Thick as pea soup, grey as ash, day after day, Beijing's smog clouds the Olympic skyline, tainting the gleaming, white sports stadium.
Despite a ban on half the city's cars and hundreds of factory closings, the choking pollution keeps coming back with a vengeance, with the Olympic opening ceremonies now less than two weeks away.
Chinese environmental officials claim that appearances don't tell the whole story.
"If we were sitting in a bathhouse, there'd be a lot of steam," said Du ShaoZhang, an environmental official. "But no pollution."
But, according to World Health Organization standards, since June 23, Beijing's air quality has been unsafe, with three times the recommended level of pollutants.
If it isn't safe for citizens to practice their daily exercise routines outdoors, the pollution could smother and potentially cripple a runner or cyclist trying to beat a world record.
"Those ingredients are toxic to the lungs of normal people, and athletes who breathe in large volumes of air when exercising are particularly at risk," said Dr. Jonathan Parsons, pulmonologist at Ohio State University Medical Center.
With thousands of athletes expected to arrive in Beijing this week to compete in high endurance events, ranging from mountain biking to marathon running, doctors warn that they might experience symptoms like coughing, shortness of breath, asthma or even serious heart problems.
In February, the Chinese instituted a plan to close 150 gas stations and oil depots by May, which they thought would be enough time to decrease the air pollution for the games. They also closed coal-fired power plants, steel mills and cement plants to cut emissions and air pollutants.
On bad smog days, many Chinese wear simple facemasks to prevent breathing in unnecessary dust. Following suit, U.S. Olympic athletes will wear much more sophisticated face masks, specially designed for their protection. The masks may even give the athletes an edge.
"No one's been able to show that wearing a mask is going to be protective in terms of letting you exercise to your optimal level," Parsons said. "But if I were an athlete in Beijing, I'd be wearing a mask."
U.S. triathlete Matt Reed suffered a major asthma attack in Beijing during last year's Olympic trials.
"It felt terrible," Reed said. "It was supposed to be a great race for me … but, once I got the asthma, my body shut down, my lungs weren't taking any oxygen anymore. I could hardly run."
Though Reed already had mild asthma, something in Beijing exacerbated his symptoms, and other athletes may be at risk of exercise-induced asthma from the smog. Reed plans to fly into North Korea, where the air quality is better, to delay arrival in Beijing. He plans to wear his mask for protection.
"During the opening ceremonies, I will think about wearing it some of the time," Reed said. "I'll definitely wear the mask if I'm walking outside the hotel."
Chinese officials and environmentalists are debating whether or not to take drastic measures. One plan is to eliminate 90 percent of the cars from the roads. During the Olympics, cars with even-numbered license plates will drive on one day, and those with odd-numbered plates will drive on the next.
The weather also plays a role. Strong wind and rain brought relief to the pollutant-clogged city on Monday. A portable air monitoring device calculated only 10 micrograms of pollutants, per cubic meter, which is an acceptable level for athletes. But with 10 days before the games, Beijing is running out of last-minute fixes, as they seek to deliver the 'green' Olympics they promised to the world.