Before the 2008 Olympics in Beijing, there was broad concern about the impact that air pollution would have on the athletes. The city's well-documented problems with ozone and fine particles were not the sort of thing conducive to fast sprint times and/or not having a stroke. So authorities cracked down, greatly reducing vehicle traffic, closing factories, and inducing rain. It worked. They curbed ground-level pollutants and improved cardio-vascular health for residents and athletes alike (and brought down CO2 emissions along the way). A team at the University of Rochester noted a "direct correlation" between reduced pollution and an immediate health impact.
Unfortunately for England, the environment has taken up a new strategy for ruining the Olympics: rain.
"My biggest worry is actually the weather," said [London 2012 Chief Executive] Paul Deighton, adding that much of the construction was carried out in torrential rain in recent months.
"We've got a lot of events that are outside. I think the impact the weather has on people's mood, how they enjoy the games, is very big.
"So for me, if I have a prayer I could make, it's every extra day of sunshine just makes for a better experience for everybody here in town."
Deighton has cause for concern. An unusually static southward shift in the jet stream combined with increased atmospheric moisture has meant one of the rainiest summers in recent memory.