In 2018, mercury emission levels from coal-fired power plants will be reduced to 26 tons, a reduction of almost 70 percent of 1999 levels. It’s hard to envision “tons” of mercury discharged into the atmosphere, so let’s try and put some perspective on the issue. In the grand scheme of power plant emissions, mercury is an extremely small portion. Let’s use an analogy with some things that you can picture … ping-pong balls and the Houston Astrodome. We’ll use white ping-pong balls to represent the emmisions from a power plant (called flue gas molecules) and red ping-pong balls to represent mercury molecules.

OK…Let’s Fill the Houston Astrodome with White Flue-Gas Ping-Pong Balls!

It will take about 27 BILLION white ping-pong balls to completely fill the Houston Astrodome to the top!

Let’s throw 15 of the red ping-pong balls in among the 27 billion white flue gas ping-pong balls.

15 red among 27 billion white ping-pong balls. 
That’s a pretty small amount in the grand scheme of …flue gas.