AK Steel Holding Corporation or otherwise known as Armco is another major player in the American Steel Industry. This company was founded in 1900 and was formerly known as the American Rolling Mills Corporation. Currently, it has its main office in West Chester, Ohio after moving from Middletown, Ohio, back in 2007.

Most of the products that AK Steel is known for include stainless or electrical steels,  carbon, cold rolled aluminum as well as coated stainless steel mostly for automakers. As a matter of fact the Armco barrier, which is installed on many auto-racing tracks, is one of its well-known products. These barriers are commonly known as Armco.

This company ranked 16th on the the Toxic 100 because their air releases was estimated at 328,418 pounds which made them garner a Toxic Score of 133,591. The EPA or Environmental Protection Agency already released an Emergency Order pursuant to the Safe Drinking Water Act and this was issued to the Butler Works of AK Steel that is located in Pennsylvania. According to the EPA,  Butler Works has released nitrate/nitrite compounds into the Connoquenessing Creek which happens to be one of the water sources of the Borough of Zelenople in the year 2000. Furthermore, the US EPA together with the Justice Department demanded that AK Steel Holding settle their environmental violations which included violations against the Clean Air Act and Clean Water Act where the company failed to dispose the hexavalent chromium properly. The company agreed to settle its violations with the sum of $1.2 million.