11.   As pollution levels dropped to half Wednesday, an apparent result of cooler air and fewer cars, traffic is to return to normal on Thursday.

12.   As the protein levels drop in the blood, patients retain salt and water and begin to swell.

13.   But after menopause, when estrogen levels drop precipitously, women tend to switch to a male pattern of weight gain, accumulating fat around the abdomen.

14.   But even if one did work when first applied, as its level of concentration dropped, bacteria could produce strains that resist it.

15.   But she modified the diet, substituting oatmeal for eggs at breakfast, and her cholesterol levels dropped.

16.   But the signs that PCB levels were dropping prompted the agency to wait.

17.   But the pill is increasingly being recommended for women approaching menopause whose own estrogen levels are dropping but who still face a risk of becoming pregnant.

18.   But when his habit begins upstaging him, the interest level drops drastically.

19.   Calcium absorption -- crucial to building and maintaining bone mass -- is linked to estrogen, and slows after menopause when the levels of naturally occurring estrogen drop.