Scientists have
found that PM
2.5, the component of PM smaller than 2.5 micrometers in diameter, penetrates easily
into most indoor environments — where people spend much of their time. While the strength of
the correlation can vary by season and location, it appears that outdoor PM
2.5 levels reasonably
represent personal exposure to PM
2.5. Exposure studies have also shown that background levels
of other, gaseous pollutants, such as ozone and nitrogen dioxide, can be surrogate indicators for personal PM
2.5 exposure.
More information on particulate matter pollution and other indoor air pollutants can be found on EPA's Web site or by contacting us.
