Living with smokers exposes non-smokers to three times more than the safe levels of particles when living with smokers, researchers find. The Scottish researchers discovered that for non-smokers, living with at least one smoker in a home is the same as living in smoke-free homes in heavily polluted cities such as Beijing or London. Additionally, the researchers found that non-smokers who move to a smoke-free home could enjoy major health benefits.

Existing evidence strongly indicates that exposure to second-hand smoke results in a wide range of negative health consequences, including respiratory and heart illness. As a result, several governments have implemented measures to reduce their population’s exposure to second hand smoke in work and leisure settings.

Fine particulate matter (PM2.5), including fine dust or soot suspended in the air, has been commonly used as a marker for second hand smoke exposure with data from bars and restaurants that show amounts of PM2.5 derived from second hand smoke that often exceed the US Environmental Protection Agency levels considered “unhealthy for sensitive groups” 24 hour limit or the World Health Organization’s guidance limits.

For the study, researchers examined fine particulate matter under PM2.5 concentrations in smoking and non-smoking homes in Scotland to determine the amount of PM2.5 inhaled by various age groups. The researchers studied data from four linked studies in Scotland between 2009 and 2013 with real time measurements of PM2.5 in homes, combining them with data regarding typical breathing rates and time-activity patterns.

Study results indicated that average PM2.5 concentrations from the 93 smoking homes were nearly 10 times more than those in the 17 non-smoking homes.

The researchers said in a statement, “These findings ultimately support the need for efforts to reduce SHS [second hand smoke] exposure in the home, most notably through the implementation of smoke free home rules and smoke free multi-unit housing policies.”

According to the Centers for Disease Control and Prevention, cigarette smoking kills over 480,000 Americans annually, with over 41,000 of these deaths due to exposure to secondhand smoke.