LONDON – Second-hand smoke kills more than 600,000 people worldwide every year, according to a new study.

In the first look at the global impact of second-hand smoking, researchers analyzed data from 2004 for 192 countries. They found 40 percent of children and more than 30 percent of non-smoking men and women regularly breathe in second-hand smoke.

Scientists estimated that passive smoking causes about 379,000 deaths from heart disease, 165,000 deaths from lower respiratory disease, 36,900 deaths from asthma and 21,400 deaths from lung cancer a year.

Altogether, those account for about 1 percent of the world’s deaths. The study was paid for by the Swedish National Board of Health and Welfare and Bloomberg Philanthropies. It was published today in the British medical journal Lancet.

“This helps us understand the real toll of tobacco,” said Armando Peruga, a program manager at the World Health Organization’s Tobacco-Free Initiative, who led the study. He said the approximately 603,000 deaths from second-hand smoking should be added to the 5.1 million deaths that smoking itself causes every year.

Peruga said WHO was particularly concerned about the 165,000 children who die of smoke-related respiratory infections, mostly in Southeast Asia and Africa.

“The mix of infectious diseases and second-hand smoke is a deadly combination,” Peruga said. Children whose parents smoke have a higher risk of sudden infant death syndrome, ear infections, pneumonia, bronchitis and asthma. Their lungs may also grow more slowly than kids whose parents don’t smoke.

Peruga and colleagues found the highest numbers of people exposed to second-hand smoke are in Europe and Asia. The lowest rates of exposure were in the Americas, the Eastern Mediterranean and Africa.