Let's face facts. Coal ash contains some pollutants. That's the bad news. The good news is that it a very small amount. The problem is that when you have a very large amount of ash, like the ash residue from a coal fired power plant. Total up all the contaminants and there is reason to be concerned. But, for you, me, your fathers factory, it isn't an issue due to the factor of scale. There just wasn't enough coal burned to give enough of a contamination level to be concerned. Coal fired power plants burn millions of tons of coal per year. If we burn 5 -6 tons of coal per year, it would tale us 200-300,000 years to amass a pile of ashes to give a similar result. At 100 tons per year, which might be a good starting point to figure your fathers factory's use, would take 10,000 years for the same thing. At that level of ash, there is a problem. Now add to the mix that the level of contamination is just big enough to be measureable with a pile of ash that big. The thing that cracks me up most is the same people that are claiming coal is such an issue are the same ones who have been specifying coal fly ash be added to all municipal/ government contracts for concrete. To make the concrete more durable and strong. Does that mean that all the goverment agencies are contaminated by their own hand????????