While the current Clean Air Act has played a role in significantly improving some of these issues, additional reductions in the emissions of SO2, NOx, and mercury are necessary to address persistent public health and environmental problems.
The Clean Air Act did nothing to improve the environment.
mnli hypothesis: The Clean Air Act did nothing to improve the environment. premise: While the current Clean Air Act has played a role in significantly improving some of these issues, additional reductions in the emissions of SO2, NOx, and mercury are necessary to address persistent public health and environmental problems.