Babies can absorb particles and gases emitted by cigarettes from walls, clothes, hair and skin -- including up to 90 percent of the nicotine found in tobacco smoke -- experts warn.

USA Today reported Aug. 6 that even smokers who refrain from lighting up with their infants in the room may not be fully protecting their children. George Matt of San Diego State University and colleagues found that babies, who explore the world by crawling and touching, can swallow, inhale, or absorb dangerous chemicals from cigarette-smoke residue, which can stay in the environment for months.

The preliminary study found that even babies whose parents only smoked outside had detectable levels of the nicotine byproduct cotinine in their bodies, perhaps from hugging their mothers. The cotinine levels of such children were 50 times lower than those of children whose parents smoked around them, but seven times higher than the cotinine levels in children of nonsmokers.

"The million-dollar question is: How dangerous is this?" said Brett Singer, a scientist at California's Lawrence Berkeley Laboratory. "We can't say for sure this is a health hazard."

Matt said contaminants can be removed by washing or replacing affected surfaces.