1.   A new study shows for the first time that smog might cause asthma, not just trigger attacks in those who already have the disease.

2.   Smog has caused entire Chinese cities to disappear from satellite photographs.

3.   This is also the first time the EPA has confronted the enormous public health challenge that smog causes in states downwind from where it is produced.

4.   Chinese health experts attribute rising death rates from cancer and respiratory ailments to pollution and say that smog causes tens of thousands of premature deaths each year.