21.   Polluted air generated by power plants in those states drifts into the park and causes serious ozone problems there each summer.

22.   Rosenfeld selected study sites where pollution tracks were somewhat isolated in a broader region of less polluted air, and thus stood out clearly.

23.   The central high ground was occupied by a church whose steeple thrust up into the polluted air.

24.   The new rules would spell out how cities would be categorized according to the severity of their polluted air and establish timetables for cleaning up their dirty air.

25.   The program is implemented in the wintertime when cold weather traps polluted air and makes breathing an even more unpleasant task.

26.   The resulting traffic has led to gridlock, polluted air and high shipping costs for companies that rely on trucks to deliver their goods.

27.   Throw in the relatively still weather, and conditions are ripe for an inversion that traps polluted air close to the ground.

28.   Unlike polluted air and contaminated water, global warming is not a local problem that can be seen or felt.

29.   Authorities in neighboring Germany were alerted to the fire as gusting winds were driving polluted air across the border, CTK said.