BEIJING (AP) The drifting smoke from forest fires sometimes makes it difficult for marathoner Heather Lieberg to take a deep breath during her afternoon training runs in the hills of Montana.
Even on days when the local advisory lists the air quality as ''unhealthy for sensitive groups,'' Lieberg is out there chugging away through the hazy and hot conditions.
No better way to acclimate her body to what awaits in Beijing for the world championships.
''I've literally trained when there's ash falling on me, where they say `Do not go outside,''' said Lieberg, a 36-year-old from Helena. ''My lungs are definitely ready.''
Seven years after the Olympics sparked talk of a dramatic clean-up of pollution in Beijing, a milky haze still covers the city on most days and is expected to be there when the marathons take place - Saturday for the men, and Aug. 30 for the women.
According to a recent study conducted by physicists at the University of California, Berkeley, 1.6 million people die each year in China from heart, lung and stroke-related problems due to polluted air. The statistic is a reminder that while the Olympics may serve to shed light on a host city's environmental problems, they don't necessarily solve them.
With the 2022 Winter Olympics set to also take place in Beijing, the environment is likely to stay in the spotlight, in part because of plans to bring tons of artificial snow to the relatively dry mountains outside Beijing.
It's as true for Rio de Janeiro today as it was for Beijing in 2008, Athens in 2004, Sydney in 2000 or almost any other host, all of which have had their problems with air and/or water, said John Karamichas, author of the 2013 book ''The Olympic Games and the Environment.''
''All these issues were, in one way or another, addressed for the duration of the games,'' Karamichas said. ''Environmental legacy will depend on the post-event political processes.''
An expert from the World Health Organization, Martin Taylor, said government figures have shown some improvements in Beijing's air quality since the Olympics left town ''but there is still some way to go before (it) meets international safe standards.''
Competition conditions for the Olympic athletes have been at the forefront recently with the Rio Games less than a year away.
An analysis commissioned by The Associated Press found viruses running rampant in Rio's sewage-strewn water. The International Olympic Committee has made no plans to test for viruses, sticking with a plan to only monitor bacteria. Some swimmers have fallen ill after competing in the water, though the direct correlation between the water and the illness is difficult to make.
Running in heavily polluted air carries some health risk because of particulates that can clog up passageways and increased ozone that mainly bothers people with asthma. It can also affect finely tuned athletes who operate at maximum lung capacity. In 2008, the marathon world record holder, asthma sufferer Haile Gebrselassie, said he wouldn't run the race. ''The pollution in China is a threat to my health,'' he said.
But he was an exception. And even though pollution readings distributed by the U.S. Embassy's Beijing Air Quality Monitor frequently shows the air quality in the ''unhealthy'' range, the races at world championships will go on.
Questions about if runners should wear masks for competition are resurfacing. Scientists think that would produce, at best, mixed results. The masks do filter out particulates but most elite runners are creatures of habit and not used to wearing them. Distance runner Galen Rupp won U.S. championships wearing a mask in 2011, but he had trained extensively with it, and it was used to filter out pollen, not pollution.
''One can't with a straight face say that it doesn't do anything,'' said Dr. Sverre Vedal, a health science professor at the University of Washington. ''But one of the issues that comes up is the practicality of wearing a mask if you're performing.''
Last October, the Beijing Marathon began with thousands of participants wearing masks. The air quality reading that day was considered hazardous, and a level at which the U.S. Embassy says everyone should avoid all outdoor exertion.
Big events such as the Olympics and world championships put authorities on timelines to mitigate the problems, at least temporarily.
For the track meet, local organizers are following a model nicknamed ''APEC Blue'' - a Chinese government program that produced blue skies last November for the Asia-Pacific Economic Cooperation summit.
This approach calls on nearby provinces to cut down on the amount of pollution drifting in from factories outside the city limits. Officials also will restrict the number of cars on the streets of Beijing starting Thursday, two days before the world championships begin. They took half the cars off the road each day starting a few weeks before the Olympics.
A handful of athletes the AP interviewed said they're heading to Beijing knowing they can't do much about the pollution.
''I'm running for only 12 seconds,'' American hurdler David Oliver said. ''Now, if I were a marathoner, maybe I'd pay more attention.''