May – Parts Per Billion (Part 2 of the Coal Ash Series)

When you start talking about disposing of coal ash, you quickly find yourself talking about the very complicated subject of potential health risks of relatively low concentrations of naturally occurring materials.

 The principal components of coal ash are similar to sand: roughly 50 percent silica, 25 percent iron oxide, 20 percent alumina, and 5 percent calcium. That said, coal ash (like coal itself) contains trace amounts of metals and minerals, including mercury, lead and arsenic.

New technology allows us to detect very low concentrations, down to parts per billion or 0.0000001 percent. As an example, detecting one part per billion is the equivalent of detecting one drop of any fluid mixed in a swimming pool full of water.

There are many potential examples but let’s start with arsenic. Most everyone knows that in high concentrations, arsenic is toxic. Most folks don’t know that low levels of arsenic are fairly common naturally. So at what level does arsenic become a health risk?

 Back in 1975, the Environmental Protection Agency developed a standard for public water systems that required an arsenic concentration of less than 50 parts per billion. In 2000, the standard was changed to less than 10 parts per billion. In some states, more than 30 percent of public water systems failed to meet the new standard.

One of the concerns expressed by environmental groups is that materials (like arsenic) that are found in higher trace amounts in coal ash would result in higher trace amounts in nearby groundwater. Recently, testing near a Duke Energy coal ash site found most, but not all, of the water samples tested for arsenic were lower than 10 parts per billion. So why were some higher than others? How much is natural and how much is from coal ash? How big a problem is this?

 As we discussed last month, it really becomes a public policy issue of how much money should we spend to attempt to reduce the health risks from NC’s historical approach to coal ash disposal? Particularly when that historical approach is still allowed by the EPA and is still used in nearly every other state.

The current solution (the result of state legislation) spends about $5 billion to change to a new approach that treats some of the 100 million tons of coal ash in NC more like hazardous waste.

Questions or comments about coal ash disposal in NC?  Please let us know at