Exposure to secondhand tobacco smoke outdoors also poses health risks, according to a new study.

Even brief exposures to secondhand smoke outdoors may have adverse effects on the heart and respiratory systems and increase the severity of asthma attacks, especially in children, said the study conducted by Stanford University researchers.

This was the first in-depth study on how smoking affects air quality at sidewalk cafes, park benches and other outdoor locations.

While the health risks associated with indoor secondhand smoke are well documented, little research has been done on exposure to toxic tobacco fumes outdoors.

The findings were published in the May issue of the Journal of the Air and Waste Management Association (JAWMA).

The Stanford team concluded that a non-smoker sitting a few feet downwind from a smoldering cigarette is likely to be exposed to substantial levels of contaminated air for brief periods of time.

"Some folk have expressed the opinion that exposure to outdoor tobacco smoke is insignificant, because it dissipates quickly into the air," said Neil Klepeis, assistant professor of civil and environmental engineering at Stanford and lead author of the study.

"But our findings show that a person sitting or standing next to a smoker outdoors can breathe in wisps of smoke that are many times more concentrated than normal background air pollution levels."

"We were surprised to discover that being within a few feet of a smoker outdoors may expose you to air pollution levels that are comparable, on average, to indoor levels that we measured in previous studies of homes and taverns," said Wayne Ott, professor of civil and environmental engineering at Stanford and co-author of the JAWMA study.

"For example, if you're at a sidewalk cafe and you sit within 18 inches of a person who smokes two cigarettes over the course of an hour, your exposure to secondhand smoke could be the same as if you sat one hour inside a tavern with smokers. Based on our findings, a child in close proximity to adult smokers at a backyard party also could receive substantial exposure to secondhand smoke," he said.

Tens of thousands of Americans die each year from secondhand tobacco smoke, according to a 2006 report by the U.S. Surgeon General.

Source: Xinhua