[Lockbox]

Portland cement production produces 2% of Total U.S mercury emissions.

Source: U.S. EPA, Office of Air Quality Planning and Standards. 1999 National Emissions Inventory for Hazardous Air Pollutants. http://www.epa.gov/ttn/chief/net/1999inventory.html#final3haps.

[trebb]

Portland cement production produces 2% of Total U.S mercury emissions.

Now the questions are:
- What is the total?
- What is considered hazardous 9pre the latest EPA edicts)?

Standing alone, the 2% stat is meaningless.