As lingering smog blanketed China's northern and central regions for a fourth consecutive day on Sunday, its influence has been felt in people's schedules, as is evidenced by bustling museums, crowded hospital respiratory departments and less cheerful parks.

On Sunday morning, the National Meteorological Center issued a yellow alert - the second highest - with smog expected to persist in Beijing and Tianjin, as well as parts of Hebei, Shandong, Henan, Shanxi and Shaanxi provinces. The authority forecast that smog, which shrouded 15 percent of China, will not ease until Thursday when a cold front is expected to bring wind.

Families with children are going less often to parks for weekend outings.