Children

While deaths due to passive smoking in children were skewed towards poor and middle-income countries, deaths in adults were spread across countries at all income levels.

In Europe's high-income countries, only 71 child deaths occurred, while 35,388 deaths were in adults. Yet in the countries assessed in Africa, an estimated 43,375 deaths due to passive smoking were in children compared with 9,514 in adults.

Pruss-Ustun urged countries to enforce the WHO's Framework Convention on Tobacco Control, which includes higher tobacco taxes, plain packaging and advertising bans, among other steps.

"Policy-makers should bear in mind that enforcing complete smoke-free laws will probably substantially reduce the number of deaths attributable to exposure to second-hand smoke within the first year of its implementation, with accompanying reduction in costs of illness in social and health systems," she wrote.

Only 7.4 percent of the world population currently lives in jurisdictions with comprehensive smoke-free laws, and those laws are not always robustly enforced.

In places where smoke-free rules are adhered to, research shows that exposure to second hand smoke in high-risk places like bars and restaurants can be cut by 90 percent, and in general by 60 percent, the researchers said.

Studies also show such laws help to reduce the number of cigarettes smoked by smokers and lead to higher success rates in those trying to quit.