  We present a study of the extinction, traced by the Balmer decrement, in HII
regions in the dwarf galaxies NGC 1569 and NGC 4214. We find that the
large-scale extinction around the most prominent HII regions in both galaxies
forms a shell in which locally the intrinsic extinction can adopt relatively
high values ($A_V = 0.8 - 0.9$ mag) despite the low metallicity and thus the
low overall dust content. The small-scale extinction (spatial resolution
$\sim$0.3'') shows fluctuations that are most likely due to variations in the
dust distribution. We compare the distribution of the extinction to that of the
dust emission, traced by Spitzer emission at 8 and 24 \mi, and to the emission
of cold dust at 850 \mi. We find in general a good agreement between all
tracers, expect for the 850 \mi emission in NGC 4214 which is more extended
than the extinction and the other emissions. Whereas in NGC 1569 the dust
emission at all wavelengths is very similar, NGC 4214 shows spatial variations
in the 24-to-850 \mi ratio. We furthermore compared the 24 \mi and the
extinction-corrected Halpha emission from HII regions in a sample of galaxies
with a wide range of metallicities and found a good correlation between both
emissions, independent of metallicity. We suggest that this lack of dependence
on metallicity might be due to the formation of dust shells with a relatively
constant opacity, like the ones observed here, around ionizing stars.

Astrophysics