Another factor is the drop in the number of adult smokers: It has now inched below 20 percent, according to 2007 CDC data. The new study found about 46 percent of nonsmokers had signs of nicotine in their blood in tests done from 1999 through 2004. That was a steep drop from 84 percent when similar tests were done in the late 1980s and early 1990s. But health officials stopped short of celebrating. "It's still high," said Cinzia Marano, one of the study's authors. "There is no safe level of exposure." Cigarettes cause lung cancer and other deadly illnesses not only in smokers, but also in nonsmokers who breathe in smoke, studies have shown. ---------Read more at: http://news.yahoo.com/s/ap/20080710/ap_on_he_me/med_secondhand_smoke