1.   Perhaps the greatest current fear is that terrorists will lace the air with lethal germs.

2.   The air was laced with the aroma of honeysuckle.

3.   The air is laced with salt and contaminated by pesticides that the wind has swept from the dry seabed.

4.   The old Rustbelt urban air was laced with the cliche gripe of so many winning sports cities, that no one ever respected them until now.