1.   Air pollution in this city of four million people, and one million cars and trucks, often approaches danger limits on warm, windless days.

2.   Air pollution levels in this city of four million hover near danger limits on most days of the year.

3.   Although no decision has yet been taken, the government has in the past banned all traffic from the city center when air pollution levels soared beyond danger limits.

4.   They emphasize the need for discussions at work on the risks of drink and more self-assessment so a drinker knows when he or she is reaching the danger limit.

5.   The government repeated urgent appeals for residents to leave their cars home as levels of ozone and other toxic gasses remained well above danger limits.