Scientists are beginning to blame local forests and pollutants blown in from overseas for the fact that concentrations of ground-level ozone-and its accompanying smog-have not declined during the past 10 years in the United States, despite cuts in ozone precursors. Thus, national smog-fighting regulations may actually be 'doing a better job than they have been given credit for, but measurably reducing ozone levels may require international efforts and rethinking forestry management.
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