Washington, D.C., residents and the millions of visitors who attended America 250 celebrations on the National Mall have been advised to limit outdoor activity following a rare "Purple" air quality alert — the second-worst category on the federal Air Quality Index — triggered by a convergence of record-breaking heat and smoke from the largest fireworks display in American history.
The Metropolitan Washington Council of Governments issued the purple alert covering Washington, D.C., and parts of northern Virginia. Purple on the EPA's Air Quality Index represents "Very Unhealthy" conditions — a level at which the EPA recommends that everyone, including healthy adults, reduce prolonged or heavy outdoor exertion.
