(Adds Potash comment)
By Jonathan Stempel and Rod Nickel
Nov 6 (Reuters) - Potash Corp of Saskatchewan Inc agreed to spend more than $52 million on plant improvements and pay a $1.3 million civil penalty to resolve U.S. charges that it violated the Clean Air Act over the emission of harmful pollutants such as sulfur dioxide, U.S. authorities said.
Thursday's accord with the world's largest fertilizer producer includes a consent decree, and is the largest in the U.S. Department of Justice's effort to address Clean Air Act violations by sulfuric acid producers.
It resolves claims by the Justice Department and the U.S. Environmental Protection Agency that three Potash units built or modified several sulfuric acid plants in ways that allowed the emission of excess sulfur dioxide into nearby communities.
Potash spokesman Tom Pasztor said that while the company disagrees with the EPA's interpretation of the Clean Air Act, "we opted, rather than litigate, to work with them and other regulators to resolve this dispute."
Sulfur dioxide has been linked to respiratory and cardiovascular problems, including premature death, and contributes to acid rain, haze and smog.
The Potash units, AA Sulfuric Corp, PCS Nitrogen Fertilizer LP and White Springs Agricultural Chemicals Inc, agreed to spend about $50 million on pollution control measures and to install emissions monitors at eight sulfuric acid plants in Florida, North Carolina and Louisiana.
PCS Nitrogen also agreed to spend an estimated $2.5 million to $4 million to reduce ammonia and nitrogen oxide emissions at a nitric acid plant in Geismar, Louisiana.
Authorities said the changes would reduce harmful emissions by more than 13,000 tons a year, including 12,600 tons of sulfur dioxide.
The settlement "will ensure cleaner air for citizens across the Southeast and will send a strong signal to the industry that noncompliance has serious consequences," Sam Hirsch, acting assistant attorney general in the Justice Department's environment and natural resources unit, said in a statement.
Potash is based in Saskatoon, Saskatchewan.
Settlement papers were filed with the U.S. District Court in Baton Rouge, Louisiana. The accord requires court approval after a 30-day public comment period.
The case is U.S. et al v. PCS Nitrogen Fertilizer LP et al, U.S. District Court, Middle District of Louisiana, No. 14-00707. (Reporting by Jonathan Stempel in New York and Rod Nickel in Winnipeg; Editing by Diane Craft and James Dalgleish)