Living with smokers is as bad as living in smoke-free homes in heavily polluted cities such as Beijing or London, researchers said.
Moving to a smoke-free home could have major health benefits for non-smokers, they noted.
"Making your home smoke-free is the most effective way of dramatically reducing the amount of damaging fine particles you inhale," said lead author Sean Semple from the University of Aberdeen in Scotland.
The researchers studied data from four linked studies carried out in Scotland between 2009 and 2013 that had real time measurements of fine particulate matter PM2.5 in homes, and combined them with data on typical breathing rates and time-activity patterns.
In all four studies, homes that were likely to have a significant additional source of PM2.5 (such as coal or solid fuel fires) were excluded.
The results showed that the average PM2.5 concentrations from the 93 smoking homes were about 10 times those found in the 17 non-smoking homes.
Non-smokers living with smokers were exposed to an annual average amounting to three times the PM2.5 exposure levels prescribed by the World Health Organization (WHO).
Many non-smokers living in smoking homes inhaled similar quantities of PM2.5 to non-smokers who lived and worked in smoke-free environments in cities such as Beijing or London, which have high levels of air pollution.
"These measurements show that second-hand tobacco smoke can produce very high levels of toxic particles in your home," Semple concluded.
The study was published online in the journal Tobacco Control.
