Although secondhand smoke has been linked to death and illness, a new study suggests that parents around the world do very little to protect their children from “passive smoking” exposure.

Heather Wipfli, Ph.D., project director at the Institute for Global Tobacco Control at the Johns Hopkins Bloomberg School of Public Health, and colleagues conducted home surveys in 31 countries.

Researchers examined the smoking histories of the adults in the homes, exposures to secondhand smoke inside the house and in the community, and attitudes toward smoking. They used air-sampling technology to gauge nicotine levels in homes and hair samples to measure individual exposure levels of non-smoking women and children.

The study appears in the April issue of the American Journal of Public Health.

Concentrations of nicotine in the air were 17 times higher in households with smokers compared to those without, and nicotine concentrations were about 12.9 times higher in homes that permitted smoking compared to households that voluntarily banned it.

Researchers found nicotine even in homes without smokers, indicating that visitors and others sometimes smoked in the homes.

Children had higher levels of nicotine than women did, and among children living with a smoker, those under 5 years old had levels nearly twice as high as children ages 5 and older did.

The United States and Western Europe were not included in the study, which comprised seven Eastern European countries, nine countries in North and South America, 12 Asian countries and three in the Middle East.