WASHINGTON, Oct 25 (Reuters) - Engine manufacturer Navistar International Corp will pay a $52 million civil penalty and has agreed to prevent at least 10,000 tons of oxides of nitrogen (NOx) emissions in a settlement with the U.S. Justice Department over Clean Air Act violations. The Justice Department said on Monday that Illinois-based Navistar, which was acquired by Volkswagen"s (VOWG_p.DE) Traton (8TRA.DE) truck unit for $3.7 billion in July, illegally introduced into commerce heavy-duty diesel engines not authorized by Environmental Protection Agency emissions rules. In 2015, the United States filed suit against Navistar over the engines. Navistar must purchase and destroy enough older diesel engines to prevent 10,000 tons of future NOx emissions, the Justice Department said, and forfeit its current NOx credits. Navistar said it had signed "a definitive settlement agreement" with the Justice Department and the EPA. "Navistar is pleased to put this legacy issue behind us and eager to focus on transportation solutions for the future," the company said. The Justice Department alleged that in 2010, after lower emission standards went into effect, Navistar introduced into commerce 7,749 diesel engines that did not meet the lower emission standards. The Justice Department lodged a proposed consent decree outlining the settlement terms, saying Navistar can destroy diesel engines used to power heavy-duty diesel "trucks, transit, intercity, or school buses, or any other on-highway heavy duty diesel vehicles" to prevent future emissions. A U.S. court held that the Navistar engines were in fact model-year 2010 engines and required to be covered by a 2010 certificate demonstrating compliance with the lower emission requirements, the Justice Department said. Acting EPA Assistant Administrator Larry Starfield said "older diesel engines without modern emissions controls emit significant amounts of air pollution that harms people’s health and takes years off people’s lives." Navistar"s mitigation of NOx emissions must take into consideration "geographic diversity and benefits to communities that are overburdened by air pollution," Starfield added.