The head of the International Olympic Committee, Jacques Rogge, ackowledged as much this summer when he visited Beijing to mark one year to go to the 2008 Opening Ceremony.
He said that some events could be delayed if the air quality next August was not up to scratch. November it may be, but it is all too easy to imagine what summer heat and temperatures in the 30s, combined with heavy pollution, could do to competitors not used to it.
There is good news. The Chinese authorities recognise the problem and seem to be doing something about it. In August they tested a series of measures to curb pollution. And when I met 2008 organisers this week, I sought assurances from them that the conditions here next summer would allow competitors from Britain and across the world to produce performances worthy of the Games.
And their young people certainly get it. I met three impressive Beijing teenagers to be quizzed by them about climate change and our plans for 2012. In flawless English, they eloquently showed how ordinary people here care and want action worldwide about global warming.
I am proud that this is not one of our worries as we plan for our own Olympic and Paralympic Games. One of the reasons why this week's fire on the 2012 Olympic Park site got so much TV coverage was that the plumes of smoke were set against a bright blue sky.
But I want to be proud too next summer of British athletes winning gold. Our athletes can be confident that the British Olympic Association and British Paralympic Association have factored the conditions into their plans from the moment Beijing won the 2008 Games.
After years of training the world's best athletes deserve a fair go. Beijing 2008 must be remembered for medals and magic and a Games that will challenge us to be at our very best four years later in London.