Six homes in the metropolit
an Boston
are
a were s
ampledbetween 6
and 12 consecutive d
ays for indoor
andoutdoor p
article volume
and m
ass concentr
ations, p
articleelement
al concentr
ations,
and
air exch
ange r
ates (AERs).Indoor/outdoor (I/O) r
atios of nighttime (i.e., p
article nonindoorsource periods) sulfur, PM
2.5 and the specific p
articlesize interv
als were used to provide estim
ates of the effectivepenetr
ation efficiency. Mixed models
and gr
aphic
aldispl
ays were used to
assess the
ability of the I/O r
atiosfor sulfur to estim
ate corresponding I/O r
atios for PM
2.5 andthe v
arious p
article sizes. Results from this
an
alysisshowed th
at p
articul
ate sulfur compounds were prim
arilyof outdoor origin
and beh
aved in
a m
anner th
at w
asrepresent
ative of tot
al PM
2.5 in Boston, MA. These findingssupport the conclusion th
at sulfur c
an be used
as
asuit
able tr
acer of outdoor PM
2.5 for the homes s
ampled inthis study. Sulfur w
as more represent
ative of p
articlesof simil
ar size (0.06-0.5
ages/entities/mgr.gif">m), providing evidence th
at thesize composition of tot
al PM
2.5 is
an import
ant ch
ar
acteristic
affecting the robustness of sulfur-b
ased estim
ationmethods.