Pollution lingers as Olympic Games near

Visitors take photos from the Drum Tower as heavy smog shrouds the Houhai Lake area in Beijing.  (Mark Ralston / AFP/Getty Images)

Traffic rolls past the smog-shrouded Tiananmen Gate in Beijing.  (Mark Ralston / AFP/Getty Images)

Traffic passes an Olympics countdown clock in Beijing.  (Frederic J. Brown / AFP/Getty Images)

Construction workers erect scaffolding for an Olympics exhibit in Beijing. The city is putting final touches on Olympic venues, although pollution worries and questions over media freedom remain.  (Oded Balilty / Associated Press)

Heavy smog and traffic remain the norm in Beijing. Smog is a major concern for the upcoming Olympic Games.  (Adrian Bradshaw / EPA)

Visitors peer through the smog near the National Stadium in Beijing.  (Peter Parks / AFP/Getty Images)

An officer guards the Olympic Green with the Water Cube, left, and the National Stadium barely visible through the smog.  (Peter Parks / AFP/Getty Images)

China’s National Stadium, known as the Bird’s Nest, is seen under polluted skies a month before the opening of the Olympic Games.  (Greg Baker / Associated Press)

Visitors view the National Stadium, known as the Bird’s Nest.  (Greg Baker / Associated Press)

Visitors pose in front of National Stadium in Beijing.  (Greg Baker / Associated Press)

Volunteers attend the opening of the Beijing Olympics Main Press Center, right, and the International Broadcast Center in Beijing.  (Andy Wong / Associated Press)

Workers clean Beijing’s Tiananmen Square a month before the opening of the Olympic Games.  (Oded Balilty / Associated Press)