Future observations of CMB anisotropies will be able to probe high
multipole regions of the angular power spectrum, corresponding to a
resolution of a few arcminutes. Dust emission from merging haloes is
one of the foregrounds that will affect such very small scales. We
estimate the contribution to CMB angular fluctuations from objects
which are bright in the sub-millimeter band due to intense star
formation bursts following merging episodes. We also consider the
effect of the intergalactic dust expelled from galaxies by strong
winds and AGN activity.  We base our approach on the Lacey-Cole merger
model and on the Kennicutt relation which connects the star formation
rate in galaxies with their infrared luminosity. We set the free
parameters of the model in order to not exceed the SCUBA source
counts, the Madau plot of star formation rate in the universe and
COBE/FIRAS data on the intensity of the sub-millimeter cosmic
background radiation. We show that the angular power spectrum arising
from the distribution of such star-forming haloes will be one of the
most significant foregrounds in the high frequency channels of future
CMB experiments, such as PLANCK, ACT and SPT. The correlation term,
due to the clustering of multiple haloes at redshift z~2-6, is
dominant in the broad range of angular scales 200<l<3000. Poisson
fluctuations due to bright sub-millimeter sources are more important
at higher l, but since they are generated from the bright sources,
such contribution could be strongly reduced if bright sources are
excised from the sky maps. The contribution of the correlation term to
the angular power spectrum depends strongly on the redshift evolution
of the escape fraction of UV photons. The measurement of this signal
will therefore give important information about galaxies in the early
stage of their evolution.