxins and metals found in the ash.
As stated that not that unusual. At 45 a man has a 0.3285% chance of death per year at 55 that bumps to 0.7766%. https://www.ssa.gov/oact/STATS/table4c6.html 3 deaths per year out of 900 works out to 0.3333%. So, depending on the age of workers that’s anything for fairly normal to low.