The company and its environmental control manager Mark Kamholz faced 19 charges of violating the Clean Air Act. A jury convicted them on 11 counts of the Clean Air Act as well as three other violations. Kamholz was also convicted of obstruction of justice for trying to hide a bleeder valve from inspectors.
The government charged Tonawanda Coke with uncontrolled releases of benzene and ammonia.
The EPA says excessive benzene exposure is known to cause cancer.
The company was also accused of failing properly handling coal tar sludge and maintaining pipes and storage tanks which can leak polluted runoff into the Niagara River.